> THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA DAVIS STATE OF CALIFORNIA DEPARTMENT OF PUBLIC WORKS DIVISION OF WATER RESOURCES o EARL WARREN. Governor C. H. PURCELL, Director of Public Works EDWARD HYATT, State Engineer BULLETIN No. 55 SAN DIEGUITO AND SAN DIEGO RIVERS INVESTIGATION 1949 LIBRARY UNIVERSITY OF CALIFORNIA DAVIS TABLE OF CONTENTS Page LETTER OF TRANSMITTAL ix ACKNOWLEDGMENT x CONSULTANTS xi ORGANIZATION xii CHAPTER I INTRODUCTION 1 Water Problems of the San Diego Region 1 Authorization 1 Prior Investigations and Reports 2 Scope 3 CHAPTER II SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 7 Water Requirements of City of San Diego 7 San Dleguito Basin 9 Description 9 Water Supply 10 Precipitation 10 Runoff 11 Water Utilization 12 Water Service Agencies Ij Other Water Users 14 Export 15 Existing Conservation Works 1^ Complete Conservation Development 15 Yield from Surface Reservoirs 15 Sutherland Reservoir 17 Pamo Reservoir 17 Lake Hodges 18 Comparison of Surface Reservoirs 19 Yield from Underground Reservoirs 21 Flood Control Works 22 San Diego River Basin 23 Conservation Reservoirs in Mission Gorge 24 TABLE OF CONTENTS ( continued) Page Mission Gorge Reservoir No. Zero 24 Mission Gorge Reservoir No. 2 24 Mission Gorge Reservoir No. 3 with Concrete Gravity Dam 24 Mission Gorge Reservoir No. 5 with Concrete Arch Dam . . 25 Comparison of Reservoirs 25 Enlarged San Vicente Reservoir 25 Conclusions 26 Recommendations }0 CHAPTER III WATER REQ,UIREMENTS OF CITY OF SAN DIEGO 31 Present Water Supply 32 Local Surface Sources and Development 32 Local Underground Sources 33 Colorado River Water 54 Transmission and Distribution System 38 Safe Yield 39 Present Water Utilization 41 Future Water Requirements 42 Population 42 Water Consumption 47 Ultimate Water Requirements 48 Supplementary Water Supply 49 CHAPTER IV DESCRIPTION OF SAN DIEGUITO BASIN 51 Topography 51 Geology 52 Ground-Water Basins 53 Climate 53 Native Cover 54 Population 54 Industry and Agriculture 55 Transportation 56 il TABLE OF CONTENTS ( continued) Page CHAPTER V WATER SUPPLY OF SAN DIEGUITO BASIN 57 Precipitation 57 Storm Types and Ocourrence 57 Precipitation Stations and Records 58 Mean Seasonal Precipitation 60 Precipitation Characteristics 6? Runoff 64 Stream Gaging Stations and Records 64 Runoff under Present Development and Cultural Conditions . . 66 Runoff Characteristics 70 Import of Water 72 Import from San Luis Rey River 72 Import from Colorado River 73 CHAPTER YI XITILIZATION OF WATERS OF SAN DIEGUITO BASIN 75 Early Use of Water 75 San Dieguito System 76 Water Service Agencies 76 . San Dieguito Irrigation District 76 Present Water Utilization 78 Ultimate Water Utilization 79 Santa Fe Irrigation District 80 Present Water Utilization 82 Ultimate Water Utilization 8? Ramona Irrigation District 83 Present Water Utilization 84 Ultimate Water Utilization 84 Del Mar Water, Light and Power Company 85 Present Water Utilization 87 Ultimate Water Utilization 87 City of San Diego 88 Present Utilization of Water from San Dieguito Basin . . 88 Ultimate Utilization of Water from San Dieguito Basin . 88 TABLE OF CONTENTS (continued) Page Other Water Users 90 Export of Water 91 Water Losses 92 Consumptive Use by Native Vegetation 92 Outflow to Ocean 95 Evaporation from Reservoirs 95 Summary of Water Utilization 97 CHAPTER VII OONSBRVATION WORKS IN SAN DIEGUITO BASIN 99 Existing Development 99 Complete Conservation Development 101 Yield from Surface Reservoirs 101 Runoff Periods 102 Evaporation 102 Draft froiD Reservoirs 104 Yield 107 Surface Reservoirs 110 Sutherland Reservoir Ill Pamo Reservoir 116 Lake Hodges 124 Comparison of Surface Reservoirs 133 Reservoirs Operated Individually 135 Reservoirs Operated Coordlnately for Complete Development 135 Reservoirs Operated Coordlnately for Partial Development I36 Sutherland and Hodges Reservoirs Operated Coordlnately . 137 Summary 13d Yield from Underground Reservoirs 141 Seasonal and Cyclic Storage 141 Reduction of Natural Consumptive Use 142 CHAPTER VIII FLOOD CONTROL WORKS IN SAN DIEGUITO BASIN 147 Areas Subject to Flood Damage 147 Flood Characteristics 148 Size and Frequency of Flood Flows 148 Flood Hydrographs 150 It TABLE OF CONTENTS ( continued) Page Flood Control 15* Effect of Conservation Reservoirs 15* Sutherland Reservoir 15* Pamo Reservoir 155 Lake Hodges 156 Future Flood Control Works l60 CHAPTER IX CONSERVATION WORKS ON SAN DIEGO RIVER l6l Ml-esion Gorge Reservoirs l6l Areas and Capacities l6l Reservoir Lands l62 Cost Estimates 164 Mission Gorge Reservoir No. Zero I65 Mission Gorge Reservoir No. 2 I66 Mission Gorge Reservoir No. 3, with Oonorete Gravity Dam I68 Mission Gorge Reservoir No. 5» with Concrete Arch Dam . 169 Comparison of Reservoirs 171 Enlarged San Vicente Reservoir 17? APPENDICES A. Agreements Authorizing Investigation and Report 175 B. Estimates of Cost of Acquisition of Water Rights Required for Development of San Dieguito Basin, G. E. Arnold, Director of Water Department, the City of San Diego, April 22, 19*8 . iBj C. Estimates of Cost of Land Acquisition for Lake Hodges and Mission Gorge Reservoirs, B. A. Etcheverry and G. F. Mellin, Consultants I87 D. "Preliminary Progress Report on Consumptive Use of Water Investigations in San Pasqual Valley, California", Division of Irrigation, Soil Conservation Service, U. S. Department of Agriculture, September 14, 1945 197 E. Monthly Precipitation Records at Stations Representative of San Dieguito Basin 209 F. Estimated or Measured Actual Monthly Runoff at Key Gaging Stations in San Dieguito Basin, 1912-1? to 1947-48, Inclusive 219 G. Data Regarding Special Census 229 H. Estimates of Costs 253 LIST OF TABLES Table Page 1. Comparison of Reservoirs in San Dieguito Basin 20 2. Reservoirs of City of San Diego 32 }, Estimated Safe Yield of Present Water Supply Development of City of San Diego 40 4. Water Consumption by City of San Diego 41 5. Special Census of San Diego County by United States Bureau of the Census 44 6. Population of County and City of San Diego 44 ?• Forecasts of San Diego City Population to I96O 46 8. Precipitation Stations in or near San Dieguito Basin 59 9. Estimated Mean Seasonal Precipitation at Stations in or near San Dieguito Basin 62 10. Estimated Average Seasonal Precipitation over Principal Drainage Areas in San Dieguito Basin 63 11. Monthly Distribution of Precipitation at San Diego 64 12. Stream Gaging Stations in San Dieguito Basin 65 13. Estimated or Measured Actual Seasonal Runoff at Key Gaging Stations in San Dieguito Basin 68 14. Average Monthly Distribution of Runoff in San Dieguito Basin ... 72 15. Estimated Import of Water to San Dieguito Basin from San Luis Rey River 73 16. Estimated Acreage of Irrigated Crops in San Dieguito Irrigation District . 78 17. Water from San Dieguito Basin Delivered to San Dieguito Irrigation District 79 18. Water from San Dieguito Basin Delivered to Santa Fe Irrigation District 82 19. Water Pumped from San Dieguito Basin by Ramona Irrigation District 85 20. Water from San Dieguito Basin Delivered to Del Mar Water, Light and Power Company 87 21. Water from San Dieguito Basin Delivered to City of San Diego ... 89 22. Estimated Average Seasonal Export of Water from San Dieguito Basin 92 23. Water Spilled from Lake Hodges 94 24. Outflow to Pacific Ocean from San Dieguito River under Present Conditions 95 25. Gross Evaporation from Lake Hodges 96 26. Estimated Average Seasonal TJtilizatlon of Waters of San Dieguito Basin 97 27. Gross Evaporation from Reservoirs in San Diego County IO3 Ti LIST OF TABLES (continued) Table Page 28. Assumed Distribution of Drafts from Reservoirs in San Dieguito Basin IO6 29' Estimated Seasonal Yield from Reservoirs in San Dieguito Basin . . 107 50. Comparative Values of I917-36 Firm Yield and Safe Yield from Reservoirs in San Dieguito Basin 110 31. Areas and Capacities of Sutherland Reservoir Ill 32. Areas and Capacities of Pamo Reservoir 117 33- Physical Features of Pamo Dam for Three Sizes of Development . . . II9 34. Summary of Estimated Costs of Pamo Reservoir and Conduit for Three Sizes of Development 124 35» Areas and Capacities of Lake Hodges 125 36. Physical Features of Hodges Dam for Five Sizes of Development . . 128 37« Estimated Costs of Required Additional Reservoir Lands for Lake Hodges Development I30 38. Summary of Estimated Costs of Lake Hodges Reservoir, Conduit and Pumping Plant for Five Sizes of Development 132 39» Comparison of Reservoirs in San Dieguito Basin 134 40. Comparison of Plans for Coordinated Operation of Sutherland and Hodges Reservoirs I37 41. Summary of Plans for Development of Lake Hodges and Sutherland Reservoir I38 42. Estimated Gross Seasonal Consumptive Use by Irrigated Crops in San Pasqual Valley I43 43. Estimated Gross Seasonal Consumptive Use in San Pasqual Valley with Water Table at Various Elevations under Present Conditions of Culture 144 44. Maximum Flood of Record in San Dieguito Basin 148 45. Estimated Magnitude and Frequency of Mean Daily Flood Flows in San Dieguito Basin under Present Conditions 148 46. Ratio of Crest Flood Flows to Maximum Mean 24-Hour Flows in San Dieguito Basin 152 47. Estimated Size and Frequency of Crest Flood Flows in San Dieguito Basin Under Present Conditions 154 48. Areas and Capacities of Mission Gorge Reservoirs I62 49. Estimated Costs of Required Additional Reservoir Lands for Mission Gorge Reservoirs I63 50. Estimated Amounts of 19'l-7 Costs of Additional Safe Yield from Reservoirs at Mission Gorge when Operated Coordinately with the Existing San Diego River Development 171 vii LIST OF PLATES Plate Page I. Sources of Supplies and Transmission Lines of Water System of San Diego Metropolitan Area .... following 32 II. Water Consumption by City of San Diego 43 III. Population, County and City of San Diego 45 17. Drainage Basin of San Dieguito River and Water Service Areas of Organized Agencies following 52 V. Isohyetal Map of San Dieguito Basin in San Diego County following 58 VI. Seasonal Precipitation at San Diego, I85O-5I to 1947-48, Inclusive 61 VII. Estimated or Measured Actual Seasonal Runoff, San Dieguito River at Lake Hodges, 1887-88 to 1947-48, Inclusive . . 69 VIII. Conservation Works for Development of San Dieguito River following 102 IX. Variation of Evaporation with Elevation and Distance from the Coast for Reservoirs in San Diego County IO5 I. Estimated Seasonal Yield from Reservoirs in San Dieguito Basin, 1914-15 to 1944-43, Inclusive 109 H. Sutherland Dam on Santa Ysabel Creek 113 211. Pamo Dam on Santa Ysabel Creek 121 XIII. Hodges Dam on San Dieguito River 129 2IV. Costs of Additional Seasonal Yield from Reservoirs in San Dieguito Basin I39 ZV. Effect of Lowering Average Levels of Ground Water on Total Gross Seasonal Consumptive Use in San Pasqual Valley . . 14 5 ZVI. Probable Frequency of Occurrence of Floods in San Dieguito Basin 149 XVII. Hydrographs of Floods of Record in San Dieguito Basin .... I5I XVIII. Probable Hydrographs of Flood Flows In San Dieguito Basin . . I53 XIX. Effect of Conservation Reservoirs in San Dieguito Basin on Crest Flows of Probable Once in IQO-Year Flood 157 ZI. Flood Control Effects of Lake Hodges on San Dieguito River . I58 XXI. Probable Volume of Water in Storage at Lake Hodges on First of April 159 YXTI. Mission Gorge No. Zero Dam on San Diego River I67 XXIII. Variable-Radius Arch Dam at Lower Mission Gorge No. 3 Site on San Diego River 173 viii C. H. PURCELL DIRECTOR STATE OF CALIFORNIA department oi ^uliltc pSorks SACRAMENTO June 17, 1949 The Council of the City of San Diego Civic Center San Diego 1, California Subject: San Dieguito and San Diego Rivers Investigation File No. 451.2 Gentlemen: Under general authority granted the Department of Public Works by Article 2, Chapter 1 of the Water Code, a cooperative agreement between the City of San Diego and the Department of Public Works was executed on February 20, 1945, providing that the Department make an investigation of water resources of the San Dieguito River and make recommendations for their further development and utiliza- tion. A superseding agreement, executed on May 11, 1945* broadene.d scope of the work to include the San Diego River. A supplemental agreement, dated May 1, 1947, provided ad- ditional funds for the investigation and report. Under terms of the three agreements, equal con- tributions by the two parties provided a total amount of .^65,000 for the investigation and for preparation of and publishing the report. Of this amount, 412,146.98 bas been expended under contracts with Fairchild Aerial Surveys, Inc., for aerial surveys and topographic maps of dam and reservoir sites. Copies of these maps have been furnished the City of San Diego. Under direction of the State Engineer, the Divi- sion of Water Resources of this Department has completed the investigation, studies and report called for under the foregoing agreements. The report so authorized, Bulletin No. 55, "San Dieguito and San Diego Rivers Investigation", 1949, is transmitted herewith. Yours very truly. Director of Public Works ix ACKNOWLEDGMENT Many of the data presented in this report and used as a basis for studies herein were contributed by public and private agencies and individuals. Particular co- operation in this respect, as well as valuable advice, was received from officials of the City of San Diego. All pertinent data in the City's files were made available. Field parties were furnished for checking topographic maps and securing additional dam site topography, and crews were supplied foi- establishment of test wells and gaging stations in San Pasqual Valley. An estimate of the cost of acquisition of water rights was also made by the City of San Diego, and is reproduced in Appendix B of this report. Likewise of assistance were the following agencies or their authorized represen- tatives: Soil Conservation Service, United States Department of Agriculture District Engineer, Los Angeles District, Corps of Engineers, Department of the Army Geological Survey, United States Department of the Interior Bureau of the Census, United States Department of Commerce Weather Bureau, United States Department of Commerce California State Office of Planning and Research San Dleguito Irrigation District Santa Fe Irrigation District Ramona Irrigation District La Mesa, Lemon Grove and Spring Valley Irrigation District San Diego County Water Authority Escondido Mutual Water Company Del Mar Water, Light and Power Company San Diego County Water Company The voluntary and valuable cooperation received from organizations find individ- uals is acknowledged with thanks. CONSULTANTS At the request of the State Division of Water Resources, and under terms of the regular cooperative agreement between the Federal government and the State of Cali- fornia, the Soil Conservation Service of the United States Department of Agriculture made an investigation and prepared a preliminary progress report on consumptive use of water in San Pasqual Valley in San Dieguito Basin. The investigation was made and report pre- pared by Harry F. Blaney, Senior Irrigation Engineer, and Dean C. Muckel, Associate Ir- rigation Engineer, of the Division of Irrigation, under direction of W. U. McLaughlin, Chief of Division. The report is reproduced in Appendix D, herein. An examination of proposed Pamo dam sites and Sutherland dam site on Santa Ysabel Creek was made by Chester Marliave, Consulting Geologist. Mr. Marliave also pre- pared a preliirinary estimate on stripping at one of the Pamo sites. B. A. Etcheverry, Consulting Civil Engineer, and G. F. Mellin, Assistant Chief Engineer, State Reclamation Board, conducted a field survey and estimated costs of acqui- sition, at present-day market values, of land and improvements required in connection with proposed reservoirs at Lake Hodges on San Dieguito River, and Mission Gorge on San Diego River. Their reports on the Hodges and Mission Gorge sites are reproduced in Ap- pendix C, herein. li ORGANIZATION STATE DEPARTMENT OF PUBLIC WORKS DIVISION OF WATER RESOURCES C. H. Purcell Director of Public Works Edward Hyatt State Engineer A. D. Edmonston Assistant State Engineer The itivestigation was conducted and report prepared under the direction of P. H. Van Etten .... Principal Hydraulic Engineer Principal Assistants W. L. Berry Senior Hydraulic Engineer G. L. Long Senior Hydraulic Engineer H. M. Crooker Associate Hydraulic Engineer D. B. Willets Associate Hydraulic Engineer Assistants W. A. Brown Senior Engineer, Dams W. A. Perkins Senior Engineer, Dams E. C. Marliave .... Senior Engineering Geologist R. M. Edmonston .... Assistant Hydraulic Engineer G. M. Norris Assistant Hydraulic Engineer C. W. Plumb, Jr. . . . Assistant Hydraulic Engineer C. J. Cortripht Assistant Civil Engineer R. L. Cox Assistant Civil Engineer J. L. James Senior Delineator R. N. Jansen Delineator C. T. Jeffryes Delineator L. N. Case Senior Stenographer-Clerk T. R. Merryweather Administrative Assistant Harry Searancke ... Acting Administrative Assistant 111 CHAPTER I INTRODUCTION Water Problems of the San Diego Region Because of its mild and equable climate, and scenic, recreational and cultural advantages, the San Diego region since the turn of the century has experienced consistent rapid growth in population. However, the tremendously accelerated increase resultant from expansion of its aircraft Industry during World War II, and of naval and military establishments throughout the area, was unanticipated. Local public agencies had planned the orderly development of water sources and supplies to meet expected demands for sev- eral years in the future, but this program was inadequate for unprecedented requirements connected with war activities. In X9^'i, despite a fortunate series of wet years up to that time, the situation had become sufficiently critical to warrant immediate emergency action. Developed water sources were so overdrawn that the occurrence of dry years, to which the region is particularly susceptible, would soon exhaust Inadequate reserves on hand. Surveys and negotiations were under way toward obtaining supplemental water from the Colorado River, a project that has since been consummated in construction of the San Diego Aqueduct, which now delivers water from the Metropolitan Water District's Colorado River Aqueduct to member agencies of the San Diego County Water Authority. However, it was desirable that investigation be made toward further development of local sources of water supply. It was known that both the San Dleguito and San Diego rivers had surplus waters, and that their safe yields could be increased by further development. The termination of World War II did not eliminate critical water problems of the San Diego region. The wartime addition to population has to a large extent estab- lished Itself permanently, and is presently being augmented by newcomers at a rate limited principally by living accommodations. Furthermore, the seasons since 1944 have been deficient in precipitation and runoff. Relief is afforded in the Colorado River supply available since December 1947, but studies indicate that eventually this source should be supplemented to assure a safe water supply for population and development that the San Diego area may now reasonably expect. It is apparent, too, that in order to meet probable ultimate demands for water, the further development of local sources offers appreciable physical and economic advantages, as compared with sole dependence upon im- ported water in this respect. Authorization The investigation and this report were initiated by a letter from the City of San Diego to the State Director of Public Works on September 1}, 1944, wherein it was proposed that the State Engineer conduct a hydrographic survey of San Dleguito River, the project to be financed in amount of *20,000 by equal cash contributions of ^10,000 from City and State, under cooperative agreement. General authority to conduct such coopera- tive Investigations is included among powers granted the Department of Public Works by Article 2, Chapter 1 of the Water Code. Preliminary investigation having established the fact that cooperative study of the San Eieguito watershed, as requested by the City, was in the State's interest, the State Director of Finance on October 4, 1944, Issued a promise of allotment of |10,000 from the Einergenoy Fund (Item 221, Chapter 62, Statutes of 1943) for this purpose, contingent on its being matched by equal funds from sources other than the State. An agreement between the City of San Diego and the Department of Public Works was executed by the two parties on February 1 and February 20, 194-5, respec- tively. It provided that the Department make necessary surveys, explorations and cost estimates connected with dams and reservoirs in the San Dieguito watershed, and trans- mission lines therefrom; make estimates of present and future water utilization in the watershed; make estimates of total and additional water yield under various combinations of reservoirs in the San Dieguito watershed, with existing and possible futur"? reser- voirs of the City, and with present and possible future development on the San Dieguito watershed; perform other field and office work agreed to by the parties; and prepare a report by January 1, 1946, containing recommendations and general plans and cost esti- mates for development of water resources of the San Dieguito watershed. It was agreed that the City of San Diego would make estimates of cost of securing necessary water rights. The City agreed to provide ^10,000, and the State $10,000 from the Emergency Fund, the moneys to be deposited in the Water Resources Fund and expended by the Depart- ment of Public Works acting by and through the State Engineer. On January 9, 19*5, prior to execution of the foregoing agreement, the Council of the City of San Diego, by Resolution No. 8044^, requested that the State Director of Finance incorporate in his budget the sum of ^40,000 for the State Engineer to make studies toward further development of waters of San Diego River and Cottonwood Creek. The resolution was too late for budget action, but the request resulted in a superseding agreement between the City and Department, executed by them on May 1 and May 11, 1945, respectively. It provided that scope of surveys, studies and report, called for in the original agreement, be increased to include San Diego as well as San Dieguito River, and increased contributions of funds to ii20,000 by each party, a total of ^40,000 for the in- vestigation. The additional State funds were provided from the Emergency Fund (Item 221, Chapter 62, Statutes of 1943), as in the case of the first agreement. Early in 1947 it became apparent that funds available were insufficient for completion of an investigation and report of scale and scope contemplated under the above agreements. A supplemental agreement was therefore executed by the City on April 24, and the Department on May 1, 1947, providing for additional funds from each party in amount of J12,500, or a total of $65,000 for the investigation. Source of the State allocation was the Emergency Fund (Item 275, Section 2, Budget Act of 1945). Copies of the three foregoing agreements are contained in Appendix A, "Agree- ments Authorizing the Investigation and Report". Prior Investigations and Reports 1. " Irrigation in Calif ornie. Part II, Southern California", William Ham. Hall, 1888 . This report ^ / the first State Engineer of California covers an investiga- tion of water resources and irrigation development in Los Angeles, San Bernardino and San Diego counties, which area then .included the present Riverside and Imperial counties. It specifically discusses San Dieguito and San Diego rivers and their existing and pro- posed development. 2. Bulletin No. 100, "Irrigation Investigation in California". U. S. Depart- ment of Agriculture, Office of Experiment Stations, I9OI. Certain changes in water laws of the State are recommended in this report, the result of an investigation of irriga- tion conditions in 1900. 3. " Report of the Conservation Commission of the State of California", 1912 . This report covers investigations during 1912 hy a special board createo to study natural resources of the State and recommend legislation for their conservation. 4. B ulletin No. 2^4, "Irrigation Resources of California and Their Utiliza- tion", U. S. Department of Agriculture, Office of Experiment Stations, 1913 . Results of a comprehensive, state-wide study of irrigation development, made in 1912, are outlined in this bulletin. 5. Water-supply Paper 446, "Geology and Ground Waters of the Western Part of San Diego County, California", U. S. Geological Survey, 1919 . This report, prepared in cooperation with the State Department of Engineering, constitutes a comprehensive geo- logical study of the San Diego region. 6. Bulletin No. 4, "Water Resources of California", Division of Engineering and Irrigation, State Department of Public Works, 192^ . This report to the 192? Legis- lature, with its appendices. Bulletins No. 5, "Flow in California Streams", and No. 6, "Irrigation Requirements of California Lands", is the first of several resulting from studies known as the "California Water Resources Investigations". These studies wers initiated by legislative enactment in 1921, further investigations being authorized in 1925 and 1929, and were carried out under direction of the State Engineer. The 1923 re- port contains an inventory of waters of the State, an estimate of gross agricultural area and irrigation water requirements, and a preliminary plan for comprehensive development of water resources of the State. 7. Bulletin No. 2^, "Report to Legislature of 1931 on State Water Plan" , Divi- sion of Water Resources, State Department of Public Works, 1930 . Under the authorization mentioned in the preceding paragraph, this report summarizes water resources and require- ments throughout California, and presents the "State Water Plan" for coordinated conser- vation, development and utilization of water resources of the State. It contains estimates of runoff from mountain and foothill drainage areas of San Diego County. 8. Bulletin No. 4-3, "Value and Cost of Water for Irrigation in Coastal Plain of Southern California", Division of Water Resources, State Department of Public Works, 1933 . Value and cost' of water for irrigation of citrus fruits and avocados in San Diego County areas are discussed In this report, prepared under cooperative agreement with the College of Agriculture, University of California. 9. " Storm Types and Resultant Precipitation in the San Diego, California, Area", Dean Blake, Monthly Weather Review, Volume 61, August 1933 » This paper presents descrip- tions of the four storm types experienced in the San Diego area, including their frequency and characteristics. 10. Bulletin Ho. 48, "San Diego County Investigation", Division of Water Re- sources, State Department of Public Works, 193^ . Under authorization contained in Chapter 278, Statutes of 1933, an investigation of water resources, flood control and water re- quirements of San Diego County was conducted during 1933 and 193'1- by the Division of Water Resources, in cooperation with the City and County of San Diego. Studies made were gener- al in nature, except those pertaining to San Diego and Tia Juana rivers. As regards the former, detailed recommendations were presented for a complete plan of conservation and flood control development. For Tia Juana River detailed analyses and recommendations were limited to flood control. 11. Bulletin No. 48-A, "San Luis Rey River Investigation", Division of Water Resources, State Department of Public Works, 1936 . This report is the result of a coop- erative investigation by the United States Works Progress Administration, Division of Water Resources, County of San Diego, City of Oceanside and Carlsbad Mutual Water Company. It supplements the general data of Bulletin No. 48 pertaining to San Luis Rey River with revised estiniates of runoff and detailed studies of proposed dams and reservoirs. 12. Technical Bulletin No. 324, "Silting of Reservoirs", U. S. Department of Agriculture, July 19?6, Revised August 1939 ' Data on rates and characteristics of silt deposition in Lake Hodges and Morena Reservoir in San Diego County are included in this bulletin. 13. " Report on Program of Water Development, the City of San Diego and the San Diego Metropolitan Area", Louis C. Hill, Lester S. Ready and J. P. Buwalda, 1937 * '^^^ foregoing authors comprised a board of consulting engineers employed by the City of San Diego to determine future demands of the City and the adjacent metropolitan area, yield from local water sources and supplementary requirements, and to prepare preliminary plans and estimates for further water supply development. Their report contains data resultant from their investigation and studies. Development of local water sources, and plans for importation of Colorado River water are discussed. 14. " Report on Municipal Water Systems - Report No. 3» San Diego Region", Com- mittee on Transportation, Housing, Works and Facilities, State Council of Defense, April 1943 . This report, prepared in collaboration with the Division of Water Resources, was made in recognition of the importance of San Diego's contribution to the war effort, and of probable crippling effects of any interruption in its already critical water supply. The report analyzes municipal water supply systems of San Diego County as to adequacy, sources of additional supply, vulnerability, potential hazards in their physical works as affecting public or military establishments, and methods of protecting vulnerable fea- tures. It recommends essential additions to the physical works, and wartime protective measures. Alternate plans for importation of Colorado River water, either by pump lift from the All American Canal in Imperial Valley, or by gravity from the Metropolitan Water District's Colorado River Aqueduct, with diversion in the San Jacinto Valley, are dis- cussed, and recommendation is made for immediate steps toward such importation by the most feasible route. 15. " Utilization of the Waters of Lower San Luis Rey Valley, San Diego County, California", Division of Irrigation, Soil Conservation Service, U. S. Department of Agri- culture, April 1943- <" Under cooperative agreement with the State Division of Water Resources, the Soil Conservation Service conducted an intensive investigation and study of irrigated areas, consumptive use of water, ground-water fluctuations, precipitation and evaporation in San Luis Rey River Valley. This report presents resultant data and contains an estimate of the amount of water salvagable from consumptive use by native vegetation. Ifa. " First Annual Report", San Diego County Water Authority, 1946 . History, organization and development of the Metropolitan Water District of Southern California and the San Diego County Water Authority are presented in this report, as well as factual data regarding the Colorado River water supply and the San Diego Aqueduct. 17. " Estimated Range for Population Growth in California to I960", State Re- construction and Reemployment Commission, November 1946 . Included in this report are forecasts of population growth in San Diego County to the year I96O. 18. " The Water Supply of the Escondido Soil Conservation District, San Diego County, California", Soil Conservation Service, U. S. Department of Agriculture, Febru- ary 19^7 ' This report contains an estimate of safe yield of ground-water basins underly- ing the Escondido Soil Conservation District, including a small portion of the San Dieguito watershed. Hydrologic data and analyses pertaining to the Escondido region are included. 19. " Report on Water Supply of La Mesa, Lemon Grove and SprinR Valley Irrlga- tlon District in San Diego County", Division of Water Resources, State Department of Public Works, April 194-7 . This is a brief study of water supply and requirements of the District, with particular reference to effects of delivery of Colorado River water through the San Diego Aqueduct, to supplement the District's local supply from San Diego River. 20. " Research Project No. 6, Part I, Population Trends in San Diego, 1900 Through I960", Department of Research, San Die'go City Schools, April l6, 194-8 . This paper is a compilation and discussion of forecasts of population of the City of San Diego to the year 1960> the forecasts being those by six Independent interested agencies. Scope Under terms of the cooperative agreements authorizing the present investigation, its purpose has been to determine the best program of development of a water supply for the City of San Diego on the San Dieguito and San Diego rivers. The foregoing agreements did not authorize study of related water supply problems of other public agencies in San Diego County. During 1933 and 1934- the Division of Water Resources made a comprehensive hy- drologic investigation of San Diego County, results of which were published in 193^.* Precipitation was inventoried, and full natural flow of Pacific slope streams, as well as their safe yield under complete development, was estimated. A compilation was made of utilization of water, and existing development of surface and underground sources was described. Estimates of future water requirements were made. As regards flood flows, their characteristics, size and frequency were evaluated, and methods of flood control discussed. Primary purpose of the report was to present plans for water conservation and flood control on San Diego River, and for flood control on Tia Juana River. For San Diego River a detailed and thorough study was made, and a specific plan for construction and operation of dams, reservoirs and flood control works was recommended. A similar study of Tia Juana River resulted in the conclusion that flood control was not economi- cally justified at that time. For remaining San Diego County streams, the studies were general in nature, without recommendations of definite plans for either conservation or flood control. It is apparent that duplication of material presented in Bulletin No. 48 Is un- necessary and unjustified. In planning work to be accomplished under the present inves- tigation, its scope was therefore limited to supplemental surveys and studies, which when used in conjunction with those of Bulletin No. 48 would be sufficient for complete analy- sis of problems of water conservation and flood control of the two watersheds. In the case of San Dieguito River these included intensive study of hydrology, culture and water requirements within the basin, together with detailed engineering and economic analysis of conservation and flood control works under a recommended plan of development. In the case of San Diego River, with such a plan already presented in Bulletin No. 48, new work under this Investigation included only required re-examination of certain phases of the earlier studies to bring them up to date, and consideration of dams and reservoirs not in- cluded in the earlier investigation. *Bulletin No. 48, "San Diego County Investigation", Division of Water Resources, State Department of Public Works, 1935. Field work for the present investigation included such surveys of proposed dam and reservoir sites by aerial photography, geologic examination of dam sites, and valua- tion surveys for purchase of necessary lands, as were required. A crop survey was made of lands in San Pasqual Valley in San Dieguito Basin. In the same valley a meteorologi- cal station, five stream gaging stations, and a number of test wells to determine ground- water fluctuations, were installed, and a program of systematic observations inaugurated. Data from these continuing observations are incomplete at this time, and therefore are not reported herein. Available data on precipitation, stream flow, utilization of water, water rights and other pertinent subjects were collected from private and public agen- cies. The five San Pasqual Valley stream gaging stations, situated so as to measure surface inflow and outflow from the valley, were designed by the Division of Water Re- sources and installed largely by the City of San Diego under the Division's supervision. Eq.uipment, including still wells, gages, houses and recorders, was furnished by the United States Geological Survey, which agency has assumed operation and maintenance of the stations and will publish the records, under terms of its general cooperative agree- ment with the State of California. The two key gaging stations on the main stream, at the upper and lower ends of the valley, respectively, are wading sections with natural control, equipped as are the other stations with staff gages, still wells and housed automatic water stage recorders. A high water station on Guejito Greek is located at the State highway bridge, while an upper station, consisting of a reiuforced-concrete Par- shall flume, measures low flows. Santa Maria Creek is measured by wading, at the restored site of previous stream gaging operations, the natural control having been raised and improved. The San Pasqual Valley Meteorological Station is located on county property, and was designed and constructed by the Division, with assistance by the City. Equipment was largely furnished by the Soil Conservation Service of the United States Department of Agriculture, and is operated and maintained by the Division. The equipment is protected by a steel fenced enclosure, and consists of an 8-inch standard rain gage, 4-foot stan- dard evaporation pan, maximum and minimum thermometers, hygro-thermograph and an anemometer. Thermometers and hygro-thermograph are housed in a standard shelter. It was necessary, preliminary to engineering and economic analysis of proposed dams, reservoirs and appurtenant works, to prepare topographic maps of suitable scales from aerial survey data. Office studies also included compilation of hydrologic data, such as precipitation, flow of streams, ground-water fluctuations and storage, consump- tive use and requirement of water under present and future conditions, and flood flows. Yield and cost of water, both firm and secondary, were studied for various combinations of existing and proposed reservoirs, under several possible systems of operation. Con- sideration was given to reservoir fend channel control of floods. Chapters IV to VIII, inclusive, of this report are concerned exclusively with data and studies pertaining to San Dieguito Basin. Chapter IX contains the result of current studies of San Diego River. CHAPTER II SUMMARY, CONCLUSIONS AND RECOMMENDATIONS In this chapter there is presented a summary of data developed in greater de- tail in subsequent chapters of this report, as well as conclusions and recommendations derived therefrom. Water Requirements of City of San Diego After many decades of sustained rapid growth prior to 19^0, the City of San Diego experienced five years of greatly accelerated expansion, coincident with and occa- sioned by World War II. This increase was accompanied by water demands in excess of de- veloped safe yield, so that reserves in storage were seriously depleted. Drought years which followed the wet season of 19^3' produced little runoff, and although water demands decreased some ten per cent from their 194-5 peak average of about 50 million gallons per day, reserves continued to decline. At the end of 19^8, reservoir storage space available to the City was filled to less than 25 per cent of its 598,000 acre-foot capacity, and safe yield from this source, defined for purposes of this report as sustained supply dur- ing the record drought from 1895-96 to 1904-05, inclusive, was an estimated 30 per cent of normal expectancy, or about 9*6 million gallons per day. However, in December 194-7 the City had received its first deliveries of Colorado River water through the newly completed San Diego Aqueduct. This conduit connects with the Colorado River Aqueduct of the Metro- politan Water District of Southern California at the west portal of its San Jacinto tun- nel, and extends to San Vicente Reservoir of the city system. The San Diego County Water Authority was organized to receive and distribute Colorado River water to its member agencies, of which the City of San Diego is by far the largest. The City's entitlement, based upon 194-5 assessed valuations, amounts to about 85 per cent of capacity of the San Diego Aqueduct. The City can depend upon firm delivery of approximately 4-8.9 million gallons per day from this source, an amount in itself great- er than present demands. Total safe supply to the City, under present conditions of de- pleted storage and Including the Colorado River water, is estimated to average 58.5 million gallons per day. San Diego is thereby relieved from immediate concern with reference to the sufficiency of its water supply. If a fortuituous series of wet years occurs, the City may attain the full measure of developed yield from local sources, and a total safe supply of 80.8 million gallons per day. It cannot be stated how soon this may occur. However, it was estimated in Bulletin No. 48* that, after construction of reservoirs on San Diego River for complete conservation development, eight years would elapse, on the average, before at- tainment of full safe yield. In the present stage of partial development, and with nearly 25 per cent of storage filled, a somewhat shorter average period might be expected. Ultimate water requirements of the City of San Diego are estimated from a con- sideration of duty of water over the gross city area under assumed ultimate cultural condi- tions. In 1943 the Division of Water Resources estimated average ultimate seasonal duty * Bulletin No. 48, "San Diego County Investigation", Division of Water Resources, State Department of Public Works, 1935. over the Raymond Basin area, consisting of the City of Pasadena and vicinity, at 1.29 aore-feet per acre. The estimate was the result of intensive surveys and studies by the City of Pasadena and the Division, and is considered reasonably authoritative. Hydrologic factors indicate that an equivalent seasonal duty for the San Diego city area is approxi- mately 1.4 acre-feet per acre. Cultural differences between the two communities under ultimate development should be compensating, except as regards military and naval estab- lishments. These features are exclusive to San Diego, and their water requirements are largely independent of ordinary area-duty relationships. Accordingly, an allowance of 15.0 million gallons per day is made for ultimate armed force needs, roughly equivalent to peak World War II demands. Application of the foregoing seasonal duty of 1.4 acre-feet per acre to the approximately 61,100 acres within the present city boundaries results in an estimate of 85,500 acre-feet seasonally, or 7b. 3 million gallons per day, for ultimate civil requirements. A further working allowance of ten per cent is provided as a factor of safety, resulting in an estimate of 100 million gallons per day as total water require- ments for the City of San Diego, under conditions of ultimate development of its present incorporate'd area. Population of the City of San Diego increased from 203,000 to 563,000 during the period from 1940 to early in 1946, a rise of about 80 per cent, and was probably even higher at the war's end In the fall of 1945. Water consumption increased at an even great- er rate, from 23.6 to 50.2 million gallons per day from 1940 to 1945, a rise of more than 110 per cent. This indicated an increase in per capita consumption from II6 to I28 gal- lons per day. After study of population forecasts by several competent authorities, it is believed that the City of San Diego may reasonably expect a population of about 500,000 by I960. Assuming average per capita daily consumption of 125 gallons, water requirements of the City in I96O will be an estimated 62.5 million gallons per day, four million gallons per day more than the estimated safe yield of 58.5 million gallons daily now available, but some 18 million gallons per day less than the estimated maximum safe yield of 80. 8 million gallons daily from the existing development, once the city reservoirs are filled. That they will fill prior to I96O, or at least be augmented sufficiently that safe yield will meet I960 requirements. Is considered probable. In view of the foregoing, it might be assumed that the City need not pursue further development of its water supply until 19bO or later. Such an assumption, however, is not conservative. Further, it does not take into account certain practical considera- tions regarding San Diego's water supply. Planning for a municipal supply should be on a sound and conservative basis. Forecasts of population growth upon which estimates of fu- ture requirements are based are inherently subject to wide error, and demand for water may be greater than now anticipated. Also, it is considered probable that in their quest for water certain communities adjacent to the City will eventually be annexed to it, thus in- creasing its overall requirements. Furthermore, accretion of additional storage in local reservoirs is dependent upon vagaries of the weather, and may or may not be attained by i960. It is also dependent upon rigid adherence to a schedule of reservoir operation for safe yield, which may or may not be followed. Finally, the City of San Diego has a large investment in real property and water rights required for further water supply development in San Dieguito Basin. The investment is secured and validated by a 1947 filing on flood waters of San Dieguito River. To protect its property and water rights and maintain the filing the City must show reasonable diligence in putting the waters to beneficial use. Several sources of additional supply are available to the City, including both San Dieguito and San Diego river basins. The remaining streams of the western slope in San Diego County present some possibilities for further development. Another source of supplementary water for the City lies in importation of additional Colorado River water, through construction of the proposed second barrel of the San Diego Aqueduct, which con- struction will approximately double the aqueduct capacity. San Dieguito Basin Because of its relatively large undeveloped water resources and favorable geo- graphic position, San Dieguito River and its tributary system merit consideration in con- nection with any program for supplementing the water supply of the City of San Diego. Description San Dieguito River, known above its confluence with Santa Maria Creek as Santa Ysabel Creek, drains a basin roughly triangular in shape, lying slightly to the north of the center of San Diego County. The basin's longer axis of about 41 miles bears from northeast to southwest, and the watershed area of ^^1 square miles has a maximum width of about 15 miles. The river, rising on the slopes of Volcan Mountain at an elevation ex- ceeding 5,500 feet, flows through a series of canyons and narrow valleys for some 53 miles, and enters the Pacific Ocean a mile north of Del Mar and about 19 miles north of downtown San Diego. The basin lies between the major watersheds of San Luis Rey River on the north and San Diego River on the south. Principal tributaries are Witch Creek, Black Canyon, Temescal Creek, Roden Canyon, Guejito Creek and Santa Maria Creek, all but the first and last named of which enter from the north. Three principal dam and reservoir sites occur along the main stream. The upper- most of these is marked by the partially constructed Sutherland Dam, located about seven miles northeast of Ramona, at streambed elevation of about 1,900 feet. Drainage area at this site is 3^ square miles- and averages 3j350 feet in elevation. The sites which have been considered for Pamo Dam are situated a little more than a mile below the mouth of Temescal Creek, where streambed elevation is approximately 85O feet, and the drainage area of 111 square miles averages 2,900 feet above sea level. Hodges Dam is located about 12 miles upstream from the ocean at streambed elevation of 200 feet. Its 303 square miles of drainage area average 1,900 feet in elevation. Lake Hodges, impounded by a concrete multiple-arch dam 115 feet in height, is a conservation reservoir with present capacity of approximately 33,600 acre-feet. Principal ground-water sources occur in alluvial deposits underlying San Dieguito and San Pasqual valleys. Ground water is also obtained from decomposed crystalline rocks beneath Santa Maria and Guejito valleys. Fractured or decomposed rooks with some water- storing capacity constitute much of the surface of the highland areas, and intermittent shallow alluvium occurs along stream channels, but these sources are not exploited to any appreciable extent. San Dieguito Basin has subtropical climatic characteristics, temperate and equa- ble near the coast, but with wider range in extremes in the interior and at higher eleva- tions. Precipitation varies from an average of approximately ten inches in seasonal depth along the coast to as much as 40 inches at the crest of the mountains. Adjoining the ba- sin, the eastern slope of the mountains is characterized by a desert climate of extremely low precipitation and wide range in temperature. Natural vegetation throughout the basin is generally sparse. However, dense stands of brush and trees occur alonp water courses, and northern slopes of hills and mountains are chaparral covered to varying degrees. Conifers occur in the mountains at elevations over 4,000 feet. San Dieguito Basin is lightly populated and contains no incorporated municipali- ties, except for the small portion of the City of Escondido lying within the basin bounda- ry north of Lake Hodges. The town of Ramona in Santa Maria Valley, with population of aoout 1,400, is the largest urban development in the basin. Highland areas contain only a few small settlements and isolated ranches. San Pasqual and San Dieguito valleys are given over to farms and ranches, while the ridge of hills north of Lake Hodges contains numerous citrus groves. A resort subdivision, Del Dios, is situated at the western ex- tremity of Lake Hodges and has an estimated population of 600. North of the river and some four miles from the coast, the community center of Rancho Santa Fe is surrounded by estate type homes and small ranches. Total population of the basin is estimated at about 5,400. Agriculture is the predominant activity in San Dieguito Basin, and the only in- dustry of importance at the present time. The San Diego County Fair and horse racing are seasonal activities In San Dieguito Valley, and scenic and mountainous portions of the area attract a moderate number of campers and tourists. From United States census data it is estimated that approximately 5,000 acres were irrigated within the watershed in 1939, with about 680 irrigated farms and |1, 000, 000 invested in irrigation enterprises. Crop surveys conducted by the Division of Water Resources in 1948 show that approximately 7,300 acres are presently irrigated within the watershed, of which about 3,000 acres are served by water imported from the San Luis Rey River. Principal irrigated crops are citrus, al- falfa and field crops. There is also a considerable amount of stock raising, dairying and dry farming of grain, hay, grapes and deciduous fruits. The area is adequately served by highway and rail transportation facilities. U. S. Highway 101 and the Atchison, Topeka and Santa Fe Railway cross San Dieguito River at its mouth. Some 15 miles inland, U. S. Route 395 crosses the watershed from north to south. Several secondary state and local highways provide lateral connections and serve the remainder of the basin. Water Supply The water supply of San Dieguito Basin is largely derived from precipitation which falls within the watershed. There is, however, an increasing import of water by the Escondido Mutual Water Company, now averaging about 2,000 acre-feet per season, from the San Luis Rey River to the north. Little, if any, of this water reaches San Dieguito River as accretion to runoff. Although diversion facilities from the San Diego Aqueduct are available, and some Colorado River water has been stored in Lake Hodges, none of this water has as yet been utilized within San Dieguito Basin. Based upon entitlements derived from 19*6 assessed valuations, it is estimated that the Santa Fe Irrigation District will ulti- mately Import about 400 acre-feet of Colorado River water to San Dieguito Basin each season. Precipitation Precipitation in San Dieguito Basin occurs principally as rainfall, although minor snowfalls are common in the high mountains. On the average, more than 70 per cent 10 of seasonal rainfall occurs in the four months from December to March, inclusive, and summers are characteristically long and dry. Precipitation increases rather uniformly with rise in elevation and distance from the coast. There is wide variation in amount of rainfall from season to season, with extremes ranging from less than 50 to more than 200 per cent of the long-time average. Because of its vital importance in this arid region, rainfall has been a sub- ject of local interest since early days, and private and public agencies have maintained numerous precipitation records, the oldest of which is that at San Diego, dating from 1850. Thirty-one precipitation stations were chosen for this study as being representa- tive of San Dieguito Basin, 14 of which were within the watershed and the remainder adja- cent to or near It. By examining the San Diego record it was determined that the 50-year period, 1891-92 to 1940-41, inclusive, was one of approximately normal precipitation, as well as one embracing the majority of rainfall records pertaining to San Dieguito Basin. Accord- ingly, it was chosen as a base period for this study, and short-term records were extended by standard methods to cover it. A map showing lines of equal precipitation was then drawn, and by planimetering the area between these isohyets in each drainage area, mean seasonal precipitation was determined for the 50-year period. For the 5O3 square miles of drainage area above Hodges Dam, seasonal precipitation for the base period averaged 20.89 inches. Similarly, for the 111 square miles above Pamo dam site precipitation averaged 26.26 inches seasonally, while for the 54 square miles above Sutherland Dam it was 28. 06 Inches. Average seasonal precipitation for the entire 3*7 square miles of San Dieguito watershed was 19. 63 inches. The season utilized in this report in connection with pre- cipitation is the so-called "precipitation season", from July to June, inclusive. Runoff • • Stream flow in San Dieguito Basin is flashy, ranging from negligible discharge in most summer seasons to occasional torrential floods of destructively high peak flow but relatively short duration, occurring during protracted winter storms. Such floods produce the greater part of total runoff, and are experienced only at intervals of five to six years, on the average. Study of runoff characteristics discloses a rather well defined periodic or "cyclic" behavior. Within an apparent 25-year runoff period, shorter periods averaging about five years in length have occurred with marked regularity, the only nota- ble non-conformity having been during the ten-year drought from 1896 to 1905, which was unbroken by an above normal season. Runoff is subject to even wider seasonal variation than precipitation, and dur- ing the 50-year normal period I89I-92 to 1940-41, inclusive, had extremes of 1.1 and 762 per cent, respectively, of the long-time seasonal mean. In only 12 seasons was average run- off exceeded, yet these accounted for approximately 74 per cent of total runoff during the 50 years. On the other hand, for seven consecutive seasons during the I896-I905 drought, average runoff was only about 11 per cent of the 50-year average. Within the season all but a minor portion of runoff occurs during winter and spring, its distribution generally following that of precipitation. Peak runoff month is usually February or March and rarely occurs after March. Stream flow falls off rapidly after final spring rains, and while there is small perennial flow in the mountains, and in valleys where shallow alluvium causes rising water, this contribution to seasonal runoff is small. 11 Recorded stream flow measurements in the basin date from 1906, but it was not until 1912 that a comprehensive stream gaging program was inaugurated by the cooperative endeavors of the Volcan Land and Water Company and the United States Geological Survey. Of particular interest to the present investigation are stream flow records at the three principal dam sites, Sutherland, Pamo and Hodges. The record for Sutherland dam site is continuous from 1912 to date. For Pamo dam site the record also starts in 1912 but is broken by a 20-year period with no record, from February 192> to October 1943. for which period runoff was estimated from its relation with that at Sutherland. Stream flow mea- surements have been continuous at the site of Hodges Dam since I916. Records presented in this report differ from those of Bulletin No. 48 in that they refer to actual runoff at the stations, rather than full natural runoff. Full natural runoff is that which would occur under natural conditions, unimpaired by upstream diversion, use and storage development and without Import of water into the basin. In many hydrologic studies, full natural flow is evaluated in order to facilitate comparison between runoff of different streams, or different points on the same stream. In the present investigation, however, it was desired to determine additional yield obtainable by construction of conservation works on San Dieguito River. An evaluation of actual runoff at the several sites was es- sential for this purpose. In order to evaluate long-time mean runoff, estimates were made of runoff at each of the three dam sites, extending back through the seasons of 1887-88. In general, these estimates for years prior to the beginning of record were made by comparison with nearby streams, utilizing relationships established during periods of mutual record. Although the relationship between rainfall and runoff in San Dieguito Basin is erratic seasonally, over a period of many years the two should conform closely. For this reason, the 50-year normal precipitation period 189I-92 to 1940-41, inclusive, was assumed also to be one of normal runoff. Mean seasonal runoff at Sutherland, Pamo and Hodges dam sites during the 50-year period is estimated to have been 15,600 acre-feet, 25,000 acre- feet and 40,700 acre-feet, respectively. These average seasonal amounts are essentially the same as would have occurred under present conditions of culture and development. The season referred to in connection with runoff is the so-called "irrigation season", from October to September, inclusive. This season is generally utilized throughout this report, except in connection with precipitation. Water Utilization Waters of San Dieguito Basin are utilized for irrigation and domestic purposes within the watershed boundaries, and by export for irrigation, domestic and municipal pur- poses in coastal areas both to the north and south of San Dieguito River. Most of the use is by those organized water service agencies which obtain their supply from Lake Hodges and then export the larger portion of it. Total average seasonal use under present condi- tions is estimated at 13,550 acre-feet. Under expected conditions of ultimate development it is estimated that about 34,000 acre-feet will be utilized. Under present conditions, only about four per cent of all precipitation falling on the San Dieguito watershed is developed for higher forms of use, such as domestic, mu- nicipal or irrigation. The remaining 96 per cent, an average of approximately 350,000 acre- feet seasonally, is lost to economic utilization, excepting for that undetermined portion consumed in production of natural grasses utilized for grazing. Even under proposed com- plete conservation development of the basin, only a little more than nine per cent of 12 precipitation will actually be put to the higher forms of beneficial use. Principal water lost is by consumptive use of native vegetation, estimated to average about 320,000 acre- feet seasonally, which has been considered as including evaporation from soil and natural water surfaces. This loss is subject to only minor reduction by feasible conservation measures. A considerable amount of water, averaging an estimated 25.000 acre-feet per season, now flows into the Pacific 0cea.n from San Dieguito River. It is from salvage of this water that further conservation may be principally achieved. Evaporation losses from reservoir surfaces, at present averaging about 5,000 acre-feet seasonally, will increase with proposed additional conservation development. Water Service Agencies Principal water service agencies utilizing water from San Dieguito Basin consist of three irrigation districts, one private corporation and the City of San Diego. By vir- tue of contractual commitments by the City to supply the San Dieguito and Santa Fe irriga- tion districts and Del Mar Water, Light end Power Company with water, these agencies are commonly known as the "Committees". San Dieguito Irrigation District serves domestic and irrigation water to a gross area of about 4,000 acres along the coast north of San Dieguito River, between Batiquitos and San Elijo lagoons. Its contract with the City of San Diego assures the District of a maximum seasonal supply of 3,200 acre-feet of water from Lake Hodges. As a result of its recently acquired membership in the San Diego County Water Authority, the District is en- titled to an estimated 500 acre-feet per season of Colorado River water, based upon 194-6 assessed valuations. No deliveries were received from this source up to the end of 194-8, The District's entitlement will increase to an estimated 1,000 acre-feet per season when the second barrel of the Colorado River Aqueduct is constructed. During the 1946-4? sea- son, 3,384 acre-feet of water were utilized by the San Dieguito Irrigation District, the excess over the Lake Hodges entitlement being purchased from Del Mar Water, Light and Pow- er Company. It is believed that this demand is in excess of average under present condi- tions, and largely attributable to drought conditions. Present water utilization by the District is estimated to average about 2,8lO acre-feet per season, the mean for the five seasons up to and including 1946-47. Under conditions of ultimate development of San Die- guito Irrigation District, it is estimated that water requirements will average about 4,800 acre-feet per season. Santa Fe Irrigation District provides irrigation and domestic water to a gross area of about 10,000 acres, most of which lies on the ridge between San Elijo Creek and San Dieguito River. By virtue of its contract with the City of San Diego the District is assured a maximum seasonal supply of 4,300 acre-feet of water from Lake Hodges. Like the neighboring San Dieguito Irrigation District, the Santa Fe Irrigation District has recently acquired membership in the San Diego County Water Authority. On the basis of 1946 assessed valuations, the resultant entitlement to Colorado River water is estimated at about 400 acre-feet per season. No deliveries were received from this source up to the end of 1948. The District's entitlement will increase to an estimated 7OO acre-feet per season when the second barrel of the Colorado River Aqueduct is constructed. It is estimated that present water utilization by Santa Fe Irrigation District averages about 3»280 acre-feet per sea- son, the mean from 1942-43 to 1946-47, inclusive, and that under conditions of ultimate de- velopment 6,200 acre-feet per season will be required. Ramona Irrigation District serves domestic water, and a small amount of irriga- tion water, to a gross area of 66O acres at the townsite of Ramone in Santa Maria Valley. 13 Its water supply is obtained from a battery of shallow pumping wells in sands of the chan- nel of Santa Maria Creek, north of the town. Present seasonal water utilizatlgn is esti- mated to average about 240 acre-feet, and is limited by safe yield of the ground-water basin. Lack of financial capacity has so far prevented development of further water sup- ply for the District. However, if the District can add to its local development, or se- cure additional water from other sources, its requirements under ultimate conditions may reach an estimated 700 acre-feet per season. The Del Mar Water, Light and Power Company, a private corporation, supplies wa- ter for domestic and municipal uses in the unincorporated coastal community of Del Mar, immediately south of San Dieguito River. Its contract with the City of San Diego assures it of a maximum seasonal supply of 724 acre-feet of water from Lake Hodges. Present water utilization is estimated to average about 250 acre-feet per season, the mean for the per- iod from 1942-4-3 to 194b-47, inclusive. Under conditions of ultimate development it Is believed that about 1,100 acre-feet of water will be required for the gross service area of approximately 1,520 acres then served by the Company. As early as 1920 the City of San Diego contracted to obtain water from Lake Hodges in an amount up to 3.0 million gallons per day, to be used in its La Jolla service area. In 1925 the City effected a lease-sale agreement with the San Dieguito Water Com- pany, then owner of Lake Hodges and related water rights, reservoir sites and regulating and distribution works, known as the "San Dieguito System", under which the City leased the system for a 30-year period, with option to buy. The agreement provided that the City assume heretofore cited obligations of the San Dieguito Water Company to the several Com- mittees. Ownership of the system was acquired by the City in 1939, through payment of the remainder due under the 1925 contract. Delivery of Lake Hodges water to La Jolla is lim- ited by capacity of existing transmission lines, and averages about 3,070 acre-feet per season at this time. Future use of water from San Dieguito Basin by the City of San Diego will be determined by the amount of additional yield developed within the basin. Under the complete conservation development recommended in this report, It is estimated that the City will realize approximately 19,000 acre-feet of water from San Dieguito Basin season- ally, the remainder after ultimate requirements of foregoing water service agencies and other users of water from the basin have been satisfied. Other Water Users In addition to the organized water service agencies described in the preceding section, waters of San Dieguito Basin are utilized by several small mutual water companies or associations, three Indian reservations and a number of individuals. In the aggregate this use is small in comparison with that by the water service agencies, and no appreciable change in this respect is expected in the future. Land irrigated by San Dieguito Basin water, other than that under water service agencies, is estimated at about 3,000 acres at the present time. Assuming an irrigation duty of 1.3 acre-feet per acre, current seasonal water utilization by such other water users averages approximately 3,900 acre-feet. Appreciable increase in use of San Dieguito Basin water by others than water service agencies is not anticipated, and such use should average about the same under conditions of ultimate development as at the present time, or approximately 3,900 acre-feet per season. 14 Export Export of water from San Dieeuito Basin is exclusively by diversion from Lake Hodges, and such exported water is utilized by the City of San Diego and the several San Dieguito Committees for irrigation, domestic and municipal purposes in areas along the coast both to the north and south of San Dieguito River. Portions of the water delivered to both Santa Fe Irrigation District and Del Mar Water, Light and Power Company are util- ized within San Dieguito Basin and do not comprise export. At the present time, export is estimated to average about 7,500 acre-feet seasonally. It is estimated that under con- ditions of ultimate development, export from San Dieguito Basin will average about 26,000 acre-feet seasonally. Existing Conservation Works Hodges dam and reservoir and related diversion, regulation and transmission fa- cilities, all of which are presently owned and operated by the City of San Diego, comprise the only important existing water supply development in San Dieguito Basin. Construction of Sutherland Dam on Santa Ysabel Creek, §.bout 6-g miles northeast of Ramona, was started by the City in 1927, but this conservation project was abandoned before completion. Hodges Dam, located on San Dieguito River about 12 miles upstream from the ocean, was completed in 1919. It is a concrete multiple-arch structure, with an overflow spillway. Capacity of the reservoir was 37,699 acre-feet when constructed, but has been reduced to approximately 33,600 acre-feet by silting. It is estimated that safe seasonal yield of the reservoir during the critical drought period from l895-9b to 1904-05, inclu- sive, would have been 6,700 acre-feet. Water is released from outlets in Hodges Dam into Hodges Conduit, consisting for the most part of open concrete-lined channel, which leads 4.b5 miles to San Dieguito Res- ervoir. San Dieguito Dam is located on a minor tributary of Escondido Creek. It is like- wise of concrete multiple-arch construction, with a siphon spillway. San Dieguito Reser- voir, with storage capacity of about 1,100 acre-feet, is utilized only for regulatory pur- poses, and water is drawn from it for delivery to the City of San Diego, the San Dieguito and Santa Fe irrigation districts and the Del Mar Water, Light and Power Company. Complete Conservation Development The objective of any plan for complete conservation development in San Dieguito Basin should be to conserve as large a percentage as possible of runoff now wasting into the ocean, as well as to effect any practicable salvage of water now wasted through con- sumptive use by natural vegetation. The three principal sites for surface reservoirs, des- ignated as Hodges, Pamo and Sutherland, have been heretofore described. The only conse- quential underground reservoirs are those underlying San Dieguito and San Pasqual valleys. Yield from Surface Reservoirs In the San Diego region water is so vital a commodity that relative yield of sev- eral proposed conservation works is of primary importance in ctiinparing their respective merits. The term "safe yield", as used in this report, refers to the amount of water which could have been supplied seasonally from a given source, without deficiency, throughout the critical period of dry years from 1895-96 to 1904-05, inclusive. However, in drawing com- parisons between proposed reservoirs in San Dieguito Basin it was desirable to utilize the best runoff information available. Reliable streamflow records are limited to the period subsequent to 1912, during which period an extended drought occurred during the 20 years 15 from 1916-17 to 1935-36, inclusive. This drought was preceded by two wet seasons, one of which was the extreme flood season of 1915-16' The occurrence of these wet seasons as- sures that proposed reservoirs would have been filled at the onset of the dry period, and imposes a definite objective on the yield studies, that is, the complete conservation of 1915-16 runoff. Yield studies, therefore, have been made to cover the period subsequent to 1914. Yield is fixed by the critical period I916-17 to 1935-36, inclusive, and is hereinafter referred to as the "1917-36 firm yield". The ten-year drought from 1895-96 to 1904-05, inclusive, was more severe than the critical period utilized for yield studies in this report. Studies based upon esti- mated runoff indicate that safe yield from proposed reservoirs during the 1896-I905 drought would have varied from 59 per cent of 1917-56 firm yield in the case of the exist- ing Lake Hodges, to 9^ per cent for an enlarged Lake Hodges of size to assure complete basin development. As regards surface reservoirs, principal factors entering into determination of yield are runoff, evaporation and draft. Runoff in San Dieguito Basin has been discussed in a prior section of this summary. In estimating evaporation losses, use was made of records of evaporation at Hodges, Morena, Barrett, Henshaw and Cuyamaca reservoirs. Aver- age gross seasonal depth of evaporation from Lake Hodges, based upon 25 years of record at that site, is 57'28 inches. For Pamo and Sutherland reservoirs, seasonal evaporation was estimated from observed variation of evaporation with elevation and distance from the coast, and its monthly distribution by comparison with records at existing reservoirs in the vicinity. Estimated average gross depth of seasonal evaporation at Pamo and Suther- land reservoirs is 64,0 and 67»0 inches, respectively. Draft upon reservoirs is governed by demand, but may be affected by character- istics of transmission and distribution works. Estimates for this report take into con- sideration assumed present use by the San Dieguito Committees, with distribution in ac- cordance with actual weighted average monthly use during recent years. The excess of yield above use by the Committees was assumed to be delivered to the City of San Diego at rates proportioned on the basis of its average monthly consumption during recent years. Utilizing the foregoing data on runoff, evaporation and draft, studies were made to determine yield of reservoirs to the City of San Diego throughout the period from 1914- 15 through 1944-45, under various assumptions as to capacities, combinations of reservoirs and methods of operation. Significant conclusions derived from the yield studies covering the period from 1914-15 to 1944-45, inclusive, are summarized below: a. The existing Lake Hodges had a 1917-36 firm seasonal yield of 11,400 acre-feet. b. Complete conservation of surface runoff above Hodges Dam would have required approximately 340,000 acre-feet of storage capacity. Resultant 1917-56 firm seasonal yield would have been about 30,000 acre-feet. c. Under various combinations of storage capacity, divided between Hodges, Pamo and Sutherland reservoirs but involving the same aggregate capacity, 1917-36 firm yield would have been approximately equal, provided Lake Hodges had sufficient capacity to prevent spill. d. Under the several plans for complete basin development studied, minimum storage capacity of Lake Hodges required to fully regulate runoff below Pamo would have been 174,400 acre-feet. 16 I Conservation reservoirs should be available far enough in advance of anticipated water demands to permit, under normal expectancy, the catchment of runoff sufficient to develop required yield. Length of this period is related to size of the concerned reser- voir as compared with average seasonal runoff. In the case of a large conservation res- ervoir at Lake Hodges, conservative analysis indicates that construction should precede demands by a period of about ten years. Even under adverse runoff conditions, sufficient yield should be attained in this time to meet initial requirements of the City of San Diego for supplementary water, with reasonable expectancy that increasing storage and yield would thenceforth keep pace with increasing demands. Sutherland Reservoir The City of San Diego commenced construction of a dam at the Sutherland site in 1927. After a considerable amount of foundation excavation had been accomplished, condi- tions were found to be unsatisfactory for the proposed concrete multiple-arch dam, and construction of a similar structure was started at a second location about 1,000 feet up- stream. After seven buttresses in this structure had been pai^tly constructed and a por- tion of the spillway excavation accomplished, the project was abandoned for reported fi- nancial and policy reasons. Assuming that the existing work has been done in accordance with the indicated contract plans and specifications, its completion is structurally fea- sible. The dam upon which construction was halted was to have had a crest length of ap- proximately 1,025 feet, and height to crest of spillway gates above streambed of I58 feet, at which elevation the reservoir storage capacity would have been 36,724 acre-feet. The spillway, consisting of an open cut in the right abutment, was to have been controlled by three drum gates. The site was core drilled by the City of San Diego in 1927, and more complete information relative to foundations resulted from actual construction operations. Foundation material consists of hard gneiss, with solid rock near the surface at streambed. For purposes of this report, a concrete pipe transmission line, 13»5 miles in length in- cluding one-half mile of tunnel. Is proposed to divert water by gravity from Sutherland Reservoir into the San Vicente Creek drainage, where it can be picked up by existing fa- cilities of the City of San Diego. Based upon April 1947 prices, capital cost for complet- ing the existing dam and reservoir and constructing the conduit is estimated at about i5, 677, 000, with annual costs of |l63,500. Pamo Reservoir Three possible dam sites have been considered in connection with Pamo Reservoir, but the one upon which planning studies of this report are based is the uppermost, at the head of a canyon reach of Santa Ysabel Creek, a little more than a mile downstream from Temescal Creek. The only available exploration data on foundation conditions pertain to a site 1,700 feet downstream from the one chose for planning studies. However, geological reconnaissance Indicates that the chosen site is the more favorable for reservoirs of re- quired capacities, and that dam structures there should be of earth-fill type. Detailed foundation explorations would be required before a final decision as to utilization of this dam site is made. Studies were made for three sizes of rolled earth-fill dam, with reservoir stor- age capacities of 90,000, 135,000 and 163,400 acre-feet, respectively. Lengths of dam at crests are 1,800 feet, 2,060 feet and 2,230 feet for the respective sizes, with heights to spillway lips above streambed of I8I feet, 208 feet and 224 feet. A reservoir of the larg- est size would be required at Pamo to retain combined runoff of the 1914-15 and I915-I6 17 seasons, less draft and evaporation. Embankment sections have a JO-foot crown width, and three to one slopes both upstream and downstream. Because of adverse topographic and geologic conditions on the abutments, spillways present a difficult problem, and one ex- pensive of solution. In order to permit comparison between yield from Sutherland, Pamo and Hodges reservoirs, costs of delivering the water to approximately equivalent points on the ex- isting system of the City of San Diego are added to reservoir storage costs in each in- stance. Plans for Pamo Reservoir route the water by gravity for I9.6 miles through a concrete pipe line to a point two miles south and one-half mile east of Hodges Dam, the proposed site of a filtration plant. From there it is conveyed by 16.7 miles of similar gravity conduit to Chesterton Tank near the south edge of Linda Vista Mesa, two miles north of San Diego River, where it is assumed that connection can be made to the existing city system. Estimated 1947 capital costs of the three sizes of development studied, includ- ing costs of dams, reservoirs and conduits, are approximately |9, 166,000, $11,972,000 and $13,525,000, respectively. Annual costs are estimated at |390,300, $507,500 and $572,300 for the respective projects. Lake Hodges The site considered for a larger Hodges Dam is immediately downstream from the present structure, the proposed new axis being 100 feet downstream at the right abutment and 155 feet at the left abutment. Core drillings were -aade in connection with construc- tion of the present dam, and the site has since been subjected to examination by competent geologists. The concensus is to the effect that dams of the type considered in present studies would be satisfactorily supported, but that their design should include allowance for seismic forces. Studies were made of five sizes of dam at the Hodges site, corresponding to a range of reservoir capacities from 104,500 to 340,700 acre-feet. The largest reservoir would be required for complete basin development by Lake Hodges alone, and would require a dam 1,050 feet in length at spillway crest, and 200 feet in height to spillway crest above streambed. The type of dam considered for estimating purposes is a concrete gravity structure with vertical upstream face, and slope of 0.8 horizontal to 1.0 vertical on the downstream face. Width of dam crest is 15 feet. An overflow spillway 400 feet in width is contemplated, to be located at the center of the dam. Enlargement of Lake Hodges would necessitate acquisition of additional lands, largely in San Pasqual Valley, and estimates also include provision for necessary relocation of roads. Yield to the City of San Diego from Lake Hodges is assumed to be pumped to a point two miles south and one-half mile east of Hodges Dam, the filtration plant site/mentioned under the discussion of Pamo Reservoir. From there it is conveyed by gravity to Chesterton Tank, near the south edge of Linda Vista Mesa, two miles north of San Diego River, where it is assumed that connection could be made to the existing city system. The amount of water to be so handled is assumed equal to yield developed at Lake Hodges, minus the amount which the City of San Diego is committed by contract to deliver to downstream users. The booster portion of the conduit consists of 1.0 miles of welded steel pipe, and 1.9 miles of concrete-cylinder pipe. Re- mainder of the line is I6.7 miles in length, and consists of reinforced-concrete-cylinder pipe. 18 Estimated 1947 capital cost of a Lake Hodges of 340,700 acre-foot storage capac- ity, including dam, reservoir, pumping plant and conduit, is about $12,755jOOO, with an- nual charges of ^656,000, including costs of pumping. Indicative of costs of a smaller development is the estimate for a 224,800 acre-foot reservoir, for which 1947 capital cost is approximately $10,919,000, and annual charges $5^4,400. Comparison of Surface Reservoirs In the San Diego region water is so valuable that a system of conservation works resulting in lowest unit cost of yield might not be the most desirable, unless it also fitted into a plan productive of the maximum yield practicable of attainment. It follows that construction of further conservation works in San Dieguito Basin should preferably be under a plan contemplating eventual complete development of water resources of the ba- sin. For purposes of this report, complete conservation development of surface runoff is arbitrarily defined as provision of a sufficient storage capacity to retain without waste to the ocean all runoff of the season of 1914-1^, and of the following record flood season of 1915-16. Comparisons of proposed reservoirs are made on the basis of amount and unit cost of additional yield derived therefrom, above that from the existing Lake Hodges develop- ment. The approximately 30 yield-cost studies of individual reservoirs and combinations of reservoirs considered, involve various combinations of storage capacity and methods of operation. Results of the most significant of these studies are summarized in Table 1 (page 20) . Neither of the first two proposals listed results in complete conservation development of San Dieguito Basin, and for this reason they are not considered suitable in themselves for a final plan. If complete basin development is achieved exclusively by enlargement of Lake Hodges, additional seasonal 1917-3t> firm yield above that of the existing development is estimated at 18,000 acre-feet, at unit cost of about $35*30 per acre-foot. With Sutherland Reservoir built to designed capacity, and Lake Hodges en- larged to accomplish complete conservation development of the basin, estimated addition- al 1917-36 firm yield of 17,800 acre-feet per season costs about $40.00 per acre-foot. Complete development by construction of reservoirs at the Pamo and Hodges sites results in estimated additional 1917-36 firm seasonal yield of l8,800 acre-feet, but unit cost is considerably greater than under previously discussed plans, amounting to about $48.50 per ecre-foot. Likewise, if complete development is achieved through reservoirs at all three of the sites, an estimated l8,800 acre-feet of additional I917-36 firm seasonal yield is obtained, but at unit cost of )50.40 per acre-foot. The foregoing comparisons show that Pamo Reservoir should be eliminated from further consideration at this time, because of high unit cost of additional yield under any plan for complete basin development which includes that reservoir. However, a reser- voir at the Pamo site may eventually be justified for terminal storage of an imported supply. Two general plans are left for further consideration, the first consisting of enlargement of Lake Hodges alone, to a capacity of 340,700 acre-feet, and the second in- volving completion of Sutherland Reservoir to designed capacity together with enlargement of Lake Hodges to. 301,700 acre-foot capacity. Estimated additional I917-36 firm seasonal yield in either case will be approximately 18,000 acre-feet. 19 TABLE 1 COMPARISON OF RESERVOIRS IN SAN DIEGUITO BASIN (Based upon Prices Prevailing in April 19*7) Reservoir or Combination of Reservoirs Storage Capacity in Acre-Feet Estimated Additional 1917-36 Firm Yield above that of Existing Development in Acre-Feet per Year Estimated Costs Capital Annual Additional 1917-36 Firm Yield per Acre-Foot per Year Sutherland 36,700 5,000 i 3,677,000 $163,500 $32.70 Pamo 163,400 14,500 13,525,000 572,300 39.50 Hodges 340,700 18,000 12,735,000 636,000 35.30 Sutherland Hodges 36,700 301,700 Total 338,400 17,800 $14,996,000 $712,600 $40.00 Pamo Hodges 163,400 174,400 Total 537,800 18,800 $21,618,000 $911,600 $48.50 Sutherland Pamo Hodges 36,700 127,800 174,400 Total 338,900 18,800 $22,156,000 $947,400 $50.40 Sutherland Hodges 36,700 310,000 Total 346,700 17,800 15,068,000 4,169,000 715,800 173,800 40.20 9.80 Savings from ten-year delay in enlargement of Lake Hodges* Adjusted co. 3tS $10,898,000 $542,000 $30.40 Note: * - As compared with costs of complete conservation development by initial enlargement of Lake Hodges to 340,700 acre-foot capacity. As has been stated hereinbefore, it is probable that presently developed vrater sources of the City of San Diego will provide a sufficient firm supply to meet city re- quirements up to the year I960. Only slightly less likely is attainment of maximum safe yield from the present development. Based on the necessity for securing additional water, the need for full conservation development of San Dieguito Basin is therefore not immed- iate. However, the City has a large Investment in reservoir sites in the basin. Further- more, it has recently filed to appropriate all excess waters of San Dieguito River. Un- less reasonable diligence is shown as regards placing these waters to beneficial use, the City's interests may be jeopardized. It follows that the plan to be adopted should permit accomplishment of full conservation development by stages, with initial steps to be taken as soon as possible. Adoption of a plan involving initial completion of Sutherland Reser- voir, and subsequent enlargement of Lake Hodges would meet the foregoing requirements. 20 Allowance should be made for silting at Lake Hodges. This may be accomplished with a reservoir of 310,000 acre-foot capacity, increasing estimated unit cost of addi- tional 1917-36 firm yield under the foregoing staged Sutherland-Hodges development by about $0.20 to $40.20 per acre-foot. Unit cost of this yield is greater than that resulting from initial construction of Lake Hodges alone but, by rational considerations as to financing the staged construction, it is considerably reduced. Since the City may conservatively expect sufficient safe yield from its present development to meet I96O re- quirements, it is probable that enlargement of Lake Hodges under a staged program for complete development would follow completion of Sutherland Reservoir by at least ten years. If, in the meantime, construction of the second harrel of the San Diego Aqueduct is undertaken, the period of delay may be much greater. If the period be conservatively taken as ten years, accrued savings in annual costs, over those for initial enlargement of Lake Hodges to the size required for complete basin development, are approximately }4, 169, 000. By crediting- these to costs of the staged development, unit cost of addition- al 1917-36 firm seasonal yield is about $30.40 per acre-foot. A rise in cost of power for pumping would further increase the indicated mone- tary advantage in complete conservation development by staged construction of Sutherland and Hodges reservoirs, rather than by initial enlargement of Lake Hodges. It may be not- ed that energy costs for required pumping have risen an average of approximately 40 per cent since the estimates for this report were made. yield from Underground Reservoirs Two possible methods of utilizing ground-water basins underlying San Dieguito and San Pasqual valleys were studied. The first consists of their use to supplement sur- face storage in the salvage of flood waters now wasting to the ocean. The second method involves lowering the ground water below the root zone of native vegetation, thereby re- ducing losses to consumptive use. From the standpoint of the City of San Diego, use of the undergroond reservoir in San Dieguito Valley is not believed to be sufficiently attractive to warrant further consideration. An enlarged Lake Hodges with capacity required for complete conservation development would rarely dplll, and draft from the ground waters of San Dieguito Valley would necessarily be replenished almost exclusively by minor local runoff. Yield of the underground basin would be greatly reduced. Furthermore, it is probable that appreciable lowering of the water table, especially near the coast, will result in contamination due to sea water infiltration. However, some further development of San Dieguito Valley ground water by overlying landowners may be practicable. It has been estimated that utilizable storage capacity of the gravels beneath San Pasqual Valley is about 13,000 acre-feet. However, if a surface reservoir with capac- ity required for complete conservation development is constructed at Lake Hodges, over half of the San Pasqual Valley ground-water basin will be drowned wi^re than 50 per cent of the time. It is apparent that surface and underground storage developments are largely incompatible. Despite this, a total amount of approximately 13,000 acre-feet is available from San Pasqual Valley ground vraters, as an emergency supply during drought periods. Studies of consumptive use show that, a moderate amount of water may be salvaged from San Pasqual Valley by a program of pumping designed to maintain the water table at levels below the root zone of native vegetation. Based upon field surveys of irrigated 21 crops and native vegetation, and upon estimated unit values of consumptive use, it is in- dicated that an average of approximately 8,800 acre-feet of water is consumed seasonally in San Pasqual Valley. By lowering the ground v.-ater eight feet below its normal level, seasonal use would be reduced to 4,0^0 acre-feet, with no change in consumptive use of presently irrigated agricultural crops. It is probable that in actual practice, however, the salvage from natural losses in San Pasqual Valley would be only about 50 per cent ef- ficient. If the City of San Diego, in securing water rights required for construction of a larger Lake Hodges, acLjUires the entire San Pasqual valley floor, it can probably con- serve an estimated 2,000 acre-feet per season by reducing consumptive use of native vege- tation, and at the same time allow full irrigation of presently irrigated lands in the upper end of the valley. Flood Control Works Damages from floods in San Dieguito Basin are largely confined to San Pasqual and San Dieguito valleys, in both of which overflow areas are principally agricultural in nature. Out of a total of about 2,100 acres in San Pasqual Valley, 485 are irrigated, and 1,250 are given over to native salt grass pasture. In the approximately 2,800 acres comprising the floor of San Dieguito Valley, culture of irrigated crops is confined to about 1,000 acres, largely in the upper end of the valley. At the lower end of this val- ley, however, in a filled area that was once tidal marsh, the Del Mar Turf Club and San Diego County Fair grounds are subject to inundation from a large flood, while highway and railway crossings of the river would be damaged. A few beach homes in the vicinity might also be damaged or destroyed. Both San Pasqual and San Dieguito valleys are narrow in relation to length of river channel. Stream channels are characterized by low banks, with waterways generally choked by brush, so that even moderate floods overflow portions of the transversely level valley floors, and major floods menace the entire areas. Preliminary study indicated that protection of these valleys by levees or chan- nel improvements is not economically feasible at this time. Any flood control reservation of storage space in reservoirs under consideration in this investigation would reduce their catchment for conservation, and could only be justified if protection were afforded a highly developed area. Such is not the case at this time. Therefore, further study of flood control in San Dieguito Basin was confined to evaluation of control derived from reservoirs under consideration, incidental to their operation for conservation. No attempt was made to determine feasibility of providing reservoir storage space exclusively for flood control purposes, supplementary to requirements for conservation. Probable size and frequency of flood flows at Sutherland, Pamo and Hodges dam sites were determined by standard methods, based upon recorded floods since I906, the greatest of which occurred on January 27, 1916. Mean flood hydrographs were computed for each of the three sites, based upon available information in connection with floods of record. A reservoir at the Sutherland site, resulting from completion of the dam as originally planned, could not be depended upon for appreciable reduction in flood damages in San Pasqual Valley, nor in areas downstream therefrom. Although the watershed above Sutherland Dam contributes about one-half of the flood waters reaching San Pasqual Valley, capacity of the reservoir would be small as compared with runoff during flood seasons. With the reservoir operated for conservation, it might be full at time of peak flows, and with drum gates there could be no storage above the conservation pool level. Possible 22 faulty gate operation might actually Increase downstream peak flows. Furthermore, under the recommended plan for complete conservation development of San Dieguito Basin, the large reservoir proposed at the Hodges site would inundate nearly 60 per cent of the floor of San Pasqual Valley, and benefits from flood control at Sutherland would be confined to the remaining area. The enlarged Lake Hodges in itself would provide a large measure of flood protection to San Dieguito Valley, and render insignificant any effects attributable to Sutherland Reservoir. A relatively small amount of flood control storage reservation in Pamo Reservoir would materially reduce crest flood flows in San Pasqual Valley. Even without such reser- vation, a conservation reservoir of 163,400 acre-foot storage capacity would reduce the once in 100-year flood crest discharge from d7,000 to 31»000 second-feet, by temporary storage above the spillway lip. However, under any plan for complete conservation de- velopment involving a reservoir at Pamo, Lake Hodges would have to be enlarged in order to conserve runoff originating between Pamo and Hodges. Such enlargement would inundate about one-half of the floor of San Pasqual Valley, and benefits from flood control at Pamo would be confined to the remaining area. The enlarged Lake Hodges in itself would provide a large measure of downstream flood protection, minimizing flood control effects of Pamo Reservoir in San Dieguito Valley. Finally, comparative costs of additional yield do not favor conservation development at Pamo. Flood control benefits that may be attributed to the development are insufficient to alter this relationship. In connection with Lake Hodges it was found that storage capacity equal to 22 per cent of mean daily flood volume would be required to regulate crest flood flows to 50 per cent of their unregulated rate. This would amount to a storage reservation of 23,000 acre-feet for a once in 100-year flood, with peak flow of 88,400 second-feet. How- ever, the reservoirs under consideration in this study should be operated for conservation, and the provision of any storage at Lake Hodges exclusively for flood control purposes may not be justified, in view of the incidental protection afforded by a large conservation reservoir. Any reservoir at Hodges with capacity of 225,000 acre-feet or more, operated solely for conservation, would reduce peak flow of the once in 100-year flood by at least 43 per cent, the reduction being achieved by ponding or temporary storage above the spill- way crest. In addition to this direct reduction of flood flows, there would be small probability of a large flood occurring at a time when a large conservation reservoir at Lake Hodges was full. Probability studies indicate that a once in 25-year flood at Hodges Dam could be accommodated within available reservoir space of a 340,700 acre-foot reser- voir 84 years out of 100, on the average. A once in 50-year flood could be similarly ac- commodated 78 years out of 100, on the average. Furthermore, it vras determined by statis- tical methods that with a 310,000 acre-foot reservoir operated exclusively for conservation purposes, the frequency of occurrence of a normal once in 25-yeer flood would be reduced to once in 215 years, at a point just belov; the dam. Similarly, a normal 100-year flood would occur, on the average, only once in 440 years. San Diego River Basin ■'■ A plan for complete development of the waters of San Diego River, including flood control as well as conservation, was presented in Bulletin No. 48.* The City of San * Bulletin No. 48, "San Diego County Investigation", Division of Water Resources, State Department of Public Works, 1935. 25 Diego has subsequently constructed San Vicente Reservoir, a conservation feature of the 1953 plan, but to a smaller storage capacity than was therein proposed. No steps have been taken to provide a conservation reservoir in Mission Gorge, as was also proposed in Bulletin TIo. 48. Consideration of San Diego River Bbsin during the current investigation was limited to further study of possible Mission Gorge reservoirs, and to increasing the size of San Vicente Reservoir to provide additional storage capacity, as suggested by the City of San Diego. Conservation Reservoirs in Mission Gorge Mission Gorge No. 2 dam site is in the upper end of Mission Gorge, about 5,100 feet downstream from Old Mission Dam. Mission Gorge No. 5 dam site is a further 1.8 miles downstream, while Mission Gorge No. Zero dam site is about 1,000 feet upstream from Old Mission Dam. Sites Nos. 2 and 5 were extensively studied for Bulletin No. 48, where- in it was shown that the proposed No. 2 reservoir v;as the more favorable economically. Mission Gorge Reservoir No. Zero was not considered in that report. Current studies of the Mission Gorge reservoirs are based upon later and more accurate survey data than v/ere available in 19J5i and include cost data corresponding with April 1947 prices. In the case of Mission Gorge Reservoir No. 2, land acquisition costs are estimated to have risen from ^600,000 to about $912,000 since 1955, while for Mission Gorge Reservoir No. 5 the estimated increase is from ^180,000 to about $211,000. Estimated lend and rights of way costs of the Mission Gorge No. Zero site are the same as those for the No. 2 site. Mission Gorge Reservoir No. Zero The dam studied for this reservoir consists of a concrete gravity section, 860 feet in length across the river channel, with an additional 600 lineal feet of rolled earth-fill embankment extending to the right abutment. Height of dam from streambed to spillway crest is 58 feet, forming a reservoir with capacity of 25,700 acre-feet. An overflow spillway is planned in the concrete gravity portion of the dam. If operated co- ordinately with existing Cuyamaca, El Capltan and San Vicente reservoirs on San Diego Ri- ver, it is estimated that the reservoir will provide additional safe seasonal yield of 1,900 acre-feet. No geologic exploration of Mission Gorge No. Zero dam site was made, but visual inspection indicates that suitable foundations can be found for a dam of moderate height. Before final decision to utilize this site is made, systematic foundation explora- tion should be conducted. Based upon April 1947 prices, estimated capital cost of the dam and reservoir is about $5,257,000, and annual costs are estimated at $156,100. Mission Gorge Reservoir No. 2 The dam considered for this site i& identical with that proposed in Bulletin No. 48, and consists of a concrete gravity structure with overflow spillway. Storage ca- pacity is 29,200 acre-feet at the spillway lip, 92 feet above streambed. If operated co- ordinately with existing Cuyamaca, El Capitan and San Vicente reservoirs, it is estimated that the reservoir will provide additional safe seasonal yield of 2,500 acre-feet. Esti- mated capital cost, based upon April 194? prices, is approximately $5,586,000, while annual costs are estintted at ^,1^0,000. These constitute increases from $2,145,000 and ^157,800 for corresponding 1935 cost estimates. Mission Gorge Reservoir No. 5 with Concrete Gravity Dam The dam considered for the No. 5 site in this study is identical with that stud- ied in Bulletin No. 48, of concrete gravity construcMon, straight in plan and with 24 spillway in the crest of dem. Height of dam from strecmbed to spillway crest Is 21b feet. Capacity of the reservoir is 29,200 acre-feet, end additional seasonal safe yield, v/hen operated coordinately with existing Cuyamaca, El Capitan and San Vicente reservoirs, is estimated at 2,b00 acre-feet. Estimated capital cost, basted upon April 194-7 prices, is about ^6,137,000, and estimated annual costs are ^.259, 000. Corresponding estimates in 1935 were i3, 666, 000 and ;237,100, respectively. Mission Gorge Reservoir No. 3 with Concrete Arch Dam In an effort to determine the most economical solution to the problem of a dam at the No. 3 site, a preliminary design was made for a variable-radius arch dam with fixed-crest overflow spillway. Geologic studies indicate that conditions at the site are not favorable to concrete arch construction. Furthermore, the topography is not ideal for an arch dam, since the canyon slopes are flatter than desirable, and contours paral- lel the thread of the stream. To meet these adverse conditions requires heavy excavation. Height of the arch dam, like that of the gravity structure considered for the same site, is 216 feet from streambed to spillway crest. Gravity abutments at the ends of the upper portions of the arch provide for thrust, which otherwise would not be satis- factorily transmitted to the canyon walls. The plan provides for a sliding joint at an elevation 20 feet above streambed, the dam below this elevation being designed to support the water load by gravity action. Estimated capital cost, based upon April 1947 prices, is about ^5,242,000, and estimated annual costs are ^220, 000. Comparison of Reservoirs If operated coordinately with existing Cuyamaca, El Capitan and San Vicente res- ervoirs, it is estimated that additional safe seasonal yield to be derived through con- struction of one of the heretofore described Mission Gorge reservoirs, No. Zero, No. 2 or No. 3, would be 1,900 acre-feet, 2,300 acre-feet or 2,600 acre-feet, respectively. It is further estimated that respective unit costs of this yield, based upon April 1947 prices, would be about v71.o0 for Mission Gorge Reservoir No. Zero, ^.65. 20 for Mission Gorge Res- ervoir No. 2, and #84.60 per acre-foot for Mission Gorge Reservoir No. 3 with a concrete arch dam. It is apparent that Mission Gorge Reservoir No. Zero is less desirable, both in amount of additional safe yield and in unit cost of that yield, than is a reservoir at the Mission Gorge No. 2 site. It is also apparent that neither changed conditions since 1933, nor substitution of an arch dam for a gravity structure at the No. 3 site, alter the con- clusion reached in Bulletin No. 48, to the effect that Mission Gorge Reservoir No. 2 is more favorable than No. 5 for conservation purposes. However, if it should ever be found desirable to provide a recreational lake in Mission Gorge, the fact that the No. 3 site comprises canyon storage with materially lower evaporation losses than upstream sites should be considered. Economic analyses of sucu dual purpose developments in Mission Gorge, which would involve higher dams to provide storage reservations for recreation as well as necessary conservation, have not been included in the present studies. Enlart^ed San Vicente Reservoir Although the existing San Vicente Reservoir has sufficient storage capacity for complete conservation of its tributary runoff, its enlargement for storage of foreign wa- ter may be desirable because of favorable geographical, clima to logical and storage charac- teristics of the site. Officials of the City of San Diego visualize a need for a strategi- cally located reservi. supply, for use in case of unprecedented drought, interruption of the Colorado River supply, or other unforseen disaster. They have suggested that an en- larged San Vicente Reservoir of 230,000 acre-foot capacity would provide 130,000 acre-feet 25 of storage, for the combined purposes of conserving San Vicente Creek runoff, storing San Diego River water transferred from the less efficient El Capitan Reservoir, and storing San Dieguito Basin water imported from Sutherland Reservoir. The remaining 100,000 acre- feet of storage capacity in San Vicente Reservoir would be reserved for Colorado River water, an amount sufficient to meet estimated ultimate water requirements of the City for nearly a year. San Vicente Dam was constructed with the consideration in mind of raising it from its present 190 feet to 310 feet in height at some future date, by adding concrete on the downstream side. While grouting was carried out to the extent necessary for the higher dam, no stepping or other special treatment was given the downstream face. Special methods will be required to properly place additional concrete on the old surface, and at the same time provide for shrinkage due to cooling and settling. A further problem is that of securing a good seal at the upstream face between the old structure and the raise. The surface between the new and old concrete must be thoroughly drained, and inspection galleries provided to permit inspection of such drainage. The plan of enlargement contemplates making the upstream face of the enlargement vertical and battering the downstream face at a slope of 0.8 to 1. Details of crest, spillway and outlet works would be reconstructed similarly to those now existing. In or- der to attain the desired storage capacity of 250,000 acre-feet the spillway would be raised to elevation 768 feet, or an Increase of llB feet above the present dam. Height of the enlarged dam would be 308 feet to spillway crest above streambed. Based upon prices prevailing In April 1947, it Is estimated that capital cost of the foregoing enlargement of San Vicente Reservoir is about $8,489,000. Annual costs are estimated at ^352,600. Conclusions Under terms of the agreements authorizing the present investigation, its pur- pose has been to determine the best program of development of a water supply for the City of San Diego on the San Dieguito and San Diego rivers. In accordance with this purpose, and based upon results of the investigation, the following conclusions have been reached: 1. Safe yield from the present water supply development of the City of San Diego, including the Colorado River supply, is sufficient to meet probable increasing demands until I960, forecast at 62.5 million gallons per day, even under extremely conservative assumptions as to interim runoff. Furthermore, there is reasonable expectation that reservoirs will fill prior to I960, and that full estimated safe yield of 80.8 million gallons per day may be attained. 2. Ultimate water requirements for the present incorporated area of the City of San Diego, including- allowance for military and naval establishments, will probably be about 100 million gallons per day, or 112,000 acre-feet seasonally. 3. In the Interest of conservatism as regards a municipal water supply of vital necessity, a supplementary supply should be made available to the City of San Diego at the earliest practicable date. 26 4. During the 50-year normsl period 1891-92 to 1940-41, inclusive, sea- sonal precipitation in San Dieguito Basin averaged an estimated 19.63 inches in depth, or a total amount of about 363. 000 acre-feet. Resultant seasonal runoff at three principal dam sites in the basin, Sutherland, Pamo and Hodges, would have averaged an estimated 15,600 acre-feet, 25,000 acre-feet and 40,700 acre-feet, respectively, under present conditions of culture and development. 5. Estimated seasonal utilization of water originating within San Die- guito Basin averages about 13,500 acre-feet at the present time, and will probably increase to approximately J4,000 acre-feet under conditions of ulti- mate development. The City of San Diego, which now receives 3.070 acre-feet, on the average, from San Dieguito Basin each season, should realize an esti- mated 19,000 acre-feet seasonally under the recommended complete conservation development of the basin, the remainder after ultimate requirements of other users of water from the basin have been satisfied. b. Waters of San Dieguito Basin lost to higher forms of economic utili- zation are estimated to average about 350,000 acre-feet seasonally under present conditions, including an undetermined amount consumed by natural grasses used for grazing. Losses consist of consumptive use by other native vegetation (including evaporation from soil and natural water surfaces), outflow to the ocean, and evaporation from reservoirs. Any salvage from these losses must be principally effected from present outflow to the ocean, estimated to average approximately 25,000 acre-feet per season. 7. Estimated safe seasonal yield from Lake Hodges, the only existing water supply development of .consequence on San Dieguito River, would have been b,700 acre-feet during the extreme ten-year drought from I895-96 to 1904-05, inclusive. During the more extended but less severe drought from I916-I7 to 1935-36, inclusive, 1917-36 firm seasonal yield would have been an estimated 11,400 acre-feet. 8. Construction of further conservation works In San Dieguito Basin should be under a plan contemplating eventual complete development of its water resour- ces. Complete development of surface runoff is arbitrarily defined as that which would have conserved the runoff of 1914-15 and prevented spill at Hodges Dam during the ensuing record flood season of 1915-16. This necessitates total storage capacity within the basin estimated at approximately 34-0,000 acre-feet, with at least 174,400 acre-feet at Lake Hodges. Resultant 1917-36 firm seasonal yield is estimated at about 30,000 acre-feet, while safe yield varies from 86 to 95 per cent of that amount, dependent upon disposition of storage. Under var- ious combinations of storage capacity, as divided between Hodges, Pamo and Sutherland reservoirs, 1917-36 firm yield is approximately the same, provided that in each case Lake Hodges has sufficient capacity to prevent spill. 9. Assuming that existing work has been done in accordance with indicated contract plans and specifications, the completion of Sutherland dam and reservoir to designed capacity of 36,700 acre-feet is practicable from the engineering standpoint. Including a gravity conduit to transmit its yield to San Vicente Reservoir, its estimated capital cost, based on 1947 prices, is about $3,677,000, with annual charges of ;i63,500. 27 10. Construction of an earth-fill dam at the Pamo site, of sufficient size to completely conserve runoff from the tributary drainage area, is prac- ticable. Such a reservoir would have an estimated storage capacity of lb3,400 acre-feet and, including; a conduit to transmit its yield to Chesterton Tank on Linda Vista Hesa, would cost an estimated #13,525»000, based upon 1947 prices. Annual costs would amount to an estimated ^572, 300. However, Pamo Reservoir should be eliminated from further consideration at this time, because studies indicate that plans for complete basin development which include that reservoir result in relatively high unit cost of additional yield. The site should be retained for possible future terminal storage of an imported water supply for the San Diego region. 11. Enlargement of Lake Hodges, to approximately 340,000 acre-feet of storage capacity required for complete basin development, by construction of a concrete gravity dam immediately downstream from the present structure, is practicable. Such a dam and reservoir, together with conduit and pumping plant to deliver yield at Chesterton Tank on Linda Vista Mesa, will involve an estimated capital outlay of Jpl2, 735>000, based upon 1947 prices. Estimated annual charges are ^636, 000. 12. If complete conservation development of Sen Dieguito Basin is achieved exclusively by enlargement of Lake Hodges, an estimated additional 18,000 acre-feet per season of 1917-36 firm yield will be derived above that of the existing development, or a total of 29,400 acre-feet, at estimated unit cost of about j35«30 per acre-foot. 13. If complete conservation development of San Dieguito Basin is achieved through completion of Sutherland Reservoir, together with enlargement of Lake Hodges, an estimated 17,800 acre-feet of additional 1917-36 firm yield will be attained seasonally, at estimated cost of about |40.00 per acre-foot. However, if an additional 8,300 acre-feet of reservoir space at Lake Hodges is provided for silt storage, and the foregoing plan is constructed by stages, with enlargement of Lake Hodges following completion of Sutherland Reservoir by a period of ten years, as is considered probable, unit cost of additional 1917-36 firm yield from, the combined development will be reduced to an esti- mated #30»40 per acre-foot. 14. Despite the present sufficiency of its water supply, it is to the Interest of the City of San Diego to undertake development of additional con- servation works in San Dieguito Basin in the near future, in order to preserve the City's large Investment in reservoir sites and maintain recent city fil- ings on excess waters of San Dieguito River. Practical as well as economic considerations indicate that development should be achieved by a program of staged construction of Sutherland and Hodges reservoirs for eventual complete basin development, with initial completion of Sutherland Reservoir, and sub- sequent enlargement of Lake Hodges to 310,000 acre-foot storage capacity. It is estimated that an enlarged Lake Hodges should be completed about ten years in advance of anticipated requirement for supplementary yield therefrom. 28 15- Under conditions of ultimate conservation development, the City of San Diego can salvage an estimated 2,000 acre-feet per season, on the aver- age, from water now lost by consumptive use of native vegetation and evapora- tion from soil and natural water surfaces in San Pasqual Valley. During drought periods an emergency supply of water, in total amount estimated at approximately 13,000 acre-feet, can be obtained from the ground-water basin underlying San Pesquel Valley. lb. Flood damages in San Dieguito Basin are largely confined to San Pasqual and San Dieguito valleys, which areas ere narrow relative to reaches of river involved, and therefore not subject to economic protection by means of levees or channel improvements. Neither can their limited size nor minor development justify reservoir control of floods as an end in itself. 17. Construction of Sutherland, Pamo or Hodges reservoirs for conserva- tion purposes will result in varying degrees of downstream flood protection, through reduction in peak flood flows by catchment in available empty reser- voir space and by ponding above spillway elevations. In the case of the planned Sutherland Reservoir such benefits will be minor and undependable. Pamo Reservoir will appreciably lower peak flows in San Pasqual Valley, but benefits will be minimized under any plan for complete conservation develop- ment of the basin, because over half of San Pasqual Valley will then lie within the Lake Hodges flow line, and Lake Hodges itself will provide a large measure of downstream flood protection. However, if a Lake Hodges with capacity of 225,000 acre-feet or more is operated solely for conservation purposes, peak flow of a once in 100-year flood will be reduced by at least 43 per cent. Furthermore, floods will usually be partly absorbed by vacant storage space in a large conservation reservoir at Lake Hodges, so that probable frequency of occurrence of given flood flows at all points dov/nstream will be greatly reduced. A portion of capital costs of an enlarged Lake Hodges may properly be charged to flood control. l8. The dam and reservoir proposed in Bulletin No. 48 for the No. 2 site on Mission Gorge on San Diego River is still found to be the most favor- able plan for conservation development at Mission Gorge. Based upon 1947 prices, its capital cost is estimated at about ^;3, 586, 000, with annual costs of ^150,000. Based upon sustained supply during the l89b-1905 drought, safe seasonal yield to be derived from its construction, above that of the exist- ing San Diego River development, is estimated at 2,300 acre-feet, at a unit cost of ^65.20 per acre-foot. Comparable i9'^7 unit cost of the estimated 2,600 acre-feet of additional safe seasonal yield to be obtained from Mission Gorge Reservoir No. 3, under the plan described in Bulletin No. 48, is esti- mated at *99.bO per acre-foot, while that for a concrete arch dam at the No. 3 site is estimated at $84.60 per acre-foot. A reservoir at the newly proposed Mission Gorge No. Zero site will produce an estimated 1,900 acre-feet of addi- tional safe seasonal yield, at estimated cost of about |71.60 per acre-foot. 19. Enlargement of San Vicente Reservoir to provide 250,000 acre-feet of storage capacity, as suggested by officials of the City of San Diego, is practicable from the engineering standpoint. Based upon prices prevailing in April 1947, capital cost of such enlargement is estimated at about ^8,489,000, with annual charges of ^352,600. 29 Recommendations With respect to development of a water supply for the City of San Diego on the San Dieguito and San Diego rivers, it is recommended: 1. That Sutherland Dam be completed substantially as originally designed, to provide a reservoir with storage capacity of 36,700 acre-feet, and that a gravity conduit be constructed to transmit water yield to San Vicente Reservoir, the project to be undertaken as soon as is practicable. 2. That an enlarged Hodges Dam, to provide a reservoir with the estimated 510,000 acre-feet of storage capacity req.uired in conjunction with Sutherland Reservoir for complete conservation development of surface runoff in San Die- guito Basin, together with necessary pumping plant and conduit to transmit water yield to the City of San Diego, be constructed approximately ten years in advance of anticipated need for supplementary yield therefrom. 5. That a program be initiated as soon as is practicable for acquisition of lands, easements and rights of way necessary for construction of an enlarged Lake Hodges with storage capacity of 310,000 acre-feet. 4. That a system of pumping wells and collecting pipe line in San Pasqual Valley, of sufficient capacity to lower the water table and effect salvage from natural consumptive use, be constructed when growing water demands of the City of San Diego indicate a need for such supplementary yield. 5, That Federal assistance be sought in construction of an enlarged Hodges dam and conservation reservoir, on the basis and to the extent of resultant re- duction In downstream flood damages. b. That Mission Gorge Dam No. 2, to provide a reservoir with storage ca- pacity of 29,200 acre-feet as required for complete conservation development of surface runoff in San Diego River Basin, be constructed when growing water demands of the City of San Diego indicate a need for such supplementary yield. 30 CHAPTER III WATER REQUIREMENTS OF CITY OF SAU DIEGO History and description of the City of San Diego and its water system heve been adequately covered in prior reports, and will be detailed herein principally as regards recent developments, particularly during and since the war period. Although the mild climate and attractive setting had for many years drawn per- manent residents and wealth to San Diego, and made it known as an all-year tourist resort, the City, even prior to World War II, was important as an agricultural, mercan- tile, industrial and shipping center. A further large factor in its economy was the presence of extensive naval installations. A modest aircraft manufacturing industry ex- isted, but commercial fishing and canning, boat building, and coastal and foreign ship- ping were also Important activities. After our entry into the war in December I9'H> tiie Federal establishments, both military and naval, were expanded many times over, and with the mushrooming aircraft industry dominated the economy of the area. Private shipping from the port ceased entirely, but governmental shipping increased as the City became a base of supply for naval and marine activities in the Pacific. Since the end of hostili- ties in August 1945) the nature of the City's economy has again undergone revolutionary change, with both military and naval activities curtailed, and the aircraft industry ac- tive but at greatly reduced scale. However, increased activity has been experienced in public and private construction. New industries and commercial firms are entering the area, and boat building, fishing, canning and the tourist trade are again important, in large measure replacing wartime activities. Commercial shipping from the port of San Diego has not been resumed to any appreciable extent. The City of San Diego, with a prior history of rapid growth, experienced an un- precedented influx of population attendant with its expanded activities during World War II. According to the Federal census, population had increased from 147,995 to 203»341 between 1930 and 19*0. In February 194-6, a special count by the Bureau of the census showed a population of 3b2,658, with some 64,000 additional residents in the metropolitan area contiguous to the City. No authentic figures are available with respect to present (1948) population. Service area of the City of San Diego's water system consists principally of the 93.5 square miles within the city limits. During the war, large naval and military establishments outside its boundaries were served by the City, but these no longer con- stitute an important water demand. The City is contractually obliged to serve water for the City of Coronado upon demand, but only very minor delivery is being made at the pres- ent time. The San Diego city limits include an area extending from a mile south of Del Mar, southerly along the coast for nearly 20 miles, and inland a distance as great as eight miles. Included are the communities of La Jolla, Pacific Beach, Mission Beach, Ocean Beach, Point Loma and Linda Vista, but the main urban portion of the City covers an area of about 13 square miles lying around, and to the east of the northern half of San Diego Bay. 31 Present Water Supply Until recent date, the City of San Diego has utilized only water from nearby sources of supply, either surface streams or ground-water basins within San Diego County. Of these, the surface sources have been hy far the more important, and no water has been pumped from underground basins for a number of years. In late 1947 a new source of sup- ply, that of imported water from the Colorado River, became available to the City, and now constitutes a major part of its water assets. Local Surface Sources and Development The City of San Diego obtains water from surface sources within the County in the watersheds of Cottonwood Creek, Otay River, San Diego River and San Dieguito River. Each of these is developed by conservation reservoirs, diversion works and transmission lines, as is shov.'n on Plate I, "Sources of Supplies and Transmission Lines of Water Sys- tem of San Diego Metropolitan Area". Characteristics of the city reservoirs are listed in Table 2. TABLE 2 RESERVOIRS OF Cirjf OF SAH DIEGO Reservoir Location Type of Dam Spillway Drainage Area in Square Miles Storageft Caoacity in Acre- Feet Remarks Type Height above Streambed In Feet Elevation of Lip in Feet Capacity in Second- Feet Available to City oWlthout consideration of silting. ^^4E3 timated by City of San Diego on basis of no deficiency during drought period, 1896-1905, Inclusive. In «c re -Feet per Year In Hi 11 ion Gallons per Day STORAGE Horena Cottonwood Creek Rock fill Side channe 1 169 3.039 50,000 120 61,200 5,600 5.0 Spillway gates removed end Up raised two feet in 19U6. Barrett Cottonwood Creek Gravity- concrete Overflow with gates li.2 1,615 60,000 130 U2,900 5,li00 U.-e Opper Otsy Proctor Valley Creek Constant radl u3 concrete arch Overflow 72 ??o 3.U60 12 2,600 Safe yield included in Lower Otay. Lower Otay Otay River Gravity- concrete Overflow with gates i:*c k9l 60,000 ^•i-' ?c,300 U-, 300 !.a Drainage area Includes Upper Otay. El Copitan San Diego River Hydraulic and rock fill Side channel 197 750 102,000 190 116,900 11,200 10.0 Completed In 1935.Stor- age capacity of 10,000 acre-feet assigned to La Mesa, Lemon Grove A Spring Valley Irriga- tion District. San Vicente San Vicente Creek Gravity- concrete Overflow 137 650 31,000 75 90,200 5,900 5.3 Completed In 19U3. HodRos San Dieguito River Plultlple con- crete arch Overflow 11? 315 00,000 303 37,700 3.300 3.0 Safe yield of 3,U00 acre-feet per year as- signed to Committees. TOTALS - - STORAGE RK 910 U08,000 35,700 31.9 Total storage capacity of 398,000 acre-feet available to City. reg;jlat:hg Hurray Tributary of Alvarado Canyon nultlple con- crete arch Siphon 107 5Ul 1,000 3.7 5,880 a Owned by La Hesa, Lemon Jrove k Spring Valley Irrigation District. Storage capacity of 5,00C (vcre-feet as- signed to City. San Dlegult Little San Elljo Creek Hultlple con- crete arch Siphon 1,1 2^U 1,230 1.2 1,128 Chollaa Tributary of Chollaa Creek Earth fill None 278 22 basins or tanks Throughout service area Concrete or 3teel 100 c TOTALS :.36c Total storage capacity of 6,506 acre-feet available to City. 32 PLATE I T. I2S. SOURCES OF SUPPLIES AND TRANSMISSION LINES WATER°SYSTEM OF SAN DIEGO METROPOLITAN AREA Scale of miles 4 8 1 I PLATE I MEXICO SOURCES OF SUPPLIES AND TRANSMISSION LINES OF WATER SYSTEM SAN DIEGO MET°ROPOLITAN AREA Scale of miles oilier features of the reservoir system have been described in earlier reports. However, two significant changes have been made in the past decade, namely, the construc- tion of San Vicente Reservoir, and the alteration of the spillway at Morena Dam. The first cited work began in 1941 and was completed in 1943- San Vicente Dam, a gravity type, concrete-masonry structure, is located about 20 miles northeast of downtown San Diego, on San Vicente Creek, a tributary of San Diego River. It is straight in plan, 190 feet in height above streambed, and 98O feet in length at the crest. Storage capa- city of the reservoir at spillway elevation of 65O feet, 12 feet below the dam crest, is 90,200 acre-feet. The overflow spillway in the central portion of the dam is 275 feet long and has a capacity of 31,000 second-feet. With a drainage area of 75 square miles, safe yield under combined operation with El Capitan Reservoir is estimated by the City at 5,900 acre-feet seasonally, or 5.3 million gallons per day, on the basis of a sustained water supply throughout the severe drought period from 1896 through 1905- Water is re- leased from San Vicente Reservoir by means of a semi-circular outlet tower on the up- stream face of the dam. Five valved ports, 30 inches in diameter, spaced at 30-foot vertical intervals, control entry of water into the tower, from vrtiich it discharges through three 5b-inch diameter pipes laid in the base of the dam. These pipes are con- trolled by valves at the downstream toe. As a result of alteration in the spillway of the dam, capacity of Morena Reser- voir was reduced by 4,600 acre-feet in 1946. The work was undertaken in interests of safety, and involved removal of gate structures to permit free passage of flood flov/s. At the same time the spillway lip was raised two feet to elevation 3>039 feet. Capacity at spillway lip is now 61,200 acre-feet, neglecting losses due to silting of the reservoir since construction. Aggregate conservation storage available to the City of San Diego is 398,000 acre-feet. Safe yield available to the City, defined as sustained supply without defic- iency during the record 1896-1905 drought, is estimated by the City at 35,700 acre-feet per season, or 31*9 million gallons per day. These figures do not take into considera- tion loss of capacity through silting of reservoirs since construction. Local Underground Sources Prior to construction of El Capitan Dam in 1936, the City of San Diego pumped a portion of its water supply from underground basins along San Diego River, but the prac- tice was discontinued when the dam was placed in operation. The wells and pumps, however, are capable of again being put to use, if desired. Effective storage capacity of the ground-water basin in upper San Diego River Valley, from Cape Horn to Old Mission Dam, was estimated by J. C. Kimble, geologist, for studies in connection with Bulletin No. 48, at 24,200 acre-feet. The basin under Mission Valley, between Mission Gorge and Old Town, was estimated to have effective storage capa- city of 10,500 acre-feet, but was productive of poor quality water. It is apparent that these two underground reservoirs, if properly charged and drained, might be used to aug- ment surface storage and increase safe yield from San Diego River. Such development would involve spreading flood waters to increase percolation into the ground-water basins, and systematic recapture of the waters by pumping. Water loss by evaporation and transpira- tion would be reduced if ground-water levels were maintained below the root zone. The Supreme Court of the State of California has confirmed the paramount right of the City of San Diego to all the waters of San Diego River, by virtue of its "pueblo" right, inherited from its Spanish and Mexican founders. An agreement with the La Mesa, 33 Older features of the reservoir system have been described in earlier reports. However, two significant changes have been made in the past decade, namely, the construc- tion of San Vicente Reservoir, and the alteration of the spillvray at Morena Dam. The first cited work began in 1941 and was completed in 1945- San Vicente Dam, a gravity type, concrete-masonry structure, is located about 20 miles northeast of downtown San Diego, on San Vicente Creek, a tributary of San Diego River. It is straight in plan, 190 feet in height above streambed, and 98O feet in length at the crest. Storage capa- city of the reservoir at spillway elevation of 65O feet, 12 feet below the dam crest, is 90,200 acre-feet. The overflow spillway in the central portion of the dam is 275 feet long and has a capacity of 31,000 second-feet. With a drainage area of 75 square miles, safe yield under combined operation with El Capitan Reservoir is estimated by the City at 5,900 acre-feet seasonally, or 5»3 million gallons per day, on the basis of a sustained water supply throughout the severe drought period from 1896 through 1905- Water is re- leased from San Vicente Reservoir by means of a semi-circular outlet tower on the up- stream face of the dam. Five valved ports, JO inches in diameter, spaced at 30-foot vertical intervals, control entry of water into the tower, from -vrtiich it discharges through three 3b-inch diameter pipes laid in the base of the dam. These pipes are con- trolled by valves at the downstream toe. As a result of alteration in the spillway of the dam, capacity of Korena Reser- voir was reduced by 4,600 acre-feet in 1946. The work was undertaken in interests of safety, and involved removal of gate structures to permit free passage of flood flovre. At the same time the spillway lip was raised two feet to elevation 3,039 feet. Capacity at spillway lip is now 61,200 acre-feet, neglecting losses due to silting of the reservoir since construction. Aggregate conservation storage available to the City of San Diego is 398,000 acre-feet. Safe yield available to the City, defined as sustained supply without defic- iency during the record I896-I905 drought, is estimated by the City at 35,700 acre-feet per season, or 31*9 million gallons per day. These figures do not take into considera- tion loss of capacity through silting of reservoirs since construction. Local Underground Sources Prior to construction of El Capitan Dam in 1936, the City of San Diego pumped a portion of its water supply from underground basins along San Diego River, but the prac- tice was discontinued when the dam was placed in operation. The wells and pumps, however, are capable of again being put to use, if desired. Effective storage capacity of the ground-water basin in upper San Diego River Valley, from Cape Horn to Old Mission Dam, was estimated by J. C. Kimble, geologist, for studies in connection with Bulletin No. 48, at 24,200 acre-feet. The basin under Mission Valley, between Mission Gorge and Old Town, was estimated to have effective storage capa- city of 10,500 acre-feet, but was productive of poor quality water. It is apparent that these two underground reservoirs, if properly charged and drained, might be used to aug- ment surface storage and increase safe yield from San Diego River. Such development would involve spreading flood waters to increase percolation into the ground-water basins, and systematic recapture of the waters by pumping. Water loss by evaporation and transpira- tion would be reduced if ground-water levels were maintained below the root zone. The Supreme Court of the State of California has confirmed the paramount right of the City of San Diego to all the waters of San Diego River, by virtue of its "pueblo" right, inherited from its Spanish and Mexican founders. An agreement with the La Mesa, 55 Lemon Grove and Spring Valley Irrigation District permits the District a total gross an- nual diversion from the entire San Diego River Basin of not to exceed 10,000 acre-feet on the average, over a ten-year period. This allowance is subject to the City's paramount rights, and includes water conserved by the District in Cuyamaca Reservoir, and water pumped from its El Monte well field in upper San Diego River Valley above Lakeside. Ground waters of this valley are also pumped by the Lakeside Irrigation District, the Riverview Farms and Lakeside Farms mutual water companies, and numerous individuals, to irrigate approximately 4,000 acres above Mission Gorge. Mission Valley lands are like- wise irrigated by pumping from the underground basin between the lower end of Mission Gorge and Presidio Hill. In order to fully convert the ground-water basins in upper San Diego River and Mission valleys to planned conservation storage for the City's own use, it would be essen- tial that pumping of the ground water by overlying landowners be stopped or rigidly con- trolled. Otherwise, benefits from spreading of floodwaters would be reaped by the over- lying owners, and the City's efforts at recapture would be inefficient. Agricultural returns from these areas, however, are of considerable importance to the economy of the City. Furthermore, the urban development and population presently dependent upon these underground sources for water supply is sufficiently large that the hardships resulting from diversion of the supply to sole use by the City might involve substantial economic adjustment throughout the surrounding area. Therefore, despite its established perpetual right to waters of the underground basins along San Diego River, the City of San Diego has not attempted to prevent reasonable use of this water by overlying landowners, and has counted on these sources only as a limited source of emergency supply. Colorado River Water The major addition to the water supply of the City of San Diego was made in De- cember 1947 1 when Colorado River water was first delivered through the newly constructed San Diego Aqueduct. All California rights to waters of the Colorado River are predicated upon the apportionment contemplated in the Colorado River Compact of 1922, and in the Boulder Can- yon Project Act of I928. Under the former, which was a Federally approved compact or agreement between the states of the Colorado River Basin, the "Upper Basin", consisting of those parts of the states of Arizona, Colorado, New Mexico, Utah and Wyoming within and from which waters naturally drain into the Colorado River system above Lee Ferry, was apportioned a total of 7,500,000 acre-feet annually for beneficial consumptive use. The "Lower Basin", consisting of those parts of the states of Arizona, California, Nevada, New Mexico and Utah within and from which waters naturally drain into the Colorado River system below Lee Ferry, was apportioned an equal amount, as well as an additional alloca- tion of 1,000,000 acre-feet annually. The Compact was ratified by legislatures of the several states and approved by Congress. Arizona, however, did not ratify the Compact un- til 1944. In accordance with provisions of the Boulder Canyon Project Act of 1928, which gave congressional approval to the Compact, the State of California in 1929 enacted legis- lation, the California Limitation Act, to the effect that its aggregate annual consumptive use (diversions less returns vo the river) of Colorado River water would not exceed 4,400,000 acre-feet annually, plus not more than one-half of any surplus waters unappor- tioned by the Compact. All of the foregoing rights were beclouded by terms of the Mexican Water Treaty, signed on February 3» 1944, between the United States and Mexico. This treaty allocated 34 to Mexico a guaranteed annual quantity of 1,500,000 acre-feet, and a conditional annual quantity of 200,000 acre-feet from the already apportioned waters of the Colorado River, and imposed an additional burden upon that limited water supply as compared to ultimate demands therefrom. The status of California and Arizona rights are presently the subject of major controversy between these states. The controversy hinges upon interpretation of the Colorado River Compact, the Boulder Canyon Project Act, the California Limitation Act, and other relevant documents. Attempts are being made to secure congressional authoriza- tion for determination thereof by the United States Supreme Court. As early as April 15, 1926, the City of San Diego had filed for 155 seoond-feet, or 112,000 acre-feet of Colorado River water annually, a right that was later broadened to apply to both City and County. Under the Seven-Party Water Agreement of 1930, execut- ed on August l8, 19?1 by California claimants to Colorado River water, the City and/or County of San Diego were apportioned 112,000 acre-feet annually, with a fifth priority. In 1933 the Secretary of the Interior contracted to provide the City 250,000 acre-feet of storage capacity in Boulder Reservoir, now Lake Head, and to deliver 112,000 acre-feet of water each year to the City and/or County at a point on the Colorado River above Imperial Dam. A further contract in 1934 authorized diversion from the All American Canal, on the west side of Imperial Valley. Studies were made and plans forciulated for pumping from this source up the eastern slope of the Peninsular Range to a 7E~niile tunnel with intake portal at elevation of 2,750 feet, and then dropping the water into the upper reaches of San Diego River. In the meantime, construction of the Colorado River Aqueduct by the Metropolitan Water District of Southern California was under way, a project completed in 1941 at cost of $191,000,000. This line, with ultimate capacity of 1,655 second-feet, di- verts at Parker Dam on the Colorado River, and, through approximately 410 miles of canals, pipes and tunnels, including pump lifts, delivers water to member agencies of the Dis- trict in the Los Angeles metropolitan area. The possibility of tapping this aqueduct for gravity delivery of Colorado River water to the San Diego region was recognized, and studies of such a route were made as alternative to the proposed pump lift from the All American Canal. No decision as to final course of action was made until 1944. At that time the rapidly increasing water demands of San Diego exceeded safe yield from local sources, and deep inroads had been made on reserves of water in storage. After a compre- hensive study of water supply in the San Diego region, as related to national defense, the State Council of Defense in 1943 made the following findings:* "6. Estimated future mean daily demands on the City of San Diego water system, based on a 50 per cent increase in use in five years including a sup- ply of 5 m. g.d. to the Coronado District system of the California Water and Telephone Company, are 44.0 m.g.d. in 1943, 48.0 m.g.d. in 1944, 50.0 m.g.d. in 1945, 52.0 m.g.d. in 1946 and 53.0 m.g.d. in 1947 .... "7. With the foregoing estimated demands for water from the City of San Diego water system based on a 50 per cent increase in use in 5 years, including 3 m.g.d. for the Coronado District system, runoff conditions obtaining in a critical period like that of 1895 to 1904, and adequate transmission capacity provided from all of the storage reservoirs to the city distribution system, the entire water supply available to the city from surface storage, except Hodges Reservoir, will be exhausted in April, 1947 ...." * + * "9. As the City of San Diego is now heavily overdrawing the safe yield of its water supply, a supplemental water supply must be obtained. *''Report on Municipal Water Systems-Report No. 3> San Diego Region", Committee on Trans- portation, Housing,, Works and Facilities, State Council of Defense, April 1943. 35 "The construction of additional storage on local streams will not insure additional safe yield to the City of San Diego and vicinity should dry sea- sons occur in the immediate future. For example, had San Vicente Reservoir been constructed in 1895 to a capacity of 75,000 acre-feet, and no draft made on it, it would not have filled until 1916.- "Therefore, the supplemental water supply must be obtained from sources outside of the County." Among the several recommendations of the Council was the following: "5. Additional Water Supply (a) Surveys and studies necessary to determine the most feasible route of a transmission line for importation of an additional water supply from the Colorado River, including ter- minal storage facilities enroute, be initiated immediately, and detailed plans and specifications on the selected route be pre- pared and construction started in time to reach completion and be in operation before the local supplies are exhausted. (b) When the most feasible route for a supplemental water supply from the Colorado River has been determined, arrangements be made with the agencies owning existing transmission facilities for the conveyance of such supplemental supply from the Colorado River to the point at which it would be delivered to the new transmission line. (c) The United States actively assist in making all neces- sary surveys, studies and negotiations, and in financing the construction of all works required to insure a full and dependable water supply for the City of San Diego, because of the large Fed- eral interests dependent upon this water supply system." In recognition of urgent need for supplemental water to assure continuation of San Diego's war activities, the President of the United States, on October 3, 19''-4, ap- pointed an interdepartmental committee to study and recommend methods of constructing and financing facilities for increasing the supply. Following the committee's recommenda- tion the President, on November 29, 1944, approved immediate construction at Government expense of a conduit, now known as the San Diego Aqueduct, to connect with the Colorado River Aqueduct near San Jacinto in Riverside County, and extend to San Vicente Reservoir on the San Diego city system. The United States Bureau of Reclamation prepared final plans, and construction under United States Navy supervision started in 19^5. However, with termination of hostilities late in that year, and consequent curtailment of naval ac- tivity, notice was given that the project was to be cancelled. After urgent representa- tion by the City and other interested local agencies, a contract was effected in October 1945 between Navy Department and City, whereby the Navy completed construction, and the City agreed to reimburse the Government at the rate of $500,000 per year until the project was paid for, without interest. Legality of this contract was questioned by the Comptrol- ler General in February 1947, hut Public Law 482 of the 80th Congress, Chapter 186- 2d Session, approved on April 15, 1948, ratified actions of concerned Federal agencies in constructing the aqueduct, authorized its completion and ratified the Navy's contract with the City. Construction had already continued to completion. In anticipation of need for an agency with powers to receive, apportion and de- liver Colorado River water to cities and public districts within the County, the San Diego County Water Authority was organized on June 9, 1944, under a special enabling act of the California Legislature. Its present membership consists of the cities of Chula Vista, National City, Ooeanside and San Diego; the Fallbrook Public Utility District; the Lake- side, San Dieguito and Santa Fe irrigation districts; and the La Mesa, Lemon Grove and Spring Valley Irrigation District. Original membership also included the City of Coronado 36 and the Ramona Irrigation District, but these agencies withdrew from the Authority in 19'l-6. An agreement between the Authority and the Metropolitan Water District, annexing the Authority to the District, was approved by voters of the Authority's service area in November 194b. It provided for merging of Colorado River water rights of San Diego City and County with those of the District; payment by the Authority of back taxes and inter- est in the District since formation, over a period of years, without further interest; payment by the District of half the costs of the San Diego Aqueduct, together with as- sumption of title to its northern portion, and responsibility for enlargement of that por- tion when required; and for assumption of remaining costs and obligations in the aqueduct by the Authority. Combined rights of the Metropolitan Water District in the Colorado River total 1,212,000 acre-feet per year, of which 550,000 acre-feet are fourth priority, and the re- mainder fifth priority, under terms of the Seven-Party Water Agreement of 1930. Based on its assessed valuation, the San Diego County Water Authority was, on June 30, 1946, en- titled to about 10.5 per cent of the District's rights, or 126,300 acre-feet per year. The City of San Diego, in turn, was entitled to about 85 per cent of the Authority's rights, amounting to 109,300 acre-feet per year, or nearly 100 million gallons per day. However, the designed capacity of the existing San Diego Aqueduct is only 85 second-feet, or 61,400 acre-feet per year, of which the City's entitlement is approximately 52,200 acre-feet per year, or about 46.6 million gallons per day. Limited experience since open- ing of the aqueduct indicates actual capacity appreciably in excess of designed. The San Diego Aqueduct, a gravity-flow conduit 71.1 miles in length, was planned under wartime restrictions as to use of critical materials. While tunnels, and some other structures, were constructed to full capacity of I65 second-feet, the present pipe lines are designed for only 85 second-feet, provision having been made to permit installation of a second identical barrel when such additional capacity is required. The aqueduct intake is at the west portal of San Jacinto Tunnel on the Colorado River Aqueduct. Two miles be- low the intake an 1,800 acre-foot reservoir regulates flow in the conduit. The line bears southwesterly across Hemet Valley, and then turns southerly, crossing Temecula Creek south- east of Temecula. It crosses San Luis Rey River east of Fallbrook, and San Dieguito River in the upper portion of Lake Hodges, having passed east of Escondido. From Lake Hodges the aqueduct bears southeasterly to San Vicente Reservoir. Seven concrete-lined tunnels, six feet in diameter, have an aggregrate length of 4.4 miles. Also included in the work is a total length of 1.75 miles of 48-inch diameter steel pipe. Remainder of the aqueduct consists of reinforced-concrete pipe, ranging in diameter from 96 to 48 inches. Cost of the project is estimated at $14,180,000, of which $12,530,000 is direct construction cost. Terminus of the aqueduct in San Vicente Reservoir permitted transmission of Colo- rado River water to the City of San Diego through an existing system, but new feeder lines were required to reach remaining members of the San Diego County Water Authority. With proceeds of a $2,000,000 bond issue, the Authority undertook construction of two such pipe lines, both of which were completed in 1948. One serves the Fallbrook Public Utility Dis- trict and the City of Oceanside, and the other serves Lakeside Irrigation District, La Mesa, Lemon Grove and Spring Valley Irrigation District, and the cities of National City and Chula Vista. The Santa Fe and San Dieguito irrigation districts, as well as the City of San Diego, are served with Colorado River water by a direct diversion from the aqueduct into Lake Hodges. The City is also constructing additional transmission lines and appur- tenances between San Vicente and Murray reservoirs to handle Colorado River water, which facilities were largely completed in 1948. 37 The San Diego County Water Authority has estimated that combined tax rates un- der the Metropolitan Water District and the Authority will average $0.55 per $100 of assessed valuation over the 30-year period from 19^8 to 1977 » inclusive. The levy is comprised of regular taxes by both District and Authority to cover costs of their respec- tive bonded indebtedness, completion and enlargement of system, and operation and main- tenance, as well as a special tax by the District to cover payment of back taxes and delinquent interest due from the Authority. It is estimated that the combined rate will have dropped to $0.27 by 1978, and that taxes will be entirely eliminated by 1998. Un- treated water delivered through the San Diego Aqueduct is charged for by the District at the rate of $8.00 per acre-foot, while the Authority charges members at the rate of $12.00 per acre-foot. Transmission and Distribution System Principal features of the water transmission and distribution system of the City of San Diego are indicated on Plate 1. They were described in 1935 in Bulletin No. 48, and In greater detail by the State Council of Defense in its 194-3 report. The City maintains three more or less separate and distinct transmission systems from its reservoirs to its service area. These are kjiown as the "Cottonwood-Otay" , "San Diego River" and "San Dieguito" systems. The following brief descriptions are based on data obtained from the City of San Diego. At the upper end of the "Cottonwood-Otay System", water released from Korena Reservoir flows down the channel of Cottonwood Creek to Barrett Reservoir, from whence it passes through Dulzura Conduit for 11 miles, emptying into the channel of Dulzura Creek. Dulzura Conduit, with present capacity of about 29 million gallons per day, consists largely of concrete-lined canal, but contains 4,300 feet of flume and 9>400 feet of tun- nel. Dulzura Creek flows into Lower Otay Reservoir. Releases from this reservoir pass through a short tunnel to the Otay Filter Plant, and then enter the 40-inoh diameter steel Otay Pipe Line, extending about ten miles to the main city service area, to the northwest. Built for gravity flow, this line since 1945 has been pumped near the filter plant, to increase its capacity from iB to 27 million gallons per day, and permit more nearly balanced drafts between the Cottonwood-Otay and San Diego River systems. At a distance of 2i miles from the filter plant the Coronado Pipe Line, a 20-inch diameter, wood-stave pipe serving the Coronado service area of the California Water and Telephone Company, branches from the Otay line. Under the "San Diego River System", water is transmitted to the city service area from El Capitan and San Vicente reservoirs, and from the new San Diego Aqueduct. Pipe line capacities, as estimated by the City of San Diego for this system, are theoreti- cal maximum figures, under the assumption of full reservoirs. The El Capitan Pipe Line extends about 131,000 feet southwesterly from El Capitan Reservoir to the University Heights Filter Plant in San Diego. The upper section, of 48-inch diameter, welded steel pipe with capacity of 53.4 million gallons per day, is 31,l80 feet in length and ends at the El Monte Pumping Plant of the La Mesa, Lemon Grove and Spring Valley Irrigation Dis- trict, where the District diverts through a 36-inch diameter line of 15 million gallons per day capacity. The middle section is 36-inch diameter, welded steel pipe with capa- city of 13«5 million gallons per day, extending 11,560 feet to the City's Lakeside Well Field, while the remainder of the line is 36-inch diameter, lock-bar steel pipe. The 58 Alvarado Pumping Plant increases terminal capacity of the line from 22.0 to 2fa.O million gallons per day, with El Capitan Reservoir full. The original San Vicente Pipe Line, with capacity of 27.2 million gallons per day, is composed of 4-2.5-inch diameter, steel cylinder cement-lined pipe, extending 21,780 feet between San Vicente Dam and Lakeside. It connects with the El Capitan line and with the new El Monte Pipe Line, to be described hereafter, thus making it physically possible for exchange of water between El Capitan and San Vicente reservoirs. In anticipation of delivery of Colorado River water to Sen Vicente Reservoir, the City voted a J6, 000, 000 bond issue on April 17» 194-5, for construction of pipe lines and appurtenances to handle this supply. This work was largely completed by the end of 1948. A second San Vicente line, with capacity of 57.9 million gallons per day, consist- ing of 48-inch diameter, reinf orced-ooncrete-cylinder pipe, extends 21,690 feet from the dam to Lakeside, connecting with El Capitan and El Monte transmission lines. Upper sec- tion of the El Monte line, from El Monte to Lakeside, consists of 11,300 feet of 48-inc)i diameter, reinf orced-concrete-cylinder pipe with capacity of 34.9 million gallons per day. Remainder of the line consists of 47,110 feet of similar 68-inch diameter pipe and 6,290 feet of 72-inch diameter, concrete-lined pressure tunnel, extending to the Alvarado Treat- ment Plant adjacent to Murray Reservoir. This new plant will soften Colorado River water and deliver it to Alvarado Reservoir, from whence it will flow to the city mains. The new Alvarado Reservoir has a storage capacity of 20 million gallons, solely for purposes of regulation. The "San Dieguito System" serves the City's La Jolla service area, and is de- scribed in more detail in Chapter VII. In brief, it includes an open concrete-lined con- duit, conveying San Dieguito River water from Lake Hodges to San Dieguito Reservoir. From this regulating reservoir a composite pipe line, with terminal capacity of 5.O million gallons per day, leads southwesterly a distance of 12.4 miles to the Torrey Pines Filtra- tion and Pumping Plant, from whence water is boosted to Torrey Pines Reservoir for regula- tion. It then flows by gravity through another five miles of pipe to the distribution mains of the La Jolla area. Service mains within the City's distribution system permit exchange of water be- tween the several principal service areas. Numerous small regulating reservoirs and tanks, with appurtenant booster pumping plants, are designed to service particular areas. Improvement and extension of its distribution system has been a continuing project with the City's Water Department. All water delivered to consumers is chlorinated and the greater part of it is filtered. All services are metered. Safe Yield For purposes of this report safe yield is defined as the sustained water supply which would have been available from the source in question without any deficiency during the most severe drougiit period of record, that from 1895-96 to 1904-05, inclusive. The season utilized in this report is the so-called "irrigation season", from October to Sep- tember, inclusive, unless otherwise specifically indicated. 39 TABLE 3 ESTIMATED SAJE YIELD OF PRESENT WATER SXJPPLY DEVELOPMENT OF CITY OF SAN DIEGO Based on No Deficiency During Drought Period, 1896-I905, Inclusive Source Theoretical With Reservoirs Filled at Start of Dry Period in Acre-Feet per Season in Million Gallons per Day Actual Under Present Conditions of Depleted Storage in Acre-Feet per Season in Million Gallons per Day Local surface streams 35,700 Colorado River 54,800 31.9 48.9 10,700 54,800 9.6 48.9 TOTALS 90,500 80.8 65,500 58.5 Table 3 shows that theoretical safe yield of water, under present development of the San Diego City system, including Colorado River water imported by the San Diego Aqueduct, is 90,500 acre-feet seasonally. However, because of overdraft resultant from wartime expansion, no such amount is actually available to the City at this time. Attain- ment of full safe yield from local surface streams requires adherence to a rigid schedule of reservoir operation, under which excess waters stored during wet seasons are drawn out and consumed at an annual rate not exceeding the safe yield. This assures that an ensu- ing dry period is entered with sufficient water in storage to provide the safe yield during each dry season. Because of unprecedented water demands, the City of San Diego has been unable to follow this desirable schedule of reservoir operation during recent years. Fortunately, up to and including the season of 194-2-43, the region had enjoyed a seven-year period during which runoff was greatly in excess of normal, and well-filled reservoirs were available to meet wartime requirements. However, since 1943-44, runoff has been deficient, and water consumption has been far greater than safe yield, with the result that at the end of 1948 city reservoirs were less than 25 per cent filled. It follows that safe seasonal yield actually available at this time from local surface streams is not 35,700 acre-feet, but rather a fraction of that amount, estimated as no greater than 30 per cent of theoretical full safe yield, or about 10,700 aore-feet per season. Because of the pattern of runoff, the City of San Diego cannot in the normal course of events expect to regain full safe yield of its existing local water supply de- velopment for a number of years. Dependent entirely upon the vagaries of future weather, the period might be as short as a single season, or as long as fifteen or twenty. As regards the Colorado River water supply through the San Diego Aqueduct, early reports Indicate a capacity of about 16 per cent in excess of design figures. During a season, inevitable shutdowns for maintenance or other causes will reduce this maximum 40 amount. An arbitrary assumption has therefore been made that overall operating efficien- cy will be such as to permit average delivery of 105 per cent of designed capacity, and that the City will be entitled to approximately 48.9 million gallons per day, or approx- imately 54,800 acre-feet per season. Since no safe yield is contemplated from local ground-water basins, total es- timated safe yield available to the City of San Diego at present, with but 25 per cent of its reservoir capacity filled, is about 65,500 acre-feet per season, or 58.5 million gal- lons per day. Present Water Utilization Historical consumption of water in the City of San Diego since I9OO is listed in Table 4, and shown graphically on Plate II, "Water Consumption by City of San Diego". Average per capita consumption during each year for which census figures are available is also shown. It will be noted that forecasts have been advanced for water consumption in 1950 and i960, which estimates will be discussed in a later section of this chapter. TABLE 4 WATER CONSUMPTION BY CITY OF SAN DIEGO Calendar Years Year Total Annual Average per Day in in in Million in Acre- Feet Million Gallons Gallons Gallons per Capita 1900 758 2,326 2.08 117 1901 750 2,302 2.06 1902 761 2,355 2.08 1903 733 2,250 2.01 1904 771 2,366 2.11 1905 761 2,355 2.08 1906 944 2,897 2.59 1907 1908 1,222 5,750 3.55 1,386 4,255 3.79 1909 1,413 4,556 5.87 1910 1,653 5,568 4.55 114 1911 1,821 4.99 1912 2,095 6,429 5.72 1913 2,504 7,685 6.86 1914 2,o41 8,105 7.24 1915 2,768 8,495 7.58 1916 2,958 9,078 8.08 1917 3,151 9,670 8.63 1918 3,623 11,119 9.95 1919 3,318 10,183 9.09 1920 3,560 10,925 9.75 131 1921 5,591 11,020 9.84 1922 3,662 11,238 10.03 1923 4,340 13,319 11.89 1924 4,482 13,755 12.25 1925 4,670 14,332 12.80 Tear Total Annual Average per Day in Million Gallons in Acre- Feet in Million Gallons in Gallons per Capita 1926 1927 1928 1929 1930 5,229 5,486 5,771 6,115 5,714 16,047 16,836 17,711 18,766 17,536 14.55 15.03 15.77 16.75 15.66 106 1931 1932 1955 1954 1955 3,804 5,513 5,536 5,946 6,369 17,812 16,919 16,989 18,248 19,546 15.90 15.06 15.17 16.29 17.45 1956 1957 1958 1959 1940 6,496 7,011 7,359 8,644 19,956 21,516 22,523 23,241 26,528 17.75 19.21 20.11 20.75 23.62 116 1941 1942 1943 1944 1945 9,567 13,228 15,401 16,579 18,309 29,360 40,595 47,264 56,188 26.21 36.24 42.19 45.50 50.16 1946 1947 16,950 16,395 52,018 50,308 4t>.44 44.91 128 1950 13,200 Forecast 50.0 125 56,000 i960 22,800 70,000 62.5 125 41 Most striking feature of past water utilization in the City of San Diego is the increase diiring the period of World War II, when consumption jximped from 20.75 mil- lion gallons per day in 1939 to 50.16 million gallons per day in 194-5 » an increase of almost 2.5 times in six years. During both 194-6 and 19*7 substantial declines from the 1945 peak have been experienced. However, there is indication that the decline is level- ing off, and that the 1947 figure of 50,300 acre-feet per year, or 44.91 million gallons per day, approximately represents average utilization under present conditions. Future Water Requirements It is readily apparent that an attempt to forecast future water demands of a city such as San Diego, with its history of rapid normal gro-wth broken by a spasmodic wartime expansion, is inherently subject to wide possible error. Extraordinary wartime requirements connected with the Army and Navy are largely unrelated to dominant peacetime uses, so that there is no firm base for projecting past requirements into the future. In order to facilitate orderly, long-range planning, however, and to permit timely construc- tion of works necessary to prevent possible disastrous water shortages, some idea of the magnitude of probable future demands is necessary. To this end only, and with no pre- tense of accurate foresight, expected population growth and resultant water requirements of the City of San Diego up to the year I96O have been evaluated. In that actual growth may prove to be greater than indicated by the present forecast, planning should include as large a factor of safety as is consistent with economic feasibility. Population Gro-vrth of population within the City of San Diego has been rapid and consistent each decade since the turn of the century. Between the 1930 and 1940 counts by the United States Bureau of the Census, population increased from 147,995 to 203,341. This was fol- lowed by the accelerated expansion of World War II, accompanied unfortunately by a dearth of reliable data as to population. There is evidence that growth of the City was accel- erated as far back as 1939, coincident with inauguration of the defense program, but the major influx occurred in 1942 and 1943, and peak population was probably reached shortly after termination of World War 11 hostilities late in 1945. While several agencies made estimates of population for one or another of the war years, the problem was so complicat- ed by large increments of transitory military personnel and dependents, and migratory civilian workers, that the estimates were necessarily crude, and in some cases inconsis- tent. At the instigation of communities concerned, the Bureau of the Census commenced special population counts throughout San Diego County in June 1944, completing the last in June 1946. These data, shown in Table 5 (page 44), are reliable as of the date of census, but a period of two years elapsed between first and last counts involving smaller cities. These years included a rise to an undetermined peak population and a subsequent decline, so that validity of the county total may be questioned. However, approximately 87 per cent of the population was counted in the first half of 1946. Only two per cent was count- ed in 1944, while the remaining population was counted in the early summer of 1945, before the probable peak figure had been reached. In the aggregate, therefore, as regards the County as a whole, the special census data are believed fairly representative of oonditionn as of early 1946. In a letter reproduced in Appendix G, "Data Regarding Special Census", the United States Department of Commerce states that military personnel stationed in the area were included in the census totals. 42 > < Q QC Ul a z o _l _J < O Z o _) _l z o t- Q. D «0 z o u _l < eo 50 40 30 20 10 1900 140 1900 < H Q- < 130 O V cr UJ Q. < tr 120 V) UJ Z Q. o 110 _l -I < o 100 PLATE n 1 62.5 / FORECA ■/- / sjy / / A / / V ^ \ 1 /- ■^ 1910 1910 i920 1920 1930 YEAR 1930 1940 1940 1950 1950 1960 I960 > FORECAST-^ \ / "^^ _^__ - — -~ / \ "" \ ^ 125 WATER CONSUMPTION BY CITY OF SAN DIEGO 43 TABLE 5 SPECIAL CENSUS OF SAN DIEGO COUNTY BY UNITED STATES BUREAU OF THE CENSUS 1944-1946 Including Military Personnel Stationed in Area City or Area Date of Census Population Chula Vista Coronado El Cajon Esoondido La Mesa National City Oceanside San Diego Unincorporated June 6, 1944 June 5, 1945 May 8, 1945 June 3, 1946 May 4, I945 May 22, 1945 June 11, 1945 February 21, 1946 April 17, 194-6 11,081 25,382 3,175 5,930 6,486 17,654 10,698 362,658 109,740 TOTAL COUNTY POPULATION 552,804 United States census totals for the County and City of San Diego, beginning in i860, are listed in Table 6, and shown graphically on Plate III, "Population, County and City of San Diego", as are estimated 1948 population figures, and forecasts for 1950 and i960. It may be noted that the proportion of total county population residing within the City increased each decade from 1880 to 1930, reaching a peak of 7O.6 per cent in the latter year. A slight decline occurred in 1940, and a dropping off to 65.6 per cent for the special census of 1946. It is reasonable to assume that the indicated trend of growth, now favoring rural areas, will continue in San Diego County in the future. TABLE 6 POPULATION OF COUNTY AND CITY OF SAN DIEGO Including Military Personnel Stationed in Area Year Population Per cent of Population Coimty in City County City i860 4,324 731 16.9 1870 4,951 2,300 46.5 1880 8,bl8 2,637 30.6 1890 34,987 16,159 46.2 1900 35,090 17,700 50.4 United States census data 1910 61,665 39,578 64.2 1920 112,248 74,361 66.2 1930 209,659 147,995 70.6 1940 289,348 203,341 70.3 1946 552,804 362,658 65.6 Estimated or forecast by 1948 575,000 375,000 65.4 State Division of Water 1950 615,000 400,000 65.0 Resources i960 780,000 500,000 64.0 44 PLATE in O Z 500 < 10 D o I I- 400 Z O 300 _) D Q. O 200 a. o US CENSUS DATA X ESTIMATED BY DIVISION OF WATER RESOURCES 1660 500 >>,00 80 60 ^ -7 ^p40 zk ^-1 20 CTq. uo Q.Q. ' o-x— J 1860 1870 1880 1890 1900 1910 1920 1930 YEAR 1940 1950 POPULATION COUNTY AND CITY OF SAN DIEGO INCLUDING MILITARY PERSONNEL STATIONED IN AREA 45 Forecasts of population for either San Diego City or County have recently been made by a number of interested agencies. In Table 7 are shown six independent fore- casts of San Diego city population to the year 196O. With exception of the first listed, all have been compiled and published by the Research Department of the San Diego City Schools.* The first listed is based on a forecast for the entire County by the State Of- fice of Planning and Research, and has been adjusted to the city area by the Division of Water Resources. In its derivation, a forecast of population for the years 1950 and I96O, published by the State Reconstruction and Reemployment Commission in 1946**, vras revised by the State Office of Planning and Research as of January 1948, the revision including an estimate of July 1947 population. The forecast was based on an intensive analysis of pop- ulation trends and their causes, throughout the Nation and the State, including considera- tion of birth and death rates, general migratory movements, and the influences of economic conditions, wartime displacements, climate, etc. The July 1947 'population of San Diego ' County was estimated by the State Office of Planning and Research at 500,000, while 525,000 was expected to be reached in 1950, and 625,000 in 196O. If, in accordance with the trend toward relatively more rapid growth in county area than in the City, it be assumed that 65.0 per cent of total county population will reside within the present city boundaries in 1950, and 64.0 per cent in I960, then the 1950 population of the City of San Diego would be 341,000, while the forecast for I96O would be 432,000. TABLE 7 FORECASTS OF SAN DIEGO CITY POPULATION TO I96O Agency Making Forecast Basis Population 1948 1950 i960 State Office of Plan- ning and Research San Diego Chamber of Commerce Pacific Telephone and Telegraph Company San Diego Gas and Electric Company Mr. John Voss San Diego City Schools Trends of migration and natural increase. Basic forecasts for County adjusted to City by State Division of Water Resources. Projected 1900-40 rate of increase, modified by postwar experience. 1948 and 1950 forecasts - present phone service. I960 forecast - guess. Projected past rate of County increase, modified by assumed wartime gain of 125,000. Logarithmic projection. Basic forecasts for County adjusted to City by San Diego City Schools. Projected rate of past increase in num- ber of gainfully employed people. Trends of migration and natural increase. 527,000'^ 381,066 372,000 376,200 365,000 379,000 341,000 408,000 401,666 396,000 390,000 403,600 432,000 666,000 550,000 627,000 490,000 503,600 Note: # - Estimated July 1947 population. *"Research Project No. 6, Part I, Population Trends in San Diego I9OO Through I96O", Department of Research, San Dlego City Schools, April 16, 1948. ♦♦"Estimated Range for Population Growth in California to I96O", State Reconstruction and Reemployment Commission, November 1946. 46 Examination of the forecasts listed in Table 7 discloses a general agreement as to present (1948) and 1950 population, with exception of the forecast by the State Office of Planning and Research, which is markedly lower than the other estimates. A wide diver- gence in the figures for I960 may be noted, and again the forecast by the State Office of Planning and Research is lowest. In connection with the original forecast by the State. Reconstruction and Reemployment Commission, upon which that of the State Office of Plan- ning and Research was based, the following is quoted from the previously mentioned report of the Research Department of the San Diego City Schools: "The Commission undoubtedly made a very intensive study and was able to draw upon facts and trends which were collected from many sources. Very care- ful estimates were made of net migration and natural increase and consideration seemed to be given to the fact that the Los Angeles and San Diego areas have experienced much more rapid growth than other areas in the state. However, .... It seems apparent that the Commission did not anticipate the post war holding power of the San Diego area. This is not surprising inasmuch as most people failed to realize that the San Diego population would become stabilized at such a high figure at the end of the war. On the attached graph which compares the various estimates listed in Table I, it seems apparent that the Commission's figures were approximately 50,000 too low in 194-6. If this error is taken into consideration the .... estimates made by the Commission appear to be much more reasonable ...." Analysis of trends of migration and of natural increase is believed to offer the most rational approach to the problem of forecasting population. It is probably more reliable than any method involving projection of past rates of increase. The respective forecasts by the State Office of Planning and Research and the San Diego Oity Schools should therefore be given more consideration than the several projections by other agen- cies. As regards rates of increase, these two favored forecasts are in rather close agreement, their differences being largely due to discrepancies in estimates of present population. In this connection, the foregoing quoted criticism concerning the State Of- fice of Planning and Research forecast is believed to be sound. If this forecast be in- creased by 50,000, totals for the years 1948, 1950 and I96O are brought into fairly close agreement with figures derived by the Research Department of the San Diego City Schools. With due allowance for Inevitable errors in any population forecast for an area of rapid change such as that of San Diego, the forecast by the Research Department of the San Diego City Schools is believed to be reasonable- Accordingly, for purposes of this study, the present (1948) population of the City of San Diego is estimated at approximately 375,000, while forecasts for 1950 and I96O are 400,000 and 500,000, respectively. Water Consumotion In the ordinary circumstance, a study of past characteristics regarding water consumption of a metropolitan area affords a reasonably sound basis for predicting future resiuirements. In the case of the City of San Diego, however, it is indicated that water demands incident to wartime activities caused a considerable departure from previously ob- served relationships between population and water consumption. This has been illustrated in Table 4, and on Plate II. It may be noted that, whereas average per capita consumption was consistently less than 120 gallons per day through 1940, with a single exception at the time of the 1920 census, in 1946 the average had jumped to 128 gallons per day. A portion of the 194b increase In unit consumption of water in the City may well be attributed to deficient precipitation in that year. However, study of fragmentary data available for the war years indicates that per capita consumption of water was high through- out the period, and that the increase was largely caused by the heavier demands of military and naval installations, and of war industries. 47 In Bulletin No. 48 an amount of 120 gallons per day per capita was assumed as a basis for estimating water requirements in the metropolitan area of San Diego County, while a figure of 125 gallons per day has been used by several public agencies in arriv- ing at similar more recent estimates. In view of probable continued military use at rates in excess of those before the war, and after consideration of relatively high current over-all rates of consumption, it is believed that an average rate of consumption of 125 gallons per day per capita should be used for estimating future requirements. Utilizing the population forecasts heretofore presented, San Diego city water consumption in 1950 would then be at an average rate of 50.0 million gallons per day, or 56,000 acre-feet per year, and in i960 would be 62.5 million gallons per day, or 70,000 acre-feet per year. Ultimate Uater Requirements In view of the uncertainty accompanying forecasts of future population of the Gity of San Diego, as demonstrated by the wide divergence in forecasts for I96O listed in Table 7» it is desirable that the problem of future water requirements be studied from some other standpoint independent of population. This may be accomplished through con- sideration of duty of water over the present gross area of the City under expected con- ditions of ultimate development. In its Raymond Basin Investigation* the Division of Water Resources in 1943 made an estimate of areas for various classes of culture in the Raymond Basin area, comprising the City of Pasadena and vicinity, under conditions of ultimate development. The estimate was based on an intensive and comprehensive joint survey and study of existing culture by the Division and by the City of Pasadena. Also, estimates of seasonal duty of water were presented for each cultural classification to which water is artificially applied. These estimates were based largely on meter records of sales by the City of Pasadena, and also upon experimental and observed data from other sources. Mean seasonal duty of water over the entire Raymond Basin area averaged 1.29 acre-feet per acre. In general, the factors pertaining to ultimate cultural classifications and duty of water in the Raymond Basin area are considered applicable within reasonable limits to the gross area of the City of San Diego. However, allowance must be made for certain sig- nificant irregularities. Culture within the two areas, although varying in detail, is roughly comparable, and most variations are compensating. In Pasadena a relatively large proportion of the area is given over to estate type of culture. Seasonal duty of water for estates, however, is almost identical with that for class A residential, a more pre- dominant type in the San Diego vicinity. Whereas ultimate area given over to parks in San Diego may be proportionately greater than in Pasadena, duty of water will be relatively less than in the Raymond Basin area where parks are more intensively developed by lawns, trees and shrubs. The City of San Diego has important industrial and military establish- ments, types of culture almost totally missing in the Raymond Basin. In compensation, San Diego has proportionately a much larger area that will be vacant under ultimate cultural development. Furthermore, its limited water supply and relatively high water rates are not attractive to heavy industrial users of water. Duty of water for industrial purposes under conditions of ultimate development should not be materially different from the aver- age for municipal, domestic and irrigation uses. *"Report of Referee, City of Pasadena vs. City of Alhambra, et al. No. Pasadena C-1323", Division of Water Resources, Department of Public Works, State of California, Referee, 1943. 48 It is indicated, however, that a substantial military and naval load on the city water system, not closely related to ordinary civilian area-duty considerations, will continue indefinitely into the future. This load, which amounted to less than ten per cent of total city consumption in 1940, rose to a peak average of 15«4 million gal- lons per day throughout the calendar year 19*5 » constituting nearly 31 per cent of the City's demand. During 19'1-b the military and naval requirements declined to an average of 11.3 million gallons per day. In light of the present trend toward dispersion of mili- tary installations and personnel, it is improbable that the heavy concentrations of World War II will be repeated in the San Diego area. However, to be conservative, an allowance of 15.0 million gallons per day has been made for use by the armed forces, over and above requirements indicated by normal duty of water as applied to the gross city area. As regards average duty of water over the San Diego city area, analysis of the hydrologic factors affecting consumptive use of water leads to the conclusion that a duty of 1.29 acre-feet per acre in the Raymond Basin corresponds to approximately 1.4 acre-feet per acre in San Diego. Pasadena's average seasonal precipitation of about 22 inches is roughly twice that of San Diego, indicating a relatively higher average duty of water in the latter community. However, this difference is in part compensated for by Pasadena's higher mean maximum temperature, averaging as it does some five degrees above that of the San Diego city area. Included in this latter factor, which favors a low duty figure for San Diego, are the effects of high humidity, cooling ocean winds and summer fogs. Application of the foregoing adjusted figure for duty of 1.4 acre-feet per acre to San Diego's gross area of approximately 61,100 acres results in an estimate of 85,500 acre-feet seasonally, or 76.3 million gallons per day, for ultimate civilian water re- quirements. To this should be added the estimate of 15.0 million gallons per day for military and naval needs. If a further working allowance of ten per cent be provided as a factor of safety, the City of San Diego, under conditions of ultimate development of its present incorporated area, should have available a firm water supply of approximately 100 million gallons per day, or 112,000 acre-feet seasonally. Supplementary Water Supply Under present conditions of depleted reservoir storage the estimated safe yield of the City of San Diego's existing water supply development, including its share of Colorado River water, totals 65,500 acre-feet per season, approximately 4,500 acre-feet less than forecast water consumption for the year I96O. However, it may be reasonably an- ticipated that by I96O, with the Colorado River supply now at hand, the City will have ad- ded to its reserves in storage, and attained added yield from local surface streams, at least sufficient to meet forecast requirements. It is possible that the maximum safe yield with existing facilities, or 90,500 acre-feet seasonally, may be realized. These premises might lead to the assumption that the City need not pursue further development of its water supply, at least until I96O. Such a conclusion, however, is not conservative, nor does it take into account certain practical considerations regarding San Diego's wa- ter supply. Attention has previously been drawn to the divergence in 196O population fore- casts, and the possible wide range of error in the forecast utilized in this study as a basis for estimating I96O water consumption. While the forecast is believed at this time to give the most probable picture of water demand, its inherent errors prescribe that it be used v.lth an ample margin of safety. 49 Although it has been shown that the City of San Diego will have an assured sea- sonal water supply more than 20,000 aore-feet in eTo.ess of its probable I96O requirements, once its existing reservoirs are filled, such is not the case as regards communities in the adjacent metropolitan area. Further growth and development of these communities, upon which the future welfare and prosperity of the City is in large measure dependent, re- quires that they be furnished an adequate supplementary water supply. It Is considered probable that in their quest for water some such areas will eventually be annexed to the City, increasing its over-all requirements. Even with the occurrence of a season or seasons of plentiful runoff, there is no positive assurance that safe yield of existing conservation reservoirs will be apprec- iably built up by any given date in the future. Attainment of additional safe yield from the present local development is dependent upon adherence to a prescribed schedule of reservoir operation, with seasonal draft rigidly limited to desired safe yield, and with demands above this amount met from the Imported Colorado River supply. Unless the high degree of discipline implicit in such a program is followed, involving as it does the purchase of imported water at times when seemingly ample quantities of "free" local water are available in reserve, these reserves may well be as depleted in the year I96O as they are today. Finally, the City of San Diego has a large investment in reservoir and dam sites and in water rights in the San Dieguito River watershed. These Investments are se- cured and validated by a filing on flood waters of San Dieguito River, made by the City on May 26, 194-7, Application No. II658, which filing can only be maintained by a showing of reasonable diligence toward putting the waters to beneficial use. In view of inescap- £.ble uncertainties as to future water supply and demand of the City of San Diego, and in the Icnowledge that ultimate water requirements of the City together with the adjacent de- pendent metropolitan area will be greater than existing developed supplies, it may be to the best Interests of the City that it take steps to maintain ics investments and rights in waters of the San Dieguito River. Several possible sources of supplementary water supply are available. Chap- ter VII of this report is devoted to studies of amounts and costs of water available under several plans for further development of San Dieguito River. Similarly, Chapter IZ con- siders supplementary water obtainable through further development of San Diego River. The remaining streams of the western slope in San Diego County all present some possibi- lities for development of additional safe yield of water, as does the Tie Juena River just below the border in Mexico, and particularly its tributary, Cottonwood Creek, which rises in San Diego County north of the border. A further source of supplementary water lies in the importation of an additional Colorado River supply through construction of the pro- posed second barrel of the San Diego Aqueduct. In addition to the ordinary legal, engineering and economic factors entering in- to choice between the several possible sources for development of a supplementary water supply, the element of time should be considered. In the case of enlargement of the San Diego Aqueduct to provide additional Colorado River water, delivery can be effected im- mediately after the period required for financing, planning and construction. For pro- jects concerned with further conservation of local surface runoff, however, a substantial additional period must be allowed after construction for accumulation of sufficient stored water to provide the required safe yield. 50 I CHAPTER IV DESCRIPTION OF SAN DIEGUITO BASIN San Dieguito River, known in its middle and upper reaches as Santa Ysabel Creek, Is one of the principal streams of San Diego County. Its source on the southwest face of Volcan Mountain, an arm of the Peninsular Range, lies about ten miles northeast of the geographical center of the County. The stream flows in a general direction trend- ing south of westerly for about 53 miles, and enters the Pacific Ocean a mile north of Del Mar. It drains an area of 347 square miles, varying in width from three to fifteen miles, and approximately 41 miles in length. Drainage area aoove the old United States Geological Survey gaging station near Del Mar is 327 square miles. The basin lies be- tween the watersheds of San Luis Rey River and Escondido Creek on the north, and San Diego River and Los Penasquitos Creek on the south. Principal geographical and cultural features of the drainage system are shown on Plate lY, "Drainage Basin of San Dieguito River and Water Service Areas of Organized Agencies". Topography The Peninsular Range is a broad, irregular mountain chain roughly paralleling the coast, and extending from the San Jacinto and Santa Ana mountains to its north, southeasterly through San Diego County of which it forms the backbone, on into the penin- sula of Lower California. Within the County its eastern slopes are steep and broken, descending rapidly in canyons tributary to the desert floor of Imperial Valley in the Great Basin. Its western slopes, however, are largely typified by the area within San Dieguito Basin, where streams drop quickly from isolated mountain peaks into small high- land valleys, and then flow on gradually decreasing slopes through a series of narrow canyons and valleys lying between steep foothills. Broad rolling mesas, incised by nar- row alluvial valleys, are characteristic of the mid-portion of the Pacific slope, from whence the streams, now confined to narrow gorges, cut through a coastal belt of hills and marine terraces, finally emerging into flat valleys and entering the ocean through shallow estuaries or marshy lagoons. From Volcan Mountain, where elevations exceed 5»500 feet above sea level, Santa Ysabel Creek descends in a distance of six or seven miles to an elevation of 3,000 feet in the mountain valley of Santa Ysabel. About four miles belov; this valley, in a narrow canyon reach. Witch Creek joins the main stream, draining an area to the southeast. The partially constructed Sutherland Dam is a further tour miles downstream, below a small valley which interrupts the canyon. Streambed elevation at the dam is about 1,900 feet, and the tributary drainage area of 54 square miles averages 3,350 feet in elevation. Black Canyon, draining a mountainous area to the north, joins Santa Ysabel Creek about two miles below Sutherland Dam. Temescal Creek, which rises on the slopes of Pine and Black mountains, flows directly south through narrow Pamo Valley to join the main stream some three miles below Black Canyon. Santa Ysabel Creek then turns south for a mile through the lower end of Pamo Valley before again entering a confined, westerly bear- ing canyon. Three sites near the upstream end of this canyon have been considered for 51 Pamo Dam. Streambed elevation is approximately 85O feet, and the drainage area of 111 square miles, averaging 2,900 feet above sea level, is largely mountainous in character. Roden Canyon is the next sizable downstream tributary, entering from the north about three miles below Pamo Valley. After a further canyon reach of approximately three miles, Santa Ysabel Creek enters San Pasqual Valley. This valley averages a little more than a half mile in width and is roughly 5g miles in length, its flat bottom lands lying at elevations from 3^0 to 460 feet. Guejito Creek, draining mesa lands to the north, joins Santa Ysabel Creek in this reach, as does Santa Maria Creek, a major tributary from the southeast. The latter stream drains the broad and rolling Santa Maria Valley, a mesa- like basin with average elevation around 1,500 feet. Santa Maria Valley is oval in out- line, three to four miles in width and eight miles in length, its longer dimension paral- leling Santa Ysabel Creek to the north. Tributary to it on the east are the much smaller Santa Teresa and Ballena valleys, at elevations of about 2,300 and 2,500 feet, respec- tively. From its junction with Santa Maria Creek downstream to the ocean the main stream is generally known as San Dieguito River. From a narrows at the lower end of San Pasqual Valley the river passes into the smaller Bernardo Valley, and then enters a confined canyon cut westerly through a belt of coastal hills. About nine miles below San Pasqual Valley, at the narrowest point in a rocky gorge, the waters of the stream are impounded by Hodges Dam. Streambed elevation at the dam, a concrete, multiple-arch structure, is 200 feet. The 3O3 square miles of drainage area average 1,900 feet in elevation, and are about 40 per cent mountainous, 30 per cent foothill and 30 per cent valley in character. Lake Hodges, at spillway ele- vation of 313 feet, extends about six miles up the canyon and into Bernardo Valley, stor- ing approximately 33,600 acre-feet of water under present conditions of sedimentation. For the first five miles downstream from Hodges Dam the river continues within its gorge, and then near the junction with La Jolla Valley, which enters from the south- east, the gorge opens into San Dieguito Valley. This flat, coastal valley, about six miles long and averaging less than a mile in width, is bordered by steep hills rising sev- eral hundred feet above the valley floor. At its lower end the valley is tidal marsh, and the river enters the Pacific Ocean from a narrow channel cut through sand bars at almost flat gradient. Geology Geologic history and characteristics of San Diego County were adequately pre- sented by the United States Geological Survey in 1919.* It was stated that, while earli- er geology of the region is obscure, in late Cretaceous or early Tertiary time the area was part of a peneplain, a low-lying body of land so reduced by erosion that comparativ- ely little topographic relief remained. A period of uplift followed, accompanied by fault- ing and folding, forming high mountains along the eastern border and partially breaking up the peneplain. At that time streams began to carve the present drainage system. Succes- sive periods of depression, elevation or quiescence followed until the present time, which movements, combined with faulting and erosion, account for topography observed today. Remnants of the ancient peneplain may be noted in the characteristic flattened tops of the *Water-Supply Paper 44b, "Geology and Ground Waters of the Western Part of San Diego County, California", United States Geological Survey, 1919. 52 PLATE 12: DRAINAGE BASIN OF SAN DIEGUITO RIVER AND WATER SERVICE AREAS OF ORGANIZED AGENCIES County's mountain peaks, and in the rolling mesa-like basins, such as Esoondido, Guejito and Santa Maria valleys. Cycles of depression and elevation, accompanied by oceanic sub- mergence and emergence in the western portion of the region, have caused the coastal belt of marine terraces, the successive terraces being separated by wave-cut plains formed during quiescent periods. At one time the land was raised as much as 200 feet above pres- ent levels, and streams cut deep channels which, during subsequent subsidence, have filled to existing levels of valley floors, forming the valuable ground-water basins found inter- mittently along stream channels. The eastern, highland portion of the Pacific drainage area in San Diego County is composed largely of crystalline rocks, mostly granitic in nature, while rooks of the western, coastal section are of sedimentary origin. In San Dieguito Basin the crystal- line rocks extend westerly to a line roughly paralleling the coast and about eight miles from it. A belt of porphyritic intrusive rocks several miles In width separates the crys- tallines from the alternate beds of shale, sandstone and limestone constituting the coast- al sediments. Ground-Water Basins San Dieguito Valley is underlain with alluvium and beach deposits which form a ground-water basin more or less coinciding with the surface expression of the valley. This underground reservoir has been exploited by pumping for many years, largely from drilled wells in the upper portion of the valley. Wells in the lower valley are reported to have encountered tight formations with relatively small yield, and water of poor quality. San Pasqual Valley is likewise underlain with deep alluvium, comprising the most important ground-water basin within the San Dieguito watershed, and one that is extensive- ly pumped for irrigation purposes. This underground reservoir is the subject of more de- tailed discussion in Chapter VII. The floor of Santa Maria Valley is composed of crystalline rocks, the surface of which, to variable depths averaging about 100 feet, is decomposed into granitic residuum with appreciable capacity for ground-water storage. Dug wells with galleries are fre- quently employed for extracting water from this formation. In this valley, too, a zone of shallow alluvium follows the course of Santa Maria Creek, but its storage capacity is small. Guejito Valley is similar to Santa Maria Valley as regards underground water con- ditions, there being some storage capacity in the prevailing decomposed granite. While the highland areas of San Dieguito Basin contain no individual ground- water sources of note, the fractured or decomposed rocks constituting much of the surface, and intermittent shallow alluvium along stream channels, do in the aggregate have suffic- ient water storage capacity to influence appreciably the relationship between precipita- tion and runoff. Climate San Dieguito Basin has climatic characteristics similar to those of the remainder of San Diego County. Along the coast the climate is temperate and equable, with small daily or seasonal variation in temperature. Killing frosts are almost unknovi-n, and summer 53 County's mountain peaks, and in the rolling mesa-like basins, such as Eacondido, Guejlto and Santa Maria valleys. Cycles of depression and elevation, accompanied by oceanic sub- mergence and emergence in the western portion of the region, have caused the coastal belt of marine terraces, the successive terraces being separated by wave-cut plains formed during quiescent periods. At one time the land was raised as much as 200 feet above pres- ent levels, and streams cut deep channels which, during subsequent subsidence, have filled to existing levels of valley floors, forming the valuable ground-water basins found inter- mittently along stream channels. The eastern, highland portion of the Pacific drainage area in San Diego County is composed largely of crystalline rocks, mostly granitic in nature, while rocks of the western, coastal section are of sedimentary origin. In San Dieguito Basin the crystal- line rocks extend westerly to a line roughly paralleling the coast and about eight miles from it. A belt of porphyritic intrusive rooks several miles in width separates the crys- tallines from the alternate beds of shale, sandstone and limestone constituting the coast- al sediments. Ground-Water Basins San Dieguito Valley is underlain with alluvium and beach deposits which form a ground-water basin more or less coinciding with the surface expression of the valley. This underground reservoir has been exploited by pumping for many years, largely from drilled wells in the upper portion of the valley. Wells in the lower valley are reported to have encountered tight formations with relatively small yield, and water of poor quality. San Pasqual Valley is likewise underlain with deep alluvium, comprising the most important ground-water basin within the San Dieguito watershed, and one that is extensive- ly pumped for irrigation purposes. This underground reservoir is the subject of more de- tailed discussion in Chapter VII. The floor of Santa Maria Valley is composed of crystalline rocks, the surface of which, to variable depths averaging about 100 feet, is decomposed into granitic residuum with appreciable capacity for ground-water storage. Dug wells with galleries are fre- quently employed for extracting water from this formation. In this valley, too, a zone of shallow alluvium follows the course of Santa Maria Creek, but its storage capacity is small. Guejito Valley is similar to Santa Maria Valley as regards underground water con- ditions, there being some storage capacity in the prevailing decomposed granite. While the highland areas of San Dieguito Basin contain no individual ground- water sources of note, the fractured or decomposed rocks constituting much of the surface, and intermittent shallow alluvium along stream channels, do in the aggregate have suffic- ient water storage capacity to influence appreciably the relationship between precipita- tion and runoff. Climate San Dieguito Basin has climatic characteristics similar to those of the remainder of San Diego County. Along the coast the climate is temperate and equable, with small daily or seasonal variation in temperature. Killing frosts are almost unknown, and summer 53 temperatures rarely exceed 90° F. At Oceanside, 16 miles north of San Dleguito River, mean annual temperature is 59° F. , and the 1946 seasonal range was only 51 degrees, from a low of 32° F. to a high of 83° F. Back from the coast and at higher elevations the extremes are greater. Escondido, 15 miles inland and four miles north of Lake Hodges, at elevation of 750 feet, has a mean annual temperature of 60.8° F., but the range in 1946 was 73 degrees, from 27° F. to 100 F. At Cuyamaca in the San Diego River watershed, near the crest of the mountains ten miles south of Santa Tsabel, at elevation 4,677 feet, average yearly temperature is 53»3° F., ranging during 1946 from 17 F. to 95° F., a dif- ference of 78 degrees. The eastern slope of the mountains has a desert climate, charac- terized by Borego Valley, 22 miles east of Volcan Mountain at elevation of 550 feet, where 1946 extremes were 23° F. and 119 F., a range of 96 degrees, and where mean an- nual temperature is 70.0 F. Precipitation occurs principally in four months, from December to March, in- clusive, with practically none between May 31st and October 1st. Some snow falls annual- ly in the higher mountains, but accounts for less than ten per cent of precipitation even there, and is almost never experienced in valley areas. Occasional periods of nocturnal fog occur along the coast in summer. Precipitation increases with elevation and with distance from the coast as far as the summit of the mountains, but the eastern slopes are extremely arid. Mean annual precipitation increases from 12.87 inches at Oceanside, to 16.67 inches at Escondido, and to 39.46 inches at Cuyamaca. At Borego Valley only I.30 Inches of rain fell during the season of 1946. Over a period of years, seasons of sub- normal precipitation are the general rule, interspersed at more or less regular intervals of five or six years by single seasons of excessive rainfall. ' During the infrequent wet seasons, storms of sufficient intensity and duration to cause destructive flood runoff sometimes occur. Native Cover Natural vegetation throughout San Dieguito Basin is generally sparse. However, along watercourses there are dense stands of willow, alder, Cottonwood, sycamore, swamp cedar and live oak, and heavy underbrush. In open valley areas, with ground water at or near the surface, there are heavy growths of tules, salt grass, yerba mansa and other water-loving vegetation. Southern slopes are largely barren except for annual range grasses. Northern exposures, however, are chaparrel covered to varying degrees, and may contain scattered single trees or small groves of cedar, oak and live oak. At elevations over 4,000 feet there are stands of conifers, including pine and fir. Nowhere can the basin be described as heavily wooded, and from the standpoint of native cover it is pre- dominantly grass or brush land. Population There is relatively little urban development and, except for a small portion of the City of Escondido, no incorporated municipality within the San Dieguito vratershed. The mountainous region is very sparsely inhabited, containing only isolated ranches, small settlements at Mesa Grande, Santa Ysabel and Witch Creek, and the Mesa Grande and Santa Ysabel Indian reservations. Total population of the mountainous area is estimated at 800. The largest urban center is Ramona in Santa Maria Valley, a community of about 1,400, serving a tributary area of small farms and scattered ranches in Santa Maria, Santa Teresa and Pamo valleys, with aggregate population of approximately 350. Upper San Pas- iiual Valley contains small farms, but the lower valley is divided into a few large ranch 54 holdings. Residents number about 500, with perhaps 50 more on upper Guejito and Bach creeks. Highlands near the basin boundary north of Lake Hodges are developed by estates and small farms centered about Escondido. Population in this locality is estimated to be approximately 1,000. Permanent residents of Del Dios, a resort type subdivision given over to small cabins, on the western shore of Lake Hodges, are about 600. The Santa Fe Ranch, north of San Dieguito River and four miles from the coast, contains the highly de- veloped community center of Rancho Santa Fe, and is broken up into estate type homes and small ranches. Its population within San Dieguito Basin is about JOO. Farms and homes in San Dieguito Valley, and scattered ranches south of the river and west of Santa Maria Valley add an estimated bOO to the basin population. Although available census information does not delineate population within boun- daries of the San Dieguito watershed, it is believed to total about 5»400 at this time. Industry and Agriculture Agriculture is the predominant activity in San Dieguito Basin, and the only in- dustry of importance at present. However, the 22nd Agricultural District property at the lower end of San Dieguito Valley, near Del Mar, is the site of the San Diego County Fair and of horse racing under auspices of the Del Mar Ta-^f Club, drawing a seasonal group of tourists, workers and race followers to that vicinity. Furthermore, the Cleveland Nation- al Forest includes large portions of the upper watershed, and is developed with roads, trails and public camp grounds, so that moderate numbers of campers and picnickers are at- tracted by the scenic and recreational features of the mountain area. According to a survey made in 193*, results of which were published in Bulletin No. 4-8, a total of 6,931 acres were irrigated from San Dieguito River at that time. This figure, however, included coastal lands outside the basin boundaries, and did not include a considerable acreage north of Lake Hodges irrigated by waters of San Luis Rey Basin. It is estimated that actual irrigated area within San Dieguito Basin was about 4,500 acres in 1934. The 1940 Federal census found 15,500 irrigated acres within San Dieguito River and Escondido Creek drainage systems in 1939, an increase of 11.4 per cent over comparable 1934 data from Bulletin No. 48. By the same ratio, irrigated acreage within San Dieguito Basin would have increased to approximately 5j000 acres by 1939» From 1940 census infor- mation it may be further deduced that there were about 68O irrigated farms, and $1,000,000 invested in irrigation enterprises in San Dieguito Basin in 1939, a farm being defined as a single holding exceeding three acres, or with agricultural returns exceeding $250. Crop surveys conducted by the Division of Water Resources in 194-8 show that approximately 7,300 acres are presently irrigated within the San Dieguito watershed, of which about 3,000 acres are served by water imported from the San Luis Rey River. Principal areas of irrigation lie in and around San Dieguito and San Pasqual valleys, and to a lesser extent in Santa Maria Valley. In the highland valleys of Santa Ysabel, Santa Teresa and Ballena there is little or no irrigation, and stock raising on natural pasture is the principal agricultural pursuit. There is also dry farming of hay and grains, and small acreages produce apples, pears and grapes. Small amounts of irri- gated alfalfa, pasture and field crops are produced in upper Pamo Valley, supporting dairy herds. Remainder of this valley is used for grazing and dry farming. In Santa Maria Valley limited irrigation supplies are drawn from wells. The 55 Ramona Irrigation District serves the town of Ramona with domestic water, as well as a small irrigated area In the immediate vicinity. Irrigated crops include citrus, avocados, truck, pasture, alfalfa, field crops, grapes, berries and deciduous fruits. Larger acre- ages are cultivated to grains and hay without irrigation, but the greater part of the land in the valley is in a natural state, utilized only for grazing. Of recent years the raising of poultry, particularly turkeys, has assumed importance. San Pasqual Valley is irrigated from surface diversions from Santa Ysabel Creek, and from wells. Dairy farming is predominant in this valley, including the raising of al- falfa, pasture, and field crops, grown on the valley floor, and non- irrigated grains and hay on the adjacent rolling slopes. In the upper end of the valley, however, truck and berry farming is carried on, and there are small orchards of citrus and deciduous fruits. Bernardo Valley supports little agriculture, except in the high slopes near the drainage divide where there are relatively large acreages of citrus and avocado. Range land in large holdings is found in the hills south of Lake Hodges. The Santa Fe Irrigation District, obtaining its water by diversion from Lake Hodges, serves lands of the Santa Fe Ranch both within and without the basin. The de- velopment is estate type, but there is material agricultural endeavor, including culture of citrus and avocado fruits, walnuts, truck and dry farming of grain and hay. The Fair- banks Ranch at the upper end of San Dieguito Valley is a large single holding within the Santa Fe Irrigation District. It obtains its water supply from the District, but has a standby source in wells in the valley floor and a small reservoir to accumulate local runoff. Agricultural development is similar to that of the Santa Fe Ranch. Truck and field crops, alfalfa and berries are also raised in upper San Dieguito Valley, irrigation supplies being pumped from the underground basin, and there is some dairy farming. Lower reaches of the valley are unsulted for agriculture because of tidal marsh, but non- irrigated beans are grown on lower portions of side slopes near the coast. Transportation San Dieguito Basin is served by transportation facilities adequate for its pres- ent population and development. The Coast Highway, U. S. 101, a modern, four-lane route, connecting San Diego with all points north, crosses San Dieguito River at its mouth. Some 15 miles inland U. S. Route 395 crosses the watershed from north to south, bridging Lake Hodges at Bernardo, and likewise connecting with San Diego, and by way of Escondido with northern points. A secondary road. State Route 78, extends from Escondido to the east, serving San Pasqual, Santa Maria, Santa Teresa, Ballena and Santa Ysabel valleys. State Route 79 joins Route 78 at Santa Ysabel, and is another through highway from north to south. In addition to these principal roads, a network of county and United States Forest Service roads serves outlying areas within the basin. Main line rail service is provided along the coast by the Atchison, Topeka and Santa Fe Railway. A branch line from Oceanside through Vista terminates at Escondido, ad- jacent to San Dieguito Basin on the north, and about 15 miles from the coast. 56 CHAPTER V WATER SirPPLY OF SAN DIEGUITO BASIN Precipitation Storm Types and Occurrence Tlie most influential factors determining general occurrence of precipitation in Southern California are the characteristic presence and seasonal displacement of semi- permanent pressure areas over the North Pacific Ocean, which areas develop from general circulation of the earth's atmosphere. To a lesser degree, continental pressure areas also have effect, particularly in the southeastern, Great Basin portion of the State. Local variations in occurrence of precipitation are largely dependent upon topography. The "Pacific" or "Hawaiian" high pressure area is an anticyclone with center generally in the region between 140 -I50 west longitude and 30 -40 north latitude. In strength and area it is greatest in late summer, v.'hen its center displaces farthest to the northeast. In January it is at a minimum, with center farthest southeast. The "Aleutian" low pressure area is cyclonic in nature, and develops in the G-ulf of Alaska near the Aleu- tians, or westward toward the Asiatic coast. Since it is caused by the flov; of cold polar air from the interior of Asia, it attains greatest extent and intensity in midwinter, at which time its center displaces farthest south. In summer it migrates north, and dimin- ishes to the point where it ceases to affect California weather. Of semi-permanent contin- ental pressure areas, the "North American High Level Anticyclone", a high pressure area forming during the summer in the upper air over New Mexico and Texas, occasionally influen- ces precipitation in San Diego County during that season. Four general storm types are experienced in the San "Diego region.* Of these, the one designated "North Pacific", from the region of its origin, is the most important and dependable, bringing on the average about 43 per cent of the total precipitation, largely during December, January and February. North Pacific storms consist of successive, wave- like masses of polar air, moving in a generally southeasterly and then easterly direction. During winter, waters of the ocean are warm relative to the polar air, and the air masses in their passage absorb moisture and heat to high altitudes, although remaining cold and dry in their uppermost strata. When they reach the North American coast the air masses are therefore unstable convectively, and so laden with water vapor that, upon being lifted in crossing the continental topography, precipitation results. Centers of these storm most frequently approach the coast north of San Francisco, in which cases only gentle rainfall usually falls in the San Diego area. However, if the oceanic pressure areas displace south- ward, the storm center may pass Inland directly across Southern California, and bring in- tense precipitation to San Diego watersheds. "South Pacific" storms consist of masses of tropical air originating at 20° to 30 north latitude, on the southwestern side of the Pacific high, around the center of which they move in a generally northeasterly and easterly direction. They do not affect * "Storm Types and Resultant Precipitation in the San Diego, California, Area", Dean Blake, Monthly Weather Review, Volume 6I, August 1935- 57 California weather when the high is in its usual position. However, under certain cir- cumstances a mass of moist, warm air from this source may pass inland over Southern Cal- ifornia. Such storm move rapidly, travel singly, are irregular in occurrence, and vary widely in production from year to year. They may result in very heavy rainfall, and bring on the average about 19 per cent of San Diego County's total seasonal precipitation. South Pacific storms occur principally in February but may appear from November through March. A third storm type, designated "Interior", produces an average of about JO per cent of total precipitation in the San Diego area. Often during the passage of storms eastward across the northern border states, or through the Canadian provinces, waves or secondary storms form in the Great Basin, bringing into San Diego County warm, moist air from the southwest. Such storms may occur in any month, but are most frequent from Febru- ary through May. Their paths are erratic, and their occurrence is unusually unpredictable. The final storm type in the San Diego area is the "Mexican" or "Sonora" thunder- storm of summer and fall. Travelling northward along the western perimeter of the North American High-Level Anticyclone, masses of warm, moist air from ocean areas on either side of Mexico or Central America may overrun a cooler air mass or become cooled in passage, with resultant convective instability. Ensuing summer precipitation is extremely important over the mountains of Arizona and other southwestern states, and occasionally produces vio- lent cloudbursts over the higher elevations of San Diego County. Sonora storms, however, are responsible for only eight per cent of the County's total precipitation. Precipitation Stations and Records Until the recent advent of Colorado River water to San Diego County, local pre- cipitation has been its sole source of water supply. It follows that precipitation has been a matter of great local interest and concern, a fact accounting for the large number of rainfall measuring stations which have been established throughout the region. Bulletin No. 48 listed I38 static ii. at which precipitation records had been maintained for various periods of time. There are at present 41 active stations on the Pacific slope in San Diego County, fairly well spaced with respect to terrain and elevation. Of active stations, 37 have records of 20 years or longer, 20 have records of 40 years or longer and six have rec- ords of 50 years or longer. Oldest record is that at San Diego, which started in I85O and is unbroken to date, although observations have been made at several locations. The Valley Center record started in I872, but contains a break of eight years. Precipitation during this period has been estimated from its observed relationship with records at three nearby stations. The Escondido record, a consolidation of observations at two stations, started in 1877 and is continuous to date. Of mountain stations, longest record is that of Julian, which started in 1893, with a gap of 12 years at the turn of the century. Precipitation during these years has been estimated by relating it to the record at Valley Center. In order to study and evaluate precipitation on the San Dieguito watershed, 31 stations were chosen as representative with respect to location and elevation, and after consideration of duration and quality of their records. Fourteen of these stations are within the watershed, and the remaining 17 are adjacent to or near it. Of stations in the watershed area, seven have records of 20 years or more, and the remainder vary from three to 15 years in length. The 3I stations utilized in precipitation studies of San Dieguito Basin, some of which have included observations at several locations in the same vicinity, are shown on Plate V, "Isohyetal Map of San Dieguito Basin in San Diego County", and listed 58 PLATE "S: T.t2S- LEGEND ^ ACTIVE STREAM CAGING STATION % INACTIVE STREAM GAGING STATION O PRECIPITATION STATION 1^^ BOUNDARY OF SAN DIEGUITO RIVER DRAINAGE BASIN mmm BOUNDARY or SUB-BASIN »LINES or EQUAL SEASONAL PRECIPITATION IN INCHES ISOHYETAL MAP OF SAN DIEGUITO BASIN IN SAN DIEGO COUNTY SCALE OF MILES in Table 8 under index numbers corresponding to those utilized in Bulletin No. 48, toge- ther witli descriptions of stations and records. Those monthly precipitation records at each of the stations not published by the United States Weather Bureau, or in Bulletin No. 48, are given in Appendix E, "Monthly Precipitation Records at Stations Representative of San Dieguito Basin". TABLE 8 PRECII'ITATION STATIONS IN OR NEAR SAN DIEGDITO BASIN Index Number Bulletin No. U8 Station Location (S.B.B.&J1. ) Elevation U.S.O.S. Datum in Peet Period or Record Years of Record to July 1, IJII4.8 Source of Record Section Township Range 23 San Felipe 30 11 S. 1,. E. 3,600 1911-1921+^ 13 San Diego Coimty Water Company 28 Matagual 22 11 S. 3 E. 3,200 1911-1916 5 n n n n n 29 Volcan Mountain 2 12 S. 3 E. It, 800 191I-I92I+ 13 .. 30 32 Santa Ysabel-Warner Divide Damrons 33 11+ 11 S. 11 S. 3 E. 2 E. 3,200 2,725 1913-1916 1911-1922 1+ 11 It N n ti n 33 36 Hens haw Dam Aniago 10 26 11 S. 10 S. 2 E. 1 E. 2,702 2,715 1911-19I+8 1912-191*1+ 37 32 San Diego County Water Company and Vista Irrigation District U. S. Weather Bureau 37 38 39 Mesa Grande (Angels) Mesa Grande Santa Ysabel Ranch 21 3 20 11 S. 12 S. 12 S. 2 E. 2 E. 3 E. 3,1+50 3,350 3,000 1912-191+8" 1905-191+8" 1900-1916" 37 29 15 C. H. Angel and San Diego County Water Company U. S. Weather Bureau, E. H. Davis and Cleason Ambler San Diego County Water Company 1+0 la Santa Ysabel Store Witch Creek 21 31 12 S. 12 S. 3 E. 3 E. 2,983 2,800 1911-191+8 1909-1916 37 7 San Diego County Water Company and Santa Ysabel Store San Diego County Water Company 1+3 Hose Glen 32 12 S. 2 E. 2,300 1911-1916 S M H ti n 11 iti+ Pamo Camp 23 12 S. 1 E. 975 191i+-1923» 10 " 1+6 Escondido Ditch Head #1 Escondido Ditch Head #2 Escondido Ditch Head #3 Valley Center #1 Valley Center #2 31 10 S. 1 E. 1,755 I895-1909" 12 Escondido Mutual Water Company li6A'= 1+7 1+6 5 33 8- 7 11 S. 10 S. 11 S. 11 S. 1 E. 1 E. 1 W. 1 W. 1,770 1,850 1,1+50 1,1+70 1909-1928" 1929- 191+8" 1872-1903 1912-192I+" 16 19 31 13 It M M II City of San Diego and S, Y. Antes San Diego County Water Company Wa" Valley Center #3 5 11 S. 1 W. 1.550 1921+-191+6 22 H. W. Lake 1+9 Wohlford Lake 33 11 S. 1 W. 1,510 1926-19I+8 22 Escondido Mutual Water Company 50 Rockwood Ranch 35 12 S. 1 w. 1+30 1893-1915 22 L. D. Rockwood 51 Ramona #1 15 13 S. 1 E. 1,1+1+0 1896-1916 20 Verlaque 52 Ramona #2 15 13 S. 1 E. 1,1+1+0 1911-1931 20 Sentinel 53 Ramona #3 10 13 S. 1 E. 1,1+1+0 1927-19I+8" 12 U. S. Weather Bureau 53A'' Ramona #1+ 15 13 S. 1 B. 1,1+50- 19I+2-19I+8 6 U. C. Upjohn 55 Escondido #1 10 12 S. 2 W. 750 1918-191+8 30 U. S. Weather Bureau 56 Escondido #2 22 12 S. 2 W. 660 1891+-1935 1+2 n II II (1 56 Escondido #3 22 12 S. 2 W. 660 1887-1897 10 Escondido Land & Town Company 57 Twin Oaks 25 11 S. 3 w. 700 1875-1887 12 Major G. P. Merriam 58 Bernardo Bridge 10 13 S. 2 W. 350 1923-19I+8" 21+ City of San Diego 60 Hodges Dain 18 13 S. 2 W. 350 1919-19I+8 30 ti II n ti 61 6an Dieguito Dam 16 13 s. 3 W. 250 192U-19I+8" 21+ .... .1 62 Santa Fe Ranch 32 13 S. 3 w. 55 1912-1915 3 M. H, Crawford 63 Poway 11+ 11+ s. 2 W. 1+60 I878-1909" 26 U. S. Weather Bureau 61+ 69 Miramar San Diego 5 11 15 s. 17 S. 2 W. 3 w. 660 87 1901-191+8" 1850-191+8= 1+2 98 G. A. Riley, S. G. Erro and B, E, Hendrlx n. S. Weather Bureau 96 101 Diverting Dam Julian 11 6 liiS. 13 S. 2 E. k E. 81iO l+,222 1899-1939 1879-19I+8" la 52 La Mesa, Lemon Grove & Spring Valley Irrigation District U. S. Weather Bureau 132" Holdredge Ranch 22 11 S. 2 E. 3,1+80 1935-19I+8 11+ F, E. Holdredge Notes: a - Broken record. b - Not listed in Bulletin No. U8. c - Compilation of several records by U. S. Weather Bureau. 59 in Table 8 under index numbers corresponding to those utilized in Bulletin No. 4-8, toge- ther with descriptions of stations and records. Those monthly precipitation records at each of the stations not published by the United States Weather Bureau, or in Bulletin No. 48, are given in Appendix E, "Monthly Precipitation Records at Stations Representative of San Dieguito Basin". TABLE 8 PRECIPITATION STATIONS IN OR NEAR SAN DIEGDITO BASIN Index Number Bulletin No. U8 station Location (S.B.B.4M.) Elevation n.s.G.s. Datum in Feet Period of Record Years of Record to July 1, 15 W Source of Record Section Township Range 23 San Felipe 30 11 S. i, E. 3,600 1911-1921*" 13 San Diego Coiinty Water Company 28 natagual 22 11 S. 3 E. 3,200 1911-1916 5 ri n n n n 29 Volcan Mountain 2 12 S. 3 E. l*,800 19II-I92I* 13 " " n „ 30 32 Santa Ysabel-Warner Divide Damrona 33 11* 11 S. 11 s. 3 E. 2 E. 3,200 2,725 1913-1916 1911-1922 1* 11 n n .. n 33 36 Hen3haw Dam Amago 10 26 11 s. 10 s. 2 E. 1 E. 2,702 2,715 1911-191*8 1912-191*1* 37 32 San Diego County Water Company and Vista Irrigation District U. S, Weather Biireau 37 38 39 Mesa Grande (Angels) Mesa Grande Santa Ysabel Ranch 21 3 20 11 s. 12 S. 12 S. 2 E. 2 E. 3 E. 3,1*50 3,350 3,000 1912-19U8* 1905-191*8* 1900-1916* 37 29 15 C. H. Angel and San Diego County Water Company U. S. Weather Bureau, E. H. Davia and Cleason Ambler San Diego County Water Company Uo hi Santa Ysabel Store Witch Creek 21 31 12 S. 12 S. 3 E. 3 E. 2,963 2,800 1911-191*8 1909-1916 37 7 San Diego County Water Company and Santa Ysabel Store San Diego County Water Company 1*3 Rose Glen 32 12 S. 2 E. 2,300 1911-1916 S It n M n H 14* Pajno Camp 23 12 S. 1 E. 975 1911*-1923* 10 n 1*6 Escondido Ditch Head #1 Escondido Ditch Head #2 Escondido Ditch Head #3 Valley Center #1 Valley Center #2 31 10 S. 1 E. 1,755 1695-1909* 12 Escondido Mutual Water Company i+eAb 1*68" 1*7 1*6 5 33 8- 7 11 S. 10 S. 11 S. 11 S. 1 E. 1 E. 1 W. 1 w. 1,770 1,850 1,1*50 1,1*70 1909-1928* 1929-191*8* 1872-1903 1912-1921** 16 19 31 13 n ti ti It City of San Diego and S. Y. Antes San Diego County Water Company Wa" Valley Center #3 5 11 S. 1 w. 1,550 192l*-19l*6 22 H. W. Lake 1*9 Wohlrord Lake 33 11 S. 1 w. 1,510 1926-191*8 22 Escondido Mutual Water Company SO Rockwood Ranch 35 12 S. 1 w. 1*30 1693-191S 22 L. D. Rockwood 51 Ramona #1 15 13 S. 1 E. 1,1*1*0 1896-1916 20 Verlaque 52 Ramona #2 IS 13 s. 1 E. 1,1*1*0 1911-1931 20 Sentinel 53 Ramona #3 16 13 S. 1 E. 1.1*1*0 1927-191*8* 12 U. S. Weather Bureau 53*" Ramona #1+ 15 13 s. 1 E. 1,1*50- 191*2-191*8 6 U. C. Upjohn 55 Escondido #1 10 12 S. 2 W. 750 1918-191*8 30 U. S. Weather Bureau 56 Escondido #2 22 12 S. 2 W. 660 1691*-193S 1*2 56 Escondido #3 22 12 S. 2 W. 660 1887-1897 10 Escondido Land & Tovm Company 57 TViln Oaks 25 11 S. 3 W. 700 1875-1887 12 Major G. P. Morrlam 58 Bernardo Bridge 10 13 s. 2 W. 350 1923-191*8* 21* City of San Diego 60 Hodges Dam 18 13 S. 2 W. 350 1919-191*8 30 " " " " 61 San Dieguito Dam 16 13 S. 3 w. 250 192l*-19l*8* 21* " " " 62 Santa Pe Ranch 32 13 S. 3 W. 55 1912-1915 3 M. H. Crawford 63 Poway 11* 1I4. S. 2 W. Wo 1878-1909° 26 U. S. Weather Bureau 61* 69 Miramar San Diego 5 11 15 s. 17 S. 2 W. 3 W. 660 87 1901-191*8* 1850-191*8'= 1*2 98 G. A. Riley, S, G. Erro and B. E, Hendrii U. S, Weather Bureau 96 101 Diverting Dam Julian 11 6 lU s. 13 s. 2 E. k E. 81*0 1*,222 1699-1939 1679- 19U6* la 52 La Mesa, Lemon Grove & Spring Valley Irrigation District U. 3, Weather Bureau 132'' Holdredge Ranch 22 11 s. 2 E. 3,1*80 1935-191*6 11* P. E. Holdredge a - Broken record. b - Not listed in Bulletin No. I4.8. c - Compilation of several records by U. S, Weather Bureau. 59 The season utilized In this report in connection with precipitation is the so- called "precipitation season", from July to June, inclusive. This corresponds with the practice of the United States Weather Bureau, and is in contrast to general use herein of the "irrigation season", from October to September, inclusive. Mean Seasonal Precipitation In order to facilitate analysis of precipitation in San Dieguito Basin, the sta- tions utilized were more or less arbitrarily divided into three precipitation sub-groups, designation of which as valley, foothill and mountain is indicative of general physical characteristics of areas in which they lie. The division was made in such manner that rainfall indices of stations in each sub-group were most nearly comparable, and for any given year approximately equal. Substantially, valley precipitation stations are those within the range of elevation from sea level to 1,000 feet, foothill stations those from 1,000 to 3,000 feet, and mountain stations those above 3,000 feet In elevation. Included with each sub-group is a control station with long, reliable record of precipitation, which was used as a base for completing or extending shorter records. Thus, the valley sub-group was related to Escondido, the foothill sub-group to Valley Center, and the moun- tain sub-group to Julian. The term "rainfall index", as used herein, denotes the ratio of depth of rain- fall for any season to mean seasonal depth over a long period of years, expressed as a per- centage. Therefore, for any chosen period, the sum of indices for any particular station equals 100 times the number of years in the period. If two or more rainfall stations have closaly comparable indices for a period of mutual record, and geographical and terrain fac- tors influencing their precipitation are similar, the assumption may reasonably be made that indices for a longer period of record at one station will equal Indices for the same period at the stations not having the longer record. Estimated long-time mean seasonal precipitation at a short record station will then be 100 times its total rainfall during its seasons of record, divided by the sum of long-time period rainfall indices for the same seasons. Estimated precipitation during any year of missing record may be derived through multiplication of the long-time mean figure by the rainfall index for the year. If a true picture is to be obtained, the period used for determination of rain- fall indices Should be one of nearly normal precipitation, and should be long enough to in- clude most short-term precipitation records. The long record at San Diego, shown graphi- cally on the bar diagram of Plate VI, "Seasonal Precipitation at San Diego, I85O-5I to 194-7-48, Inclusive", offers the best opportunity for determination of normal periods. Rainfall indices based on the 95-year period, I85O-5I to 1944--43, inclusive, were computed for this station, and cumulative departures from the mean were plotted against time. The resulting graph, also shown on Plate VI, indicates that the 50-year period, 1891-92 to 1940-41, inclusive, was essentially one of normal precipitation. It was also a period which included those short-term precipitation records of significance to San Dieguito Basin, and was therefore chosen as a base period for further analysis of precipitation. In sup- port of this choice, If records of the control stations, Escondido, Valley Center and Jul- ian, are related to the San Diego record, and their rainfall over the 95-year period esti- mated, close relationship between 50 and 95-year mean seasonal rainfall at each station is shown. This is illustrated in the following tabulation: 60 PLATE m: NOTE 95 YEARS. FROM 1650 - 51 TO I944 - " I O z z o t- Q. U UJ a: o" ilh 1 Hill lllilllll 1 llilli 1 Q- leso 1 880 1890 1900 1910 1920 PRECIPITATION SEASON ENDING JUNE 30 DEPTH OF PRECIPITATION SEASONAL PRECIPITATION AT SAN DIEGO 1850-51 TO 1947-48, INCLUSIVE 61 station Estimated Mean Seasonal Precipitation in Inches 95-Year Period, 1850-51 to 1944-45, Inclusive 50-Year period, 1891-92 to 1940-41, Inclusive San Diego Escondido Valley Center Julian 10.13 16.27 19.01 30.88 10.11 16.64 19.16 31.61 AVERAGE 19.08 19.38 Having chosen a suitable base period, mean seasonal precipitation during that period was estimated for all stations of significance to San Dieguito Basin. From con- siderations heretofore discussed, each station was assigned to one of the three precipi- tation sub-groups, valley, foothill or mountain. For each sub-group, those relatively long and reliable precipitation records were related to the record at the concerned con- trol station, and their indices computed for seasons of record. These indices were consolidated, and an average index for the sub-group derived for each season of the base period. Finally, utilizing these average sub-group indices, long-time mean seasonal pre- cipitation at stations with short records was derived. Estimated average seasonal pre- cipitation during the 50-year normal period, 1891-92 to 1940-41, inclusive, at each of the stations utilized in this study, is listed in Table 9. TABLE 9 ESTIMATED MEAN SEASONAL PRECIPITATION AT STATIONS IN OR NEAR SAN DIEGUITO BASIN 50-Year Normal Period, 1891-92 to 1940-41, Inclusive Precipita- tion Sub -Group Mountain Foothill Station San Felipe Matagual Volcan Mountain Santa Ysabel- Warner Divide Damrons Mesa Grande (Angels) Mesa Grande Santa Ysabel Ranch Santa Ysabel Store Witch Creek Julian Holdredge Ranch Henshaw Dam Amago Rose Glen Mean Seasonal Precipitation in Inches of Depth 20.43 21.81 31.96 29.94 31.72 31. b2 31.59 25.77 26.45 26.40 31.61 32.66 27.86 27.44 21.96 Mean Seasonal Precipita- tion Station Precipitation in Inches Sub-Group of Depth Foothill Escondido Ditch Head 25.32 It Valley Center 19.16 If Wohlford Lake 19.90 " Ramona 18.91 It Twin Oaks 14.96 Valley Pamo Camp 18.08 ti Rockwood Ranch 14.20 If Escondido 16.64 11 Bernardo Bridge 15.69 II Hodges Dam 15.45 M San Dieguito 13.04 Dam II Santa Fe Ranch 9.49 II Poway 16.17 II Miramar 13.89 II San Diego 10.11 II Diverting Dam 16.89 62 The isohyets, or lines of equal precipitation, of Plate V were drawn up from long-time mean seasonal rainfall values for the stations, due consideration being given terrain factors and the known trend of increase in rainfall with elevation. Average sea- sonal precipitation over drainage areas above key stream gaging stations in the San Die- guito watershed is given in Table 10, and was derived by planimetering between lines of equal precipitation on the Isohyetal map. For the entire San Dieguito drainage area of 347 square miles, seasonal precipitation averaged 19-63 inches in depth, or an amount of 363,300 acre-feet. TABLE 10 ESTIMATED AVERAGE SEASONAL PRECIPITATION OVER PRINCIPAL DRAINAGE AREAS IN SAN DIEGUITO BASIN 50-Year Normal Period, I89I-92 to 1940-41, Inclusive Gaging Station Area Above Gaging Station in Square Miles Average Seasonal Precipitation over Area in Inches San Dieguito River at Lake Hodges Guejito Creek near Escondido Santa Maria Creek near Ramona Santa Ysabel Creek near Ramona Santa Ysabel Creek near Mesa Grande 303 28 bO 111 54 20.89 20.22 19.50 26.26 28.06 Precipitation Characteristics Precipitation in San Diego County occurs principally as rainfall, although snow falls in the higher mountains during most seasons. Snows are usually light, aggregating less than ten per cent of total precipitation even at the highest elevations, and melt in a short time, so that their effect on runoff is inconsequential. Nocturnal summer fogs are a material factor in maturing of agricultural crops near the coast, but have no mea- surable effect on runoff. In 1919* it was demonstrated that precipitation in western San Diego County in- creased with altitude from the ocean to the crest of the mountains, the average increase amounting to O.56 inches of precipitation for each 100-foot rise in elevation. This re- lationship was generally confirmed in 1935 in Bulletin No. 48. During the present study, mean rainfall of each principal drainage area of San Dieguito Basin was plotted against its mean elevation. A straight line drawn through these points indicated 9»3 inches of precipitation at sea level, and 38.2 inches at 5,000-foot elevation, an average increase of 0.58 inches of rainfall for each 100-foot rise in elevation. As has been shown in earlier studies, precipitation in San Diego County is marked by wide variation from season to season. Throughout the period of record, maximum seasonal totals have exceeded twice the long-time seasonal average at many stations, whereas minimum seasonal totals are only about half the mean. In many instances, precipitation during the maximum month of record is in excess of the mean seasonal total. * Water-Supply Paper 446, "Geology and Ground Waters of the Western Part cf San Diego County, California", U. S. Geological Survey, 1919. 63 Monthly distribution of precipitation at San Diego, which is Indicative of that throughout the County, is shown in Table 11. San Diego County is characterized by a short, wet, winter season and long, dry summer. In excess of 70 per cent of annual precipitation falls in four months, from December to March, inclusive, and less than ten per cent in five months, from May to September, inclusive. During the present investigation it was determined that for San Dieguito Basin 94- per cent of precipitation fell during seven months, from October to April, inclusive, and that monthly distribution closely followed the relationships established in earlier studies. TABLE 11 MONTHLY DISTRIBUTION OF PRECIPITATION AT SAN DIEGO In Per Cent of Normal Seasonal Total 95-Year Period, I85O-5I to 1944-45, Inclusive Month Average During Period Maximum During Period Minimum During Period July 0.5 13.0 August 0.9 19.7 September 1.1 26.0 October 4.7 46.7 November 9.1 49.7 December 20.6 93.4 January 15.7 76.3 February 21.0 91.3 March 15.7 79.5 April 7.1 34.2 May 3.0 23.6 June 0.6 6.9 TOTAL 100.0 Runoff Stream Gaging Stations and Records First recorded stream flow measurements in the San Dieguito watershed were made by the United States Geological Survey in January I9O6 at a station on Santa Ysabel Creek in upper San Pasgual Valley {"near Escondido"). Measurements at this location continued until 1912, when a more comprehensive stream gaging program was inaugurated by the Volcan Land and Water Company cooperatively with the same Federal agency. Eight stream gaging stations are presently active on San Dieguito River or its tributaries, and measurements have been made at 16 different sites during various periods subsequent to 1906. Location, drainage area, and duration of record at each of the 16 stations are listed in Table 12, (pace 65) under index numbers corresponding to those used in Bulletin No. 48. Locations of the stations are shown on Plate 7. 64 lABLE 1.2 STREAM CAGING STATIONS IN SAN DIEGOITO BASIN Index Number Bulletin No. 46 Stream Station Location (S.B.B.IM. ) Drainage Area in Square Miles Period of Record to September 1948 Source of Record Section Township Range ,, Santa Ysabel Creek Near Santa Ysabel lb 12 S. 5 E. 15 Aug. 1915-Sept. 1914 U. S. Geological Survey 23 Santa Ysabel Creek (At Sutherland) 21 12 S. 2 E. 54 Deo. 1912-Sept. 1928 " " " Near Mesa Grande Oct. Oct. 1928-S6pt. 1936-S8pt. 195b 1948 F. D. E. Green'' S. Geological Survey 2i Black Canyon Creek Near Mesa Grande 17 1? S. 2 E. 15 Feb. 1915-Sept. 1924 " " 25 Temesoal Creek Near Almond 23 12 S. 1 E. 52 Feb. 1915-Nov. 1915 " .. n .. Je Santa Ysabel Creek Near Ramona (At Pamo) 27 12 S. 1 E. 111 Feb. Oct. 1912-Feb. 194J-Sept. 1925 1948 " n 27 Santa Ysabel Creek Near Escondido 31 12 S. 1 E. 128 Jan. 1906-Sept. 1912 " " ^va" Santa Ysabel Creek Near San Pasjual 31 12 S. 1 E. 128 Apr. 1947-Sept. 1948 " " " " 28 East San Pasqual Ditch Near Escondido J6 12 S. 1 U. - June 1912-Sept. 1915 " " " " 29 Guejito Creek Near Escondido (At San Pasqual) 55 12 S 1 U. 28 Feb. Oct. Oct. 1915-Sept. 191b-Sept. 1919-Sept. 1915 1917 1924 F. E. Green Oct. 1921-Sept. 1922 Volcan Land & Water Cc. Oct. 1946-Sept 1948 U. S. Geological Survey 2 9A'' Guejito Creek Near San Pasqual 23 12 S. 1 W. 24 Jan. 1947-Sept 1948 " „ JO West San Pasqual Ditch Near Escondido 34 12 S. 1 y. - May 1912-Sept. 1915 " .. 31 Santa Maria Creek Near Ramona 11 13 S. 1 u. 60 Oct. 1911-Sept 1924 F. E. Green'' Nov. 1912-May 1920 0. S. Geological Survey Oct. 1919-Sept 1925 Volcan Land * Water Go. Oct. 194fa-Sept 1948 D. S- Geological Survey 32a'= San Dleguito River Near San Pasqual 1 13 S. 2 u. 250 Apr. 1947-Sept 1948 " ., 32 San Dieguito River At Bernardo 11 13 S. 2 U. 270 Apr. 1912-Jan. 1916 " " " " 33 San Dieguito River At Lake Hodges 18 1} S. 2 W. 503 Jan. 1916-Sept 1948 " .1 .. n yi San Dieguito River Near Del Mar 32 15 S. 5 U. 527 Oct. 1912-Sept. 1914 " .. a - Not published in Bulletin No. 48 b - Private records of F. E. Green, hydrographer for City of San Diego. Stream gaging stations at three proposed dam sites are of particular importance to the present investigation. The record for Sutherland dam site, Station No. 23, Santa Ysabel Creek near Hesa Grande, is continuous from December 1912 to date. It is published by the United States Geological Survey, except for the period from October 1928 to Sep- tember 1936, which is available from the City of San Diego. For Pamo dam site. Station No. 2d, Santa Ysabel Creek near Ramona, the record as published by the United States Geological Survey also starts in 1912 and runs to date, but is broken by a 20-year period of no record, from February 1923 to October 1945. Runoff for the period of missing record was estimated from its relationship with that at Suther- land, established during years of mutual record. Seasonal runoff figures at the two sta- tions were plotted against each other, and a straight line drawn through the points, using the method of least squares. It was thus indicated that Pamo runoff is about I.60 times that at Sutherland. 65 RuBoff at Hodges Dam, Station No. 35» San Dieguito River at Lake Hodges, is computed by tlie United States Geological Survey in cooperation with the City of San Diego, and the record is complete from January I916 to date. The computation Involves correction of observed change in storage for release, spill and leakage at the dam, and for evapora- tion and rainfall on the reservoir surface. For the period from April 1912 to January 1916, runoff at the dam was derived from the record for San Dieguito River at Bernardo by addition of estimated runoff between the two stations. Monthly runoff at Sutherland, Pamo and Hodges dam sites during the 3b-year per- iod of record is given in Appendix F, "Estimated or Measured Actual Monthly Runoff at Key Gaging Stations in San Dieguito Basin, 1912-13 to 1947-48, Inclusive". It should be noted that this tabulation refers to actual runoff at the three stations, rather than full natu- ral runoff. Full natural runoff is that which would occur under natural conditions, unim- paired by upstream diversions, uses and storage development, and without import of water into the basin. In many hydrologic studies full natural flow is evaluated in order to facilitate comparison between runoff of several streams, or different points on the same stream, and was evaluated and so used for San Dieguito River in Bulletin No. 48. In the present investigation, however, it was desired to determine additional yield obtainable by construction of conservation works on San Dieguito River. An evaluation of actual runoff at the several sites was essential for this purpose. In the cases of the Sutherland and Pamo stations, actual and full natural runoff are essentially equal, since only negligible diversions affect the natural regimen of the stream above them. At the Hodges station, however, actual runoff varies from full natural runoff, the difference being due to effects of irrigation diversions and use in San Pasqual Valley. In this connection, it may be ob- served that for many months, and for some entire seasons, runoff at Hodges is less than at Pamo. This apparent anomaly is explained by losses between the two stations, consisting principally of consumptive use by irrigated crops and native vegetation in San Pasqual Val- ley, including evaporation from soil and natural water surfaces. In addition to the ahove key gaging stations currently maintained in San Die- guito Basin, records are being obtained by the United States Geological Survey at five sta- tions in or adjacent to San Pasqual Valley. These stations were established or re-estab- lished cooperatively by the City of San Diego during the present investigation, for the purpose of determining surface inflow and outflow of the valley. Runoff Under Present Development and Cultural Conditions Runoff at a given site under present development and cultural conditions repre- sents the amount of water available at the site for further conservation development, with- out change in the existing regimen of upstream diversion and use. Therefore, in order to determine additional yield obtainable from further conservation works in San Dieguito Basin, actual runoff at the three principal dam sites has been evaluated in this report. Stream flow measurements in San Dieguito Basin commenced in 1906, and runoff rec- ords at Sutherland, Pamo and Hodges dam sites are available only since 1912. However, es- timates of runoff during earlier years are desirable for comparative purposes, particularly for those seasons encompassing the extreme ten-year drought from 1895 to 1903* In order to estimate runoff in the absence of discharge measurements, unsuccess- ful efforts were made to relate measured precipitation to measured runoff. The results indicated excessive influence by undetermined factors, such as rainfall intensity, storm 66 frequency, soil conditions, etc. As has been the case in prior investigations, it was concluded that the rainfall-runoff relationship in San Diego County is too erratic to be of value for estimating purposes. Estimates of seasonal full natural flow at Sutherland and Hodges dam sites were presented in Bulletin No. 48, extending back through the season of I887-88. For the per- iod from 1906 to 1912 they were based on the record for Santa Ysabel Creek near Esoondldo. By first multiplying runoff figures at this station by the ratio of its drainage area with that above Pamo dam site, runoff at the latter station was derived. There being no period of mutual record for direct comparison, the assumption that unit area-runoff relationships at the two stations were approximately equal was confirmed by comparison of each with that of the station at Henshaw Dam on San Luis Rey River. Having thus arrived at Pamo runoff for the I9O6-I912 period, Sutherland and Hodges seasonal runoff was estimated from rela- tionships with Pamo established during periods of mutual record. For the period 1887 to 1905, estimates of Sutherland and Hodges seasonal runoff were based on their relationship with runoff of San Luis Rey River at Henshaw Dam, established during the period from 1906 to 1933, of which the years from 1913 to 1933 were ones of mutual record. The Henshaw record in its early years was in itself an estimate, being based on runoff of San Luis Rey River near Pala from 1903 to 1911, on runoff of Boulder Creek at Cuyamaca Reservoir, Sweetwater River at Sweetwater Dam and San Jacinto River at Hemet Reservoir from l895 to 1902, and on runoff of Boulder Creek and Sweetwater River prior to I893. Since the Bul- letin No. 48 estimates involved full natural runoff, that for Hodges dam site included a correction for estimated irrigation diversions and uses in San Pasqual Valley. Measured runoff at Sutherland dam site was assumed equal to full natural runoff, there being only inconsequential use above the station. Further study during the present investigation disclosed no better methods of estimating runoff in San Dieguito Basin than those utilized for Bulletin No. 48. The un- fortunate dearth of early stream flow measurements, and lack of a dependable precipitation- runoff relationship, dictated further use of the roundabout methods of the earlier study. Accordingly, the several relationships between runoff at various stations, as heretofore described, were adjusted to incorporate measured runoff data from 1933 to date. Since present estimates are for actual rather than full natural runoff, correction of the Hodges record for irrigation diversions and uses in San Pasqual Valley was eliminated. Runoff at Pamo dam site during seasons without record was derived from its relationship with Suther- land runoff, as previously discussed, i.e., Pamo runoff equals 1.6 times that at Sutherland. Estimated or measured seasonal runoff at the three key stations in San Dieguito Basin for the 61-year period, I887-88 to 1947-48, inclusive, are presented in Table 13 (page 68) • Runoff at Lake Hodges is shown graphically in the bar diagram of Plate VII, "Estimated or Measured Actual Seasonal Runoff, San Dieguito River at Lake Hodges, I887-88 to I947-48, Inclusive". The season referred to in connection with runoff is the one generally utilized throughout this report, the so-called "irrigation season", from October to September, in- clusive. Although the rainfall-runoff relationship in San Dieguito Basin was found to be erratic seasonally, over a period of many years the two should conform closely. Precipita- tion being the sole source of runoff in the watershed, over a long-time period the several factors affecting the relationship between them should assume average proportions. A per- iod of long-time mean runoff, therefore, should be approximately identical with one of long-time mean precipitation. It has been demonstrated herein that the 50-year period. 67 TABLE 13 ESTIMATED OR MEASURED ACTUAL SEASONAL RUNOFF AT KEY GAGING STATIONS IN SAN DIEGUITO BASIN in Acre-Feet At At At Sutherland Pamo Hodges Season Dam Site Dam Site Dam Station Station Station No. 23 No. 26 No. 33 1887-88 8,400 13,400 16,100 1888-89 18,900 30,200 43,800 1889-90 27,800 44,500 70,400 1890-91 25,800 41,300 b4,100 1891-92 11,700 18,700 24,200 1892-93 13,200 21,100 28,100 1893-94 4,800 7,680 7,580 1894-95 55,300 88,500 163,000 1895-96 3,000 4,800 3,650 1896-97 9,800 15,700 19,300 1897-98 2,200 3,520 1,650 1898-99 1,600 2,560 850 1899-00 1,500 2,400 460 1900-01 6,000 9,600 10,400 1901-02 3,800 6,080 5,260 1902-03 5,600 8,960 9,300 1903-04 2,600 4,lb0 2,850 1904-05 14,900 23,800 32,800 1905-06 53,700 54,600 80,100 1906-07 19,100 30,900 42,900 1907-08 6,000 9,730 9,530 1906-09 25,100 40,800 58,500 1909-10 18,100 29,400 40,400 1910-11 11,900 19,000 24,100 1911-12 8,690 14,100 16,400 1912-13 4,520^ 5,780 2,070^ 1913-14 10,500 19,800 21,500° 1914-15 31,100 49,800 73,600^" 1915-16 95,200 149,000 310,000 1916-17 13,700 24,300 32,000 MEAN - 50-year norm al period. 1891-92 to 1940-41, inclusive: 15,600 25,000 40,700 At At At Sutherland Pamo Hodges Season Dam Site Dam Site Dam Station Station Station No. 23 No. 26 No. 33 1917-18 7,360 12,400 25,600 1918-19 4,810 5,870 3,430 1919-20 12,500 17,600 14,500 1920-21 3,170 4,070 1,490 1921-22 47,200 79,700 118,000 1922-23 9,560 15,800° 16,100 1923-24 2,740 4,390 4,750 1924-25 3,470 5,550 1,730 1925-26 15,300 24,500 34,300 1926-27 49,500 79,500 157,000 1927-28 3,620 5,800 8,900 1928-29 4,890 7,820 8,500 1929-30 8,010 12,800 15,500 1930-31 3,090^ 4,950 4,810 1931-32 31,300'' 50,000 71,300'' 1932-33 7,600^ 12,200 17,^00 1933-34 1,180^ 1,880 1,550 1934-35 4,640!^ 7,420 8,520 1935-36 6,330^ 10,100 11,100 1936-37 47,600 76,100 163,000 1937-38 29,600 47,400 91,600 1938-39 10,800 17,400 40,100 1939-40 6,980 11,200 18,100 1940-41 43,000 68,800 179,000 1941-42 9,120 14,600 39,600 1942-43 18,000 28,800° 46,700 1943-44 12,900 19,400 22,200 1944-45 9,630 14,400 17,800 1945-46 7,170 10,500 16,400 1946-47 2,490 3,710 1,440 1947-48 1,200 1,600 - 270® Notes: Runoff at all stations for the period I887-88 to 1911-12, Inclusive, and at Pamo dam site for the period 1922-23 to 1942-43, inclusive, estimated by the Division of Water Resources. Remaining values are from records of the United States Geo- logical Survey, except as noted: a - Observed or estimated by F. E. Green, City of San Diego. b - Runoff between Bernardo and Hodges dam site estimated by Division of Water Resources, and added to Bernardo runoff. c - Partly estimated by Division of Water Resources. d - Corrected by Division of Water Resources for rainfall on the reservoir surface as was done by United States Geological Survey for all other seasons, since construction of Hodges Dam in 1919. e - Notation by United States Geological Survey: "For months when inflow to the reservoir was small and other elements were large, negative or discordant figures of runoff may appear. To the extent that such discrepancies may be attributed to changes in reservoir capacity since the time of the rating used, or to uncertainties in the rating, quantities too small for periods of falling stage in the reservoir are compensated by quantities too large for periods of corresponding rising stage." 68 PLATE 21 o z 0. 1 200 < 2 (T O 300 z Q £«oo UJ a: fcsoo 2 TOO o o < eoo , 1 \ NOTE. 50 YE INCLUSIVE, ARS, PROM 1691-92 TO I9«0 -41 UTILIZED AS NORMAL PERIOD ^ , / ^ \ \ A \J V \ - \ \ \ \ \ A K r\ \ M \\ r \ s A fV \ / \ \ \i \/ 1910 I9l5 1920 1925 1930 -OFF SEASON ENDING SEPTEMBER 30 ACCUMULATED DEPARTURE FROM NORMAL SEASONAL RUN- OFF ^ 300 U < o §200 z i 0- 1 jII j_i_ .1 - -• ..^jIi.Iii >..! Ii.. . 1 -__a_H_i I....II1. II... 1 1 1906 iSii iyi6 1921 1926 RUN -OFF SEASON ENDING SEPTEMBER 30 RUN -OFF ACRE -FEET ESTIMATED OR MEASURED ACTUAL SEASONAL RUN-OFF SAN DIEGUITO RIVER AT LAKE HODGES 1887-88 TO 1947-48, INCLUSIVE 69 1891-92 to 1940-41, Inclusive, was normal as regards precipitation. Assuming this period also to be one of normal runoff, accumulated departure from normal runoff in San Dieguito River at Lake Hodges has been plotted for the 61 seasons of measured or estimated record. This graph is also shown on Plate VII. It will be noted that the normal period embraces two complete and well defined runoff periods or "cycles", each of 25 years' duration, the first from I89I-92 to I915-I6, and the second from 1916-17 to 1940-41, both inclusive. Comparison of early records of irrigation and other uses of water above Lake Hodges with those of the present day indicates only slight changes since the beginning of runoff measurement. Furthermore, it can be shown that consumptive use of water by native vegetation in San Pasqual Valley is equal to or greater than that by irrigated crops re- placing the natural growth. Net effect of past changes in upstream diversions on runoff at Lake Hodges has probably been relatively small. Recorded runoff in San Dieguito River at Lake Hodges throughout the period of measurement is therefore not materially different than it would have been under present development and cultural conditions. Since estt- cnates for prior seasons are based upon runoff during the period of record, they too may be considered as referred to present conditions. With regard to Sutherland and Pamo dam sites, measured runoff is approximately equal to full natural runoff, and no changes of consequence have occurred during the period of runoff measurement. Therefore, seasonal runoff at the three key gaging stations in San Dieguito Basin, throughout the 50-year nor- mal period, 1891-92 to 1940-41, inclusive, as given in Table I3, is essentially the same as under present conditions. Mean seasonal runoff under present development and cultural conditions is estimated at 15,600 acre-feet, 25,000 acre-feet and 40,700 acre-feet for Sutherland, Pamo and Hodges dam sites, respectively. Runoff Characteristics Runoff of San Dieguito River and its tributaries is similar in general character- istics to that of other streams of San Diego County. Stream flow is extremely flashy, ranging from very small or zero discharge in summer to torrential floods of destructively high peak flow but short duration, occurring during protracted winter storms. Such floods, which produce the major proportion of total runoff, are experienced only at intervals of five or six years on the average, with the result that runoff for any one year, or even a period of several years, is unpredictable within a wide range. Examination of the graph of accumulated departure from normal runoff at Lake Hodges on Plate VII discloses that, in addition to apparent complete runoff periods of 25-year duration, shorter periods averaging about five years in length have occurred with marked regularity. Characteristic pattern for these short periods is three or four sub- normal seasons followed by a single season of excessive runoff, the flood season mentioned heretofore. Only notable nonconformity as regards occurrence of the five-year period or "cycle" came during the ten-year drought from I896 to 1905, which was unbroken by an above normal season. During the 50-year normal period, 189I-92 to 1940-41, inclusive, seasonal runoff in San Dieguito River as measured or estimated has varied from 1.1 to 762 per cent of the seasonal mean. In only 12 seasons was mean runoff exceeded, yet these accounted for ap- proximately 74 per cent of total runoff during the 50-year period. Furthermore, in 28 sea- sons runoff was less than half the mean, in 19 seasons less than a quarter, and in ten sea- sons less than ten per cent of the mean. During ten years from I895-96 to 1904-05, inclu- sive, runoff averaged about 21 per cent of the long-time seasonal mean. For seven 70 consecutive seasons during this drought, average runoff was approximately 11 per cent of the 50-year average, while for three consecutive seasons it was only 2.4 per cent. On the other hand, the five seasons from 1936-37 to 1940-41, inclusive, averaged about 240 per cent of normal runoff, and were followed by two substantially normal seasons, beyond limits of the 50-year period. All but a minor portion of runoff in the San Dieguito watershed occurs during winter and spring, its distribution within each season generally following that of pre- cipitation. There is no appreciable snowpack in the mountains to support stream flow prolonged into summer, and while much of the basin is composed of absorptive materials, with considerable water-storing capacity, drainage from this source does not contribute greatly to summer and fall stream flow. Runoff from granitic residuum of mountains and foothills is rapid immediately following heavy rains, but soon subsides to the point where it is largely consumed by evaporation, and consumptive use of natural vegetation. First rains of fall or early winter are usually absorbed in making up soil moisture deficiencies, or lost to evaporation and consumptive use, and little runoff results. As the rainfall season progresses, storms increase in frequency and intensity, and soil moisture defic- iencies are met, with resultant greater runoff relative to precipitation. In an extreme flood year this trend may continue until practically all rainfall goes into immediate sur- face runoff. This condition was approximated in January 1916, as is indicated in the fol- lowing tabulation showing relationship between precipitation and resultant runoff, the assumption being made that measured precipitation at a representative location above the gaging station was uniform over the watershed area. Storm Period, 1915-16 Precipitation at Santa Ysabel Store in Inches Runoff at Sutherland Dam Site in Per Cent of Precipitation over Drainage Area Dec. 31 - Jan. 1, inclusive Jan. 4 - Jan. 6, inclusive Jan. 8 - Jan. 10, inclusive Jan. 14 - Jan. 19, inclusive Jen. 24 - Jan. 29, inclusive 1.17 0.54 2.11 15.82 10.61 1.0 3.7 2.9 50.0 Over 100.0 at this station Peak runoff month is usually February or March and rarely occurs after March. Stream flow falls off rapidly after final spring rains, and while there is small perennial flow in the mountains, and in valleys where shallow alluvium causes rising water, the con- tribution to seasonal runoff during summer and fall is very small. Only during extremely wet years does flow in the lower river continue through summer. Average monthly distribu- tion of runoff at Sutherland, Pamo and Hodges dam sites is shown in Table 14 (page 72). 71 TABLE 14 AVERAGE MONTHLY DISTRIBUTION OF RUNOFF IN SAN DIEGUITO BASIN In Per Cent of Seasonal Total 33-Year Period, 1912-13 to 1944-45, Inclusive Month At Sutherland Dam Site Station No. 23 At Pamo Dam Site Station No. 26 At Hodges Dam Station No. 33 October 0.5 0.5 0.3 November 0.9 0.9 0.3 December 5.5 3.5 5.5 January l8.0 18.0 22.3 February 26.1 26.8 28.5 March 22.3 22.1 23.1 April 14. b 14.6 12.9 May 7.8 7-5 ^'3 June 2.9 2.b 1.3 July 0.9 0.8 0.1 August 0.4 0.4 0.1 September 0.3 0.3 0.1 TOTALS 100.0 100.0 100.0 Import of Water Up to late in 1948, import of water into the San Dieguito watershed was limited to that by the Escondido Mutual Water Company, utilized for irrigation of citrus and avo- cado lands, and minor domestic demands, in an area lying around the rim of the San Die- guito Basin south of Escondido. However, Lake Hodges lies below the hydraulic grade line of the San Diego Aqueduct, which crosses above Bernardo, and the reservoir can therefore be used for regulating a portion of the Colorado River supply. On November 23, 1948, Colorado River water was first delivered to Lake Hodges from a diversion structure located on the aqueduct south of the lake. By the end of December in excess of 1,000 acre-feet had been so diverted for temporary storage and use by the City of San Diego. It is also planned to use this diversion to serve Colorado River water to the Santa Fe and San Die- guito irrigation districts. However, service areas of the City, San Dieguito Irrigation District and a part of the Santa Fe Irrigation District are outside the San Dieguito watershed, and only that part of the Colorado River supply used by the Santa Fe Irrigation District on the portion of its service area within the basin boundaries is considered an import to San Dieguito Basin. Import from San Luis Rey River The Soil Conservation Service of the United States Department of Agriculture has recently made estimates of import of San Luis Rey River water into the San Dieguito 72 watershed by the Escondido Mutual Water Company.* These estimates, presented in Table 15, are based on meter records. TABLE 15 ESTIMATED IMPORT OF WATER TO SAN DIEGUITO B.^SIN FROM SAN LUIS HEY RIVER By Escondido Mutual Water Company Season April to March, Inclusive Import in Acre-feet Per Cent of Total Water Deliveries By Company 1939-40 1944-45 1945-46 1,315 1,707 1,984 17 22 24 In 1946 the import by Escondido Mutual Water Company was utilized for irrigation of a gross area of 2,550 acres of citrus and avocado groves, and for 28O domestic services in San Dieguito Basin. This constituted 48 per cent of orchard lands under the Company, and 43 per cent of the irrigated acreage. Crop surveys by the Division of Water Resources in 1948 showed that approximately 3,000 acres within the San Dieguito watershed were ir- rigated by water imported by the Escondido Mutual Water Company. It will be noted that this import is increasing in q^uantity, as well as in relation to total watei deliveries by the Company, and that with maturing of young, groves and the present trend toward increased plantings, ultimate import to San Dieguito Basin from the San Luis Rey River may consider- ably exceed the present figure of about 2,000 acre-feet per season. In addition to evaluating the foregoing import into San Dieguito Basin, the Soil Conservation Service, in its 1947 report, made estimates of return flow from irrigation as regards this imported supply. For the ten-year period, 19}^ to 1945, inclusive, average annual return flow from the entire Escondido Mutual Water Company service area was estimat- ed at 2,300 acre-feet. During the season 1945-46 (April to March, inclusive) 24 per cent of this total amount was estimated to have occurred v;ithin San Dieguito Basin, or approxi- mately 550 acre-feet. An undetermined portion of this return flow is known to be inter- cepted on the surface or pumped from the ground water, and again applied to irrigation or domestic use. A further portion goes into consumptive use of natural vegetation, or evap- oration along drainage channels leading toward Lake Hodges. Resultant net accretion to runoff of San Dieguito River as measured at Hodges Dam is believed to be inconsequential. Import from Colorado River On the basis of 1946 assessed valuations, and assuming that deliveries in the present San Diego Aqueduct will average IO5 per cent of designed capacity, entitlement of the Santa Fe Irrigation District to the Colorado River supply, derived from its membership in the San Diego County Water Authority, is estimated at about 400 acre-feet per season. It is further estimated that the entitlement will increase to about 700 acre-feet when the second barrel of the San Diego Aqueduct is constructed and the full supply is made available * "The Water Supply of the Escondido Soil Conservation District, San Diego County, Cali- fornia", Soil Conservation Service, U. S. Department of Agriculture, February 1947. 75 for use. However, it is shown in Chapter VI of this report that average seasonal water utilization by the District under present conditions is approximately 1,000 acre-feet less than its contractual entitlement to San Dieguito Basin water developed at Lake Hodges. Until such time as its water demands increase by 1,000 acre-feet per season, the District may therefore make a choice between use of Colorado River and San Dieguito Basin water, except in times of extreme drought when the local supply may be inadequate. Average cost to the Santa Fe Irrigation District in 1946 for San Dieguito Basin water purchased from the City of San Diego was .J15.15 per acre-foot. The San Diego County Water Authority presently charges $12.00 per acre-foot for Colorado River water delivered to member agencies, in addition to taxes and payments which are independent of water use. It is reported that the City will charge the District $1.50 per acre-foot for transmission and necessary regulation of this foreign water in Lake Hodges and San Dieguito Reservoir, plus a proportionate share of transmission and evaporation losses. The present price dif- ferential between San Dieguito and Colorado River water purchases is therefore very small, and the superior quality of the local water may influence its preferred use until such time as increasing demands of the District dictate utilization of the Colorado River supply. Entitlement of the Santa Fe Irrigation District in the San Diego County Water Authority's Colorado River supply is proportional to respective assessed valuations of the two agencies. Similar considerations govern the Authority's entitlement as a member of the Metropolitan Water District of Southern California. The relative valuations of these agencies may change materially in the future. However, if it be assumed that the relation- ship will remain as in 19'l-6, the Santa Fe Irrigation District will be entitled to about 700 acre-feet of Colorado River water per season under conditions of ultimate development. On this assumption, and based upon present proportions of irrigated areas of the District in- side and outside the basin, it is estimated that approximately 57 per cent of the entitle- ment, or about 400 acre-feet per season, will be used within San Dieguito Basin under con- ditions of ultimate development, and will constitute import of Colorado River water to the basin. 74 CHAPTER VI UTILIZATION OF WATERS OF SAN DIEGUITO BASIN Of water originating within the San Dieguito watershed, a portion is used lo- cally for irrigation of agricultural crops, and for minor domestic and municipal require- ments. A larger portion is exported for irrigation, domestic and municipal uses along the coast to the north and south of San Dieguito Basin. Some of the water supports the growth of natural grasses utilized for grazing, but the relatively large remainder is lost to economic use through consumptive use by other native vegetation, evaporation from reser- voir surfaces, or outflow to the Pacific Ocean. Early Use of Water First development and use of water supplies in San Diego County was by the Spanish Mission Fathers, who early in the nineteenth century built masonry diversion dams, and ditches and conduits for irrigation and domestic purposes. There is no evidence, how- ever, of such mission activities in San Dieguito Basin, and earliest irrigation there was probably under the East San Pasqual Ditch, built in 1853, shortly after San Pasqual Valley was settled. Earliest filings to divert water from Santa Ysabel Creek in this valley are said to have been made in 1876, in connection with the above ditch. There was probably only minor irrigation outside of San Pasqual Valley prior to the land boom accompanying completion of the California Southern Railway (now the Atchison, Topeka and Santa Fe Rail- way) in 1885. That event precipitated great general interest in lands throughout the County susceptible of irrigation. The West San Pasqual Ditch was built in I887. In I888* it was reported that a total of about 400 acres was irrigated in the San Dieguito drainage area, consisting of 100 acres in San Dieguito Valley, I50 to 200 in San Pasqual Valley, 100 in Santa Ysabel Valley, and 20 to 23 along Guejito Creek. Development was confined to direct diversion from unregulated streams, largely by individual farm ditches. At this early date a project involving conservation storage at Pamo Valley was under promotion. The plan, which failed to materialize, contemplated export of water for irrigation on Linda Vista Mesa, north of San Diego, as well as on lands along the conduit. By 1912** some 1,500 acres were irrigated within the watershed, but no regula- tion or conservation improvements had been achieved. The Volcan Land and Water Company was planning construction of reservoirs in Pamo and Santa Naria valleys, together with power development, transmission conduits, and delivery of irrigation water on Linda Vista Mesa. Principal irrigated area was San Pasqual Valley, viAiere about 1,000 acres of alfalfa, vegetables and deciduous fruits were under ditches of the East San Pasqual Ditch Company and West San Pasqual Water Company, unincorporated mutual associations formed many years earlier. A fev/ wells had been drilled in this valley, and artesian flow was reported. In San Dieguito Valley I50 acres were under irrigation, with principal crop of alfalfa. Three wells were drilled there in 1909 by the Del Mar Water, Light and Pov.-er Company, for muni- cipal supply to the town of Del Mar. In the vicinity of Ramona in Santa Maria Valley, 102 acres were reported under irrigation. ♦"Irrigation in California, Part II, Southern California", William Ham. Hall, I888. **"Report of the Conservation Commission of the State of California", 1912. 75 San Dlegulto System First, and to this date the only major water supply development in San Dieguito Basin came with construction of Hodges Dam and related structures, commonly known as the "San Dieguito System", completed by the San Dieguito Mutual Water Company in 1919. Owner- ship of the system, comprised of Hodges and San Dieguito dams, reservoir lands and water rights; Pamo and Sutherland reservoir lands; Hodges Conduit, between Hodges and San Die- guito reservoirs; the "Joint Gravity" and "Lockwood Mesa-Torrey Pines" pipe lines to the San Diego city limits; and a regulating reservoir below San Dieguito Dam, was transferred from the San Dieguito Mutual Water Company to' its successor, the San Dieguito Water Com- pany, in 1925. On October 5, 1925, the City of San Diego leased the system for a 30-year period, with option tc buy for |3, 750, 000, subject to option payment of $500,000 before January 1, 1926. The ^500,000 payment, raised by bond issue, was made on December 1, 1925, on which date the City assumed possession and operation of the system. The lease contract provided for monthly payments, a portion of each payment to be applied to the purchase price, and the remainder to rental. Under the contract the City assumed responsibility for commitments of the Company to sell specified annual amounts of water to the Santa Fe and San Dieguito irrigation districts and the Del Mar Water, Light and Power Company. These three agencies are commonly termed the "Committees". Ownership of the San Dieguito System was acquired by the City of San Diego in 1939, through payment of the remainder due under the 1925 contract to the San Diego Water Supply Company, successor in interest to the San Dieguito Water Company. Water Service Agencies Three irrigation districts, one private corporation, and the City of San Diego comprise the principal water service agencies utilizing water from San Dieguito Basin. Boundaries of the City are delineated on Plate I, while service areas of the remaining organized agencies are shown on Plate IV. There are also several loosely organized mutual water companies, and three Indian reservations within the watershed, but their water re- quirements are of relatively minor importance, and will be considered generally in a later section of this chapter. San Dieguito Irrigation District This District was organized on March I8, 1922, under the California Irrigation District Act, to provide irrigation and domestic water to a gross area of about 4,000 acres along the coast between Batiquitos and San Elijo lagoons. It was consolidated with the older Cardiff Irrigation District on September 26, 1922. The area, which includes the un- incorporated communities of Leucadia, Encinitas and Cardiff, is outside the San Dieguito watershed, so that the District's water supply from Lake Hodges constitutes an export from San Dieguito Basin. Under a contract, dated January 18, 1923, the Santa Fe Land Improvement Company agreed to furnish the District a maximum of 3j200 acre-feet of water during each contract season from November to October, inclusive, delivery and measurement to be made by the Com- pany at San Dieguito Reservoir. Rates were if0.03 and ^0.075 per 100 cubic feet for irri- gation and domestic water, respectively, with minimum seasonal charges scaled up to $41,600 after I928-29. On August 24, 1925 > a contract between the San Dieguito Water Company, suc- cessor in interest to the Santa Fe Land Improvement Company, and the San Diego County Water Company provided that the latter company furnish supplementary water from San Luis Key watershed during drought periods, sufficient to assure the District a seasonal supply of 76 75 per cent of 3,200 acre-feet, this contract to terminate upon development of additional water supply in San Dieguito Basin by the San Dieguito Water Company. The City of San Diego having, on October 5, 1925, assumed obligations of the San Dieguito Water Company to supply water to the District, an agreement between District, City and Company was signed on March 12, 1926, perpetuating terms of the original 192? contract with Santa Fe Land Improvement Company. On April 2, 1935, an agreement between District, City and San Diego Water Supply Company, successor in interest to the San Die- guito Water Company, temporarily released the District from the |41,600 minimum payment, rates at the same time being increased to #0.035 and ^^0.08 per 100 cubic feet for Irriga- tion and domestic water, respectively. These changes held until back payments due, plus interest, had been paid by the District. The District, in anticipation of need for water to supplement its entitlement of 3,200 acre-feet annually from the San Dieguito System, employed A. L. Sonderegger, Con- sulting Engineer, to investigate additional sources. His report of January 1947 considered the relative advantages of developing new storage and yield on San Dieguito River below Hodges Dam, or of obtaining Colorado River water through membership in the San Diego County Water Authority. In August 1946 the District filed an application with the Division of Water Resources for 30,000 acre-feet per annum of flood waters of San Dieguito River at Santa Fe dam site, three miles below Hodges Dam, but this filing was cancelled in Septem- ber 1947 at the request of the District. Following this, the District applied for entry into the San Diego County Water Authority, and use of its Colorado River supply. The ap- plication was approved by the Authority and the Metropolitan Water District, and in Novem- ber 1948 by the electorate of the San Dieguito Irrigation District. On the basis of 194b assessed valuations, entitlement of the San Dieguito Irri- gation District to the Colorado River supply is about 5OO acre-feet per season, and will increase to about 1,000 acre-feet when the second barrel of the San Diego Aqueduct is con- structed and the full supply is made available for use. Up to the end of 1948 the Dis- trict had received no Colorado River water. The San Diego County Water Authority present- ly charges *12.00 per acre-foot for Colorado River water delivered to member agencies, in addition to taxes and payments which are Independent of water use. It is reported that the City of San Diego will charge the District il.50 per acre-foot for transmission and necessary regulation of this foreign water in the San Dieguito System, plus a proportion- ate share of transmission and evaporation losses. Initial development of the San Dieguito Irrigation District was financed by pro- ceeds of a ^400,000 bond issue. A 7E-mile, wood-stave pipe line was built from San Die- guito Reservoir to the District's lands in 1923. This line, consisting of 3b,700 feet of 26-inch and 3,630 feet of 24-inch diameter pipe, has present capacity of about seven second-feet. It was extensively repaired with Federal Works Progress Administration as- sistance in 1938 and 1939, but is still in poor condition and barely adequate for present demands. The District now proposes a ^400,000 bond issue to replace this line with a 27- inch main, approximately 40,000 feet in length, made up principally of centrifugally-spun, reinforced -concrete pipe. Capacity would be 14.5 second-feet, sufficient for ultimate ex- pected demands of the District. A complete distribution system serves district lands, including pumps and reservoirs to reach 1,526 acres of high lands above the gravity main, with average lift of about 125 feet. All services are metered, and the water is chlorin- ated. In 194b the District constructed a dam and reservoir, Lake Nunn, of 100 acre-foot 77 capacity, in the hills one mile east of Encinitas. This regulating reservoir floats on the main supply line. Its cost was about 480,000. Lands of the District are rolling and well drained. Soils, as classified by the United States Department of Agriculture, are deep, medium to fine-grained sandy loams, underlain with moderately compact sandstone. They contain no alkali, are easily worked, and in conjunction with the favorable coastal climate, are suited to production of high return irrigated crops. However, a reduction in irrigated acreage has occurred since 1936. As cultivated areas are subdivided and sold for home sites they are replaced by new plantings, but with some loss in cultivated area. Table I6 shows that irrigated lands decreased I67 acres between I936 and 1948. In the period 1936 to 19*6 irrigation service meters increased from 615 to 991, and domestic meters from 69I to 1,252, indicating reduc- tion in average size of farms, and a trend toward small homesites. Population within the District was 4,575 in 1947, nearly twice the estimated 2,400 in 1936. TABLE 16 ESTIMA.TED ACREAGE OF IRRIGATED CROPS IN SAN DIEGUITO IRRIGATION DISTRICT Crop From Annual District Report to California District Securities Commission for 1936 From 1948 Crop Survey by Division of Water Resources Citrus 8 4 Avocados 1,089 791 Truck 395 461 Flowers 150 186 Miscellaneous 46 79 TOTALS 1,688 1,521 Average cost of water to the District in 1946 was $l8.19 per acre-foot, and pump- ing costs for 535 acre-feet boosted were $6.08 per acre-foot. Consumers paid |0.04 and #0.11 per 100 cubic feet, respectively, for irrigation and domestic water, and |0.01 in ad- dition in the case of boosted water. The district tax levy amounted to $60,303, a $3.00 rate being assessed against 3,520 acres with valuation of $2,010,359. Financial condition of the San Dieguito Irrigation District has improved, after difficulties during the depression years in the 1930s. At the end of 1946 only $164,000 in bonds were outstanding, the original issue having been refinanced by the Federal Reconstruc- tion Finance Corporation in 1935. District assets totalled $427,227, and .capital surplus was $158,150. Present Water Utilization As is shown by Table 17 (page 79), purchases of water by the San Dieguito Irri- gation District during 1945-46 and 1946-47 averaged 3,270 acre-feet, an amount approxi- mately 1,000 acre-feet greater than the mean for the five preceding seasons. While these recent unprecedented demands reflect in part the growth and development of the District, the marked deficiencies in precipitation during both seasons probably had as great an 78 influence. It is believed, therefore that present water utilization by San Dieguito Ir- rigation District averages about 2,8lO acre-feet per season, the mean for the five seasons from 1942-43 to 1946-47, inclusive. TABLE 17 WATER FROM SAN DIEGUITO BASIN DELITERED TO SAN DIEGUITO IRRIGATION DISTRICT Season In Million Gallons In Acre- Feet 1926-27 418 1,281 1927-28 408 1,252 1928-29 548 1,682 1929-50 636 1,951 1930-31 747 2,292 1931-32 661 2,030 1932-33 651 1,999 1933-34 772 2,370 1934-35 665 2,040 1935-36 863 2,648 1936-37 671 2,060 Season In Million Gallons In Acre- Feet 1937-38 753 2,310 1938-39 778 2,388 1939-40 756 2,320 1940-41 632 1,940 1941-42 643 1,973 1942-43 782 2,400 1943-44 817 2,506 1944-45 856 2,625 1945-46 1,030 3,159 1946-47 1,103 3,384 It should be noted that deliveries to the District in 1946-47 were in excess of its 3,200 acre-foot entitlement from the San Dieguito System. The excess amount was pur- chased on short-term contract from the Del Mar Water, Light and Power Company, and was from San Dieguito Basin sources. Of water received by the District, about 80 per cent is used for irrigation, 15 per cent for domestic purposes, and losses average about five per cent. Ultimate Water Utilization While gross area of the San Dieguito Irrigation District is 4,020 acres, only about 3,300 acres are considered suitable for irrigated agriculture or domestic settlement under conditions of ultimate development. The District will probably then be character- ized by a mixed culture of suburban homes and small farms and groves, in continuation of the present trend. It is probable that water use will be predominantly for irrigation, as it is at this time. It was found in Bulletin No. 48 that average annual gross allowance of water for irrigation in San Diego County is about 1.3 acre-feet per acre. Application of this duty to the foregoing 3,300 acres of suitable land results in a seasonal water re- quirement of about 4,300 acre-feet. If a further working allowance of ten per cent be pro- vided as a factor of safety, the San Dieguito Irrigation District, under conditions of ul- timate development of its present service area, should have available a firm water supply of approximately 4,800 acre-feet per season. 79 If it be assumed that the relationship between assessed valuations of the San Dieguito Irrigation District, San Diego County Water Authority and Metropolitan Water District will remain as in 19^6, the San Dieguito Irrigation District will eventually receive its entitlement of about 1,000 acre-feet of Colorado River water per season. The District will continue to receive its present seasonal entitlement of 3,200 acre-feet of San Dieguito Basin water. It is considered probable that the District's requirement for supplementary water to meet its ultimate demand, in an estimated amount of bOO acre- feet per season, will be met by water from San Dieguito Basin. This follows from geo- graphical situation of the San Dieguito Irrigation District relative to the Basin and its established use of the water. Santa Fe Irrigation District This District was organized on February 26, 1923, under the California Irriga- tion District Act, and provides irrigation and domestic water to a gross area of about 10,000 acres, most of which lies on the ridge between San Elijo Creek and San Dieguito River. The area, which includes the unincorporated communities of Solana Beach and Rancho Santa Fe, is partly inside and partly outside the San Dieguito watershed. A portion of the District's water supply from Lake Hodges therefore constitutes an export from San Dieguito Basin. The District initially obtained water under a contract with the Santa Fe Land Improvement Company, dated June 16, 1924. This was superseded on November 1, 1923, when a contract was signed with the San Dieguito Water Company, successor in interest to the Santa Fe Land Improvement Company, providing for a maximum supply of 6,376 acre-feet to the District during each contract season from November to October, inclusive. The Company agreed to deliver and measure the water at a point on Hodges Conduit, at San Dieguito Res- ervoir, and at Lockwood Mesa near the coast. Prescribed rates were $0.03 and $0,075 per 100 cubic feet for irrigation and domestic water, respectively, with minimum seasonal charges scaled up to $87,933.17 after 1930-31« Also, on November 1, 1925 a contract be- tween District, San Dieguito Water Company and San Diego County Water Company provided that the latter company furnish supplementary water from San Luis Rey watershed during drought periods, sufficient to assure the District a seasonal supply of 75 per cent of 6,576 acre-feet, this contract to terminate upon development of additional water supply in San Dieguito Basin by the San Dieguito Water Company. The City of San Diego had already, on October 5, 1925, agreed to assume obliga- tions of the San Dieguito Water Company to the District. An agreement between District and City, on September 17, 1935 > reduced minimum seasonal payments to $71,000 for a five- year period, the differentials and back payments due to be paid with interest at the end of the period. Rates In the meantime were raised to $0.03525 and $0.088l25 per 100 cubic feet for irrigation and domestic water, respectively. On February 2fa, 19^5, a further agreement between District and City reduced the District's entitlement to 4,300 acre-feet per season, and set rates at JO. 035, $0,075 and $0.03 per 100 cubic feet for Irrigation, domestic and golf course irrigation water, respectively. Monthly payments to the City were established, limited to charges for water actually delivered to the District, with no minimum. On September 29, 1941, the Santa Fe Irrigation District filed an application with the Division of Water Resources, No. 10292, for four second-feet of water from San Dieguito River, to be diverted from January 1 to July 1 of each year at a point below Hodges Dam. The application did not include provision for storage facilities. In 80 addition, the District may acquire all or a portion of rights, claimed by the Douglas Fairbanks Estate, to pump 1,000 acre-feet of water annually from the San Dieguito River bed on the Fairbanks Ranch. During 1948 the District applied for entry into the San Dieguito County Water Authority, and use of its Colorado River supply. The application was approved by the Authority and the Metropolitan Water District, end in November 1948 by the electorate of the Santa Fe Irrigation District. On the basis of 1946 assessed valuations, entitlement of the Santa Fe Irriga- tion District to the Colorado River supply is about 400 acre-feet per season, and will increase to about 700 acre-feet when the second barrel of the San Diego Aqueduct is con- structed and the full supply made available for use. Up to the end of 1948 the District had received no Colorado River water. The San Diego County Water Authority presently charges ^12. 00 per acre-foot for Colorado River water delivered to member agencies, in ad- dition to taxes and payments which are independent of water use. It is reported that the City of San Diego will charge the District jl.^O per acre-foot for transmission and neces- sary regulation of this foreign water in the San Dieguito System, plus a proportionate share of transmission and evaporation losses. With proceeds from a ^700,000 bond issue, the Santa Fe Irrigation District in 1924 purchased a water distribution system from the Santa Fe Land Improvement Company. Main pipe lines on Lockwood Mesa, and joint use of the Joint Gravity Pipe Line were also secured from the San Dieguito Mutual Water Company. Costs of these properties were *459,228, and remainder of the bond proceeds were spent on the distribution system over a period of years. The present system includes approximately 30 miles of steel and concrete mains from 12 to 30 inches in diameter, and some 50 miles of laterals ranging from two to ten inches in diameter. A little more than half the water consumed is lifted an average of 80 feet by 15 booster pumps. The system contains necessary regulating tanks and reser- voirs, and all water is chlorinated. Services to consumers are completely metered. Lands of the District are generally rolling and well drained. Soils, as clas- sified by the United States Department of Agriculture, consist of loams or sandy loams near the coast, giving way to shallow adobe soils underlain with hardpan farther inland. Since development of most of the area has been to estate type units, irrigated acreage is limited by desire of property owners to retain lands in their natural state. An l8-hole golf course is maintained in connection with the somewhat exclusive community center at Rancho Santa Fe. Solana Beach is composed of beach cottages and highway commercial estab- lishments, and has enjoyed growth during and since the war. According to a district report to the California District Securities Commission, irrigated lands totalled 2,760 acres in 1936. In 1948 a crop survey conducted by the Division of Water Resources showed an irriga- ted area of 2,379 acres within the District. Included were 1,629 acres of citrus fruits, 206 acres of avocados, 208 acres of truck crops, 215 acres of irrigated pasture, 27 acres of flowers and 94 acres of miscellaneous crops. Approximately 57 per cent of the irri- gated lands, or 1,355 acres, lie within the San Dieguito Basin. The remaining 1,024 irri- gated acres are in the drainage basin of Escondido Creek, to the north. Population in- creased from about 8OO in 1936 to 2,000 in 1946. Water meters included 478 domestic and 517 irrigation services in 1946, while corresDonding figures for 1936 were 253 and 400, respectively. 81 Average cost of water to the District in 1946 was $15.15 per acre-foot, and pumping costs for 2,060 acre-feet boosted were $2.J4 per acre-foot. Consumers paid 10.03 per 100 cubic feet for irrigation water. Domestic rates per 100 cubic feet scaled from $0.15 for the first 1,000 cubic feet to $0.10 for the next 1,000, and |0.08 there- after. The district tax levy amounted to $46,2-89, a |3.20 rate being assessed against 6,751 acres with valuation of $1,446,540. Financial condition of the Santa Fe Irrigation District is now apparently sound, after some difficulties during the 19303* At the end of 1946, outstanding bonds of the District amounted to #331,500, the original issue having been refinanced by the Federal Reconstruction Finance Corporation. On the same date, district assets totalled |897»638, and capital surplus was $504,651. Present Water Utilization Inspection of Table 18, showing seasonal water deliveries to Santa Fe Irriga- tion District, reveals no significant changes in recent years. While average utilization during the past two seasons was some 350 acre-feet in excess of the mean for the past five seasons, this is in large measure accounted for by marked deficiencies in precipitation during 1945-46 and 1946-47. It is therefore believed that present water utilization by Santa Fe Irrigation District averages about 3,280 acre-feet per season, the mean for the five seasons 1942-43 to 1946-47, inclusive. TABLE 18 WATER FROM SAN DIEGUITO BASIN DELIVERED TO SANTA FE IRRIGATION DISTRICT Season In Million Gallons In Acre- Feet 1926-27 414 1,270 1927-28 555 1,704 1928-29 743 2,279 1929-30 793 2,434 1930-31 976 2,996 1931-32 852 2,616 1932-33 906 2,779 1933-34 1,208 3,709 1934-35 852 2,614 1935-56 1,131 3,470 1936-37 848 2,604 Season In Million Gallons In Acre- Feet 1937-38 936 2,872 1938-39 94 6 2,903 1939-40 947 2,907 1940-41 869 2,667 1941-42 836 2,564 1942-43 1,017 3,121 1943-44 1,047 3,212 1944-43 914 2,806 1945-46 1,220 3,746 1946-47 1,144 3,509 About 85 per cent of water received by the District is used for irrigation, six per cent for domestic purposes, and losses average about eight per cent. A very minor quantity is sold outside the district boundaries. 82 Ultimate Water Utilization Vhile gross area of the Santa Fe Irrigation District is 10,106 acres, only about 7,200 acres are considered suitable for irrigated agriculture or domestic settle- ment. Of this susceptible land, it is anticipated that not more than bO per cent, or about 4,300 acres, will actually be utilized under conditions of ultimate development. In keeping with the present trend, it is probable that the remainder will be preserved in its native state. Under these assumptions, the District will then be characterized by estate type residences and groves, and water use will be predominantly for irrigation, as it is at this time. Application of an average annual gross duty of water for irrigation of 1.3 acre-feet per acre to the foregoing 4,300 acres of suitable land results in a sea- sonal water requirement of about 5f600 acre-feet. If a further working allowance of ten per cent be provided as a factor of safety, the Santa Fe Irrigation District, under con- ditions of ultimate development of its present service area, should have available a firm water supply of approximately 6,200 acre-feet per season. If it be assumed that the relationship between assessed valuations of the Santa Fe Irrigation District, San Diego County Water Authority and Metropolitan Water District will remain as in 1946,' the Santa Fe Irrigation District will eventually receive its entitlement of about 7OO acre-feet of Colorado River water per season. The District will also receive its present seasonal entitlement of 4,300 acre-feet of San Dieguito Basin water. It is considered probable that the District's requirement for supplementary water to meet its ultimate demand, in an estimated amount of 1,200 acre-feet per season, will be met by water from San Dieguito Basin. This follows from geographical situation of the Santa Fe Irrigation District relative to the basin and its established use of the water. Ramona Irrigation District This District was organized under the California Irrigation District Act on July 27, 1925 > with principal purpose of providing a domestic water supply to the unin- corporated community of Ramona. Approximately 36 of the 66O acres within the district boundaries are irrigated at this time. Water is obtained from shallow pumping wells in sands of the channel of Santa Maria Creek, north of the townsite. At the time the District was formed, residents of Ramona depended upon many small wells to obtain a domestic supply of poor quality from shallow ground water beneath their properties. Bonds in amount of ^91>000 were voted in May I926 to purchase I65 acres of water-bearing land along Santa Maria Creek, develop a water supply thereon, and con- struct a distribution system. The purchase included a battery of eight existing wells, from 28 to 40 feet in depth, pumped by a six-inch centrifugal pump through a common suc- tion. Included also were water rights resulting from a filing for 1,000 miner ' s-inches of the waters of Santa Maria Creek, made on March 4, 1912 by W. E. Woodward, and maintained thereafter, at least in part, by surface diversion and pumping from sands of the channel. The District added four wells to the field, and constructed a circular, concrete sump of 350,000-gallon capacity. From the sump, water was boosted 160 feet to a 100,000-gallon red- wood tank situated some 1,300 feet to the southeast. The distribution system consisted of about eight miles of riveted and tubular steel pipe, ranging in diameter from three to ten inches. Water was first delivered through the system in August 1927. It is reported that, within four years of completion of the works, trouble was experienced from corroding pipe lines, probably due to inferior or defective materials in the original installation, and in 1932 the vendor furnished without cost a considerable 83 amount of pipe for replacement. During the next six years most of the original distribu- tion system was replaced, with State Emergency Relief Administration and Federal Works Progress Administration assistance, cast-iron mains being substituted for the bulk of the steel. In I938 an 800,000 gallon, circular concrete reservoir was added, and from time to time additional shallow wells have been sunk in the creek channel. Six wells were drilled in the first half of 1947, bringing the total to 27- The District's water is un- treated. All services are metered. Lands of the Ramona Irrigation District lie between 1,400 and 1,300 feet in el- evation, and, with exception of a little hillside, slope gently toward the channel of Santa Maria Creek on the north. Soils, consisting mostly of sandy loams, are shallow and lie over a subsoil of decomposed granite. Drainage is good and there is no alkali. Prom a stage station in the Eighties, Ramona grew to a town of about 750 resi- dents when the District was formed in 1925. Present development is toward residential lots, business blocks and small homesites. There were over 250 individual properties in the 460 acres assessed in 194-6, largest holding being about ten acres. Along with a popu- lation increase from about 900 in 1936 to an estimated 1,500 in 19*6, metered water ser- vices of the District have increased from 164 to 288. According to a crop survey con- ducted by the Division of Water Resources in 1948, present irrigated acreage includes 21 acres of citrus, 9 acres of deciduous fruits, 2 acres of vineyard and 4 acres of pasture, a total of 36 acres. Poultry raising is the most important agricultural pursuit in the Ramona area. Although the Ramona Irrigation District has experienced no serious financial difficulties, its small size and limited valuation have prevented desirable development of additional water supplies. At the end of 1946 the original bond issue of $91,000 was still outstanding, retirement commencing in 1947* District assets totalled $120,847, and capital surplus was |28,797. The tax levy amounted to $6,787, an $8.00 rate being asses- sed against 460 acres, with valuation of 300 acre-feet less than the record- ed historical average, or 23,900 acre-feet. 95 TABLE 23 WATER SPILLED FROM LAKE HODGES Season In Million Gallons In Acre- Feet Season In Million Gallons In Acre- Feet 1918-19 1933-34 1919-20 1934-35 1920-21 1935-36 1921-22 29,290 89,900 1936-37 42,330 129,910 1922-23 2,990 9,180 1937-38 25,080 76,970 1923-24 1938-39 9,020 27,680 1924-25 1939-40 1,500 4,600 1925-26 4,500 13,810 1940-41 51,130 156,920 192b-27 48,170 147,830 1941-42 9,540 29,280 1927-28 790 2,420 1942-43 10,580 32,470 1928-29 1943-44 2,320 7,120 1929-30 1944-45 1,420 4,360 1930-31 1945-46 740 2,270 1931-32 16,020 49,170 1946-47 1932-33 1,610 4,940 29-Year Pe riod, I918-] 9 to 1946-47, Inclusive In Million Gallons In Acre- Feet Total spi3 .1 257,030 788,830 Mean seasc nal spill 8,860 27,200 An estimate of runoff originating below Hodges Dam was made from the mean rela- tionship between runoff and average elevation of the watershed, previously established for nujnerous (leaaured streams of San Diego County. A curve showing this relationship was de- veloped during studies for Bulletin No. 48, in order to estimate runoff from minor streams. Including adjustment to the 50-year normal period 1891-92 to 1940-41, inclusive, it is found that average rate of seasonal runoff from the 23.8 square miles of tributary drainage area between Hodges Dam and the old Del Mar Gaging Station is 71»6 acre-feet per square mile. For the remaining 20.2 square miles below the station it is 68.3 acre-feet per square mile, and total runoff from the area below the dam averages about' 3,100 acre-feet per season. With the previously derived spill from Lake Hodges, average seasonal inflow to the area downstream from Hodges Dam is therefore estimated at 27,000 acre-feet under pres- ent conditions of culture. The above estimate of runoff from the area below Hodges Dam assumes average or normal conditions of consumptive use by native vegetation. For the service area of Santa Fe Irrigation District within the basin, it is assumed that the gravity irrigation supply from Lake Hodges is entirely consumed by transpiration and evaporation, with no net effect 94 on outflow to the ocean. On the floor of San Diegulto Valley, however, a considerable area is given over to irrigation from local wells, while the marsh near the coast is the source of consumptive use greater than average for native vegetation. Based upon a 1948 crop survey by the Division of Water Resources, it is estimated that the area irrigated from local underground sources is about 1,000 acres, for which net seasonal consumptive use of water is estimated at 1.3 acre-feet per acre, or a total of about 1,300 acre-feet. Approximately 200 acres of marsh land are estimated to consume 3«0 acre-feet per acre seasonally, in addition to direct precipitation, or a total of 600 acre-feet. Average seasonal outflow to the ocean is then obtained by subtracting this total increase of 1,900 acre-feet in consumptive use over that of normal native vegetation, from the pre- viously estimated total inflow to the area below Hodges Dam. Computations of outflow are shown in Table 24. It is estimated that under pres- ent conditions 25»iOO acre-feet of water on the average flow into the Pacific Ocean from San Dieguito River and are wasted each season. TABLE 24 OUTFLOW TO PACITIC OCEAN FROM SAN DIEGUITO RITER UNDER PRESENT CONDITIONS Estimated Average Seasonal Amount in Acre-Feet Historical spill from Lake Hodges Increase in present over historical diversions above Hodges Dam Spill from Lake Hodges under present conditions Runoff originating below Hodges Dam Total inflow to area below Hodges Dam Net consumptive use by irrigated crops and marsh land in San Dieguito Valley 27,200 3,300 23,900 3,100 27,000 1,900 OUTi'LOW TO PAUii'lG OUKAW 25,100 Evaluation of outflow under conditions of ultimate development involves so many variable factors and conjectures that it has not been attempted in this study. It may be observed, however, that water presently wasting into the ocean is the principal source of additional yield from this watershed, and with probable future development of additional conservation works, and increased diversions for use both within and without the basin, outflow of water to the ocean will be greatly reduced. Evaporation from Reservoirs Under the present stage of water supply development in San Dieguito Basin, sig- nificant water losses are experienced through evaporation from Lake Hodges, and to a much smaller extent from San Dieguito Reservoir. Remaining reservoirs of the basin have an ag- gregate storage capacity of less than 500 acre-feet, and their losses through evaporation are so minor as to be of little consequence v.'hen considering water supply of the basin as a whole. 95 Gross evaporation from Lake Hodges, baaed upon floating evaporation pan measure- ments, has been recorded since the reservoir was placed in operation in 1919, and, as is shown in Table 25, has averaged 5,170 acre-feet per season. It has previously been noted that the 29-year period, 1918-19 to 1946-47, inclusive, since construction of Hodges Dam, was one of approximately normal runoff in San Dieguito River. Average seasonal evapora- tion from the reservoir during that period may be considered about normal for the long- time runoff period. TABLE 25 GROSS EVAPORATION FRON LAKE HODGES I In In Season Million Acre- Gallons Feet 1918-19 204* 626* 1919-20 912 2,800 1920-21 978 3,000 1921-22 1,876 5,7bO 1922-23 2,416 7,410 1923-24 2,095 b,430 1924-25 1,573 4,830 1925-26 1,768 5,430 192b-27 1,904 5,840 1927-28 1,892 5,810 1928-29 2,033 5,240 1929-30 1,902 5,840 1930-31 1,776 5,450 1931-32 2,026 6,220 1932-35 1,825 5,600 Season 1933-34 1934-35 1935-36 1936-37 1937-38 1938-39 1959-40 1940-41 1941-42 1942-43 1943-44 1944-45 1945-46 1946-47 In Million Gallons 1,732 1,281 1,189 1,762 1,856 1,809 1,828 2,110 1,766 1,755 1,779 1,668 1,866 1,268 29-Year Period, I918-I9 to 194o-47, Inclusive Average seasonal evaporation In Million Gallons 1,684 In Acre- Feet 5,320 3,930 3,650 5,410 5,700 5,550 5,610 6,480 5,420 5,390 5,460 5,120 5,730 3,890 In Acre- Feet 5,170 Note: * - Partial season. Diversion and use of water from the San Dieguito System has increased over the period since 1919, so that the average amount of water stored in Lake Hodges would be less under present conditions than the historical average, and evaporation losses would be cor- respondingly reduced. However, even with the reservoir at high stages, a reduction of 3,300 acre-feet in storage, the full amount of increased seasonal use under present condi- tions over the historical average, would reduce the water surface area only about 90 acres. Gross seasonal evaporation at Lake Hodges is about five feet of water depth, so it may be 56 J roughly estimated that average seasonal evaporation under present conditions would be ap- proximately 450 acre-feet less than the historical average, or about 4,720 acre-feet. Storage in San Dieguito Reservoir, used exclusively for regulation of San Die- guito Basin water, until recently was maintained at less than designed capacity in the Interest of safety, and evaporation losses consequently averaged only about 200 acre-feet seasonally. With repairs to the dam completed in early 1948, storage has been increased and average seasonal evaporation will reach a figure of about 300 acre-feet, an amount as- sumed to be the average under present conditions. Total average seasonal evaporation losses from San Dieguito Basin reservoirs are therefore estimated at approximately 5,000 acre-feet, or about 1,630 million gallons, under present conditions. It Is reasonable to believe that additional works to conserve the large incre- ment of runoff in San Dieguito River now wasting into the ocean will be constructed in the future. The construction will involve new dams, or enlargement or completion of existing structures, to provide additional water storage capacity. With this increased capacity, and increase in average area of water surface, will come increased losses from evaporation. The magnitude of such losses under conditions of ultimate development can only be deter- mined by complex reservoir studies based upon definite plans for the new works. The matter is further considered in Chapter VII, wherein a comparison is made between several plans for ultimate conservation development of the basin. SiimTTiary of Water Utilization Those estimates as to present and expected future disposition of the waters of San Dieguito Basin, which were developed and presented in preceding sections of this chap- ter, are summarized in Table 26. TABLE 26 ESTIMATED AVERAGE SEASONAL DTILIZATION OF WATERS OF SAN DXEGUITO BASIN in Acre-Feet » Under Present Conditions Under Ultijnate Development By Uater Service Agencies San Dieguito Irrigation District® 2,810 3,800 Santa Fe Irrigation District^ 3,280 5,500 Ramona Irrigation District 240 700 Del Mar Uater, Light and Power Company 250 1,100 City of San Diego® 3,070 19,000 Subtotals 9.650 30,100 By Other Water Users 3,900 3,900 TOTAL UATER UTILIZATION 13,550 34,000 Exported Water (included in above) 7,5*0 26,200 Uater Losses Under Present Cond itlons Consumptive use by native vegetation 319 ,700 Outflow to ocean 25 100 Evaporation from reservoirs 5 000 TOTAL 3*9 800 Notes; a - Excludes water supplied from sources outside San Dieguito Basin, b - Includes water consumed by natural grasses utilized for grazing. 97 Demands upon water sources within San Dieguito Basin, predominantly for export and use outside the watershed, have increased until they now approach and in some partic- ular cases exceed the developed dependable supply. While no large future increase in utilization of this water within the basin is foreseen, continued growth is probable in the service area of present exporters, and their ultimate water requirements should be much greater than at this time. The pressure of future demands will probably be suffic- ient to assure eventual full development of all San Dieguito Basin water sources. At such time, it is estimated that total developed safe yield from the basin by all users will amount to an estimated 3''-fOOO acre-feet seasonally. Of this total amount, it is be- lieved that the City of San Diego will utilize about 19,000 acre-feet seasonally, after export to its service area. Estimates presented in this chapter have been based upon the conception of safe yield, which implies in this instance a dependable water supply with no deficiencies dur- ing the extreme drought period from I896 to 1905, inclusive. An additional yield of a secondary nature may be obtained, however, during certain series of years when runoff is above normal. Such secondary yield is dependent entirely upon the vagaries of the weather, and should not be considered in planning to meet the rigid domestic, municipal and irriga- tion water requirements of an area with characteristics such as those of the San Diego region. i i 98 CHAPTER VII CONSERVATION WORKS IN SAN DIEGUITO BASIN Commencing along with the activity and speculation in irrigation enterprises following completion of the railroad to San Diego County in the Eighties, a number of plans have been advanced for more or less complete exploitation of the relatively large water resources of San Dieguito Basin. However, until construction of Hodges Dam, started in 1917 and completed in 1919 by the San Dieguito Mutual Water Company, all of the propos- als had failed. Subsequent to the Hodges project, construction of a dam was started in 1927 at the Sutherland site by the City of San Diego, but after a series of misadventures this conservation project was abandoned before completion. Existing Development Major water supply development in San Dieguito Basin is limited to Hodges Dam and related diversion, regulation and transmission works, which are presently owned and operated by the City of San Diego. Hodges Dam, a concrete multiple-arch structure, has a crest length of 729 feet, is I30 feet in height, and has an overflow spillway 3^3 feet long at the right end of the dam. The multiple-arch portion is ^8a feet long, consisting of 24 reinforced-concrete arches, with spans of 24 feet from center to center of plain con- crete buttresses. The left I6 arches, comprising a length of 384 feet, have a crest ele- vation of 330 feet. The remaining 200 feet of dam is capped with a curved concrete slab, to form an overflow weir crest at elevation 315 feet. Remainder of the spillway was made by excavating the right abutment, and constructing a concrete spillway crest and apron. The spillway approach was deepened and improved in 1930, and a 50-foot concrete apron, 145 feet in length, was placed at its right end in 1936« Estimated capacity of the spillway is 90,000 second-feet. The dam was reinforced in 1936 by constructing reinforced-concrete web bracing in vertical planes between buttresses of alternate bays. Original construc- tion cost was about $350,000, but spillway improvements in 1930, and strengthening of but- tresses in 1936, both of which jobs were at the insistence of the State Engineer in inter- ests of public safety, added materially to capital costs. Reservoir capacity was 37,699 acre-feet when built, but silting from a watershed area of 303 sc^uare miles has reduced the storage to approximately 33»600 acre-feet. Water is released from Lake Hodges through six openings at 10-foot vertical intervals in the upstream face of the dam. The 20-inch openings, protected by fixed screens, are connected with l6-inch, cast-iron, vertical pipe risers to 20-inch gate valves mounted on a 36-inch manifold. This in turn connects with Hodges (or Carroll) Conduit, 4.b5 miles in length, leading to San Dieguito Reservoir on San Elijo Creek, a tributary of Escondido Creek. Most of this conduit is open concrete- lined channel, but just below Hodges Dam there is a 300-foot length of 36-inch diameter, wood-stave pipe, and several ravines are crossed by concrete siphons, or metal flumes on timber trestles. Present conduit capacity is 17 second-feet or 11 million gallons per day. Diversions for irrigation and domestic use are made at three points on Hodges Conduit. San Dieguito Dam, built in I918 by the San Dieguito Mutual Water Company, is likewise of concrete multiple-arch construction. Its height is 51 feet, and crest length 650 feet, and it is provided with a siphon spillway of 1,150 second-foot capacity. There 99 is one foot of freeboard above the spillway lip at elevation 2^0 feet, at which elevation storage capacity is 1,128 acre-feet. Drainage area above the dam is only 1.2 square miles, and the reservoir is used only for regulation of the Hodges diversion. In the in- terest of safety and under order of the State Engineer, storage was maintained for some time at less than designed capacity. However, in early 1948 the City of San Diego rein- forced the structure in order to utilize full capacity of the reservoir. The reinforce- ment included guniting the upstream faces of the arches, adding pre-stressed tensile steel to the arch groins, and constructing lateral counterforts on each side of the but- tresses. Water is drawn from San Dieguito Reservoir by pipes at four points in the dam, deliveries being made through pipe transmission lines to the San Dieguito and Santa Fe irrigation districts, the Del Mar Water, Light and Power Company and to the City of San Diego. Only one of the conduits from San Dieguito Reservoir Is actually included in the San Dieguito System and owned by the City of San Diego, that terminating in the City's La Jolla service area. Remaining conduits are owned and maintained by the San Dieguito and Santa Fe irrigation districts, respectively. First section of the city-owned line, known as the "Joint Gravity Pipe Line", is 8,9 miles in length, and leads southwesterly to Lockwood Mesa Reservoir, with storage capacity of 378,000 gallons, at elevation 205 feet. The line is constructed of 24-, 26- and 27-inch diameter, reinforced-concrete pipe and has capacity of 3.9 million gallons per day, or 6.0 second-feet. The second conduit section, the "Lockwood Mesa-Torrey Pines Pipe Line", extends southerly for 5*3 miles to the Torrey Pines Filter Plant, at elevation 10 feet. The line is composed of varying lengths of l8-inch diameter, wood-stave, steel and cast-iron pipe, and 20-inch diameter concrete and steel pipe, and has capacity of 3.0 million gallons per day, or 4.6 second-feet. From the filter, water is pumped to an aerator at elevation 437 feet, from which It passes to Tor- rey Pines Reservoir, a concrete-lined basin with storage capacity of 3«5 million gallons, at elevation 431 feet. From the reservoir an l8-inch diameter, concrete pipe leads south- erly about 26,000 feet to the La Jolla service area. It has been estimated that during the most critical drought period of record, from 1895-96 to 1904-05, inclusive, safe seasonal yield from present water supply develop- ment in San Dieguito Basin would have been 6,700 acre-feet. During the less critical per- iod, from 1916-17 to 1935-36, inclusive, used hereinafter in this chapter for purposes of comparing several proposed plans for further conservation works, the existing development in San Dieguito Basin would have had a "I917-36 firm" seasonal yield of 11,400 acre-feet. This terminology is used in connection with sustained yield during this later period to differentiate it from "safe" yield during the I896-I905 drought. Actual average seasonal draft from the San Dieguito System during the five-year period 1942-43 to 1946-47, inclusive, was approximately 5,410 acre-feet. Of this seasonal amount, about 3,070 acre-feet on the average was delivered to the City'of San Diego, 3,280 acre-feet to the Santa Fe Irrigation District, 2,8lO acre-feet to the San Dieguito Irriga- tion District, and 250 acre-feet to the Del Mar Water, Light and Power Company. These mean quantities are believed to represent approximately the average seasonal drafts of the respective agencies from the waters of San Dieguito Basin under present conditions. As has heretofore been stated, the City of San Diego is contractually committed to furnish the above three agencies, the so-called "Committees", a total amount of water not to ex- ceed 8,224 acre-feet per season. This amount, plus the present draft of approximately 3,100 acre-feet by the City, closely approaches 1917-36 firm yield of the existing develop- ment, and greatly exceeds safe yield during the period from 1895-96 to 1904-05. 100 J Complete Conservation Development Ttie objective of any plan for complete or ultimate development of water sources in San Dieguito Basin should be to conserve as large a percentage as possible of runoff now wasting into the ocean, as well as to effect any practicable salvage of water now wasted through consumptive use by natural vegetation in the watershed. It was shown in Chapter VI that these two major sources of present loss account for many times the water put to economic use. As regards further conservation of surface runoff, one or more storage reser- voirs with aggregate capacity of five to seven times the average seasonal runoff would be required for maximum conservation. This is illustrated by the fact that 33 per cent of total runoff at Hodges Dam during the 22-year period 1914-15 to 1935-56, inclusive, oc- curred in a single season, while combined runoff during the five largest seasons was near- ly 78 per cent of the 22-year total. Yield studies show that 70 per cent of runoff mea- sured at Hodges Dam in this period could have been conserved for beneficial use if suf- ficient storage capacity had been available. About 30 per cent of the runoff would have been lost by evaporation from reservoir surfaces. Complete development of surface runoff in San Dieguito Basin would require approximately 340,000 acre-feet of storage capacity. With this capacity, a I917-36 firm yield of approximately 30,000 acre-feet seasonally could have been realized, and a safe yield of approximately 28,000 acre-feet during the seasons from 1894-95 to 1913-14, inclusive, which included the most critical drought per- iod of record. There are three principal reservoir sites on San Dieguito River and its tribu- taries, those designated as Hodges, Pamo and Sutherland, relative locations of which are shown on Plate Till, "Conservation Works for Development of San Dieguito River". Inas- much as approximately 40 per cent of total runoff in San Dieguito Basin originates below the Pamo site, any plan to attain maximum conservation must include provision for increas- ing capacity of the existing Lake Hodges. Underground reservoirs in San Dieguito Basin, of sufficient capacity to warrant consideration in connection with possible use for seasonal and cyclic storage, are limited to those underlying San Dieguito and San Pasqual valleys. Use of the former by the City of San Diego is believed to be precluded because of its unfavorable geographic position and the possibility of salt water invasion if the water table is appreciably lowered. As regards San Pasqual Valley, such use of the ground-water basin is possible. Likewise, salvage by the City of water now wasted through consumptive use by natural vegetation would probably be limited to that occurring in San Pasqual Valley. This salvage might be effected through a system of pumping from the ground water sufficient to lower the water table below the root zone of native vegetation. Yield from Surface Reservoirs In the San Diego region, where water is so scarce and vital a commodity, the relative amounts of water to be realized from one or more of several proposed conservation works are of primary importance in comparing respective merits of the projects, and under certain circumstances may outweigh economic considerations. As regards surface reser- voirs, principal factors entering into determination of yield, in order of their usual im- portance, are runoff, evaporation and draft. Runoff In San Dieguito Basin has been the subject of detailed discussion in Chapter V, and recorded or estimated monthly values of actual runoff at Hodges, Pamo and Sutherland dam sites, covering the period from 1912-13 101 to 1946-47, inclusive, are listed in Appendix F. For the yield studies the basic assump- tion vras made that past runoff experience will, on the average, be repeated in the future. The remaining factors affecting yield of reservoirs in San Dieguito Basin, evaporation and draft, are discussed in later sections of this chapter. Runoff Periods The term "safe yield", as used in this report, refers to the amount of water which could have been supplied seasonally from a given source, without deficiency, throughout the critical period of dry years from 1895-96 to 1904-05, inclusive. However, in drawing comparisons between several reservoirs to develop maximum yield in San Die- guito Basin, xt was desired to utilize the most reliable runoff information available. Although stream flow measurements were made on San Dieguito River at Bernardo from 1906 to 1912, it was not until 1912 that the United States Geological Survey began the comprehen- sive program of cooperative stream gaging and records on the river and its tributaries that has continued to the present date. While records at different stations are not con- tinuous since 1912, runoff relationships established during periods of record, vrhen com- bined with observations by the City of San Diego and others, provide sufficient basis for estimating monthly runoff during periods of missing record with acceptable accuracy for evaluating reservoir yield. In the period since the beginning of reliable runoff record, an extended drought occurred during the 20 years from 1916-17 to 1935-36, inclusive. This critical period was preceded by two wet seasons, that of 1914-15 which was above normal, and the record flood season of I915-I6 in which runoff at Lake Hodges was more than 750 per cent of the long- time normal. The occurrence of these wet seasons assured that reservoirs would have been filled at the onset of the ensuing dry period, and imposed a definite objective on the yield studies; that is, the complete conservation of I915-I6 runoff. Basic yield studies of this report, therefore, were made to cover the period subsecjuent to 1914. Yield of the different reservoirs was fixed by the critical period I916-I7 to 1935-36, inclusive, and is herein referred to as "I917-36 firm yield". An exception is the existing Hodges Reser- voir, which had a critical period from I917-I8 through 1920-21. The period studied began with the season of 1914-15, and yield as determined for the above critical periods held true through the 1944-45 season, the termination of studies. In order to show relative severity of the critical period I895-96 to 1904-05, in- clusive, the most extreme of record, with that of the twenty years following I915-I6, semi- seasonal yield studies of the earlier period were made, based on estimated runoff. These less reliable runoff data for early years indicated that safe yield from the existing Lake Hodges during the drought from I896 through I905 would have been 59 per cent of I917-36 firm yield. In the case of an enlarged Lake Hodges for complete conservation development of the basin, the corresponding ratio would have been 95 per cent. For other reservoirs, or combinations of reservoirs studied, the percentage varied between these extremes, depen- dent upon the amount and disposition of storage and method of reservoir operation. Evaporation Evaporation from reservoir surfaces in the San Diego region is a subject of pri- mary importance in yield studies. For proposed larger capacity reservoirs at Lake Hodges the mean seasonal net evaporation loss was found to be over 40 per cent of corresponding 1917-36 firm seasonal yield. Net evaporation from a reservoir is the actual or gross evap- oration less the precipitation on the reservoir surface. 102 PLATE •VTTT T 1 1 s. T.I2S. EXISTING LAKE HODGES CONSERVATION WORKS FOR DEVELOPMENT OF SAN DIEGUITO RIVER SCALE OF UILE5 1R2E PLATE 2ni CONSERVATION WORKS FOR DEVELOPMENT OF SAN DIEGUITO RIVER Evaporation studies made in connection with Bulletin No. 48 Indicated that the depth of evaporation from a reservoir surface increases with distance from the coast and with rise in elevation. It is apparent that the Pacific Ocean moderates the coastal cli- mate by reducing summer temperatures and raising the humidity. Toward the interior, sum- mer temperatures become higher end the humidity lower, while reservoirs near the crest of the mountains, such as Morena and Cuyamaca, are exposed to dry hot winds from the desert which further Increase the rate of evaporation. In estimating evaporation losses from proposed reservoirs in San Dieguito Basin, use was made of records of observed gross evaporation at Hodges, Morena, Barrett, Henshaw and Cuyamaca reservoirs, data for which are summarized in Table 27. These records are based upon measurements by floating and land evaporation pans, as indicated in the table, to which measurements suitable coefficients have been applied in order to evaluate actual evaporation from reservoir surfaces. For Lake Hodges a record of monthly evaporation since February 1919, when the reservoir was placed in operation, was obtained from the City of San Diego. Records for Morena and Barrett were likewise originally obtained from the City, and the Cuyamaca record was furnished by the La Mesa, Lemon Grove and Spring Valley Irrigation District. The record of evaporation at Lake Henshaw was obtained from the San Diego County Water Company. GROSS EVAPOHATIOH PROM RKSERVOIRS IN SAN DIEOO COUNTY Month Measured Estimated 1 Lake Hodges Lake Henshaw Barrett Reservoir Horena Reservoir Cuyamaca Reservoir Pamo Dam Site Sutherland Dam Site Percent of Mean Seasonal Mean Depth in Inches Percent of Mean Seasonal Mean Depth in Inches Percent of Hean Seasonal Hean Depth in Inches Percent of Mean Seasonal Hean Depth in Inches Percent of Mean Seasonal Hean Depth in Inches Percent of Hean Seasonal Hean Depth in Inches Percent of Mean Seasonal Hean Depth in Inches October 8.31 1*.76 8.32 5.66 8.96 5.90 8.60 5.78 9.07 6.60 8.63 5.52 8.63 5.78 November 6.1tO 3.67 5.1*8 3.73 5.82 3.83 5.98 1*.02 ,6.12 l*.l*5 5.76 3.69 5.76 3.86 December U.71 2.70 3.1*0 2.31 3.98 2.62 1*.1*2 2.97 !*.00 2.91 3.93 2.52 3.93 2.63 January l*.lli 2.37 2.98 2.03 3.57 2.35 3.51 2.36 3.85 2.80 3.35 2.11+ 3.35 2.21* February 3.68 2.22 3.20 2.18 3.1*9 2.30 3.21 2.16 5.01* 3.67 3.30 2.11 3.30 2.21 Harch 6.09 3.1*9 5.16 3.51 5.1*1* 3.58 1*.98 3.35 6.38 1*.6I* 5.19 3.32 5.19 3.1*8 April i.ia l*.25 7.01+ 1*.79 7.32 !*.82 6.77 1*.5S 6.1+9 1».72 7.01* U.51 7.01* 1*.72 nay lO.Oli 5.75 10.1a 7.08 10.05 6.61 9.01 6.06 9.28 6.75 9.82 6.28 9.82 6.58 June 11.1*3 6.55 12. ll* 8.26 12.02 7.92 12.60 8.1*7 11.92 8.67 12.26 7.85 12.26 8.21 July 13.61 7.79 15.17 10.32 ll*.33 9.1*3 ll*.72 9.90 13. 61 9.90 ll*.7l* 9.1*1* li*.7l* 9.88 August 13.09 7.50 ll*.68 9.98 13.97 9.19 llt.06 9.1*5 13.01 9.1*6 ll*.2l* 9.11 U+.2U 9.51* September 10.88 6.23 12.02 8.18 11.05 7.27 12.14 8.16 11.23 6.18 11.71* 7.51 11.71* 7.87 Seasonal 57.28 63.03 65.82 67.23 72.75 6I+.00 67.00 Period of Record 1920-1914* 25 years 1923-1937 15 years 1922-1933 12 years 1916-1933 18 years 1912-1933 22 years Elevation In Feet liOO 2,600 1,600 3,000 U,600 1.1 )0 2,10 D Distance from Coast in mies 10 33 29 36 1*2 ?5 3 D Authority City of San Diego San Diego County Water Company City of San Diego City of San Diego La Hesa, Lemon Grove and Spring Valley Irrigation District Estimate Division Resource i by of Water Estlmat Divlslo Resourc 3d by T of Water 33 Pan: Floating }• X i' X 18" 3' X 3' X 18" 3' I 3' » 18" 3' I 3' I 18"" y X y X le-^ — - -- Ground — - -- Pan dimensions from 1916 to 1919, Inclusive, were 1912-1920, Inclusive. 1912-1933, Ineluaive. 103 Evaporation studies made in connection with Bulletin No. 48 indicated that the depth of evaporation from a reservoir surface increases with distance from the coast and with rise in elevation. It is apparent that the Pacific Ocean moderates the coastal cli- mate by reducing summer temperatures and raising the humidity. Toward the interior, sum- mer temperatures become higher end the humidity lower, while reservoirs near the crest of the mountains, such as Morena and Cuyamaca, are exposed to dry hot winds from the desert which further increase the rate of evaporation. In estimating evaporation losses from proposed reservoirs in San Dieguito Basin, use was made of records of observed gross evaporation at Hodges, Morena, Barrett, Henshaw and Cuyamaca reservoirs, data for which are summarized in Table 27. These records are based upon measurements by floating and land evaporation pans, as indicated in the table, to which measurements suitable coefficients have been applied in order to evaluate actual evaporation from reservoir surfaces. For Lake Hodges a record of monthly evaporation since February 1919, when the reservoir was placed in operation, was obtained from the City of San Diego. Records for Morena and Barrett were likewise originally obtained from the City, and the Cuyamaca record was furnished by the La Mesa, Lemon Grove and Spring Valley Irrigation District. The record of evaporation at Lake Henshaw was obtained from the San Diego County Water Company. GROSS EVAPORATION FDOH RESERVOIRS IN SAN DIEOO COOTTY Honth Measured Estimated 1 Lake Hodges Lake Henshaw Barrett Reservoir Morena Reservoir Cuyamaca Reservoir Pamo Dajn Site Sutherland Dam Site Percent of Mean Seasonal Mean Depth in Inches Percent of Mean Seasonal Mean Depth In Inches Percent of He an Seasonal Mean Depth In Inches Percent of Mean Seasonal Mean Depth in Inches Percent of Mean Seasonal Mean Depth In Inches Percent of Mean Seasonal Mean Depth In Inches Percent of Mean Seasonal Mean Depth in Inches October 8.31 1*.76 8.32 5.66 8.96 5.90 6.60 5.78 9.07 6.60 8.63 5.52 6.63 5.78 November 6.1).0 3.67 5.1*8 3.73 5.62 3.83 5.98 1*.02 6.12 l*.l*5 5.76 3.69 5.76 3.86 December lt.71 2.70 3.1*0 2.31 3.98 2.62 U.U2 2.97 1*.00 2.91 3.93 2.52 3.93 2.63 January V.lli 2.37 2.96 2.03 3.57 2.35 3.51 2.36 3.85 2.80 3.35 2.11* 3.35 2.21* February 3.68 2.22 3.20 2.18 3.1*9 2.30 3.21 2.16 5.01* 3.67 3.30 2.11 3.30 2.21 March 6.09 3.1*9 5.16 3.51 5.1*1* 3.58 1*.98 3.35 6.36 li.61* 5.19 3.32 5.19 3.1*6 April 7.1*2 1*.25 7.01* U.79 7.32 1*.62 6.77 1*.S5 6.1*9 1*.72 7.01* 1*.51 7.01* 1*.72 May lO.Olt 5.75 10.1*1 7.08 10.05 6.61 9.01 6.06 9.26 6.75 9.82 6.26 9.82 6.56 June 11. 1(3 6.55 12.11* 6.26 12.02 7.92 12.60 8.1*7 11.92 6.67 12.26 7.85 12.26 8.21 July 13.61 7.79 15.17 10.32 li*.33 9.1*3 ll*.72 9.90 13.61 9.90 li*.7U 9.1*k 11*. 71* 9.88 Augxiat 13.09 7.50 ii(.6a 9.98 13.97 9.19 ll*.06 9.1*5 13.01 9.1*6 ll*.2l* 9.11 li*.2l* 9.51* September 10.88 6.23 12.02 8.18 11.05 7.27 12.11* 8.16 11.23 8.18 11.71. 7.51 11.71* 7.87 Seasonal 57.28 66.03 65.62 67.23 72.75 61*. 00 67. OD Period of Record 1920-19144 25 years 1923-1937 15 years 1922-1933 12 years 1916-1933 18 years 1912-1933 22 years - Elevation In Feet 1*00 2,600 1,600 3,000 1*,600 1.1 )0 2,10 D Distance from Coast in Miles 10 33 29 36 1*2 '5 3 D Authority City of San Diego San Diego County Water Company City of San Diego City of San Diego La Mesa, Lemon Grove and Spring Valley Irrigation District Estimate Division Resource i by of Water Es timet Dlvlslo Resourc sd by 1 of Water S3 Pan: Floating 3' I 3' X 18" 3' I 3' I 18" i- X 3' X 18" y X y X 16"° 3' I 3' I 16"" — - -- Ground — ■-- — - - - Notes; a - Pan dimensions from 1916 to 1919, inclusive, were I*. 63' X 7.31'. b - 1912-1920, Inclusive. c - 1912-1933, inclusive. 103 In connection with yield studies of reservoirs at Lake Hodges, evaporation losses during the period of record were estimated on the basis of observed net depth of evaporation on the existing reservoir, by subtracting recorded rainfall from measured gross evaporation. For months prior to February 1919, evaporation was estimated by sub- tracting estimated monthly rainfall from average monthly gross evaporation , as recorded through the 23 complete seasons following 1919. At Sutherland and Pamo dam sites, mean gross depth of seasonal evaporation was estimated by graphical interpolation of average recorded seasonal values at Hodges, Barrett, Henshaw and Cuyamaca reservoirs. Semi-logarithmic plots of average gross sea- sonal depths of evaporation at these reservoirs, against elevation and distance from the coast, resulted in the relatively smooth curves shown on Plate IX, "Variation of Evapo- ration with Elevation and Distance from the Coast for Reservoirs in San Diego County". For Pamo Reservoir, values taken directly from the graphs, on the basis of both elevation and distance from the coast, differ by only one-half inch in depth of average seasonal gross evaporation. Corresponding difference for the Sutherland site is 1.1 inches of depth. The nearest even inch was selected for estimating gross seasonal depth of evapo- ration for use in yield studies of reservoirs at these sites. Monthly distribution of estimated seasonal gross evaporation at Pamo and Suther- land was taken as the average of mean monthly percentages for Henshaw, Morena and Barrett reservoirs. These three reservoirs are more nearly comparable to Pamo and Sutherland, as regards elevation and distance inland, than are other reservoirs in San Diego County. Net depth of evaporation for the Pamo and Sutherland sites was computed from monthly gross depth of evaporation, derived as outlined above, and from estimated monthly rainfall. Total quantitative monthly net evaporation loss from each reservoir was finally obtained by multiplying the average water surface area during the month by the estimated or recorded net depth of evaporation for the same month. Draft from Reservoirs In making yield studies for proposed conservation works, the factors of runoff and evaporation, which are inherently subject almost exclusively to the laws of nature, were evaluated upon the assumption that past experience would, on the average, be repeated in the future. The factor of draft, however, is governed by anticipated demands under con- ditions of present or future cultural development, and may be affected by characteristics of transmission and distribution works. It was found that under certain combinations of proposed reservoirs In San Die- guito Basin, and under certain methods of operation, 1917-J6 firm yield from Lake Hodges would have been less than assumed use of this water under present conditions by the San Dieguito Committees, taken as 5,300 acre-feet per season. When 1917-36 firm yield from Lake Hodges was less than 5,300 acre-feet per season, therefore, seasonal draft was dis- tributed in accordance with weighted average monthly use by the Committees during the five- year period from 1939-40 through 1943-44. It must, of course, be assumed that in a de- velopment wherein yield from Lake Hodges would be less than entitlements of the Committees, the difference would be supplied from upstream storage. When 1917-3t. firm yield from Lake Hodges exceeded 5,300 acre-feet per season, that amount was distributed as before, but the 104 PLATE rx: 10 u I o z 0.1 ELEVATION IN 1000 FEET 0.5 LO 20 3 4 5 70 CUYAMACA z o (- < a. o a. < > 65 < 2 O W 60 < in UJ 70 65 < z o (/) < ui _l < z o < u < z O H Q Q < 100 200 300 400 TOTAL COMBINED RESERVOIR STORAGE CAPACITY - 1000 ACRE - FEET ESTIMATED SEASONAL YIELD FROM RESERVOIRS IN SAN DIEGUITO BASIN 1914-15 TO 1944-45, INCLUSIVE 109 Average seasonal results of semi-seasonal yield studies for the period 1894-95 to 1913-14, inclusive, herein termed "safe yield", are listed in Table 30, which also com- pares their values with those of corresponding studies for the period 1914-15 to 1944-45, inclusive, herein termed "1917-36 firm yield". It is shown that safe yield during the early period would have varied from 59 to 95 per cent of 1917-36 firm yield of the later period, dependent upon amount and disposition of storage, and method of reservoir opera- tion. While yield studies covering the prior period are not considered as reliable as those for the period following 1914, they are of value in indicating more nearly absolute values of safe yield to be expected from proposed reservoirs in San Dieguito Basin. TABLE 30 COMPARATIVE VALUES OF 1917-36 FIRM YIELD AND SAFE YIELD FROM RESERVOIRS IN SAN DIEGUITO BASIN Study No. Storage Capacity in Acre-Feet 1917-36 Firm Yield in Acre-Feet Safe Yield Total In Per Cent of 1917-36 Firm Yield Hodges Sutherland Total A-1 33,600 33,600 11,400 6,700 58.8 A-2 104,500 104,500 20,200 11,900 58.9 A- 3 157,300 157,300 24,000 15,600 65.0 A-4 224,800 224,800 26,800 20,600 76.8 A- 5 338,000 338,000 29,400 28,100 95.5 C-1 33,600 36,700 70,300 16,400 9,700 59.1 C-5 301,700 36,700 338,400 29,200 25,100 86.0 In the San Diego region with its characteristic wide seasonal range in runoff, it is essential that a new conservation reservoir be completed well in advance of anticipated need. A number of years may be required for catchment of sufficient runoff to develop re- quired yield. The average period for development of maximum yield will be long when the reservoir's capacity is large as compared with average seasonal runoff, and short when capacity and runoff are more nearly equal. In the case of a large conservation reservoir at Lake Hodges, with storage capacity approximately eight times average seasonal runoff, conservative analysis indicates that construction should precede demands by a period of about ten years. While development of the maximum possible amount of yield might not be attained in this period, sufficient runoff should be accumulated even under adverse condi- tions to meet the City's initial demands upon this source for supplementary water. There would be a reasonable expectancy that increasing storage and yield would thenceforth keep pace with increasing demands. In the case of Sutherland Reservoir, with storage capacity about 2.4 times average seasonal runoff, the period between completion of construction and initial requirement for water might be much shorter, probably no more than four years, on the average. For other sizes of reservoirs studied at both Pamo and Hodges, the period for development of required initial yield would vary between the foregoing extremes. Surface Reservoirs In studies and comparisons of reservoirs at the three principal sites in San no ^ Dieguito Basin, only one location for a dam was considered at each of the Hodges and Sutherland sites. Three possible locations, "A", "B" and "C", were surveyed and examined to a limited degree at Pamo, but studies for this report were based upon an earth-fill type of structure at site "C", furthermost upstream of the Pamo locations. Sutherland Reservoir The site of Sutherland Dam is on Santa Ysabel Creek, in the N. W. ^ of Section 21, T. 12 S., R. 2 E. , S.B.B.iM. , approximately 6-^ miles northeast of Ramona. The reser- voir area comprises portions of Sections 20, 21, 22, 27 and 28 in the same township. Streambed elevation of the dam is 1,912 feet. A topographic survey, and map of the reservoir site to elevation 2,110 feet, at scale of one inch to 300 feet, with contour interval often feet, were made for the City of San Diego by Dessery and West, engineers of Los Angeles, in September 1911. Datum of lev- els of the 1911 survey was approximately 17 feet lower than mean sea level datum of the United States Geological Survey, and indicated elevations were correspondingly high, as is evidenced by corrected tables of capacities placed on the original map by the City in June 1928. A topographic map of the dam site at scale of one inch to 50 feet, with contour in- terval of two feet, was made by the City of San Diego in August 1927. In making studies and estimates for Sutherland Reservoir in connection with the present investigation, use was also made of cross sections, profiles and structural plans made by the City of San Diego, and by Quinton, Code and Hill, consulting engineers of Los Angeles. Storage capacities of Sutherland Reservoir at ten-foot intervals of water surface elevation, as computed from areas compiled by the City of San Diego, are given in Table ^l* TABLE 31 AREAS AND CAPACITIES OF SUTHERLAND RESERVOIR Depth of Water at Dam in Feet Water Surface Elevation (U.S.G.S. Datum) in Feet 1 Water Surface Area^ in Acres Capacity in Acre-Feet 1,912 40 1,952 52 728 48 1,960 73 1,227 58 1,970 108 2,124 68 1,980 143 3,377 78 1,990 184 5,004 88 2,000 231 7,073 98 2,010 280 9,624 108 2,020 329 12,663 118 2,030 384 16,230 128 2,040 444 20,378 138 2,050 513 25,145 148 2,060 580 30,618 158 2,070° 640 36,724 Notes: a - Data from City of San Diego- fa - Capacities computed from areas at two-foot differences in elevation. c - Planned normal vrater surface with reservoir filled. Ill The electorate of the City of San Diego approved a bond issue on October 19, 1926, to acquire certain riparian rights and to construct Sutherland Dam, Sutherland Aque- duct to the head of San Vicente Creek, San Vicente Dam to a height sufficient for diver- sion of water to the San Vicente Pipe Line, and the 36-inch diameter San Vicente Pipe Line to Lakeside, to connect there with the El Capitan Line. Bids were received by the City on January 24, 1927, for construction at the lower Sutherland site of a concrete multiple-arch dam, I6I feet high and approximately 780 feet long. A low bid of $896,742 was received for construction of the dam, outlet works, spillway and Ij miles of access road. The lower site was subsequently abandoned due to unsatisfactory foundation conditions, and construction of a similar structure was started at a location about 1,000 feet upstream. Construction was finally stopped alto- gether, after seven buttresses were partly built and a portion of the spillway excavation accomplished. A structural analysis of plans for the partially completed Sutherland Dam to de- termine its stability, if completed, was conducted in 1945 by the Supervision of Dams Branch of the Division of Water Resources. The following is quoted from the report on this study: "....In making this study numerous plans were examined and an effort made to determine which plans were the proper ones to use. Mr. Verne L. Peugh who was resident engineer during part of the construction, has stated, by letter, he considered the dam was constructed in accordance with the plans made by ^uinton, Code and Hill. These plans were not completed in sufficient detail to get all basic data necessary for an analysis and in order to get this nec- essary information, several other plans were used. It is thought that plans as analyzed reasonably cover the dam as constructed; however, photographs showing the steel projecting out of the upstream face of the haunch does not indicate any uniformity in the amount of steel used. The conclusions of this study are as follows: 1. The present, partially completed structure, if completed according to the assumed contract plans and specifica- tions, will be a safe structure...." Prior to resuming construction operations at Sutherland Dam, verification should be ob- tained that existing work is in accordance with satisfactory plans and specifications. The upper site at Sutherland, upon which construction was started, was explored by the City of San Diego in the summer of 1927. Seventeen core holes, eleven on the dam axis and six approximately on the alignment of the cutoff wall, were drilled to depths ranging from 40 feet to 110 feet. Data resulting from these corings were assembled on drawing No. N-89 of the City of San Diego, dated September fa, 1927. More complete informa- tion relative to subsurface materials resulted from actual construction of foundations for seven buttresses and a portion of the cutoff wall. Foundation material, as Indicated by logs of the test holes, consists of hard gneiss, with solid rock near the surface at streambed. The depth of disintegrated and fractured overburden varies from 10 to 30 feet on the right slope, and from 15 to 60 feet on the left slope, as is shown in the bottom of completed portions of the cutoff wall, together with logs of borings. The structure, as planned for the upper site, layout of which is shown on Plate 21, "Sutherland Dam on Santa Ysabel Creek", consists of 17 reinf orced-concrete arch spans, 60 feet from center to center of buttresses, resulting in a total crest length of approxi- mately 1,025 feet. Top of the parapet wall is at elevation 2,074 feet, or I62 feet above 112 I PLATE 21 PLAN Spinas Q 2050 ELEVATION LOOKING UPSTREAM SECTION A -A SUTHERLAND DAM ON SANTA YSABEL CREEK SCALE OF FEET K rOO '50 k 113 streambed. Normal full reservoir water surface is at the top of drum gates in the spill- way, at elevation 2,070 feet, at which level storage capacity is 36,724 acre-feet. Fixed crest of the spillway is at elevation 2,036 feet. Outlet works, as planned by ^uinton. Code and Hill, include a trash rack, and an emergency 5- by 5-foot caterpillar gate on the inclined face of one arch ring, with the bottom of the opening approximately at ele- vation 1,950 feet, or 38 feet above streambed. A 48-inch diameter steel pipe with flared entrance connects the emergency gate with a 48- by 36-inch balanced needle valve, installed in the 48-inch diameter steel conduit pipe. An alternate arrangement of a double wye and two 36- by 24-inch balanced valves is also shown on the plans. While estimates for this report are based on quantities taken from these plans, it is believed that some changes should be considered in the event of future construction, because of recent knowledge of cavitation which results from partial gate openings in closed conduits with high head dif- ferentials. Crown thickness of the arches varies from 1 foot 6 inches to 5 feet 4 inches, and the haunch thickness from 2 feet 2 inches to 6 feet. The arches have a central angle of 140 degrees. Intrados radius is 27 feet for the central 76 degrees, compounded to a radius of 21 feet 6 inches through 32 degrees of central angle adjacent to the haunches. The extrados consists of a single arc, with radius varied to accommodate the arch ring thickness. Reinforced-concrete buttresses are planned, with a thickness of approximately 9 feet 6 Inches at streambed level, and 3 feet 4 inches at the top of the dam. Upstream slope of the buttresses is 1:1, while the downstream edge has a slope of 0.125 down to el- evation 2,000 feet, below which the slope is 0.40. Lateral stability of the buttresses is accomplished by arched struts at elevations 1,9^0 and 2,000 feet, and by bridge arches at the top of the dam. A reinforced-concrete roadway across the top of the dam is planned, with a width of 21 feet between curbs. The spillway, which has been partly excavated, consists of an open cut in the right abutment, with width of channel between concrete retaining walls of 164 feet. The spillway control consists of a hollow concrete weir section with three 50- by 14-foot drum gates. Two concrete piers, 6 feet 8 inches thick, between the gates, support the bridge over the spillway. Alignment of the bridge is the same as over the dam but on a grade of three per cent. The plans provide a six-inch concrete apron extending 50 feet upstream from the weir section, and 12-inch bottom paving between ten-foot high side walls for a dis- tance of 265 feet downstream. Estimated discharge capacity of the spillway, with reservoir water surface at elevation 2,073 feet and the gates completely lowered, is approximately 57,000 second-feet. Estimated crest flow of a flood of once in 100-year frequency 1b 37,300 second-feet, with 65,300 second-feet for a once in 1,000-year flood. It is believed that the structure will withstand overflow for infrequent short periods without serious erosion or damage. Coarse aggregate and a portion of fine aggregate required for concrete were crushed from stone quarried near the dam site, but in the event of completion of Suther- land Dam a considerable additional amount of fine aggregate will have to be imported. Cost estimates for this report assume that all fine aggregate will be imported. The City of San Diego has acquired title to approximately 1,600 acres of reser- voir and adjacent marginal lands. It will probably be necessary to acquire an additional 40 acres of privately owned land, together with 40 acres of State land, and to secure flow- age rights within several parcels of National Forest lands. For purposes of this report, it is estimated that required additional lands can be acquired for $2,500. 114 No public roads will be inundated by the reservoir. Sutherland dam site is accessible by two routes from Ramona. One route com- prises a county road extending northeast from Ramona along Rinoon Refugio. The alternate road includes approximately 5g miles of State Route No. 78 and 2i miles of county and private roads. Initial plans for development of Sutherland Reservoir included a 36-inch dia- meter concrete pipe transmission line, approximately 14 miles long, extending southwester- ly from the reservoir around the east and south sides of the town of Ramona to Daney Can- yon, a tributary of San Vicente Creek. Terminus of the line in Daney Canyon was in Section 33, T. 13 S., R. IE., at a point about 6^ miles upstream from San Vicente Dam. A similar conduit, 15.5 miles long, but including one-half mile of tunnel, and with capac- ity of approximately 45 second-feet, is considered in cost estimates for this report. Based upon prices prevailing in April 194-7, it is estimated that completion of Sutherland Dam, in accordance with the Quinton, • Code and Hill plans, will cost $2,342,800, including allowances of ten per cent for administration and engineering, 15 per cent for contingencies, and three per cent interest on capital investment during one-half of the estimated construction period of two years. Annual costs are estimated at $105,500, with- out consideration of previous capital expenditures at the Sutherland site, but only of those for completion of the dam in its present state. Annual charges include interest at three per cent per annum, amortization over a 50-year period, depreciation of the dam on the basis of 100-year life, and operation and maintenance charges of $10,000. These esti- mated costs are detailed in Appendix H, "Estimates of Costs". Estimates of cost for the transmission line from Sutherland Reservoir are based on use of centrifugally-cast, reinf orced-concrete pipe, 30 and 36 inches in diameter for gravity and low head portions, and of 36-inch diameter, concrete-cylinder pipe for the higher head portion. With allowances for administration, engineering, contingencies and in- terest during construction on the same bases as for completion of the dam, estimated April 1947 capital cost of the conduit is $1,334,600. Assuming interest at three per cent per annum, amortization over a 50-year period, depreciation on the basis of 80-year life, and operation and maintenance charges of O.I5 per cent of the capital investment, annual costs are estimated at $58,000. Detailed cost estimates for the conduit are also presented in Appendix H. In addition to the foregoing studies, a rough cost estimate was made for a rolled earth-fill dam at the present Sutherland site. Estimated cost for this type of structure proved to be greater than that for completion of the multiple-arch dam. Plans for the multiple-arch dam contemplate normal full reservoir water level at the top of raised drum gates, at elevation 2,070 feet. This proposal is considered satisfactory, since failure in gate operation during a flood will result only in overflow of the concrete structure, and it is probable that both dam and foundation rock will withstand infrequent overflow of this type. However, in design of an earth-fill dam, consideration was given to a fixed spillway crest at elevation 2,070 feet, with the top of the fill 20 feet higher at elevation 2,090 feet in order to provide necessary freeboard. In addition to this requirement for a higher dam crest, a greatly increased length of concrete-lined spillway channel would be required for an earth-fill type of dam. These factors account for the conclusion that construction of such a structure would be uneconomic as compared with completion of the multiple-arch dam. 115 Pamo Reservoir The three dam sites considered for Pamo Reservoir are located within a one-mile reach of Santa Ysabel Creek, approximately li miles downstream from its junction with Temesoal Creek, in Section 27, T. 12 S. , R. IE., S.B.B.ftM. Dam site "A" is located near the west line of Section 27. Site "B" is approximately three-quarters of a mile upstream from site "A", while site "C" is about 1,700 feet upstream from site "B" and approximately 800 feet west of the east line of Section 27. As a result of considerations hereinafter discussed, cost estimates of this report are based on an earth-fill dam at site "C". Surveys and foundation explorations at sites "A" and "B" were begun by the Volcan Land and Water Company as early as 1913. A number of maps compiled from these sur- veys were made available by the City of San Diego from its files. More complete and ac- curate maps of the reservoir and dam sites were made in July 19^5 by Fairchild Aerial Surveys, Inc., in connection with the present investigation. These consisted of the follow- ing: (a) Pamo Reservoir Topography scale 1 inch = 400 feet; contour interval, 10 feet; in 2 sheets. (b) Pamo Dam Site C scale 1 inch - 100 feet; contour interval, 5 feet. (c) Pamo Dam Site A scale 1 inch = 200 feet; contour interval, 10 feet; (enlarged from 1 inch = 400 feet reservoir map). (d) Pamo Dam Sites B and C scale 1 inch = 200 feet} contour interval, 10 feet; (enlarged from 1 inch = 400 feet reservoir map). Reservoir areas and capacities above the three dam sites, as determined from the 1945 reservoir map, are given in Table 52 (page II7) . The narrow canyon of Santa Ysabel Creek, in which the three dam sites are situ- ated, is within an extensive area of granite. At many places old seismic action has frac- tured and crushed the rock structure, and this, together with weathering, has resulted in some extensive and deep areas of disintegrated rock. The Volcan Land and Water Company made core drill borings at both sites "A" and "B", and in addition dug open test pits at site "B". Logs of the borings at site "A" were not available for this investigation. How- ever, site "A" is at the narrowest point in the canyon, and has the best foundation condi- tions of the three sites. It is believed suitable for a gravity-masonry structure, not ex- ceeding 200 feet in height. The following is quoted from a letter dated December 2, 1945, by Chester Marliave, consulting geologist, following his brief visual inspection of the site: "Location A-A at the downstream site offers possibilities for a concrete gravity type of dam having a height of about 200 feet with crest at elevation 1,000. The right abutment is fairly substantial. The channel section shows bedrock in blocky outcrops almost entirely across the channel. An overpour spillway could be used here. Location A-A is also adaptable for an earth dam having a crest elevation of about 1,000 feet. The right abutment ridge could be used for the spillway location and only a concrete lining over the ridge at the end of the dam would be required. The ravine below it would serve as a wasteway and not have to be lined. For a higher dam at this location, with crest at about elevation 1,100, the right end should be moved upstream placing the axis at the location A-A'. For this height of dam an earth dam seems to be the most feasible type both from a geologic and topographic point of view. Because of the good alignment of the wasteway ravine on the right abutment of this side appears to be more favorable than the left side for the location of the spillway. A cut and cover outlet could be satisfactorily constructed along the left side of the channel section." 116 TABLE 32 AREAS AND CAPACITIES OF PAMO RESERVOIR Elevation (U.S.G.S. DatxMi) in Feet Dam Site "A" Dam Site ' B" Dam Site ' •C" Water Surface Area in Acres Capacity in Acre-Feet Vater Surface Area in Acres Capacity in Acre-Feet Water Surface Area in Acres Capacity in Acre-Feet 805 810 1 820 1 8 830 4 33 84Q 10 102 850 17 236 1 3 860 27 453 5 30 1 1 870 42 799 13 132 6 36 880 63 1,334 34 376 20 169 890 117 2,244 80 944 64 591 900 156 3,610 113 1,917 96 1,389 910 229 5,535 182 3,400 161 2,672 920 285 8,101 233 3,477 209 4,521 930 347 11,259 290 8,095 264 6,886 940 413 15,057 331 11,302 322 9,815 950 492 19,580 423 15,183 393 13,391 960 581 24,947 509 19,856 475 17,736 970 670 31,206 593 25,370 556 22,895 980 769 38,402 687 31,769 647 28,915 990 868 46,586 781 39,105 739 35,848 1,000 981 55,833 889 47,452 845 43,769 1,010 1,147 66,475 1,050 57,147 1,004 53,013 1,020 1,287 78,647 1,186 68,326 1,138 63,720 1,030 1,428 92,224 1,322 80,866 1,272 75,768 1,040 1,579 107, 2bl 1,469 94,819 1,417 89,212 1,050 1,735 123,832 l,bl9 110,258 1,565 104,120 l.ObO 1,920 142,107 1,800 127,354 1,744 120,664 1,070 2,081 162,110 1,956 146,133 1,898 138,871 1,080 2,249 183, 7bO 2,120 166,511 2,060 158,657 1,090 2,389 206,950 2,255 188,385 2,193 179,921 1,100 2,517 231,478 2,378 211,551 2,314 202,460 1,110 2,b40 257,265 2,498 235,933 2,433 226,197 1,120 2,769 284,310 2,623 261,536 2,555 251,136 117 Thirteen core borings made at site "B" by the Volcan Land and Water Company in 1914 lA-ould all be within the area covered by a dam 70 feet in height above streambed. The borings showed solid granite to be 15 feet below streambed, and from 30 to 60 feet below the surface on the right abutment. Solid rock was from five to 40 feet below the surface on the left abutment. The overburden consisted of disintegrated granite. Information se- cured from test pits dug in 1913 was less extensive than from the borings. One test pit on the right abutment, 150 feet above streambed, was 45 feet deep, all in disintegrated granite. The following is quoted from Chester Marliave's comments on this site: "The granite here shows some hard outcrops in the channel section only, but this hard rock may not be continuous. The abutments are decomposed and deeply weathered. An earth type of dam seems to be most suited for this lo- cation. A spillway could probably be constructed over either abutment beyond the ends of the dam. An outlet tunnel could well be constructed through the left abutment or placed in cut and cover along the left bank of the channel section." No exploration has been done ac site "C". It is evident that a considerable depth of decomposed rock underlies much of the site, especially the right abutment. The following is quoted from Chester Marliave's comments on site "C": "The bedrock over this site appears to be a deeply weathered granite with practically no hard outcrops, except near the crest on the right side. The foundation conditions and topography suggest the desirability of an earth type of dam. For a dam with a crest elevation of 1,100 it seems desirable to curve the right end of the axis so that the dam would follow along the ridge. Here the axis should be so placed that the upstream toe slope would fall along the ravine. The toe slope of the channel section should also follow along the base of the hill where bedrock is exposed. The ridge needs only about four feet of stripping so that the location of the axis is not very important as the ridge is quite sound, and needs only a good layer of impervious material on the up- stream side of it. A spillway could be constructed across the right abutment ridge about as indicated upon the map, but it would have to be concrete lined for a considerable distance till clear of the downstream toe of the dam. The channel section at this site is quite wide but it does not show hard block rock outcrops that would necessitate blasting in order to prepare the foundation for the compacted fill. The channel also offers sufficient room for the manipula- tion of equipment, which is a handicap in narrow sections. This site is nearer the borrow pits for earth material than any of the other sites considered. For the same height of dam this site offers the most reservoir storage. In general, this upper site has many favorable features that suggest it being the most fea- sible location for a dam to store about 200,000 acre-feet." A reservoir with storage capacity of 163,000 acre-feet would be required at the Pamo sites to retain combined runoff of the 1914-15 and 1915-16 seasons above the sites, less draft and evaporation. This capacity would necessitate a dam approximately 264 feet high at site "A", or 224 feet high at site "C". From the foregoing preliminary geologic information, it is believed that dams of such heights at any of the Pamo sites should be earth-fill structures. Cost estimates for this report were therefore predicated on rolled earth embankments. Likewise, because of geologic considerations favoring site "C" in the case of a dam to create a large capacity reservoir, estimates of cost were limited to structures at that site. Site "B", probably the least favorable location from the geologic standpoint, was not considered in the estimates. It is shown in the following paragraph that cost of dam structures for comparable reservoirs at sites "A" and "C" would be approx- imately equal. Embankment material for any of the three sites would have to come from borrow pits located in the wide canyon area upstream from site "C". Additional haul of approxi- mately one mile between sites "A" and "C" was estimated to cost about $0.08 per cubic yard. A dam to impound 163,000 acre-feet of water at site "A" would require approximately 950,000 cubic yards less borrow than a structure with equal capacity at site "G". However, the 118 saving in quantity of borrow material would be offset by cost of increased haul, to the extent that cost of embankments for comparable structures at sites "A" and "C" would be approximately equal, if the unit price for borrow material at site "C" were ^O.JO per cubic yard. Cost estimates were made for three sizes of rolled earth-fill dams at site "C", with respective reservoir capacities of 90,000, 135>000 and 163,400 acre-feet. Main phys- ical features of the three sizes of dam considered are listed in Table 33, while Plate XII, "Pamo Dam on Santa Ysabel Creek", shows a typical embankment section. Embankment sections have a 30— foot width of crown, and }'.l slopes both upstream and downstream. Provision for stone riprap, four feet thick on the upstream face, and two feet thick on the down- stream face, is included in the estimates. A cutoff trench ten feet in depth below the gen- eral stripping level, and 200 feet v/ide at elevation 880 feet, tapering to 100 feet at the dam crest, is provided on both abutments. TABLE 33 PHYSICAL FEATURES OF PAMO DAM FOR THREE SIZES OF DEVELOPMENT Reservoir Capacity in Acre-Feet 90,000 133,000 163,400 Elevation of crest of dam, U.S.G.S. datum, in feet 1,061 1,088 1,104 Elevation of crest of spillway, in feet 1,041 1,068 1,084 Height of dam to spillway crest, above streambed, in feet Length of dam at crest, in feet 181 1,800 208 2,060 224 2,230 Net length of spillway crest, in feet 300 230 200 Capacity of spillway with 5-ft. freeboard, in second-feet Spillway channel 66,000 55,000 44,000 Length, in feet 1,300 1,200 1,200 Width of bottom lining, in feet 70 70 75 Height of side lining, in feet 20 20 16 Embankment Volume, compacted earth fill, rock fill and riprap, in cubic yards Upstream slope 3,727,000 3:1 5,697,000 3:1 6,945,000 3:1 Downstream slope 3:1 3:1 3:1 Width of crest, in feet 30 30 30 It is assumed that stripping will reach sufficiently tight material in the chan- nel below elevation 880 feet so that a cutoff will not be required. Assumed portions of materials removed in connection with contingent work are to be incorporated in the embank- ment. These more pervious materials will be placed in outer zones of the dam. In strip- ping the dam abutments, it is assumed that 50 per cent of the material will be hauled di- rectly to the embankment and the remainder wasted, as will be the case with common excava- tion for the spillway. In stripping the channel at the dam site, 70 per cent of the 119 material is assumed to be stockpiled for later use, and 30 per cent wasted. All common excavation from strip borrow at the dam, and rock, including disintegrated, from the spillway excavation, will be placed directly into the embankment. It is further assumed that all rock from the diversion tunnel excavation will be stockpiled, while material from common open cut excavation for the diversion tunnel will be wasted. Preliminary examina- tion indicates that a sufficient quantity of suitable impervious material for the main portion of the embankment will be available from borrow pits, conveniently located up- stream from site "C". If resultant cost estimates had indicated the Pamo reservoir de- velopment to be economically favorable, it was planned to make sufficient explorations to verify availability of these materials. Spillways present a difficult problem, and one expensive of solution, at all Pamo sites. At site "C", cost of the spillway is 30 per cent of total cost of a 90,000 acre-foot reservoir, and 17 per cent of total cost of one of 163,400 acre-foot capacity. Steeply sloping canyon walls necessitate deep cuts along upper sides of spillways. In ad- dition, it is necessary to set invert grades of spillway channels at relatively low eleva- tions in order to avoid fill across small gullies. High channel velocities dictate the provision of gradual changes in vertical and horizontal alignment, and make necessary a concrete lining for the entire length of channel. Spillway crests are proportioned to pass 25 per cent more than an estimated flood of once in 250-year frequency, with reser- voir water surface five feet belo\\f the crest of the dam. The flood is routed through each size of reservoir, using an approximated 24-hour hydrogxaph, with momentary peak equal to 2.8 times the mean 24-hour rate, and with crest of approximately seven hours' duration at the mean 24-hour rate. The estimates include provision for a concrete-lined spillway channel, with an ogee weir section at the upper end, in the right abutment. A concrete apron 50 feet wide is provided upstream from the gravity ogee weir, and a cutoff structure at the downstream end of the channel. Bottom width of the channel is gradually reduced in the first 400 to 600 feet below the weir. Depth of the channel is kept constant, to allow increased free- board in lower reaches where velocities exceeding 80 feet per second will be experienced. No special provision for dissipation of high velocity flows is made at the outlet end of the channel. It is reasoned that the deflecting lip and cutoff structure will be ample for this purpose for a long period of time, due to infrequency of spill. If detrimental erosion should occur at any time, necessary corrective measures can then be determined, and placed more economically and effectively than during initial construction. The estimate for the 90,000 acre-foot reservoir includes no provision for a di- version tunnel. It is believed that embankment for this size of structure, together with the spillway, can be completed in one season, if preceded by adequate preliminary opera- tions, such as stripping, excavation, etc. However, construction of a concrete-lined diversion tunnel, of l8-foot inside diameter, and 1,700 feet in length, is included in es- timates for the two larger dams. It is assumed that a sufficient amount of embankment will be placed during the first summer season to form a coffer dam about 90 feet high. This head will result in a tunnel discharge capacity of 12,000 second-feet which, together with 13,000 acre-feet of available storage capacity, will handle a two-day flood of mag- nitude 25 per cent in excess of that of January 27-28, I916. This is considered a reason- able risk. 120 PLATE XH Crest El 1068' PLAN . Spillway Crest El 1066' Crest El 1088 ELEVATION LOOKING UPSTREAM DEVELOPED PROFILE I' Rip Bap-, Cut -Off Trerict\-'' TYPICAL SECTION PAMO DAM ON SANTA YSABEL CREEK RESERVOIR CAPACITY - 135,000 ACRE -FEET SCALE OF FEET 100 too 200 300 121 Outlet works Include a reinforced-ooncrete intake tower, at the entrance of a conduit near the upstream toe of the embankment on the left side of the channel. Esti- mates for the tower are based on the design used at El Capitan Dam on San Diego River. For the 90,000 acre-foot reservoir, the tower is assumed to have an inside diameter of ten feet. Intake is through five JO-inch saucer valves at different levels, the lowest being at elevation 89O feet. Three similar valves are to be located inside the tower at its base, to control flow through the 60-inch diameter concrete conduit. This conduit, 1,300 feet in length, is estimated on the basis of concrete-cylinder pipe with a 15-inch reinforced-concrete encasement, placed in an excavated trench along the toe of the left abutment. Outlet towers for the two larger reservoirs are assumed to be connected to the inlet of the diversion tunnel, which Is to be plugged. The towers are 12 feet in inside diameter, and have six 30-inch inlet saucer valves. Outflow is through four 36-inch sau- cer valves, connecting to 36-lnch diameter cast-iron pipes extending through the connect- ing block and tunnel plug. Estimates for the two larger reservoirs also include provision for two 36-inch diameter welded steel pipes extending to the downstream end of the tunnel. The City of San Diego has acquired title to approximately I,l60 acres of land comprising portions of Pamo dam and reservoir sites. However, there remains to be ac- quired areas of 1,320, 1,730 and 1,960 acres of land for the 90,000, 133,000 and 163,400 acre-foot reservoirs, respectively. The bulk of required additional land is located in the narrow valley along Temescal Creek, and some of this area is cultivated. Cost esti- mates provide for acquisition of 2,483 acres of additional land :n the case of each size of reservoir considered. Area required for the smallest reservoir considered includes the better land of affected ownerships, and the access road to Pamo Valley will be inundated. It is therefore concluded that the entire holdings of affected ownerships will have to be acquired. Land prices are estimated by applying a factor of four to the assessed value of unimproved property, and a factor of five to the assessed value of improved property. No very important public road will be affected by construction of Pamo Reservoir. The principal existing route affected is the county road from Ramona, which enters Pamo Valley just upstream from dam site "C", and extends on to the north about four miles to a ranch at the upper end of the valley. Pamo Ranger Station is located along this road about one mile north of dam site "0", and will be within the flow line of all reservoirs con- sidered. Estimates of this report provide for relocation of 1.0 miles of the connection between the foregoing road and another county road, extending down the Santa Ysabel Canyon past the dam sites. In addition, costs of 0.25 miles of road from a truck trail to connect with the bridge over the dam spillway; 3.6 miles of truck trail relocation around the north end of the reservoir; and 2.25 miles of new road to connect the area near the present Pamo Ranger Station with the Rincon Refugio road, are included in cost estimates. In order to permit definite comparison between water yield from Sutherland, Pamo and Hodges reservoirs, costs of delivering the water to approximately equivalent points on the existing system of the City of San Diego should be added to reservoir storage costs in each instance. It may be remembered that for Sutherland Reservoir a 13.5-niile gravity pipe line was proposed in order to deliver water to San Vicente Reservoir, where it could be further transmitted through existing pipe lines. The ensuing estimates for both Pamo and Hodges reservoirs include provisions for routing water to a point two miles south and one- half mile east of Hodges Dtun, the proposed site of a filtration plant. From this point, at elevation 65O feet, the water is conveyed to Chesterton Tank near the south edge of Linda Vista Mesa, two miles north of San Diego River. Hydraulic gradient at Chesterton 122 Tank is at elevation 525 feet, and connection can there be made to existing distributing lines and regulating reservoirs on the city system. Detailed economic studies required for final construction planning might result in choice of a lower terminal elevation, with distribution to higher service areas by means of booster pumping plants. For the gravity conduit from Pamo to the filtration plant, a concrete pipe trans- mission line, 19.6 miles in length, is included in the estimates. Dependent upon yield of the reservoir under the several studies, pipe line sizes vary from 21 to 42 inches in dia- meter, and capacities range from eight to 36 second-feet. To determine pipe sizes, a di- rect release to Santa Ysabel Creek from Pamo Reservoir is assumed, sufficient to provide a seasonal yield at Lake Hodges of 8,200 acre-feet, equal to the total amount of present com- mitments from the latter reservoir. The amount of this release is subtracted from yield of Pamo Reservoir, and the remainder considered to be conveyed in the pipe line. Pipe line capacities are based on average demand during July. Except for three inverted siphons, the first 12.1 miles of the conduit consist of non-pressure or low-pressure reinforced-concrete pipe. Between mile 12.1 and 12.9 there are 0.8 miles of 6.5-foot diameter, concrete-lined tunnel, and the remaining 6.7 miles of conduit consist of reinforced-concrete, steel- cylinder pipe. The transmission line follows along the left side of Santa Ysabel Canyon to a point about a mile east of the west end of San Pasquel Valley, from whence it turns more to the south through the hills, and crosses U. S. Highway 395 near its junction with Green Valley Road, two miles south of the Bernardo Bridge. It crosses the San Diego Aqueduct one mile east of U. S. Highway 395 1 at which point its hydraulic grade line is approximately at elevation 78O feet. Hydraulic grade line of the San Diego Aqueduct at this point is at el- evation 910 feet. The conduit from the filtration plant to Chesterton Tank is lb. 7 miles in length, and consists of reinforced-concrete-cylinder pipe, with minimum cover of three feet. Dur- ing periods of maximum flow, head on the conduit will generally be less than I50 feet, but several canyon crossings involve heads exceeding 3OO feet. Diameter of the pipe varies with yield under different plans of development, and is chosen so that the hydraulic gra- dient is at elevation 525 feet at Chesterton Tank. Diameter for high-pressure canyon cross- ings is assumed as }b inches in the case of all lines involving pipe of that or greater diameter. Table 34 (page 124) presents a summary of estimated capital and annual costs of the Pamo Reservoir development, including the transmission conduit, for each of the three sizes studied. The costs are based on prices prevailing in April I947. Detailed cost es- timates for dam and reservoir with storage capacity of 163,400 acre-feet, and for a 39-inch diameter conduit, are presented in Appendix H. Annual charges include interest of three per cent per annum, and amortization over a 50-year period. In the case of the dam and ap- purtenant structures, depreciation is on the basis of 100-year life, while annual operation and maintenance costs are assumed at $14,500. In the case of the conduit, depreciation is based upon an 80-year life, with annual operation and maintenance costs of 0.10 per cent of the capital investment. 123 TABLE 34 SUMMARY OF ESTIMATED COSTS OF PAMO RESERVOIR aND CONDUIT FOR THREE SIZES OF DEVELOPMENT (Based upon Prices Prevailing in April 1947; Reservoir Capacity in Acre-Feet 90,000 135,000 163,400 CAPITAL COSTS Dam and reservoir Conduit $5,289,000 3,876,700 $7,893,000 4,079,100 $9,268,400 4,256,700 TOTALS $9, 165,700 $11,972,100 $13,525,100 ANNUAL COSTS Dam and reservoir Conduit 4223,600 166,700 $332,100 175,400 $389,300 183,000 TOTALS 4390,300 $507,500 $572,300 Lake Hodges The existing Hodges Dam, located iu Section I8, T. 13 S., R. 2 W. , S.B.B.ftM. , about 25 miles north of San Diego and seven miles southwest of Escondido, has been described in some detail in an earlier section of this chapter. When full, Lake Hodges covers an area of l,l80 acres, extending about six miles upstream from the dam, with an average width of 0.3 miles. The reservoir is largely contained within the Bernardo Grant. The Volcan Land and Water Company made a topographic map of the Hodges reservoir area in I916 at scale of one inch to 400 feet, with contour interval of ten feet to eleva- tion 315 feet, the present normal full reservoir level. The Soil Conservation Service of the United States Department of Agriculture surveyed the reservoir area in July 1935 in connection with silting studies, and prepared a revised map of .the same scale and elevation as the earlier one, but with a five-foot contour interval. In July 1945, in connection with the present investigation, Fairchild Aerial Surveys, Inc., made an aerial survey and established surface controls, from which that company prepared a topographic map of the reservoir showing a water surface at elevation 312.8 feet, and with ten-foot contours from elevation 320 feet to elevation 400 feet, at scale of one inch to 400 feet. This map, en- titled "Super Hodges Reservoir Topography", consists of four sheets, three of topography and one delineating the triangulation system of surface control. The site under considera- tion for a larger Hodges Dam is located immediately downstream from the present structure. The City of San Diego made a topographic map of this area in 1942, at scale of one inch to 50 feet, with contour interval of five feet to elevation 400 feet. Above this, between elevations 400 and 500 feet, the contour interval is ten feet. In the summer of 1946 the City extended the map 3OO feet downstream, below elevation 265 feet, in order to include the site of a possible spillway stilling basin. 124 Previously accepted reservoir area capacity data were revised for studies of this report, in order to partially account for sedimentation since the original informa- tion was compiled. The Soil Conservation Service reported that the July 1935 sedimenta- tion survey of Lake Hodges revealed a l6|-year accumulation of 1,822 acre-feet of sediment, causing a reduction of 120 acres in water surface area at full reservoir stage*. It was also found that 80 per cent of the sediment lay within 25 feet of crest level near the head of the reservoir. Reservoir capacities from elevation 215 feet to elevation 275 feet, inclusive, presented in Table 55, were computed from water surface areas taken from "Report on Water Supply for City of San Diego", by H. N. Savage, 1923, based on the Volcan Land and Water Company's I916 survey. For elevations from 285 to 305 feet, inclusive, areas were also taken from the Savage report, but reduced by the estimated sedimentation. Sedimentation to 1947 was estimated on the basis of results of the 1935 survey. Areas above elevation 305 feet were measured from the contours of the 1945 Fairchild survey. TABLE 35 AREAS AND CAPACITIES OF LAKE HODGES Reservoir Gage Height in Feet Elevation (U.S.G.S. Datum) in Feet Water Surface Area in Acres Capacity in Acre-Feet 200 10 210 15 ZI5 4 10 25 225 10 81 35 235 26 262 45 245 56 670 55 255 115 1,526 65 265 234 3,270 75 275 351 6,193 85 285 472 10,505 95 295 631 15,820 105 305 886 23,407 112.8 312.8 1 ,096 31,139 115 JI5 1 180 33,643 120 320 1 .387 40,060 130 3J0 1 .951 56,751 140 340 2 ,396 78,488 150 550 2 799 104,464 160 360 3 710 137,011 170 J70 4 401 177,566 180 380 5 046 224,801 190 390 5 767 278,865 200 400 6 610 340,747 * Technical Bulletin No. 524, "Silting of Reservoirs", United States Department of Agriculture, July 1936. Revised August 1939^ 125 Foundation conditions at the site of Hodges Dam are good. The rock is of mixed origin and very hard. The following comments are taken from "Geologic Report on Lake Hodges Dam", by Chester Narliave, consulting geologist, written in January 1932, in con- nection with studies made to determine safety of the existing dam during earthquakes: "The rocks in the vicinity of the dam site are classified as belonging to the 'crystalline complex'. They are the oldest rocks of the region and form the floor upon which the later rocks and sediments rest. They are of pretertiary age, metamorphic in character and composed of a complex mixture of granites, volcanics and altered sediments. "There is no fault of major activity at the dam site, but a shear zone runs down the canyon and passes through the right abutment of the dam be- neath the wasteway section. There is evidence of crushing and indications point to the existence of a fault along this shear zone, but there are no signs of recent movement. "The channel section of the dam is composed of hard, dense, massive, blocky volcanic rock somewhat basic in character. It is traversed by three systems of fracturing which is prevalent throughout the site. The fractures are tight and allow practically no leakage through the bedrock. It is stated that the buttress excavations were dug to a depth of from 4 to 8 feet where sound rock was encountered. "The left abutment of the dam is rather steep. The quality of the rock is excellent, being similar to that in the channel section. Fracture planes are prominent in the rock, but appear to be tight with little disintegration along the planes. One large smooth face of rock forms a bluff at the extreme end of the dam. This face represents one of the systems of fracture vrtiich Is nearly normal to the axis of the dam and is inclined steeply at about 70 de- grees toward the river. The fracture planes become tight with increased dis- tance from the surface, and the rock is divided by the fractures into rather large blocks. Very little seepage was observed coming around the abutment of the dam, and there appeared to be no evidence of landsliding or faulting on this side of the canyon. This abutment of the dam is entirely satisfactory. "The structure of the right abutment is somewhat complex. The basic vol- canic rocks are more acid than under the main section of the dam and give way to rhyolitic material at the extreme end of the dam, while in the transition section under the wasteway there are remnants of agglomeratic material. The bedrock, especially under the flat top section of the wasteway, is much softer than that found at other parts of the site. The weakened condition of the rock under the ogee spillway section has been augmented by fault movement along the shear zone but there is no evidence of recent movement along this fault. The flat top section of the wasteway rests upon rocks of softer quality. The ex- treme end of the section is in contact with rocks of rhyolitic character, but under the central portion of the deck, agglomeratic material is known to ex- ist. As a whole the bedrock under the right abutment of the dam is of satis- factory quality." During construction of the dam, core borings with a shot drill were attempted, but progress was limited to several Inches a day due to hardness of the rock. The shot drill was then replaced with a diamond drill, with which It is known that at least two holes were drilled, one to a depth of 50 feet and the other to a depth of 19 feet. Both holes were in hard rock for almost their entire depth. A visual examination of the site was made on August 19, 1947, by Elmer C. Marliave, geologist of the Division of Water Resources. The following comments comprise his more important observations: "The area in the vicinity of the dam site contains a series of old volcanics and sediments that have been intruded by granitic material and have been meta- morphosed to varying degrees. No major faults were noted in the area, but shear- ing and minor faulting are found at many localities. This general area is con- sidered to be seismically active. "Rocks at the proposed dam site appear to be meta-volcanics, with the more basic rocks in the left abutment and channel sections giving way to a more acid type on the upper right abutment. Considerable of the rock in the present 126 i spillway area is a meta-rhyolite and more of this rock is found at higher eleva- tions, both upstream and downstream from the site. Practically all of the rock, when freshly exposed, is hard and durable and capable of carrying the load of the dams being considered. "All the foundation rook at the site is strongly jointed. Some local orushine and shearing is noted and gougy seams are found in the more weathered upper portions. The most notable set of joints ison the right abutment where a dip of 25 to 40 degrees toward the channel is joined. These joints cut the rook into slabs, five to ten feet in thickness, and produce sliding planes that may require some special consideration. A nearly vertical joint system parallel to the channel is also quite pronounced. There is a set of streamward dipping joints on the left abutment, quite similar in nature to the set on the right abutment. It was observed in the road cuts below the zone of weathering (approximately 30 feet normal to the surface) that the joints were tighter and cleaner and it appears that they could be properly treated by washing and grouting. "A strong shear zone exists on the right abutment at elevation 325« It strikes approximately N. 72° E. and dips into the abutment approximately 40 degrees. It extends upstream under the existing spillway apron and down- stream beyond the limits of the location considered for a future dam. Material in the zone appears to be a soft light colored tuffaceous material and may have developed from crushing of the meta-rhyolite. This material may improve with depth, but it should be considered a zone of weakness and accorded special treatment. This shear zone is about 23 feet in thickness and has been eroded to depths of over 20 feet by water flo'wing over the ex- isting spillway. "It is estimated that stripping about 30 feet deep normal to the sur- face will be necessary over the abutment areas excepting on a portion of the right abutment area where spill from the existing reservoir has partially cleaned the loose and fractured rock. On this latter area, the strioping will be on the order of five to eight feet. It is estimated that the required stripping in the channel will be from five to ten feet below the bottom of the talus and large boulders. A portion of the channel is relatively clean, but there is some talus and material wasted from the previous construction which has a maximum depth of about 12 feet. "An overpour spillway can be adapted to this site with moderate protec- tion to the rock at the downstream toe of the dam. If infrequent spilling is contemplated, the protection may be a minimum in the original construction with subsequent maintenance as the need is demonstrated. "The design of the dam should allov for seismic forces." In studies for this report, cost estimates were made for five sizes of dam at the Hodges site, principal physical characteristics of which are given in Table 36 (page 128). Layout and a typical section are shown on Plate XIII, "Hodges Dam on San Dieguito River". It may be noted that the largest reservoir considered in the estimates is of 340,700 acre-foot capacity, rather than the 338,000 acre-foot capacity indicated by the yield studies as necessary for complete conservation development of San Dieguito Basin solely by enlargement of Lake Hodges. The excess capacity is provided with elevation of spillway crest at 400 feet, U. S. G. 3. datum, the nearest even foot to that for the ideal 336,000 acre-foot capacity indicated by yield studies. The estimates are base;? on concrete gravity structures, with vertical upstream faces, and a slope of 0.8 horizontal to 1.0 vertical on downstream faces. Intersection of planes of the upstream and downstream faces is 15 feet above the spillway crest in all cases. The dam axis assumed for the estimates is 100 feet downstream from the axis of the present dam at the right abutment, and 155 feet downstream at the left abutment. Width of dam crests is 15 feet, to provide for a single lane roadway, to be carried over the spill- v/ay by a reinforoed-conorete bridge. 127 tabu: 36 physical features of hodges dam FOR FITE SIZES OF DEVELOPMENT Reservoir Capacity in Acre-Feet 104,500 157,300 224,800 310,000 340,700 Elevation of crest of dam, U.S.G.S. datum, in feet Elevation of crest of spillway, in feet Height of dam to spillway crest, above streambed, in feet Length of dam at crest, in feet Net length of spillway crest, in feet Capacity of spillway, in second-feet Mass concrete in dam, in cubic yards 568 550 150 900 400 116,000 265,980 382 365 165 940 400 106,000 315,900 396 380 180 970 400 97,000 367,900 410 395 195 1,015 400 88,000 425,000 416 400 200 1,050 400 97,000 445,000 Depth of stripping is assumed to be 50 feet normal to the slope on both right and left abutments, and from 12 to 15 feet in the channel bottom. Allowance is made for the shear zone on the right abutment by assuming an excavation 60 feet in depth below nor- mal foundation level, and 40 feet in width, to be filled with concrete. An ogee overflow spillway is contemplated, with net length of 400 feet, to be located over the middle section of the dam. A deflecting lip or bucket is provided near the downstream toe, to deflect the high velocity flow into the air. An estimate of cost was also tentatively made for a stilling basin, to dissipate energy of the overflow by a hydraulic jump. However, this proposal was abandoned in view of its relatively high cost, character of foundation rock, and after consideration of the rarity and short duration of spill that would be experienced with larger dams at Lake Hodges. The spillway is divided by training walls into a 200-foot central section, flanked by 100-foot sections on either side. The deflecting lip of the central section is at elevation 230 feet, or JO feet above streambed, and lips of the two side sections are at elevation 28O feet, to accommo- date the sloping canyon walls. No gates or other regulating devices are provided in the spillway. Freeboard, from spillway crest to top of the dam, varies from 16 to I8 feet for the several sizes of dam considered, and is just sufficient to pass an estimated once in 1,000-year flood, of 163,200 second-feet peak flow, without overtopping the structures. An estimated once in 250-year flood, with peak flow of 119,000 second-feet, will pass over the spillways with freeboard of approximately three feet. I The water supply outlet works include a series of dual 36-inch diameter conduits eciuipped with double disc gate valves, and extending from the upstream face about 20 feet into the dam, to a vertical well of six-foot diameter. The dual outlets are located at three levels about 50 feet apart, with the lowermost pair at elevation 250 feet. Trash racks, semicircular In plan, are provided on the face of the dam at each level. Main out- let conduits consist of two 42-inch diameter, welded steel pipes, extending from the bot- tom of the vertical well to the downstream face of the dam. Topography of the site and disposition of the spillway favor the right abutment for location of the outlets. In addition to the foregoing, estimates also include provision for an emergency 36-inch dia- meter, high-pressure outlet near the base of the dam. This outlet is provided with trash racks, 3»5-foot S4uare emergency slide gate, and a 36-inch balanced regulating valve. 128 i PLATE Xm ^ V Crest El 4101, Foundation Along A«is — "^ "^ ELEVATION LOOKING DOWNSTREAM SECTION A-A SECTION B-B HODGES DAM ON SAN DIEGUITO RIVER RESERVOIR CAPACITY - 310.000 ACRE - FEET SCALE OF FEET 129 The City of San Diego ovms a considerable amount of land within the Hodges res- ervoir site, much of which extends up to contour elevation 395 feet. However, acquisition of additional land is a major element in estimated cost of Hodges Reservoir, and varies between 17 and 20 per cent of total cost for the several sizes of reservoir studied. Estimates of cost of land acquisition below contour elevations 368, 382, 396 and 4l6 feet, respectively, were prepared. Two consultants, B. A. Etcheverry and G. F. Mellin, were re- tained on this work. Table 37 presents a summary of the estimates, based upon their re- port which is included in Appendix C herein, "Estimates of Cost of Land Acquisition for Lake Hodges and Mission Gorge Reservoirs". TABLE 37 ESTIMATED COSTS OF REQ,UIRED ADDITIONAL RESERVOIR LANDS FOR LAKE HODGES DEVELOPMENT ( Based on 19*7 Market Values) Elevation of Crest of Dam (U.S.G.S. Datum) in Feet 368 382 396 416 Elevation of spillway crest, in feet 350 365 380 400 Reservoir storage capacity, in acre-feet 104,500 157,300 224,800 340,700 Area flooded (excluding presently city-owned land), in acres Area to be acquired (excluding presently city-owned land), in acres 717 1,222 1,316 2,422 2,003 4,148 3,216 4,871 ESTIMATED COSTS Land i 381,400 i 565,200 $ 846,600 $ 904,200 Improvements 547,000 584,200 753,000 785,700 Damages 96,900 202,700 115,600 120,600 TOTALS $1,025,300 $1,352,100 $1,715,200 $1,810,500 In preparation of the estimates it was assumed that land would have to be ac- quired to the elevation of the dam crest, which was considered to be the maximum reservoir flood pool elevation. The estimates are based upon real estate market values as of the spring of 1947» Appraisal of land values was accomplished by applying appropriate factors to 1946 assessed values of the Oounty Assessor, whose information on each property and its improvements was very complete. Factors were determined from an analysis of sales since 1941, for which period due allowances were made in actual sales prices to adjust them to 1947 prices. It was decided to use a factor of five for all farm properties (including lands and improvements), and a factor of six for all subdivision property in Campo Del Dios, as respective ratios of 1947 market values to 1946 assessed values. The estimates include cost of lands and improvements to be purchased, together with accompanying damages, and the cost of relocating affected power and telephone lines. Because the water supply and main pipe line for the Del Dios Subdivision will be flooded with reservoir water surface at elevation 568 feet, it is considered necessary to purchase the entire subdivision in the case of each of the reservoirs studied. 130 As is shown in Table 57 > the relative increment of cost of land acquisition be- tween elevations 39d and 4l6 feet is considerably less than for lower elevations. This follows partly from the assumption that a large ranch and dairy in San Pasqual Valley can continue to operate if the maximum reservoir water level is kept at elevation 382 feet or lower. For larger reservoirs it is concluded that the entire holdings of this ranch will have to be purchased. Cost estimates for the several sizes of reservoir include provision for reloca- tion of 9.83 miles of unsurfaced county road, and of 2.14 miles of State Highway No. 78. Estimates of annual costs of water yielded by Lake Hodges include charges for a pumping plant, and for 2.9 miles of conduit to deliver water to the City's proposed fil- tration plant site, already mentioned under the discussion of Pamo Reservoir. Also in- cluded are costs of lb. 7 miles of gravity pipe line to carry the water to Chesterton Tank on Linda Vista Mesa at elevation 525 feet, where it is assumed that connection can be made to the existing city distribution system. The total estimates therefore permit direct comparison between costs of pumped yield from Hodges, and gravity yield from both Pamo and Sutherland reservoirs. In each case, water is delivered to points roughly equivalent as regards elevation, geographic position and relation to existing transmission lines. Treatment plant costs are not included in any of the estimates. As was stated in the dis- cussion of Pamo Reservoir, detailed economic studies required for final construction plan- ning might result in choice of a lower terminal elevation, with distribution to higher service areas by means of booster pumping plants. The amount of water to be handled by the conduit from Lake Hodges and by the pumping plant is assumed equal to I917-56 firm yield of the several sizes of reservoir, minus 8,200 acre-feet seasonally which the City of San Diego is committed by contracts to deliver to downstream users, distribution throughout the season being proportional to ac- tual draft by the City and San Dieguito Committees during recent years. It is assumed that the Committees will continue to be served by the existing Hodges Conduit to San Die- guito Reservoir. The gravity portion of the conduit, from the filtration plant to Chesterton Tank, Is similar in characteristics to that described under the discussion of Pamo Reservoir. The conduit from Lake Hodges to the filtration plant consists of 1.0 miles of welded steel pipe, supported above ground by ring girders on concrete piers, and 1.9 miles of concrete- cylinder pipe buried with a minimum cover of three feet. The steel pipe extends downstream along the right bank a distance of about 0.6 miles from the dam, where it crosses the river through an inverted siphon, and continues up a side canyon about 0.4 miles. From this point, concrete-cylinder pipe extends 1.9 miles farther, to relatively flat ground at ele- vation 650 feet. Size of the pipe line varies with capacity of the reservoir. Estimates of costs have been made for pumping plants of various capacities, cor- responding with yield to the City by five sizes of dam at Lake Hodges, and under three methods of operation. As a basis for estimating, it is assumed that the pumping plant will be located on the right side of the river downstream from the dam and over the 131 conduit. The plant includes three pumping units of equal size. Installed capacities are based on an assumed minimum reservoir water surface at elevation 225 feet, static lift to elevation 6^0 feet, plus friction head in 2.9 miles of pipe, overall plant efficiency of 70 per cent, and installed capacity sufficient for 125 per cent of average rate of water demand in July. Energy cost is based on lift from the approximate average reservoir water surface elevation during the critical period utilized in yield studies. The price of el- ectrical energy is based on steam generation with oil fuel, under schedule P-2, with the price of oil at |1.45 per barrel. Estimated capital and annual costs for five sizes of development of Lake Hodges, based upon prices prevailing in April 1947, are summarized in Table 58, including costs of reservoir, diversion conduit and pumping plant. Capital costs include allowances of ten per cent foi' administration and engineering, 15 per cent on construction items for contin- gencies, and, in the case of the reservoir, three per cent interest on capital investment during one-half of the estimated construction period of three years. Annual charges in- clude interest at three per cent per annum; amortization over a 50-year period; deprecia- tion on the basis of lives varying from 100 years in the case of the dam, to 80 years for the conduit, to 50 years in the cases of dam outlet works and pumping plant; and estimated operation and maintenance costs. Annual costs of the pumping plant also include estimated electrical energy and power demand charges. However, they do not include costs of funding such energy and demand charges in perpetuity beyond the end of the amortization period. TABLE 38 SUMIARY OF ESTIMATED COSTS OF LAKE HODGES RESEaVOI.R, CONDUIT AND PUMPING PLANT FOR FIVE SIZES OF DEVELOPMENT (Based upon Prices Prevailing in April 1947) Reservoir Capacity in Acre-Feet 104,500 157,300 224,800 310,000 340,700 CAPITAL COSTS Dam and reservoir *5, 965,100 *7, 139, 500 $8,373,100 $9,432,000 $9,785,200 Conduit Dam to filtration plant 263,800 346,500 435,100 435,100 435,100 Filtration plant to Chesterton Tank Pumping plant 1,770,000 117,800 1,972,400 129,800 1,972,400 138,200 2,368,100 145,000 2,368,100 146,500 TOTALS *8, lib, 700 ♦9,588,200 $10,918,800 $12,380,200 $12,734,900 ANNtJAL COSTS Darn and reservoir 1250,800 ^299,100 *349,300 $393,200 $408,000 Conduit Dam to filtration plant 12,200 16,100 20,300 20,300 20,300 Filtration plant to Chesterton Tank Pumping plant 76,100 74,100 84,800 90,100 84,800 100,000 101,800 104,900 101,800 105,900 TOTALS $413,200 $490,100 $554,400 $620,200 $636,000 132 A detailed cost estimate for Lake Hodges with storage capacity of 310,000 acre- feet is presented in Appendix H to serve as an example and indicate unit costs utilized in similar estimates summarized in Table 38. Costs of pumping water from Lake Hodges to the point 2^ miles southeast of Hodges Dam, at elevation 65O feet, are likewise given in Appendix H, under a number of different reservoir storage combinations and assumed methods of operation. A detailed cost estimate of a 36-inch diameter conduit from the filtration plant to Chesterton Tank is presented in the cost estimate in Appendix H for the proposed Pamo reservoir development. Equivalent conduits for Lake Hodges viould have similar char- acteristics, but sizes and costs would vary with the several sizes of proposed development. Comparison of Surface Reservoirs In selection of sites and capacities for reservoirs to be included in a program for further conservation development in San Dieguito Basin, much weight should be given to the amount of supplemental yield to be derived therefrom. Water resources of the San Diego region are so limited that a development resulting in lowest unit cost of additional yield might not prove to be the most desirable, unless it also fitted into a plan that would pro- duce an amount of yield near the maximum possible of attainment. It follows that a primary condition in comparison of different reservoirs is that any unit adopted should fit into a plan for complete development of the basin. Complete development should be such as to give maximum supplemental yield over that of the existing development, and at reasonably low unit costs for the water. For purposes of this report, complete development of San Dieguito Basin is arbi- trarily defined as the provision of sufficient storage capacity to conserve the entire runoff of the season of 1915-lb. Economic comparisons of reservoirs are made on the basis of unit costs of additional yield to be derived from their construction, above that from the existing development. Seasonal yields from Sutherland, Pamo and Hodges reservoirs, un- der various combinations of storage capacity and method of operation, were listed in Table 29, values for which were determined for the period since October 1, I9I*. Estimated capital and annual costs for the reservoirs, as given in earlier de- tailed discussions, -are primarily intended to serve as bases for comparison of the several proposals, rather than to constitute exact statements of financial outlays involved. Since cost estimates for each of the several reservoirs are derived on an equivalent basis, the following economic comparisons will not be greatly affected by any general variation in construction costs. First step in comparison of reservoirs is to establish minimum storage capacity required at Lake Hodges under any combination of reservoirs to effect complete development of San Dieguito Basin. In an earlier discussion in this chapter this was stated to be 174,400 acre-feet, and was determined as the capacity necessary to retain combined runoff of the 1914-15 and I913-I6 seasons from the watershed between Pamo and Hodges dam sites. Lake Hodges, with capacity of 174,400 acre-feet, operated only with runoff below Pamo dam site, would have had a I917-36 firm seasonal yield of 8,800 acre-feet, and would have spilled in 1941, 1942 and 1943. Storage capacity of approximately 205,000 acre-feet would have been required to avoid all spill in these latter years. Data pertaining to yield, and to capital and annual costs of Sutherland, Pamo and Hodges reservoirs, have been assembled in Table 39 (page 134), to afford ready comparison of the different reservoirs under various plans of development. 135 TABLE 39 COMPARISON OF RESERVOIRS IN SAN DIEGUITO BASIN (Based upon Prices Prevailing In April 19U7) Study No. Reservoir Storage Capacity In Acre-Feet Additional 1917-30 Firm Yield Above that of Existing Development In Acre-Feet per Year Capital Costs Annual Costa Total Storage per Acre-Foot Additional 1917-36 Firm Yield per Acre-Foot per Year Total Additional 1917-36 Firm Yield per Acre-Foot per Year Increment of 1917-36 Firm Yield from Increase In Storage per Aore-Poot per Ye«r A, OPERATED INDIVIDUALLY C-1 Sutherland 36,700 5,000 t 3,677,1*00 ♦63.83 » 735 ♦163,500 $ 32.71 D-1 Sutherland" 36.700 (9,300)' 3,677,1*00 63.83 (395)' 163,500 (17.58)° B-1 B-2 Pamo Pano 90,000 135,000 11,100 13,1*00 9,165,700 11,972,100 58.77 58.1*7 826 893 390,300 507,500 35.16 37.87 ) )^50.9l* ) 58.95 ) B-3 Pamo 163,1*00 il*,Soo 13,525,100 56.72 933 572,300 39.1*7 A- 2 Hodges 101+, 500 8,800 8,116,700 57.08 922 ia3,2oo 1*6.95 ) ) 20.21* ) ) 22.96 ) ) 31.35 ) 31.50 A-3 Hodges 157,300 12,600 9,588,200 1*5.39 761 1*90,100 36.90 A-lt Hodges 22lj,800 15,1*00 10,918,800 37.25 709 551*. 1*00 36.00 A-6 A-5 Hodges Hodges 310,000 31*0,700 17,500 18,000 12,380,200 12,73l+,900 30.1*3 28.72 707 707 620,200 636,000 3S.U* 35.33 B. OPERATED COORDINATELY FOR COMPLETE DEVELOPMENT c-5 Sutherland 36,700 9,800 $ 3.677,1*00 ♦63.83 $163,500 C-6 Hodges 301,700 8,000 11,318,300 30.99 51*9,100 Totals 338,1*00 17,800 $11*, 995, 700 ♦3l*.58 $ 81*2 $712,600 $ 1*0.01* Sutherland 36,700 9,800 3,677,1*00 63.83 163,500 0-7' Hodges 310,000 8,000 11,390,300 30.1*2 552,300 Totals 31*6,700 17,800 $15,067,700 $33.96 $ 81*6 $715,800 $ 1*0.22 Sutherland 36,700 9,800 Hodges 310,000 6,000 Totals 31*6,700 17,600 Costs under plan of study N =. C-6 15,067,700 33.96 81*6 715.800 1*0.22 Savings from ten-year delay of Lake Hodges Adjusted Coats In enlargement l*,169,300 12.02 231* 173,600 9.71 $10,896,1*00 $21.91* $ 612 $51*2,000 $ 30.!t5 D-8 Sutherland' 36,700 (U*,100)' 3,677,1*00 63.83 163,500 B-1* Hodges 277,800 5,800 10, 991*, 100 32.67 510,900 Totals 311*, 500 19,900 $11*, 671, 500 $36.32 $(737)" $671*, 1*00 $(33.89)" Pamo 163,1*00 21,1*00 11*, 137, 900 56.72 598,600 G-1 Hodges 171*, 1*00 -2,600 7,1*80,000 1*2.89 313,000 Totals 337,800 18,800 $21,617,900 $1*9.56 $1,150 $911,600 $ 1*8.1*9 Sutherland 36,700 9.700 3,677,1*00 63.83 163 , 500 Pamo 127,800 11,700 10,999,100 58.61 1*70,900 Hodges 17l*,l*00 -2,600 7,1*80,000 1*2.69 313,000 Totals 338,900 18,800 $22,156,500 $51.09 $1,179 $91*7,1*00 $ 50.1*0 C. OPERATED COORDINATELY FOR PARTIAL DEVELOPMENT E-1 Sutherland' 36,700 (ll*,100)' $ 3,677,1*00 $163,500 Pamo 90,000 8,200 7,715,300 327,900 P-1 Hodges'* 33.600 -6,900 Totals 160,300 15,1*00 |ai,392,700 $1*7.61 ♦ (71*0)' ♦1*91,1*00 ♦(31.91)' Sutherland 36,700 9,800 3,677,1*00 163,500 Pamo 127,800 11,100 10,381*, 700 1*1*1*, 500 Hodges'^ 33,600 -6,900 Totals 198,100 li*,000 $ll*,062,100 $1*9.61* $1,001* $608,000 $ 1*3.1*3 a - Sutherland Reservoir operated for secondary yield, rather than 1917-36 firm yield. b - Estimated from curves, c - Identical with study No. C-6, but with costs reduced by savings resultant from ten-year delay In enlargement of Lake Hodges, as compared with costs if Initial development had been under plan of study No, A-5. d - Elxlsting Lake Hodgea. 134. Reservoirs Operated Individually The data under heading "A" of Table 39 are based on assumed individual operation of the several reservoirs for maximum 1917-56 firm yield. In the cases of Sutherland and Pamo reservoirs, of course, such operation is in conjunction with the existing Lake Hodges. It may be noted from these comparisons that development of Lake Hodges stands out most fa- vorably as regards unit costs for larger increments of 1917-36 firm yield. However, if Sutherland Reservoir is operated for secondary water, as shown in study No. D-1, an addi- tional average seasonal yield of 9,300 acre-feet of such water is realized, at relatively low unit cost. No attempt has been made to relate the value to the City of San Diego of such secondary water, as compared with that of 1917-36 firm yield. Reservoirs Operated Coordinately for Complete Development. From inspection of unit costs of additional 1917-36 firm yield listed under head- ing "A" of Table 39, it appears that no combination of reservoirs for complete development results in lower unit costs than can be attained by operating Lake Hodges alone, with the possible exception involving operation of Sutherland Reservoir for secondary water, in con- junction with operation of Lake Hodges on a 1917-36 firm yield basis. However, a compari- son of several plans for complete development, including either Sutherland or Pamo reser- voirs, or both, operated coordinately with Lake Hodges, is given under heading "B" of Table 59. Unit costs of combined additional 1917-36 firm yield from reservoirs at both Pamo and Hodges are greater than those for any reservoir at Hodges alone, having capacity greater than 174,4-00 acre-feet. If complete development of San Dieguito Basin is accomplished by providing storage of 174,400 acre-feet at Lake Hodges, and the remaining 163,400 acre-feet at Pamo, as shown in study No. B-4, resulting additional 1917-36 firm seasonal yield of l8,8O0 aore-feet probably constitutes the highest possible ratio of such yield to storage capacity. However, unit cost of the additional yield is $48.49 per acre-foot, as compared with *35»33 per acre-foot in study No. A-3» for complete development at Lake Hodges alone. For any development that will conserve the runoff originating between Pamo and Hodges, in- cluding as it must increased capacity at Lake Hodges, costs of remaining storage capacity at Pamo required for complete development of San Dieguito Basin are several times as great as those for equivalent capacity at Hodges, if the latter capacity is provided in the in- itial development. It may be noted that study No. B-4 shows additional 1917-36 firm yield from Lake Hodges to be a negative quantity. This is explained by the fact that large upstream storage will conserve much runoff presently reaching Lake Hodges. While enlargement of Lake Hodges is necessary even under such circumstances, to completely conserve runoff orig- inating below Pamo Reservoir, the yield to be realized from the enlarged Lake Hodges is less than that of the existing development. Total yield from the combined development of study No. B-4 is much greater, of course, than under present conditions. Similar consider- ations account for negative additional 1917-36 firm yield from Lake Hodges, noted in studies Nos. G-1, E-1 and F-1. Studies of coordinated operation of reservoirs at Sutherland and Hodges were made, with Sutherland operated both for 1917-36 firm yield and for secondary water with maximum diversion rate of 42.4 second-feet. A reservoir of 36,700 acre-foot capacity was the only one considered at Sutherland, the capacity if the dam is completed in accordance with origi- nal plans. If operated for 1917-36 firm yield from Sutherland, 301,700 acre-feet of storage 135 capacity is required at Lake Hodges to effect complete basin development. This, as is shown in study No. C-5 of Table 59, results in additional 1917-^6 firm seasonal yield of 17,800 acre-feet at unit cost of iAQ.OA- per acre-foot. This figure may be compared with that for complete development by means of Lake Hodges alone, which provides approximately the same amount of additional 1917-36 firm yield, at unit cost of $35»35 per acre-foot. If complete basin development is achieved by the foregoing Sutherland-Hodges oombination, but with enlargement of Lake Hodges deferred after construction of Sutherland Reservoir until required by increased water demand, the comparative cost advantage of com- plete development at Lake Hodges alone is reversed. It is considered conservative to take this period of delay as ten years, particularly in view of the fact that other factors, such as construction of the second barrel of the San Diego Aqueduct, may defer construction of an enlarged Lake Hodges for a much longer period. Savings in annual costs by construc- tion of Sutherland Reservoir, as shown in study No. C-1 of Table 39, rather than initial enlargement of Lake Hodges to the size required for complete basin development demonstrated by study No. A-5, amount to approximately $4,169,000 in a period of ten years. These sav- ings consist of charges for interest on and amortization of the capital investment in res- ervoir, conduit and pumping plant; depreciation of the physical works; and operation and maintenance. Including power costs for pumping. If costs of Lake Hodges are credited on the basis of these savings, resultant unit cost of additional 1917-36 firm yield from the Sutherland-Hodges oombination for complete basin development is $30.45 per acre-foot, as is shown in study No. C-7. If Sutherland Reservoir is operated for secondary water, the seasonal diversions vary from 1,130 to 30,710 acre-feet and average 14,100 acre-feet. Under such circumstan- ces, storage capacity of 277,800 acre-feet at Lake Hodges effects complete development of the basin, and 1917-36 firm seasonal yield of 17,200 acre-feet is realized from Lake Hodges alone. This is shown in study No. D-8 of Table 39» Total average seasonal yield under this plan, including secondary water, amounts to 31,300 acre-feet, a figure 19,900 acre-feet in excess of that of the existing development. Unit cost of the additional yield is $33»89 per acre-foot. Under the combination demonstrated in study No. G-1 of Table 59, Lake Hodges is constructed to a capacity of 174,400 acre-feet. Sutherland Reservoir is completed to its planned capacity of 56,700 acre-feet, and remaining storage necessary to effect complete basin development is furnished by 127,800 acre-feet at Pamo. Combined capacity amounts to 558,900 acre-feet and resultant additional 1917-56 firm seasonal yield is l8,800 acre-feet at unit cost of $50.40. Reservoirs Operated Coordinately for Partial Development Results of two studies for coordinated operation of Sutherland, Pamo and Hodges reservoirs under partial development of the basin are given under heading "C" of Table 59. Assumed storage capacity of Sutherland Reservoir is 56,700 acre-feet, while storage capac- ities of Pamo Reservoir are taken at 90,000 acre-feet and 127,800 acre-feet, respectively. In study No. E-1, Sutherland Reservoir is considered to be operated for secondary water, while the 90,000 acre-feet of storage at Pamo is operated on a 1917-36 firm yield basis. Secondary yield from Sutherland averages 14,100 acre-feet per season, while 1917-36 firm seasonal yield from Pamo is 8,200 acre-feet. However, 1917-36 firm yield of the ex- isting Lake Hodges is reduced from 11,400 acre-feet to 4,500 aore-feet, seasonally. 156 Average additional seasonal yield for the entire development is 15,400 acre-feet, at unit cost of ^31.91 per acre-foot. In study No. F-1, all reservoirs are operated on a 1917-36 firm yield basis, and complete development of the basin above Pamo is attained by assiomlng storage capacity of 127,800 acre-feet at Pamo Reservoir. Combined storage capacity Is 198,100 acre-feet, which results in additional 1917-3° firm seasonal yield of 14,000 acre-feet, at unit cost of »45.43 per acre-foot. Sutherland and Hodges Reservoirs Operated Coordinately In order to consider all possibilities for salvaging the past investment in Sutherland Dam, and to seek justification for the additional expense required to complete it, estimates were made of unit costs of combined additional seasonal yield for reservoirs of various' capacities at Lake Hodges when operated coordinately with Sutherland Reservoir. Parallel studies were made, involving operation of Sutherland Reservoir for both secondary water and for 1917-36 firm yield. The results are given in Table 40, and shown graphic- ally on Plate XIV, "Costs of Additional Seasonal Yield from Reservoirs in San Diegulto Basin". TABLE UO (Based upon Prices Prevailing In April 19U7) Study No. Method of Operation Storage Capac In Ac re -Feet ty Additional Seasonal Yield Above that of Existing Development in Acre-Feet Capital Coats Annual Costa Total storage per Acro-Poot Additional Yield per Ac re -Foot per Year Total Additional Yield per Acre-Foot per Year 1917-36 Firm Yield Secondary Yield Hodge a Sutherland Hodges Sutherland Total Hodges Sutherland Total Sutherland C-1 1917-36 ripm yield 1917-36 firm yield 33,600 36,700 70,300 -U,800 9,800 5,000 « 3,677,liOO »63.83 $735 ♦163,500 »32.71 C-2 1917-36 rirm yield 1917-36 firm yield 10i;,500 36,700 iia,2oo 1.700 9.800 11.500 11.097,500 58. 8U 965 510,900 4U.U3 C-3 1917-36 firm yield 1917-36 firm yield 157.300 36,700 19U,000 5,000 9.800 iii.eoo 12,531.300 Ue.88 6li7 586,900 39.65 ck 1917-36 firm yield 1917-36 firm yield 22U,eoo 36,700 261 , 500 6,U00 9,800 16,200 lli,001,900 U0.90 86U 652,200 U0.26 c-5 1917-36 firm yield 1917-36 firm yield 301,700 36,700 338.UOO 8,000 9.800 17.600 14,995.700 34.58 8i+2 712,600 Uo.oU C-6 1917-36 firm yield 1917-36 firm yield 310,000 36,700 3ll6, 700 8,000 9.800 17,800 15,067,700 33.96 846 715,800 40.22 D-1 1917-36 firm yield Secondary yield 33,600 36,700 70,300 -U,800 -U,800 lU.ioo 3.677,U00 63.83 395 163.500 17.58 D-3 1917-36 firm ylelde Secondary ylelde 33.600 36,700 70,300 8,600 3.677.UOO 63.83 416 163,500 18.58 D-5 1917-36 rirni yield Secondary yield 10U,500 36,700 IUI.2OO 1,600 1,600 lii.lOO 11,095,300 58. eu 707 509.600 32.U6 D-6 1917-36 firm yield Secondary yield 157,300 36,700 19U.000 3,^00 3.1*00 lii.lOO 12,1|88,900 48.86 714 577,200 32.9a D-7 1917-36 firm yield Secondary yield 22U,800 36,700 261,500 li,800 U,800 lli.lOO 13.763,100 40.96 728 633.600 33.53 I>-8 1917-36 firm yield Secondary yield 227.600 36,700 314,500 5,800 5.800 U+,100 1U,671,500 36.32 737 67U,4oo 33.89 D-9 1917-36 firm yield Secondary yield 310,000 36,700 3U6,700 5,800 5,800 14,100 15,028, Uoo 3 3.96 755 690,700 3U.73 Hote: •- 1,500 acre-feet of dead storage In Lake Hodges. 17,200 acre-feet of reserve storage In Sutherland Reservoir for release to Lake Hodges. 137 Summary A brief examination of the foregoing comparisons of reservoirs is sufficient to show that Pamo Reservoir may be eliminated from further consideration at this time, be- cause of high unit cost of additional yield under any plan for complete basin development which Includes that reservoir. The possibility remains, however, that Pamo Reservoir may eventually be justified in connection with terminal storage of an imported water supply for the San Diego region. Two general plans are left to be considered for present adop- tion, the first consisting of enlargement of Lake Hodges alone, and the second involving completion of Sutherland Reservoir to designed capacity, together with enlargement of Lake Hodges. Further examination discloses that the most favorable proposals under the respec- tive general plans are as follows: 1. Construction of Lake Hodges alone, with storage capacity of 340,700 acre-feet, as described under study No. A-5. 2. Combined development, including construction of 301,700 acre-feet of storage capacity at Lake Hodges, and 36,700 acre-feet at Sutherland Reservoir, as described under study No. 0-5. Additional I917-36 firm seasonal yield in the case of either of these developments is ap- proximately 18,000 acre-feet. A summary of studies Nos. A-5 and C-5, together with several related studies, is given in Table 41 for convenient reference. This table also sets up comparisons between the plans on the basis of safe yield during the record drought of 1895-96 to 1904-05, Inclusive. TABLE 41 SUMMARY OF PLANS FOR DEVELOPMENT OF LAKE HODGES AND SUTHERLAND RESERVOIR (Based upon Prices Prevailing in April 1947) Study No. Costs Storage Capacity in Acre-Feet Additional Seasonal Yield in Acre-Feet Additional Yield per Acre-Foot per Year Hodges Sutherland 1917-36 Firm Yield Safe Yield Capital Annual 1917-36 Firm Yield Safe Yield A-5 C-5 C-6 C-7* C-1 340,700 301,700 310,000 310,000 33,600 36,700 36,700 3b, 700 36,700 18,000 17,800 17,800 17,800 5,000 21,400 18,400 18,400 18,400 3,000 $12,734,900 14,995,700 15,067,700 10,898,400 3,677,400 1636,000 712,600 715,800 542,000 163,500 $35.33 40.04 40.22 30.45 32.71 $29.72 38.73 38.90 29.46 54.50 Note: * - Identical with study No. C-6, but with costs reduced by savings resultant from ten-year delay in enlargement of Lake Hodges, as compared with costs if initial development had been under plan of study No. A-5. It may be noted from Table 41 that the increment of safe yield to be obtained under the listed plans for complete conservation development of San Dieguito Basin is great- er than the corresponding increment of 1917-36 firm yield. This is true because 1917-36 firm yield as related to safe yield is proportionately greater in the case of the small ex- isting Lake Hodges than in the cases of large capacity reservoirs required for complete 138 PLATE XIV 20 / L- tirtnr.F^ and siithfri ano 1- U UJ RESERVOIRS (SECONDARY YIELD FROM SUTHERLAND) 1 1 1 U. 18 1 U LIMIT OF HODGES "^^ cc o < o o '« HODGES AND SUTHERLAND o RESERVOIRS o I (1917-36 FIRM YIELD FROM SUTHERLAND) >- 14 _J < z \/ 1 w o PAMO RESERVOIR • ' \ \ ADDITIONAL SEA o rv> / \ \ / / V V - LAKE HO DGES s ■ lO 20 30 40 50 80 70 COST OF ADDITIONAL SEASONAL YIELD DOLLARS PER ACRE -FOOT PER SEASON COSTS OF ADDITIONAL SEASONAL YIELD FR OM RE. SERVOK «IN s; \N DIEG lUITO B ASIN 139 conservation development. As an example, under study No. C-5 total 1917-36 firm seasonal yield is increased from 11,400 acre-feet for the present Lake Hodges to 29,200 acre-feet with complete development, an amount of 17,800 acre-feet. However, under the same study, total seasonal safe yield increased correspondingly from 6,700 to 25,100 acre-feet, an amount of 18,400 acre-feet. These considerations account for the greater indicated unit costs of additional 1917-36 firm yield, as compared with corresponding costs for addition- al safe yield, for studies Nos. A-5, C-3, C-6 and C-7. In finally selecting a plan for complete conservation development of San Dle- guito Basin certain practical and intangible factors merit consideration. Estimates pre- sented in Chapter III of this report indicate that the City of San Diego now has a water supply development sufficient to meet its probable demands well beyond the year I960, if, as- is probable, runoff sufficient to re-establish full safe yield of the existing storage system occurs before that date. Based on the necessity of securing additional water the need for full conservation development of San Dieguito Basin is not immediate. However, other factors should be considered. The City of San Diego has a large investment in reservoir sites in San Dieguito Basin, and has recently made filings to appropriate all excess waters of the river. Value of water in this semi-arid region is so great as to assure further development of this at- tractive source by other agencies, public or private, unless the City takes steps to con- summate these filings. To accomplish this, reasonable diligence must be shown as regards placing the water to beneficial use. While additional San Dieguito Basin water is not im- mediately required by the City, it may be put to beneficial use in lieu of presently pur- chased Colorado River water. A plan permitting accomplishment of full conservation de- velopment of the basin by stages, with Initial steps to be taken as soon as possible, will accomplish this desirable end. Adoption of the plan outlined in study No. C-5 accomplishes such staged develop- ment of the basin, through initial construction of Sutherland Reservoir to a storage capa- city of 36,700 acre-feet, and subsequent enlargement of Lake Hodges to 301,700 acre-foot capacity. However, a very similar plan. No. C-6, provides 310,000 acre-feet of storage at Lake Hodges, and has certain practical advantages. At increased capital cost of only 472,000, additional storage capacity of 8,300 acre-feet is provided. This increment com- pensates for future losses of storage space by silting, and in the meantime provides regu- latory capacity for possible imported water. In Table 41 estimated unit cost of additional 1917-36 firm seasonal yield under the plan of study No. C-6 is shown to be ^.40. 22 per acre-foot, compared to ^35.33 under study No. A-5. However, by rational considerations as to financing, cost of yield under study No. C-6 is reduced if this plan ie constructed by stages. From the standpoint of costs, an ideal program of water supply development is one involving a graduated schedule paralleling the increase in demand. On the basis of present trends of population growth and per capita consumption of water, a period of at least ten years will elapse after com- pletion of Sutherland Reservoir before enlargement of Lake Hodges is required. This per- iod may be appreciably increased by other factors, but in ten years the savings in annual costs over those of the plan of study No. A-5 amount to #4,169,000. If this accrued sav- ing is credited to costs of Lake Hodges under the plan of study No. C-6, reduced unit cost of additional I917-36 firm seasonal yield is ^0.45 per acre-foot, as is shown under study No. C-7. 140 It may be noted that a rise in cost of power for pumping further increases the monetary advantage indicated in study No. C-7 for complete development by staged construc- tion of Sutherland and Hodges reservoirs, rather than by initial enlargement of Lake Hodges. Since the estimates for this report were made, energy costs for re(iuired pumping have risen an average of approximately 40 per cent. Construction of Sutherland Reservoir by itself provides additional I917-36 firm seasonal yield of 5,000 acre-feet at unit cost of $32.71. If operated for secondary water, average seasonal yield is 8,800 acre-feet at unit cost of $18.58. While these unit costs are less than result from any plan for complete conservation development of the basin, it is believed that any plan for only partial utilization of local water resources is inad- visable in the San Diego region, and that municipal water supply for the City of San Diego should be planned on a firm or safe yield basis. Moreover, the intrinsic value of second- ary water is largely indeterminate, dependent as it is upon ability of the City to utilize the water approximately at the time of its occurrence. Several additional factors tend to favor a plan including Sutherland Reservoir. The existence of this reservoir will provide the City with greater flexibility of opera- tion between its several major systems, and a higher diversion level and gravity delivery for a portion of the additional yield. With this plan completed, 9,800 acre-feet, or 55 per cent of the additional I917-36 firm seasonal yield, can be diverted from Sutherland Reservoir to the San Diego River system by gravity. On the other hand, with a plan in- cluding Lake Hodges alone, the entire amount of additional yield must be lifted an average hei£ht of approximately 3OO feet. Yield from Underground Reservoirs The only underground water basins within the San Dieguito watershed of sufficient size to warrant consideration in connection with further conservation development are those underlying the San Dieguito and San Pasqual valleys. Any appreciable additional yield of water from San Dieguito Basin must necessarily come about through salvage of flood waters now wasting into the ocean o r in reduction in natural consumptive use. To this end, the possibility of utilizing underground reservoirs for seasonal and cyclic storage of flood waters should be considered, as well as any possibility of their use for conserving water presently utilized by consumptive use of natural vegetation. Seasonal and Cyclic Storage In 1919* Charles H. Lee estimated that effective area of the ground-water basin underlying San Dieguito Valley was 1,220 acres, and that the water table could be practic- ably lowered an average depth of 30 feet. With estimated specific yield of 20 per cent, utilizable storage capacity of the underground reservoir was therefore 7,300 acre-feet. A review by J. C. Kimble, Jr., engineer-geologist of the Division of Water Resources, in 1934, confirmed results of Lee's earlier studies. In estimating yield, Lee arrived at an annual amount of 2,430 acre-feet, based on the assumption that after three years of drought, ac- cumulated draft from the ground water would be completely replenished by surface runoff in the fourth year. * Water Supply Paper 446, "Geology and Ground Waters of the Western Part of San Diego County, California", U. 8. Geological Survey, I919. 141 The assumption that replenishment of the ground-water basin would be accomplish- ed in the fourth year in a drought period will not be true if Lake Hodges is constructed to the capacity required for complete basin development under coordinated operation with Sutherland Reservoir. A reservoir of such capacity will spill only at rare intervals, and replenishment from the drainage area below Hodges Dam will be very slow. Furthermore, the low elevation of the San Dieguito Valley will prevent appreciable lowering of the water table, especially at the lower end of the valley, because of the menace of infiltration of sea water. For these reasons, it is believed that development of the underground water basin in San Dieguito Valley is not sufficiently attractive to warrant further considera- tion, except by overlying land owners. Charles H. Lee in 1919 estimated that utilizable storage capacity of the San Pas^jUal Valley ground-water basin -.ras 15,200 acre-feet. J. C. Kimble, Jr., in his 1934 review arrived at the same capacity. A reservoir at Lake Hodges, having capacity sufficient for complete basin de- velopment under coordinated operation with Sutherland Reservoir, will drown over half of the San Pasqual Valley ground-water basin more than 50 per cent of the time. This condi- tion will make utilization of the basin on a safe yield basis impracticable from the oper- ating standpoint. However, the basin will be available as an emergency source of supply during drought periods, and water in the total amount of approximately 13,000 acre-feet can then be obtained. Reduction of Natural Consumptive Use Conservation of water lost by consumptive use of native vegetation in San Die- guito Basin is considered practicable only in San Pasqual Valley, where, through lowering of the water table below the root zone a sufficient distance and maintaining it at that elevation, a moderate amount of water can be salvaged by a program of pumping and deliver- ing the water into Lake Hodges. A complete field survey of irrigated crops and native vegetation in San Pasqual Valley was conducted in 1945. Aerial photographs covering the valley, taken in the year 1959, also are available, from which a reasonably accurate picture of culture in 1939 was obtained. As is shown in Table 42 {page 143), a small decrease in the area given over to irrigated agriculture occurred between 1939 and 1945. However, for purposes of this study the mean between 1939 and 1945 survey values was taken as representing present conditions. Unit values of consumptive use were based on preliminary estimates made by the Soil Conservation Service of the United States Department of Agriculture, at the request of and in cooperation with the Division of V/ater Resources*. These values were derived from experimental data obtained by the Soil Conservation Service in connection with its compre- hensive hydrologic investigation of the adjacent San Luis Rey Valley, and were adjusted to conditions existing in San Pasqual Valley. Application of unit consumptive use values to areas of native vegetation and man-made culture determined by the crop surveys results in an estimate of total gross seasonal consumptive use in San Pasqual Valley, under present * Preliminary Progress Report, "Consumptive Use of Water Investigations in San Pasqual Valley, California", Division of Irrigation, Soil Conservation Service, U. S. Department of Agriculture, September 14, 1945, included as Appendix D, herein. 142 conditions, of approximately 8,800 acre-feet. Of this total seasonal use in San Pasqual Valley, about 1,400 acre-feet constitute consumptive use by man-made culture, while the remaining 7,400 acre-feet are lost through consumptive use by native vegetation, or evapo- ration from soil and natural water surfaces. TABLE 42 ESTIMATED GROSS SEASONAL CONSUMPTIVE USE BY IRRIGATED CROPS IN SAN PASQ,UAL VALLEY Type of Crop 1939 Crop Survey 1945 Crop Survey Area in Acres Consumptive Use Area in Acres Consumptive Use in Feet of Water in Acre-Feet in Feet of Water in Acre-Feet Alfalfa 124.8 3.4 424 225.4 3.4 766 Sudan grass 71.8 3.4 244 70.2 3.4 239 Grain 5.8 1.5 9 1.5 Field crops 243.9 1.5 366 115.4 1.5 173 Orchard 68.8 2.4 165 44.3 2.4 106 TOTALS 515.1 1,208 455.3 1,284 1939 and 1945 Crop Surveys Mean area of irrigated crops 485 acres Mean unit consumptive use 2.57 feet of water Mean total consumptive use 1,246 acre-feet In order to determine the amount of water that might be salvaged in San Pasqual Valley by lowering the ground water from its normal levels, consumptive use was estimated with water levels successively lowered by stages to a maximum of eight feet. It was as- sumed that present irrigated agricultural crops would be maintained by surface irrigation. Unit consumptive use values for various depths of water table below the ground surface were likewise based on data secured from the Soil Conservation Service. Results of apply- ing these consumptive use values to present types of vegetation throughout the valley are listed in Table 43 (page 144), and shown graphically on Plate XV, "Effect of Lowering Av- erage Levels of Ground Water on Total Gross Seasonal Consumptive Use in San Pasqual Val- ley". It may be noted that by lowering the ground water eight feet below the normal level a theoretical saving of approximately 4,750 acre-feet can be effected seasonally. Further- more, over 75 per cent of this salvage results from an average lowering of the ground water of only two feet, and over 92 per cent from a lowering of foiir feet. It is probable that in actual practice, however, the salvage from natural losses in San Pasqual Valley will be only about 50 per cent efficient. 145 TABLE 43 ESTIMATED GROSS SEASONAL CONSUMPTIVE USE IN SAN PAS^UAL VALLEY WITH WATER TABLE AT VARIOUS ELEVATIONS UNDER PRESENT CONDITIONS OF CULTURE I Average Ground-Water Levels Total Consumptive in Acre-Feet Use Normal 8,800 Lowered one foot 6,490 Lowered two feet 5,200 Lowered three feet 4,640 Lowered four feet 4,390 Lowered five feet 4,220 Lowered six feet 4,130 Lowered eight feet 4,050 If the City of San Diego, in securing water rights in San Pasqual Valley requir- ed for construction of a larger Lake Hodges, acquires the entire valley floor, it can prob- ably conserve an estimated 2,000 acre-feet per season by reducing consumptive use of na- tive vegetation, and at the same time allow full irrigation of presently irrigated lands In the upper end of the valley. This will involve installation of a system of wells, pumps and pipe lines to systematically lower the water table, and dump the conserved water into Lake Hodges. The increment to gross evaporation from Lake Hodges caused by this relatively small amount of additional supply will be inconsequential except during rare periods of very low reservoir stages, since the reservoir water surface area will not be materially increased at normal stages. In operation of such a conservation project, the upper portion of the ground-water basin will automatically be utilized for cyclic storage, as the basin will probably refill in all except extremely dry years. 144 PLATE XSC rt 1 2 UJ u li. 1 °^ 3 H < O z D 4 O tr o L. o z QC U o _l 6 7 8 ^ ^ ^ / ' / / / 40 E G C 00 5000 6000 7000 8000 90 CONSUMPTIVE USE - ACRE - FEET FFECT OF LOWERING AVERAGE LEVELS OF .ROUND WATER ON TOTAL GROSS SEASONAL .ONSUMPTIVE USE N SAN PASOUAL VALLEY 00 145 CHAPTER VIII FLOOD CONTROL WORKS IN SAN DIEGUITO BASIN The general statements presented in Bulletin No. 48 relative to history of floods, characteristics of flood occurrence, and variation of flood flows on San Diego County streams are directly applicable to San Dieguito River. The following discussion of floods and flood control is largely limited to developing and presenting the effect of conservation reservoirs upon floods in San Dieguito Basin. Flood flows in San Dieguito Basin are under further stu_,y by the Division of Water Resources in connection with a State-wide investigation of water resources, author- ized by Chapter IS^-l* Statutes of 1947, The results of these more refined studies may vary in detail from those presented herein, but it is believed that they will not be such as to modify present conclusions and recommendations with respect to flood control on San Dieguito River. Areas Subject to Flood Damage Overflow and damage by floods in San Dieguito Basin occur principally in San Pasqual and San Dieguito valleys. San Pasqual Valley lies between elevations 350 and 460 feet, and extends along the river for approximately 5.5 miles, with an approximate average width of 3»000 feet. The transversely level valley floor comprises about 2,100 acres, of which only about 485 acres are devoted to irrigated crops. The remainder of the area is given over to native vegetation, including about 1,250 acres of salt grass pasture, and stream channel. Most of the cropped land and improvements are located in the upper one and one-half miles of the valley, which is least subject to overflow. Throughout the remainder of the valley the river channel is shallow, and between floods becomes choked with dense growth of na- tive brush. Capacity of the channel is so limited that the larger portion of the valley Is subject to overflow with only moderate floods, while large floods menace the entire 2,100 acres of valley floor. San Dieguito Valley extends upstream from the coast highway a distance of ap- proximately six miles, and derives only negligible flood protection from Lake Hodges, some five miles above it. The valley floor, as measured from U. S. G. S. maps, covers an area of approximately 2,800 acres, and has an average width of approximately 3,800 feet. Culture of irrigated crops is confined to an area of about 1,000 acres, largely in the upper part of the valley. Because of past flood experiences, the area given over to per- manent crops and improvements within the valley floor is limited. San Dieguito Valley, for its lowermost one and one-half miles, was originally a tidal marsh, but near the ocean there are now concentrated a number of improvements, consisting of the Del Mar Turf Club and San Diego County Fair grounds, highway, railroad, and utility crossings, and a number of beach homes between the highway and ocean. The turf club and fair grounds, located on property of the 22nd District Agricultural Association, would.be completely inundated by a large flood under present conditions. Short span portions of highway and railroad crossings would also be damaged, and a small number of beach homes probably ser- iously damaged or destroyed. 147 Flood Characteristics While general characteristics of floods in San Diego County were described in Bulletin No. 48, it was necessary during the present investigation to make detailed studies of size and frequency of flood flows in San Dieguito Basin, as well as analyses of flood hydrographs. These data were used largely in determining probable effects of proposed conservation reservoirs on flood flows. Size and Frequency of Flood Flows In Table 44 are listed runoff characteristics of the maximum flood of record in San Dieguito Basin, that of January 27, 1916. TABLE 44 MAXIMUM FLOOD OF RECORD IN SAN DIEGUITO BASIN January 27, I916 Location Mean Daily Flow in Second-Feet Peak Flow in Second-Feet Total per Square Mile Total per Square Mile Sutherland dam site Pamo dam site Hodges Dam 10,800 14,100 37,200 200 127 123 21,100 28,400 72,100 390 236 238 Probable size and frequency of mean daily flood flows at Sutherland, Pamo and Hodges dam sites, under present conditions, are tabulated in Table 45j and shown graphic- ally on Plate XVI, "Probable Frequency of Occurrence of Floods in San Dieguito Basin". TABLE 43 ESTIMATED MAGNITUDE AND FREQUENCY OF MEAN DAILY FLOOD FLOWS IN SAN DIEGUITO BASIN UNDER PRESENT CONDITIONS Period of Record Mean Daily Flows Equaled or Tributary Utilized Exceeded, in Second-Feet, Probably Location Drainage Area in in Study Occurring on the Average Once in Square Miles Inclusive Number 10 23 50 100 230 Dates of Years Years Years Years Years Years Sutherland dam site 34 1913-1924 1936-1947 23 4,000 7,000 9,000 12,000 16,000 Pamo dam site 111 I9O6-I923 17 8,000 14,000 19,000 24,000 32,000 Hodges Dam 303 1906-1930 25 14,000 27,000 38,000 52,000 70,000 The foregoing estimates of probable flood frequencies at Sutherland dam site are based upon the 23 years of available runoff record of Santa Ysabel Creek near Mesa Grande. These records cover the periods from January 1913 to September 1924, and from October 1936 to September 1947, inclusive. It will be noted that the period covered does not Include 148 PLATE - XVI 5 1 2 to tr < LiJ > •■^ 5 ul () z 10 UJ tr D O J o O >- u z UJ O UJ 50 cr U- 100 200 \ i / y 1 I / / / 1 '' / / / / / / / / / / / y J ' I ' PAMO DAM SITE / 1 SUTHERLAND DAM 5ITE- ) / / ) / r / / 1 / / / / / / / / / / / t 1 / / / / r J ■ / / / / / / / X * 1 / / ,/ / / A i 1 ! i 1 1 / / / A / c_ HC )DGES DAM 1 i ! / / / / 1 / y / ' 1/ / / 1 i>^ / / X y /' '■ / \A y* ' X y^ y ' ' 1 ; 1 i .^ ' ^ 1 i i ' 1 1 I 2 5 1 2 5 10 20 50 MEAN DAILY FLOW -EQUALED OR EXCEEDED IN 1000 SECOND - FEET 00 PROBABLE FREQUENCY OF OCCURENCE OF FLOODS IN SAN DIEGUITO BASIN UNDER PRESENT CONDITIONS 149 the February 1927 flood, which flood was probably next in magnitude to that of February 1916. Probable flood frequencies at Pamo dam site are based upon runoff records of Santa Ysabel Creek near Escondido for the period from I906 to 1911f and upon records for Santa Ysabel Creek near Ramona for the period from 1912 to 1923^ Estimated flood frequencies at Hodges Dam, presented herein, are taken from Bulletin No. 48, and were based upon the 25-year period from 1906 to 1930. Mean daily flood flows for the period from 19O6 to 1912 were estimated from recorded flows of Santa Ysabel Creek near Escondido. Flood flows for the period from 1912 to I916 were based upon recorded flows of San Dieguito River at Ber- nardo, with estimated contribution of the drainage area between Bernardo and Hodges Dam added. Runoff records directly applicable to Hodges Dam were available for the period from 191b to 1930. The method used in estimating probable size and frequency of flood flows was as follows: 1. Mean dally flows of each flood of record were listed in order of their magnitude. 2. The number of times a given mean daily flow was equaled or exceeded in the period of record was converted to the number of times the flow would be equaled or exceeded in 100 years, by multiplying by the number of times the period of record was contained in 100 years. 3. Values of mean dally flows were plotted on a logarithmic graph in relation to their frequencies. 4. Trend of the plotted points was extended by a smooth curve through and beyond the plotted points. Flood Hydrographs Only a few hydrographs of flood flows on San Dieguito River are available, and most of these have been computed from records of reservoir operation, or from observed gage heights and rating curves extended by estimates of flow based on surface velocities or Kutter's formula. In consequence, they are considered only approximate. Available flood hydrographs at Sutherland and Pamo dam sites and at Hodges Dam are shown on Plate XVII, "Hydrographs of Floods of Record in San Dieguito Basin", wherein peak flow is ex- pressed as its ratio to maximum mean 24-hour flow. It will be noted that a computed mean hydrograph has been drawn for each of the three sites. In order to evaluate possible effect of the several reservoirs on floods, and to establish spillway and freeboard requirements, it was necessary to compile a design, or "probable" hydrograph of flood flow under present conditions. The ratio of crest flov/ to maximum mean 24-hour flow, for various floods of record at the three proposed reservoir locations, is given in Table 46 (page 152). Hydrographs of design floods for the three locations are shown on Plate XVIII, "Probable Hydrographs of Flood Flows in San Dieguito Basin", in which the hourly rate of flow is expressed as a ratio of the maximum mean 24- hour rate, and may be converted to second-foot values for a given frequency of flood by applying mean daily flood flows given in Table 45. The mean hydrograph for the Sutherland site, shown on Plate XVII, was accepted as the design flood hydrograph for that location. In this case the ratio of crest flow to maximum mean 24-hour flow is 3«11 to 1.0. Duration of recorded flood crests at the mean maximum 24-hour rate varies from five to eight and one-half hours. Corresponding duration on the probable flood hydrograph is seven hours, wftiile average volume of the crest above the mean 24-hour rate is 28 per cent of maximum 24-hour volume. 150 PLATE YVn o IT D O I -i (\j Z < UJ D 2 X < 5 z o IT o 10 D o LJ z z z 25 20 15 10 5 5 10 15 20 25 HOURS BEFORE HOURS AFTER CREST CREST SUTHERLAND DAM SITE 2« 20 16 12 8 ■< HOURS BEFORE CREST HOURS AFTER CREST PAMO DAM SITE HOURS BEFORE CREST 30 25 20 15 10 5 HOURS AFTER CREST 5 10 15 20 25 30 5 1 LEGEND o k _, o_ FEB, 14 1927 APR. B 1926 i \ — JAN IT I9re a. D O ^ l-'O t.\ z < , fm 5 D /■^ Wi 'i ^ ^. X < n ^ iJ _/ V HYDROGRAPHS OF FLOODS OF RECORD IN SAN DIEGUITO BASIN HODGES DAM i51 TABLE 46 RATIO OF CREST FLOOD FLOWS TO MAXIMUM ME-fL^I 2 4 -HOUR FLOWS IN SAN DIEGUITO BASIN Ratio to Unity Location Date of Occurrence Jan. 17, 1916 Jan. 27. 1916 Mar. 12, 1918 Dec. 20, 1921 Dec. 26, 1921 Feb. 16, 1927 Mar. 2, 1938 Average Sutherland dam site 1.95 3.38 4.26 2.84 3.11 Pamo dam site 3.94 1.58 2.76 Hodges Dam 1.51 1.67 1.45 1.48 For Pamo dam site the probable hydrograph has a ratio of crest flow to mean maximum 24-hour flow of 2.8 to 1.0. The 54 square miles of drainage area above Suther- land and the 57 square miles between Pamo and Sutherland are quite similar in length, ele- vation, range and slope. However, mean elevation of the basin above Sutherland is greater than that for the area between Sutherland and Pamo. It is estimated, from observed varia- tion of rainfall intensity with elevation, that the area above Sutherland contributes 51 per cent of a major flood flow at Pamo dam site. Channel distance between the two points is approximately six miles and is traversed by flood flows in about an hour. Proportions of the probable hydrograph of Pamo were therefore determined by the summation of two prob- able hydrographs for Sutherland dam site, with a lag of one hour between them, the hydro- graphs being adjusted in the proportions of 0.49 to O.5I, in accordance with the runoff ratio discussed above. Volume and shape of the resulting flood crest are similar to those for the mean hydrograph shown on Plate 2VII. At Hodges Dam the mean ratio of crest flood flow to maximum mean 24-hour flow, for three floods listed in Table 46, is 1.48 to 1.00. However, analysis of available hydrographs of floods on other streams in San Diego County indicated that the mean hydro- graph on Plate XVII was not representative of flood conditions to be expected at Hodges Dam. The probable hydrograph of flood flow at Hodges Dam, shown on Plate XVIII, is there- fore based on mean hydrographs of floods occurring not only in San Dieguito River at Lake Hodges, but also in San Luis Rey River near Mesa Grande and San Diego River near Santee, in adjoining drainage basins. Resultant probable crest flow is I.70 times the maxlmiun mean 24-hour flow. Estimated frequency and mag/iitude of probable crest flood flows at Sutherland and Pamo dam sites, and at Hodges Dam, are listed in Table 47 (page 154). 152 PLATE XSm D o Z I (OliJ o p Hi Zx o 25 20 15 10 5 HOURS BEFORE CREST 5 10 15 20 25 HOURS AFTER CREST SUTHERLAND DAM SITE 300 ?? 5 ^t 200 O (V D X < O 25 20 15 10 5 HOURS BEFORE CREST 5 10 15 20 HOURS AFTER CREST S3 uj -I U^ q: kj cr Q. D z° $^ o w 25 20 15 10 5 HOURS BEFORE CREST 5 10 15 20 HOURS AFTER CREST PAMO DAM SITE HODGES DAM SITE PROBABLE HYDROGRAPHS OF FLOOD FLOWS IN SAN DIEGUITO BASIN UNDER PRESENT CONDITIONS 155 TABLE 47 ESTIMATED SIZE AND FREQUENCY OF CREST FLOOD FLOWS IN SAN DIEGUITO BASIN UNDER PRESENT CONDITIONS Location Tributary Drainage Area Ratio of Crest to Maximum Mean 24 -Hour Flow Crest Plow Exceeded, in Sec , Equaled or ond-Feet, Probably Area in Square Miles Average Elevation in Feet 25 Years 50 Years 100 Years 250 Years Sutlierlanca dam site Pamo ciam site Hodges Dam 54 111 303 3,350 2,900 1,900 3.11 2.80 1.70 21,800 39,200 45,900 28,000 53,200 64,600 37,300 67,200 88,400 49,800 89,600 119,000 Flood Control On the basis of preliminary studies, the control of large floods in San Pasqual and San Dieguito valleys solely by levees or channel improvements is not considered to be economically feasible at this time, with possible exception in the case of a short chan- nel at the lower end of San Dieguito Valley. Adequate flood channels in these valleys would occupy areas out of proportion to the lands and improvements protected. Levees con- structed from the friable native soils would require expensive protection, and costly con- nections to lateral drainage channels would be necessary. Maintenance costs would be high on some portions of channel, due to the heavy growth of brush and trees encouraged by the high water table. It is reasonable to suppose that some degree of flood control in San Dieguito Basin, by reservoirs alone or In combination with Improved channels, might be justified. However, in the San Diego region conservation of water is paramount, and a plan of reser- voir operation which would reduce the catchment for conservation could only be considered if protection were offered to a highly developed area of concentrated population and cul- ture. Such is not the case at present in San Dieguito Basin. Any flood control reserva- tion in reservoirs under consideration would reduce their catchment for conservation. In this study, no attempt has been made to determine economic feasibility of providing res- ervoir storage space exclusively for flood control purposes, supplementary to require- ments for conservation. However, it has been found that a considerable reduction in size and frequency of crest flood flows on San Dieguito River below Lake Hodges would automat- ically result from normal operation of the complete development for conservation purposes. Effect of Conservation Reservoirs Sutherland Reservoir The 54 square miles of watershed above Sutherland Dam constitute only about 40 per cent of the drainage area tributary to the upper end of San Pasqual Valley. This val- ley is the first downstream area in San Dieguito Basin subject to appreciable flood dam- age from Santa Ysabel Creek. Although the Sutherland watershed is of relatively high run- off productivity, it contributes only about one-half of the flood Vcratc-srs reaching San Pasqual Valley. The valley, therefore, would be subject to continuing flood damage, even though Sutherland Reservoir were completely effective as regards flood control. However, no such control would be realized from a reservoir of 36,700 acre-foot capacity at the ]54 Sutherland site, the size which would be obtained by completing the dam as originally planned. This capacity is relatively small as compared with runoff at the site during flood seasons. Since it is assumed that the reservoir would be operated exclusively for conservation purposes, it might be full, or nearly full, to crest of spillway drum gates at times of occurrence of peak flood flows. With drum gates, there could be no storage of flood waters above the conservation pool level, and possible faulty gate operation might actually increase downstream peak flows. Effect of Sutherland Reservoir upon the probable once in 100-year flood is shown on Plate XIX, "Effect of Conservation Reservoirs in San Dieguito Basin on Crest Flows of Probable Once in lOO-Year Flood". Under the plan for complete conservation development of San Dieguito Basin rec- ommended hererin, a conservation reservoir of 310,000 acre-foot capacity is proposed at the Hodfes site, to be operated coordinately with the completed Sutherland Reservoir. This enlargement of Lake Hodges would flood more than 1,200 acres, or nearly 60 per cent of the entire floor of San Pasqual Valley, and any possible benefits from reservoir flood control at Sutherland would be confined to the remaining relatively small area. They would be of minor significance and undependable. The effects of Sutherland Reservoir on flood flows in San Dieguito Valley would be negligible. Sutherland Reservoir controls only a little over 15 per cent of the drain- age area above San Dieguito Valley, and the Sutherland watershed contributes less than one-quarter of the flood waters reaching the valley. Furthermore, it will be shown here- inafter that under the recommended plan for complete conservation development of San Dieguito Basin, the enlarged Lake Hodges in itself would provide a very large measure of flood protection to San Dieguito Valley, and v.ould render insignificant any effects at- tributable to Sutherland Reservoir. Pamo Reservoir Flood control storage at Pamo Reservoir would materially reduce crest flood flows In San Pasqual Valley. On the basis of the probable flood hydrograph of Plate XVIIl, crest flows at Pamo dam site could be reduced 30 per cent by flood control storage amounting to Ifa per cent of the maximum 24-hour flood volume. For a once in 100-year flood, this flood control storage reservation would amount to approximately 8,000 acre- feet. A conservation reservoir at Pamo, with capacity of 163,400 acre-feet, and with spillway crest 200 feet in length, would reduce the once in 100-year peak flood flow from 67,000 to 31,000 second-fe t, by temporary storage above the spillway crest. This is il- lustrated in Plate XIX. However, it has been shown in Chapter VII that under any plan for development of San Dieguito Basin which Included a reservoir at the Pamo site. Lake Hodges would have to be enlarged to a capacity of at least 174,400 acre-feet, in order to conserve runoff originating between Pamo and Hodges. Such enlargement of Lake Hodges would inun- date about one-half of the floor of San Pasqual Valley, and benefits from reservoir flood control at Pamo would be necessarily confined to the remainder. Under present conditions, with the existing Lake Hodges, effects of flood con- trol storage at Pamo Reservoir would be material as far downstream as San Dieguito Valley. However, with Lake Hodges enlarged to the capacity required for complete conservation development of the basin under coordinated operation with Pamo Reservoir, the enlarged Lake Hodges in itself would provide a very large measure of flood protection to San Dieguito Valley. Flood control effects of Pamo Reservoir in San Dieguito Valley would be minimized. 155 Comparative costs of additional yield from San Dieguito Basin reservoirs, as presented in Chapter VII, do not favor conservation development at Pamo. Flood control benefits that may be attributed to Pamo Reservoir are insufficient to alter this rela- tionship. Lake Hodges It has been stated that an enlarged Lake Hodges would provide a substantial amount of flood protection to San Dieguito Valley. The amount of storage capacity re- >;uired to regulate flood flows to a given proportion of their unregulated peak discharges at Hodges Dam, expressed as a ratio of mean daily flood volume, is shown by the uppermost graph of Plate XX, "Flood Control Effects of Lake Hodges on San Diegultc^ River". From the graph it may be determined that storage capacity equal to 22 per cent of the mean daily flood volume would be required to regulate crest flood flows to 50 per cent of their unregulated rate. This amounts to a storage reservation of 23,000 acre-feet for a once in 100-year flood. However, the reservoirs under consideration in this study should be operated for conservation. The provision of storage exclusively for flood control purposes may not be justified in this instance, in view of the incidental protection afforded by a large conservation reservoir at the Hodges site. The effect of conservation storage at Lake Hodges on crest flood flows in San Dieguito River is shown on both plates XIX and XX. By ponding or temporary storage above the spillway crest level, a conservation reservoir with capacity of 157,300 acre-feet would reduce peak flow of the probable once in 100-year flood from 88,400 to about 57,000 second-feet, or approximately 65 per cent of the unregulated flow. Similarly, a conser- vation reservoir with capacity of 224,800 acre-feet would achieve a reduction of the 100- year crest flood discharge to about 50,000 second-feet, while one of 340,700 acre-foot capacity would reduce such a flood peak to about 48,000 second-feet, or approximately 54 per cent of the unregulated rate of flow. No attempt has been made to evaluate flood protection benefits to San Dieguito Valley which would result from construction of an enlarged Lake Hodges, to be operated exclusively for conservation purposes. It is appar- ent, however, that such benefits would be substantial, and that a portion of the capital costs of the conservation reservoir could properly be charged tcj flood control. In addition to the foregoing direct reduction of flood peaks resultant from a large conservation reservoir at Lake Hodges, there would be small probability of floods occurring when such a reservoir was full. The probable amount of storage space available on April 1st in a large reservoir at Hodges operated exclusively for conservation purposes can be derived from the curve on Plate XXI, "Probable Volume of Water in Storage at Lake Hodges on First of April". The 24-hour volume of the probable once in 25-year flood at Hodges Dam is 53>600 acre-feet, or about I6 per cent of the storage capacity of a 340,700 acre-foot reservoir. Water in storage on April 1st would equal or exceed 84 per cent of total reservoir capacity in about 16 years in 100, on the average. The flood, therefore, could be accommodated within available reservoir space 84 yetrr out of a hundred, on the average, or 84 per cent of the time. In the same manner, it may be ascertained that the maximum 24-hour volume of a probable once in 50-year flood would be available, on the average, about 78 per cent of the time. The probable frequency of occurrence of a given regulated flood crest discharge may be estimated by combining probable frequencies of occurrence of vacant reservoir stor- age space, and of crest flood flows. For all reservoir stages above the spillway lip. 156 PLATE XK 1 \ LEGEND \ S SPILLWAY / \ -^ — -^ -"""^ J / LEGEND INFLOW TO / — FLOW OVER SPILLWAY / 1 /' r-- y / ^ — ^^j ~- -^CT =^- ^ » 20 16 12 e 4 HOURS BEFORE CREST HOURS AETER CREST SUTHERLAND DAM SITE MEAN DAILY PLOW 12.000 SECOND -FEET >0 16 12 8 4 4 S 12 16 20 HOURS BEFORE CREST HOURS AFTER CREST PAMO DAM SITE MEAN DAILY FLOW 24,000 SECOND-FEET t. 80 70 o _J U- 20 1 1 1 - LEGEND - rWFLOW TO RESERVOIR- FLOW OVEH SPILLWAY, WITH RESERVOIR CAPACITY OF IS7.300 ACRE -FEET . 224.800 ACRE -FEET 340700 ACRE-FEET k \ / \ / \ / ,^ \~ \. 1 •^ t* K. y J k r \ \ k J ,', w \ N f^ ^ ^ -^ HOURS BEFORE CREST 4 e 12 16 20 HOURS AFTER CREST HODGES DAM MEAN DAILY FLOW 52.000 SECOND -FEET NOTE RESERVOIRS ASSUMED FULL TO SPILLWAY CHEST AT TIMES OF FLOOD OCCURRENCE. EFFECT OF CONSERVATION RESERVOIRS IN SAN DIEGUITO BASIN ON CREST FLOWS OF PROBABLE ONCE IN 100 -YEAR FLOOD 157 PLATE XC RATIO OF CREST OUTFLOW TO CREST INFLOW 3 o o o o c \ \ \ \^ "^^ ^-- 20 .40 .60 .80 RATIO OF FLOOD CONTROL STORAGE TO MEAN DAILY FLOOD VOLUME WITHOUT FLOOD CONTROL RESERVATION 1- Hj 120 Q Z 100 O u UJ f^ 80 60 to ^ 40 O 20 CO 5 ° \ \ '^^^ \:z 50 YEAR FLO OD "-. i: 100 YEAR FLOOD 'v ^ 1.25 1 i-EAR FLOOD 100 200 300 CAPACITY IN 1000 ACRE -FEET WITH FLOOD CONTROL RESERVATION FLOOD CONTROL EFFECTS OF LAKE HODGES ON SAN DIEGUITO RIVER 158 PLATE YVT STORAGE VOLUME EQUALED OR EXCEEDED IN PERCENT OF TOTAL CAPACITY 10 20 30 40 50 60 70 80 100 PROBABLE VOLUME OF WATER STORAGE AT LAKE HODGES ON FIRST OF APRIL Based on 340,700 Acre -Foot Reservoir Operated for 1917-36 Firm Yield (Reservoir Assumed Full on April L 1916) 1^9 routing of the flood through the reservoir is involved. If probable frequencies of occurrence of vacant storage space and of floods at Lake Hodges are combined as unrelated events, by statistical methods, the probable frequencies of occurrence of given regulated crest flood flows below Hodges Dam are as tabulated below. Frequencies for the regulated flood are based upon 310,000 acre-feet of storage capacity in Lake Hodges, operated for conserve. t ion purposes. Crest Discharge in Second-Feet Unregulated flood, probable frequency of occurrence, once in Regulated flood, probable frequency of occurrence, once in 45,900 64,600 88,400 25 years 215 years 50 years 320 years 100 years 440 years The upper limits of magnitude and frequency of occurrence of floods to which the foregoing analysis or reasoning may be applied are not definite. However, it is observed that complete development of San Dieguito Basin for water conservation, as defined earlier in this report, would have completely retained all flood flows of the past 42 years, from 1906 to 1948, inclusive. Future Flood Control Works Findings of the present studies support the conclusion that complete development of San Dieguito Basin for conservation will limit future flood control works to the por- tion of the basin below Hodges Dam, namely, San Dieguito Valley. As was developed in Bul- letin No. 48 and mentioned heretofore, water conservation is the priinary consideration in the San Diego region, and storage space reserved for flood control should be considered only above that required for conservation. A conservation reservoir at Lake Hodges with storage capacity exceeding 225,000 acre-feet would reduce crest flow of the probable once in 100-year flood by not less than 40 per cent. In addition to this direct reduction of large flood crests by temporary storage above the spillway level, v.ith complete development of San Dieguito Basin for con- servation there would usually be sufficient vacant storage space available to absorb most floods having a magnitude less then the probable once in 50-year flood. It therefore may be concluded that some proportion of the cost of a large conservation reservoir at Lake Hodges could- properly be charged to flood control. The amount of such participation should be based on capitalization of the reduction in estimated average annual flood dam- ages. Studies of probable future flood damage should recognize the percentage of time that vacant storage space would be available in conservation reservoirs, as well as the effects of temporary storage above spillway levels. 160 CHAPTER IX CONSERVATION WORKS ON SAU DIEGO RIVER Bulletin No. 48 presented a plan contemplating the most economic complete de- velopment, utilization and control of waters of the San Diego River for all consumptive purposes and for flood control, in coordination with the then existing development. This plan included a reservoir on San Vicente Creek and one on San Diego River in Mission Gorge. San Vicente Reservoir has since been constructed by the City of San Diego, but to a smal- ler capacity than was recommended in the 1935 report. As regards reservoirs in Mission Gorge, Bulletin No. 4-8 presented studies and cost estimates for two alternative sites, namely, Mission Gorge Reservoir No. 2 and Mission Gorge Reservoir No. 3> and it was shown that the first of these was the more favorable economically. A current comparison of res- ervoirs in Mission Gorge is presented in this chapter, and studies for an additional site. Mission Gorge No. Zero, have been included. A cost estimate has also been prepared for increasing the size of San Vicente Reservoir to provide additional capacity suggested by the City of San Diego for storage of imported water, as well as for conservation of local supplies. Mission Gorge Reservoirs Mission Gorge No. Zero dam site is located about 1,000 feet upstream from the Old Mission Dam, at the extreme upper end of Mission Gorge. Mission Gorge No. 2 dam site is approximately three-quarters of a mile downstream, at a point 3.100 feet below Old Mission Dam. The No. 3 dam site is a further 1.8 miles downstream, and about one-half mile above the upper end of Mission Valley. Streambed elevation at the Mission Gorge No. Zero site is 278 feet, compared with 244 feet at the No. 2 site and 100 feet at the No. 3 site. Areas and Capacities An aerial topographic survey of the Mission Gorge reservoir area was made by Fairchild Aerial Surveys, Inc., in July 1945, in connection with the present investiga- tion. The survey included elevations up to 330 feet, and extended downstream sufficiently far to include dam site No. 3, the lowest site. The following maps were compiled from the survey, by Fairchild Aerial Surveys, Inc.: (a) Mission Gorge Reservoir Topography, San Diego River topography: scale 1 inch ^ 400 feet; contour interval, 10 feet; in 2 sheets. triangulation : scale 1 inch = 2,000 feet. (b) Mission Gorge No. Zero Dam Site topogj-ephy: scale 1 inch = 200 feet; contour interval, 10 feet. Areas and capacities of the three reservoirs, computed from data of the 1945 sur- vey, are given in Table 48 (page 1d2). Reservoir storage capacities, computed from areas measured on the more accurate topographic maps made in 1945» differ a little from capaci- ties given in Bulletin No. 48 for Mission Gorge reservoirs Nos. 2 and 3. The 1945 survey found 2,230 acre-feet less capacity at elevation 350 feet, and 3»050 acre-feet less at elevation 350 feet, for Mission Gorge Reservoir No. 2. Dams at this site would therefore 161 have to be from 1.2 feet to 1.5 feet higher than those described in Bulletin No. 48, in order to provide storage capacities considered therein. Similarly, a dam at Mission Gorge No. 3 site to provide 29,200 acre-feet of storage capacity would have to be 1.0 feet higher than contemplated in Bulletin No. 48. However, for remaining reservoir capacities considered in Bulletin No. 48 for the No. J site, results of the 194^ survey made no ap- preciable difference in heights of dams. TABLE 48 AREAS AND CAPACITIES OF MISSION GORGE RESERVOIRS Based on 1945 Topographic Survey by Fairchild Aerial Surveys, Inc. Dam Site No. 3 Dam Site No. 2 Dam Site No. Zero Elevation {U.S.G.3.) Water Capacity Water Capacity Water Capacity Datum Surface in Surface in Surface in in Feet Area in Acre- Area in Acre- Area in Acre- Acres Feet Acres Feet Acres Feet 97 100 110 1 7 120 42 150 14 139 140 18 297 150 22 497 160 28 745 170 40 1,084 l80 47 1,522 190 56 2,056 200 68 2,655 210 80 5,598 220 90 4,255 250 104 5,227 240 120 6,548 250 156 7,650 2 9 260 IbO 9,110 7 51 270 188 10,848 Id 165 280 221 12,895 50 594 1 7 290 280 15,401 65 865 28 155 500 404 18,818 165 1,994 121 896 510 629 25,978 559 4,602 508 5,057 520 977 32,006 674 9,768 612 7,655 550 1,484 44,312 1,147 18,872 1,071 16,048 540 2,165 62,545 1,792 55,567 1,699 29,897 350 2,788 87,299 2,585 54,450 2,278 49,786 Reservoir Lands A reservoir with maximum normal water surface at elevation 556 feet would have storage capacity of 25,700 acre-feet with a dam at Mission Gorge No. Zero site, and 29,200 acre-feet with a dam at Mission Gorge No. 2 site. A capacity of 29,200 acre-feet would be obtained from Mission Gorge Dam No. 5 with water surface at elevation 316 feet. Corres- ponding elevations of dam crests in the cases of the two maximum water levels would be 555 and 531 feet, respectively. If it be assumed that land would have to be acquired to ele- vations of the crests of dams, purchase of 2,268 acres would be required for the foregoing Mission Gorge No. Zero and No. 2 reservoirs, and 1,202 acres for Mission Cksrge Reservoir No. 5. 162 As was demonstrated in Bulletin No. 48, cost of reservoir lands for Mission Gorge No. 2 and No. 5 reservoirs would be a considerable portion of total reservoir costs. Estimated rights of way costs in Bulletin No. 48 were based upon 1929 appraised values as determined by Tax Factors, Incorporated. For the current investigation, costs of land acquisition were estimated by B. A. Etcheverry and G. F. Mellin, consultants, whose re- port is included in Appendix 0. The estimates correspond with 194? values and were de- rived by a method similar to that described for Lake Kodges in Chapter VII of this report. The following factors were applied to 1946 assessed valuations in order to convert them to 1947 market values: Type of Property Factor Unimproved farm land Improved property land improvements Scripps and Good ranches land improvements (mostly farm buildings) 4 4 6 4 5 ^ Estimated costs of reservoir lands for Mission Gorge No. Zero and No. 2 reser- voirs include cost of a levee to protect improvements on the San Diego County Farm. A summary of estimated rights of way costs is given in Table 49. I TABLE 49 ESTIMATED COSTS OF REQUIRED jUDDITIONAL RESERVOIR LANDS FOR MISSION GORGE RESERVOIRS (Based on 1947 Market Values) Mission Gorge Reservoir No. 2 and No. Zero No. 3 Elevation up to which land would be acquired, in feet Area flooded (excluding presently city-owned land), in acres Area to be acquired (excluding presently city-owned land), in acres ESTIMATED COSTS Land Improvements Dama ge s 353 2,161 2,268 * 247,000 551,500 113,200 331 1,163 1,202 * 58,700 127,600 24,900 TOTALS $ 911,700 $ 211,200 Estimated 1935 costs based on 1929 market values $ 600,000 $ 180,000 Costs of reservoir lands for Mission Gorge reservoirs No. Zero and No. 2 might be reduced by acquiring title in fee only up to some elevation lov.-er than crests of the dams, and securinf flowage easements on remaining higher properties. In Bulletin No. 48 163 it was developed that probable crest flood flov;s at Nission Gorge No. 2 dam site, with comolete conservation development of San Diego River, would be as follows: Probable crest flood flow occurring, on average Once in 25 years Once in 50 years Once in 100 years Once in 250 years Crest flood flow, in second-feet Corresponding reservoir water surface elevation, in feet 336.0 16,200 340.6 33,100 343.3 50,100 345.7 This assumes a 500-foot length of spillway at elevation 33° feet, with weir coefficient of 3.33. In view of the foregoing, it might be considered sufficient to secure title to farm land up to about elevation 341 feet, and flowage rights between that level and elevation 353 feet. It would not be advisable to permit dwellings below elevation 350 feet. Cost Estimates In Bulletin No. 48, estimates of cost were presented for reservoirs at Mission Gorge No. 2 and No. 3 sites, both reservoirs involving concrete gravity dams with fixed- crest overflow spillways. Cost estimates for similar reservoirs have been made during the present investigation, but with costs revised to correspond to construction and rights of way prices prevailing in April 1947. In addition, estimates have been prepared, on the basis of April 1947 prices, for a reservoir with a concrete variable-radius arch dam at the No. 5 site, and for one with a combined concrete gravity and rolled earth-fill dam at the Mission Gorge No. Zero site, both dams having spillways of the fixed-crest overflow type. Since publication of Bulletin No. 48 in 1935, general construction costs have increased from 80 to 100 per cent, but for some items, including heavy excavation and mass concrete, the increased cost has been somewhat less, amounting to from 50 to 60 per cent. During the same period prevailing interest rates have declined from the five per cent fig- ure utilized in Bulletin No. 48 to an estimated three per cent for the current studies, so that annual costs of financing a given project have not increased in proportion to the rise in capital costs. Although estimated 1947 capital cost of Mission Gorge Reservoir No. 2 as presented herein is 68 per cent greater than the estimate for 1935, annual costs for this project increased only nine per cent in the same period. The greater proportion of increased costs for the 1947 estimates is reflected in major items of concrete, relocation of roads and pipe line, and lands and improvements. Cost of concrete is based upon obtaining aggregates and hauling them from commercial sources along San Diego River. Cost of relocating a county road is based upon a 30-foot wide roadbed in sidehill locations and a 36-foot wide roadbed in flat terrain. The relo- cated road is provided with a 22-foot width of asphaltic pavement. Cost of relocating a 5o-inch diameter pipe line assumes replacement of the existing steel line with concrete- cylinder pipe. However, some saving over this might be effected by salvaging and re-laying the existing pipe. Costs of pumping water from Mission Gorge reservoirs to the city distribution system are not included in the estimates. The City tentatively plans that water would be 164 I pumped easterly throucli the existine El Capitan Pipe Line to Santee, to a hydraulic grade line elevation of about 575 feet. From this point it would flow through the existing El Monte Pipe Line to the new Alvarado Treatment Plant adjacent to Murray Reservoir. In the cases of Mission Gorge reservoirs Nos. Zero and 2, average pumping lift would be about 330 feet, whereas in the case of Mission Gorge Reservoir No. 3 it would be approximately 350 feet. The estimates include allowances of ten per cent for administration and engin- eering, 15 per cent for contingencies on construction items, and three per cent interest on capital investment during one-half the estimated construction period. Annual costs include interest at three per cent per annum, amortization over a 50-year period, depre- ciation of dams on the basis of 100-year life and of outlet works on the basis of 50-year life, and operation and maintenance charges. Mission Gorge Reservoir No. Zero A cost estimate was made for a dam and reservoir at Mission Gorge No. Zero site havint maximum storage capacity of 25,700 acre-feet, with water surface at elevation 556 feet. The estimate is based on a concrete gravity section 86O feet in length across the river channel, with an additional 6OO lineal feet of rolled earth fill extending from the right end of the concrete structure to high ground on the right abutment. The concrete gravity dam section used in the estimate is 75 feet in heisht from streambed to top of non-overflow abutments, or 58 feet from streambed to spillway crest. It has a vertical upstream face, while the downstream face has a slope of 0.8 horizontal to 1.0 vertical, and intersects the upstream face at elevation 355 feet, the crest of the non-overflow por- tion. The estimate includes provision for a concrete cutoff at the upstream edge, sxtend- ing ten feet below the general level of the dam foundation. The non-overflow portion of the gravity dam has a crest width of 15 feet. The reservoir spillway consists of 515 lineal feet of ogee overflow section, centered above the channel, in the concrete gravity portion of the dam. After deducting 15 feet for a gate pier, net length is 500 feet. Crest of the spillway is at an elevation of 336 feet, and its discharge capacity with reservoir water surface at elevation 353 feet is 116,500 second-feet. A concrete bucket is provided at the toe, to deflect the spill and reduce streambed erosion. Streambed at the site is approximately 250 feet vd.de, and it is assumed that the spillway bucket will be sloped transversely on either side of the channel, to fit the general slope of the foundation rock. No exploration was made of the foundation at this site. Visual inspection of the site, and of exposed rock at Old Mission Dam, indicates that suitable foundation will be found for any type of dam of moderate height. However, no definite decision to utilize Mission Gorge No. Zero site for a dam should be made without systematic exploration. For purposes of the estimate, required stripping is assumed to be to a depth of 20 feet for the concrete structure, and to a depth of five feet for the rolled earth fill. A relatively flat bench occurs along the ri^ht abutment at the site, above ground surface elevation 325 feet. This is the location of the rolled earth fill, v.ith crest width of 30 feet, and side slopes of three horizontal to one vertical. Crest of the earth fill is at elevation 358 feet, and it laps and imbeds the crest of the concrete section for a distance of 100 feet. 165 The cost estimate includes provision for two water supply outlets and one emer- gency, or sluice outlet. Each outlet consists of a JO-inch diameter steel pipe imbedded in concrete of the dam, and controlled by a 30-inoh slide valve located in a chamber. Center of the inlet of the pipes is at elevation 285 feet, or seven feet above streambed. Trash racks are located around a semi-circular concrete shaft built on the upstream face of the dam, and extending from the foundation up to the dam crest. Facilities for remov- al of trash racks and emergency gates consist of a hoist located on a pier constructed on the overflow section at the downstream side of the semi-circular shaft. Access to pier and hoist house is through a gallery constructed into the dam. The cost estimate includes charges for relocating 5-9 miles of county road, and an equal length of 36-inch diameter pipe line within the reservoir area. Based upon prices prevailing in April 1947, it is estimated that Mission Gorge Reservoir No. Zero will cost i5, 237, 500, while annual costs are estimated at $136,100. Detailed estimates of capital and annual costs are given in Appendix H. Layout of the dam is shown on Plate XICII, "Mission Gorge No. Zero Dam on San Diego River". A concrete gravity main structure, with rolled earth fill on the right abutment, provides a relatively simple layout for a dam at the Mission Gorge No. Zero site, and is comparable to the type of structures used for cost estimates in Bulletin No. 48 for dams at Mission Gorge No. 2 and No. 3 sites. However, cost estimates were also made for major items of a reinforced-concrete slab and buttress dam, and for a combination rock and earth fill structure. It is indicated that the slab and buttress design would cost about the same as the concrete gravity structure. A rock-earth-fill barrier would probably cost less than the concrete gravity dam, but the advantage would be largely offset by addition- al costs of spillway weir and outlet tower. Mission Gorge Reservoir No. 2 It was concluded in Bulletin No. 48 that the most economical plan for complete conservation of the water resources of the San Diego River Basin would include a reservoir at the Mission Gorge No. 2 site of 29,200 acre-foot capacity. The dam, upon which cost estimates for a reservoir of this capacity were based, consisted of a concrete gravity section with fixed-crest overflow spillway. The dam was 109 feet in height from streambed to top of non-overflow abutments, or about 92 feet in height from streambed to spillway crest. The upstream face of the dam section was vertical, while the downstream face had a slope of 0.807 to 1, and intersected the upstream face at elevation 353 feet, the crest of the non-overflow portion. Orest width of abutments was ten feet, and their downstream faces were vertical to their intersection with the downstream slope of the dam. The reservoir spillway, 510 feet in length, and with ogee overflow section, oc- cupied the greater part of the length of the dam. With spillway crest 1? feet below that of the dam, the estimated peak flow from a flood which might occur once in 1,000 years, on the average, would pass over the spillway without overtopping the abutment portions. Along the downstream toe of the dam, at the stream channel, a 300-foot length of concrete bucket section was provided. Concrete-lined channels along the toe of the dam were designed to collect waters from extremities of the spillway and discharge them into the stream channel over the bucket section. Service outlets consisted of two 30-inch diameter steel pipes at elevation 250 feet, imbedded in concrete of the dam and connecting with a delivery line leading from the 166 PLATE XXn PLAN 100 100 200 Crest El 353 "^*^ Spillway Crest El 336- - Crest El 356-, Trash Rack- -f^^ Ground Surface-- J^^m^-^" J^WT ELEVATION LOOKING UPSTREAM 00 '00 200 2-6' nip "ap-";^ '— 6'Sand & Gravel I '-6" dp Rap ,'12' Semi -Circular Tower t I " I Gale Hoist Control Tower SECTION B-B 30 60 SECTION A-A 30 30 60 MISSION GORGE NO. ZERO DAM ON SAN DIEGO RIVER SCALES AS SHOWN 167 reservoir. Control of flow in each pipe was provided by 30-inch diameter slide valves located in a chamber, access to which was from a gallery running through the dam. Up- stream from the valve in one of the service outlets, a 30-inch diameter pipe branched out to provide a sluiceway. This line, likewise provided with a slide valve, extended through the dam and discharged into the spillway bucket. The plan included a semi-circular con- crete gate tower, 12 feet in outside diameter, on the upstream face of the dam. The tower extended from the foundation line to the top of a pier located on the spillway crest, and was surmounted by a circular gate house. Control of water entering the tower was by means of three 30-inch diameter slide valves operated from the gate house, one located opposite the outlet pipes, and the other two at the one-third points between the lowest valve and the spillway crest. A semi-circular trash rack, raised by a hoist in the gate house, was provided for protection of the gates. Geology of the dam site was studied by Chester Marliave, geologist, whose report thereon was quoted in Bulletin No. 48. He was aided by information from drill holes and test pits, furnished by the City of San Diego. It is indicated that the site is suitable for construction of a concrete gravity dam and spillway as described herein. However, fur- ther exploration and study of foundation conditions should be made prior to entry into a construction program at the site. Based upon prices prevailing in April 1947, it is estimated that capital cost of Mission Gorge Reservoir No. 2, with 29,200 acre-foot capacity, and with dam and appurten- ances as described in Bulletin No. 48, is ^3, 586, 100, and that annual costs are $150,000. Corresponding estimates of 1935 costs, as published in Bulletin No. 48, were $2,142,700 and $137,800, respectively. A detailed estimate of 1947 capital and annual costs is given in Appendix H. Mission Gorge Reservoir No. 3 with Concrete Gravity Dam In Bulletin No. 48 a cost estimate was presented for a reservoir of 29,200 acre- foot capacity at the Mission Gorge No. 3 site, the concrete gravity dam being located at the so-called "lower" site. The dam was 231 feet in height from streambed to top of non- overflow abutments, or 21b feet from streambed to spillway crest. The upstream face of the dam section was vertical, while the downstream face had a slope of O.807 to 1, and in- tersected the upstream face at elevation 33I feet, the crest of the non-overflow portion. Crest width of abutments was ten feet, and their downstream faces were vertical to their intersection with the downstream slope of the dam. The reservoir spillway, 65O feet in length, and with ogee overflow section, oc- cupied the greater part of the length of the dam. With spillway crest 15 feet below that of the dam, the estimated peak flow from a flood which might occur once in 1,000 years, on the average, would pass over the spillway without overtopping the abutment portions. Along the downstream toe of the dam, at the stream channel, a 150-foot length of concrete bucket section was provided. Concrete-lined channels along the toe of the dam were designed to collect water from extremities of the spillway and discharge them into the stream channel over the bucket section. Service outlets consisted of two 30-inch diameter steel pipes at elevation 110 feet, imbedded in concrete of the dam and connecting with a delivery line leading from the reservoir. A third 30-inch diameter pipe line, running through the dam and discharging into the spillway bucket, comprised the sluiceway. Control of flow in each pipe was pro- vided by 30-inch diameter slide valves located in a chamber, access to which was from a 168 gallery running through the dam. The pltn included a semi-circular gate tower, 20 feet in outside diameter, on the upstream face of the dam. The tower extended from the founda- tion line to the top of a pier located on the spillway crest. The pier was surmounted by a circular gate house. Control of water entering the tov;er was by means of five 30-inch diameter circular slide valves, operated from the gate house, one located opposite the outlet pipes and the other four at the one-fifth points between the lowest valve and the spillway crest. A semi-circular trash rack, raised by a hoist in the gate house, was pro- vided for the protection of the gates. Geology of the dam site was studied by Chester Marliave, geologist, whose re- port thereon was quoted in Bulletin No. 48. He was aided by information obtained from earlier explorations, including data from test holes and pits at the upstream No. 3 site. It is indicated that the lower site is suitable for construction of a concrete gravity dam and spillway as described herein. However, further exploration and study of founda- tion conditions should be made prior to entry into a construction program at the site. Based upon prices prevailing in April 1947, it is estimated that capital cost of Mission Gorge Reservoir No. 3, with 29,200 acre-foot capacity and with concrete gravity dam and appurtenances as described in Bulletin No. 48, is |d, 157,200, and that annual costs are ^259, 000. Corresponding estimates of 1935 cost, as published in Bulletin No. 48, were ^3,oo5,bOO and |237,100, respectively. A detailed estimate of 1947 capital and annual costs is given in Appendix H. Mission Gorge Reservoir No. 3 with Concrete Arch Dam In an effort to determine the most economical solution to the problem of a dam at Mission Gorge No. 3 site, a preliminary design and cost estimate were made for a variable-radius arch dam with fixed-crest overflow spillway at the lower site. Geology of the dam site was studied by Chester Marliave, geologist, who was aided by information ob- tained from earlier explorations, including data from test holes and pits at the nearby "upper" site. That foundation conditions are not favorable for an arch design is apparent from the following quotations from his report: "Conditions for concrete arch construction are not as favorable on the abutments as for gravity loading. "From a geological viewpoint the present topographical features are not inducive for an arch dam. The system of fracturing exemplified in shear zone "G" on the right abutment offers a very unfavorable attitude for this abutment to resist arch thrust. "The preparation of the abutments for an arch dam at this site would in- volve a large amount of excavation which the writer believes would be eco- nomically prohibitive. "As there are serious geological problems to be contended with in con- sideration of each type or new location for a dam in this locality it is of paramount Importance that recognition be given to structural and physical conditions of the abutments in the design of any dam in this portion of the gorge." From the standpoint of topography, the site is not ideal for an arch dam, since the slope of the canyon walls is flatter than desirable and the contours are parallel with the thread of the stream. However, it is seldom that a site can be found with fa- vorable convergence of contours in a downstream direction, and this adverse condition at I the Mission Gorge No. 3 site might be overcome by heavy excavation. 169 Height of the arch dam, like that of the gravity structure considered for the same site, is 21b feet from streambed to spillway crest at elevation 316 feet. The dam is designed in accordance with a formula providing for gradual thickening of the arch from crovm to abutments, thus providing for a practically equal intensity of stresses at the crown and the abutments. Gravity abutments at the ends of the upper portions of the arch provide for thrust, which otherwise would not be satisfactorily transmitted to the hill- sides. Overall lenpth of the dam at spillway crest elevation is 96I feet, and of the arch proper 8II feet. The gravity section on the right abutment is 90 feet in length, while that on the left abutment is 60 feet in length. The plan provides for a sliding joint at elevation 120 feet, the dam below this elevation being designed to support the water load by gravity action, although arch action will add appreciably to its stability. Were it not for this provision, the probable ab- rupt change in profile at this elevation, after excavation has been completed, might cause severe localized stresses in the arch. In order to minimize tension in the abutments, the arch layout was made with central angles of 120 degrees or larger. This is the minimum angle without resultant ten- sion for a value of thickness divided by radius of 0.2. With a similar ratio of 0.3, the required central angle is 140 degrees. Excavation is assumed on the basis of radial contact at the abutments, and a depth to sound rock of 20 feet at the intrados. If it is found necessary to excavate to a greater depth at this point, a variation of ten degrees from radial is permissable, which would amount to about seven feet for an abutment thickness of 40 feet. The reservoir spillway consists of t)25 lineal feet of ogee overflow section cen- tered above the channel, with training walls five feet in thickness at either end. Dis- charge capacity with reservoir water surface at elevation 331 feet, the crest of the non- overflow abutments, is about 131,000 second-feet. The estimate includes provision for a concrete slab apron, ten feet thick below elevation I6O feet, and varied in thickness above that elevation to four feet near the top. Streambed at the site is approximately I60 feet wide, and it is assumed that the apron is sloped transversely at either side of the channel to fit the general slope of the foundation rook. The apron parapet wall is ten feet in thickness at the base, and five feet at the crest. No reinforcing steel is provided for the apron, or apron parapet and curtain walls, the structures being considered sufficiently massive to accomplish their purposes without reinforcement. While a parapet wall on the apron is included in the estimate, final design might prove this feature to be desirable only on the sloping portions above tail water level. In its lower portions, the wall may tend to produce eddies in a vertical plane, causing more undercutting at the toe than would be the case if the water flowed freely in a horizontal direction off the flat unobstructed floor. Outlet works include a 36-inch diameter steel pipe manifold, mounted on the up- stream face of the dam and encased in reinforced concrete. Five 30-inch diameter inlet valves are spaced at equal increments of elevation on the manifold. These gates are pro- tected by steel trash racks, and are operated by hydraulic cylinder controls from a gate house located on top of the gravity thrust section at the left abutment. The manifold ex- tends downstream in a concrete-filled trench beneath the dam and apron, from where it leads to the service main, being controlled by a gate valve. 170 Based upon prices prevailinf in April 19^7. it is estimated the capital cost of Mission Gorre Reservoir No. 3, with 29,200 acre-foot capecity and with a variable-radius concrete arch dam at the lower site, is ^5,241,900, and that annual costs are ^220,000. A detailed estimate of 1947 capital and annual costs is £,iven in Appendix H. Layout of the d«m is shown on Plate XXIII, "Variable-Radius Arch Dam at Lower Mission Gorge No. 3 Site on Sen Diego River". Comparison of Reservoirs Studies for Bulletin No. 48 indicated that the most desirable storage capacities for the then proposed San Vicente and Mission Gorge reservoirs were 174,^00 and 29,200 acre-feet, respectively. Although San Vicente Reservoir was actually built to a capacity of only 90,200 acre-feet, the increment to safe yield of the entire San Diego River system to be derived from a reservoir at Mission Gorge is no different than with a 174,500 acre- foot San Vicente Reservoir. This follows from the fact that during the I896-I905 critical period no spill would have occurred from either a 90,000 or 174,500 acre-foot San Vicente Reservoir, so that inflow and yield of Mission Gorge reservoirs would have been indepen- dent of this source in either case. Additional safe seasonal yields to be derived from construction of Mission Gorge reservoirs Nos. 2 and 3, respectively, under present condi- tions and with coordinated operation of the entire San Diego River development, are there- fore identical with those 'determined during the Bulletin No. 48 studies. Corresponding yield to be obtained from construction of Mission Gorge Reservoir No. Zero was determined by studies conducted during the current Investigation. The increments to total seasonal yield of the San Diego River development resultant from each of the reservoirs considered for Mission Gorge, together with unit costs based on 194? construction, rights of way and financing prices, are given in Table 50. TABLE 50 ESTIMATED AMOUNTS AND 1947 COSTS OF ADDITIONAL SAFE YIELD FROM RESERVOIRS AT MISSION GORGE WHEN OPERATED COORDINATELY IHTH THE EXISTING SAN DIEGO RIVER DEVELOPMENT Safe Yield Based on Critical Period 1895-96 to 1904-05, Inclusive Mission Gorge Reservoir No. Type of Dam Storage Capacity in Acre-Feet Additional Safe Seasonal Yield in Acre-Feet Annual Costs Reservoir Safe Yield per Acre-Foot Zero 2 3 3 Combination concrete gravity and earth fill Concrete gravity Concrete gravity Concrete arch 25,700 29,200 29,200 29,200 1,900 2,300 2,600 2,600 1136, ]00 150,000 259,000 220,000 i71.65 65.20 99.60 84.60 It is shown in Table 50 that Mission Gorge Reservoir No. Zero is less desirable than a reservoir at the Mission Gorge No. 2 site, both in amount and unit cost of addi- tional safe yield. It is also shown that increases in cost of construction and of reser- voir lands have not altered the conclusion reached in Bulletin No. 48 to the effect that Mission Gorge Reservoir No. 2 is more favorable than No. 3. As has been stated, costs of 171 pumping yield from Mission Gorge reservoirs to the San Diego city distribution system are not included in the foregoing cost estimates. If this item were included, the already high relative cost of yield from Mission Gorge Reservoir No. J would be further increased, as compared with that from either Mission Gorge Reservoir No. Zero or No. 2. However, if it should ever be found desirable to provide a recreational lake in Mission Gorge, the fact that the 'No. 3 site comprises canyon storage with materially lower evaporation losses than upstream sites should be considered. Economic analyses of such dual purpose develop- ments in Mission Gorge, which would involve higher dams to provide storage reservations for recreation as well as necessary conservation, have not been included in the present studies. Enlarged San Vicente Reservoir Although the existing San Vicente Reservoir of 90,200 acre-foot capacity is more than adequate to effect complete conservation of runoff from the tributary San Vicente Greek watershed, its enlargement for storage of foreign water may be desirable because of favorable geographical, climatological and storage characteristics of the site. Water from San Vicente Reservoir can be delivered by gravity to the Alvarado Filtration Plant, from which point about 85 per cent of the City's presently utilized service area can be served by gravity. The reservoir is characterized by small water sur- face area as related to storage capacity, and in this respect is highly efficient. Fur- thermore, the site is only rarely subject to hot desert winds, and average net depth of unit evaporation is not excessive, as in the case of reservoirs at higher elevations in San Diego County. The City of San Diego states that San Vicente Reservoir has the least evaporation losses for long-time storage of any of the City's reservoirs. Officials of the City of San Diego visualize a need for local water storage ca- pacity, in addition to that required for complete conservation of runoff from local water sources. Such a strategically located reserve would provide an emergency supply in case of unprecedented drought, destruction or interruption of the San Diego Aqueduct, or other unforseen disaster. Supplemental storage space in San Vicente Reservoir would also permit transfer of water from the less efficient El Capitan Reservoir, and thereby increase yield of the San Diego River. Water from the proposed Sutherland Reservoir in San Dleguito Basin might likewise be imported to San Vicente Reservoir for regulation and long-time storage. It has been suggested by officials of the City of San Diego that a San Vicente Reservoir of 250,000 acre-foot capacity would provide 150,000 acre-feet of storage for the combined purposes of conserving San Vicente Creek runof i , storing San Diego River wa- ter transferred from El Capitan Reservoir, and storing San Dieguito Basin water imported from Sutherland Reservoir. Under the City's plan, the remaining 100,000 acre-feet of storage capacity in San Vicente Reservoir would be reserved for Colorado River water, an amount in itself sufficient to supply estimated ultimate water requirements of the City for nearly a year. The present San Vicente Dam is a straight concrete gravity structure, with cen- tral overpour spillway ending in a concrete bucket section. It is I90 feet in height to spillway ccest above streambed, and has a crest length of 980 feet. The outlet works con- sist of a semi-circular tower on the upstream face of the dam. At JO-foot increments of 172 PLATE -^narr PLAN Spill.ay Crtst Elev 3160-^ Cres* Eltv 3310'-, Stripping Line - ^Ongindl Ground Line Elev 316 ELEVATION LOOKING UPSTREAM fGROUND PROFILE ON t OF AFiCH RINGS) Ele> 3160 Elev. I700S -^ Trash Racks Elev 1360' SECTION A -A SECTION B-B VARIABLE RADIUS ARCH DAM AT LOWER MISSION GORGE NO 3 SITE ON SAN DIEGO RIVER 175 elevation saucer valves are provided, which are operated from a control platform at the top of the tower. Three 56-lnch diameter cast-iron outlet pipes discharge through the dam from the base of the tower. Two of the outlet pipes are provided with valves at a valve house at the downstream toe of the dam, and the third is covered by a blind flange. The dam was constructed with the consideration in mind of raising it to 310 feet in height at some future date, by adding concrete on the downstream side. Grouting was carried on to the extent necessary for the higher dam. However, no stepping or other spec- ial treatment was given to the downstream face. Studies indicate that this condition is not insurmountable, but that special methods of construction will be required to properly place the additional concrete on the old surface, and at the same time provide for shrink- age due to cooling and settling. A further problem presented is that of securing a good seal at the upstream face between the old structure and the raise. The surface between the new and old concrete must be thoroughly drained, and inspection galleries must be pro- vided to permit inspection of such drainage. The upstream slope of the present San Vicente Dam is battered at a slope of 0.1 to 1 below elevation 600 feet, and at a slope of O.O5 to 1 above that elevation. The downstream face has a slope of O.76 to 1. The plan of enlargement upon which cost estimates for this report are based contemplates making the upstream face of the enlarge- ment vertical, and battering the downstream face at a slope of 0.8 to 1. Details of crest, spillway and outlet works would be reconstructed similarly to those now existing. The outlet tower would be raised by removing the existing operating platform, and then extending the tov;er. In order to achieve the desired storage capacity of 250,000 acre- feet, the crest of the spillway would be raised to elevation 768 feet, or an increase of 118 feet above the present dam. Height of the enlarged dam would be 3O8 feet to spillway crest above streambed. Costs of the present dam, completed in 19*3 by the City of San Diego, were ap- proximately jf2,767|000, including costs of rights of way. The City of San Diego now owns all rights of way required for the enlargement, and no highway or utility relocation would be involved. Based upon prices prevailing in April 1947, it is estimated that capital cost of enlarging the existing San Vicente Reservoir to storage capacity of 250,000 acre-feet is |8, 489,500, and that annual costs are |352,600. A detailed estimate of 1947 capital and annual costs of the enlargement is given in Appendix H. 174 » » APPENDIX A AGREEMENTS AUTHORIZING INVESTIGATION AND REPORT Page No. Agreement between the Department of Public Works of the State of California and the City of San Diego for Investigation of and Report upon Water Resources of San Dieguito River, February 20, 1945 177 Agreement between the Department of Public Works of the State of California and the City of San Diego for Investigation of and Report upon Water Resources of the San Dieguito River and the San Diego River, May 11, I945. . 179 Supplemental and Amendatory Agreement between the State Department of Public Works and the City of San Diego for the Investigation of and Report upon Water Resources of the San Dieguito River and the San Diego River, May 1, 1947 181 175 AGREEMENT BETWEEN THE DEPAIiT^[ENT OF PUBLIC WORKS OF THE STATE OF CALIFORNIA AND THE CITY OF SAN DIEGO FOR INVESTIGATION OF AND REPORT OTON WATER RESOURCES OF SAN DIEGUITO RIVER This agreement, executed in triplicate, entered into by and between the De- partment of Public Works of the State of California, acting by and through the State Engineer, hereinafter referred to as "Departmert" and the City of San Diego, herein- after referred to as "City"; WITNESSETH: WHEREAS, City is desirous of having Department, acting by and through the State Engineer, make an investigation of the water resources of the San Dieguito River in San Diego County and other water resources usable in combination therewith for the pur- pose of determining the best program of development of a water supply on the San Dieguito River for City and of having Department prepare a written report thereon; and WHEREAS, City has the sum of Ten Thousand Dollars ($10,000.00) available to match an equal sum to be provided by the State of California for said investigation and report; and WHEREAS, the State of California has a paramount interest in the use of water and in the protection of the public interest in the development of water resources, and Department, acting by and through the State Engineer, is authorized in the Water Code to cooperate with any city in investigation of any water supply; and WHEREAS, the Director of Finance of the State of California has made emergency fund allotment promise No. 842, dated October 4, 1944, to the Division of Water Resources of the Department of Public Works, in the sum of Ten Thousand Dollars ($10,000.00) for said investigation and report, lAhich sum is to be matched by a like sum from sources other than the State; NOW, THEREFORE, in consideration of the premises and of the several promises to be faithfully performed by each as hereinafter set forth, the parties do hereby mutually agree as follows: ARTICLE I WORK TO BE PERFORMED The work to be performed by Department under this agreement shall include but not be limited to the following: (a) The making, where necessary, of topographic and other field surveys of dam and reservoir sites on the San Dieguito watershed and transmission lines therefrom. (b) The exploration of dam sites on the San Dieguito River. (c) Estimates of present and probable maximum future utilization of the water resources in the San Dieguito watershed. (d) Estimates of water yield both total and additional from San Dieguito watershed with various combinations of reservoirs on that stream with existing and possible future reservoirs of the City of San Diego and with present and possible future development on the San Dieguito watershed. (e) Estimates of cost of construction of dams and reservoirs for various sites and capacities and of transmission lines therefrom. Estimates of cost of securing necessary water rights under the several conditions are to be made by City at its own expense and submitted to Department. (f ) Other field and office work that may be mutually agreed upon by the parties hereto during the progress of the investigation. (g) Preparation and submission to City of a written report based upon the studies and investigations outlined herein on or before January 1, 1946, which will contain recommendations and general plans and estimates of cost for a program of development of the water resources of the San Dieguito watershed. 177 ARTICLE II FUNDS City upon execution by it of this agreement shall forward to Department, for expenditure in the performance of said work, the sum of Ten Thousand Dollars (^10,000.00) . Said sum shall be deposited in a trust account in the Special Deposit Fund in the State Treasury and thereafter transferred to the Water Resources Fund. If the Director of Finance within thirty (5O) days after receipt by Department of said sum from City shall not have allocated from the Emergency Fund (Stats. 194-3, Ch. b2. Item 221), the sum of Ten Thousand Dollars (HflO,000.00) to Department for expen- diture in the performance of said work, said sum so transmitted shall be returned to City upon demand, if such demand is made after the expiration of said thirty (30) days and prior to the making of said allocation. Department shall under no circumstances be obligated to expend for or on ac- count of the work provided for under this agreement any sum in excess of the Twenty Thousand Dollars (^20,000.00) as provided for in this agreement, and in the event of inad- equacy of funds shall be obligated to make only such investigation and report as funds available therefor shall permit. Upon completion of and final payment for the work provided for in this agree- ment Department shall furnish to City a statement of all expenditures made under this agreement and of any expenditures made on account of said work from funds, if any, other than those allocated for said work from said Emergency Fund. If any balance shall remain of the sum of Twenty Thousand Dollars (^20,000.00) as made available as aforesaid, there shall be returned to City one-half of said balance. AETICLE III CONTINGENT UPON ALLOCATION Notwithstanding anything contained in this agreement contrary hereto or in con- flict herewith, this agreement is made contingent upon the Director of Finance making the necessary allocation of funds to Department to meet its share of the cost of said work as provided for in this agreement. This agreement shall become effective only after said allocation is made. ARTICLE IV AVAILABILITY OF RECORDS All data and records pertaining to the work covered by this agreement in the possession or control of City or Department shall be made fully available to the other for the due and proper accomplishment of the purposes and objects hereof. IN WITNESS WHEREOF, the parties have affixed their signatures and official seals. City on the 1st day of February, 1945, and Department on the 20th day of February, 1945. Approved: C. H. PURCELL THE CITY OF SAN DIEGO Director of Public Works (SEAL) By A. H. Henderson By F. A. Rhodes Assistant Director Acting City Manager Approved: R. M. Dorton Deputy Director of Finance Approved: DEPARTMENT OF PUBLIC WORKS OF THE STATE OF CALIFORNIA J. F. Du Paul City Attorney of San Diego By Edward Hyatt By B. L. Comparet, Deputy State Engineer Approved: C« C. Carleton Chief Attorney, Department of Public Works Approval Recommended: Spencer Burroughs Principal Attorney, Division of Water Resources 178 (SEAL) AGREEMENT BETWEEN THE DEPARTMENT OF PUBLIC WORKS OF THE STATE OF CALIFORNIA AND THE CITY OF SAN DIEGO FOR INVESTIGATION OF AND REPORT UPON WATER RESOURCES OF THE SAN DIEGUITO RIVER AND THE SAN DIEGO RIVER. Superseding Former Agreement Limited to Investigation of and Report Upon the Water Resources of San Dieguito River. This agreement, executed in triplicate, entered into by and between the Depart- ment of Public Works of the State of California, acting by and through the State Engineer, hereinafter referred to as "Department" and the City of San Diego, hereinafter referred to as "City", WITNESSETH: WHEREjS^, City is desirous of having Department, acting by and through the State Engineer, make an investigation of the water resources of the San Dieguito River and of the San Diego River in San Diego County and other water resources usable in combination therewith for the purpose of determining the best program of development of a water sup- ply on the San Dieguito and on the Sen Diego rivers for City and of having Department prepare a written report thereo ; and WHEREAS, under an agreement heretofore entered into by and between the parties hereto, executed by City on February 1, 19'>-5, and by Department on February 20, 1945, an investigation has been commenced of the water resources of the San Dieguito River and the total sum of Twenty Thousand Dollars (j20,000.00) has been made available for said inves- tigation and a report thereon. Ten Thousand Dollars {,plO,000.00 ) by each party; and WHEREAS, it is now the desire of each party that an additional sum of Twenty Thousand Dollars (♦20,000.00) shall be provided. Ten Thousand Dollars ($10,000.00) by each party; that said investigation and report to be made thereafter shall include the San Diego River as well as the San Dieguito River; and that said investigation as en- larged shall continue and terminate in a report upon both rivers, the same as if the pre- vious agreement had provided for a total sum of Forty Thousand Dollars ($40,000.00) , one-half from each party, for investigation and report upon both rivers; and WHEREAS, the State of California has a paramount interest in the use of water and in the protection of the public interest in the development of water resources, and Department, acting by and through the State Engineer is authorized in the Water Code to cooperate with any city in investigation of any water supply; NOW THEREFORE, in consideration of the premises and of the several promises to be faithfully performed by each as hereinafter set forth, the parties do hereby mutually agree as follows: ARTICLE I WORK TO BE PERFORMED The work to be performed by Department under this superseding agreement shall include but not be limited to the follovang: (a) The making, where necessary, of topographic and other field surveys of dam and reservoir sites on the San Dieguito and the San Diego watersheds and transmission lines therefrom. (b) The exploration of dam sites on the San Dieguito and the San Diego rivers. (c) Estimates of present and probable maximu_n future utilization of tae water resources in the San Dieguito and San Diego watersheds. (d) Estimates of water yield both total and additional from San Dieguito and San Diego watersheds with various combinations of reservoirs on those streams with existing and possible future reservoirs of the City of San Diego and with present and possible future development on the San Dieguito and San Diego watersheds. (e) Estimates of cost of construction of dams and reservoirs for various sites and capacities and of transmission lines therefrom. Estimates of cost of 179 securing necessary water rights under the several conditions are to be made by City at its own expense and submitted to Department. (f) Other field and office work that may be mutually agreed upon by the parties hereto during the progress of the investigation. (g) Preparation and submission to City of a written report based upon the studies and investigations outlined herein on or before January 1, 1946» which will contain recommendations and general plans and estimates of cost for a program of development of the water resources of the San Dieguito and San Diego watersheds. ARTICLE II FUNDS City upon execution by it of this superseding agreement shall transmit to De- partment, for expenditure in the performance of said work, the sum of Ten Thousand Dol- lars {$10,000.00). Said sum shall be deposited in a trust account in the Special Deposit Fund in the State Treasury and thereafter transferred to the Water Resources Fund. If the Director of Finance within thirty (30) days after receipt by Department of said sum from City shall not have allocated from the Emergency Fund (Stats. 1943, Oh. 62, Item 221), the sum of Ten Thousand Dollars ($10,000.00) to Department for expendi- ture in the performance of said work, and within the same period shall not have re- allocated, or otherwise made available, for expenditure for the purpose of this superseding agreement the Ten Thousand Dollars (^10,000.00), or all thereof remaining unexpended, which was previously allocated by Executive Order No. E-I306, dated March 9, 1945, the Ten Thou- sand Dollars ($10,000.00), transmitted by City upon execution by it of this superseding agreement, shall be returned to City upon demand, if such demand is made after the expira- tion of said thirty (JO) days and prior to the making of said allocation and said re-allocation. City agrees that the Ten Thousand Dollars (|10,000.00) heretofore forwarded by it and deposited in the State Treasury pursuant to said previous agreement relative to the San Dieguito River, or all thereof remaining unexpended, shall be used in carrying out the enlarged purpose of this superseding agreement. Both parties agree that expenditures heretofore made and expenses incurred under said previous agreement shall be chargeable against, and payable under, this superseding agreement the same as if this superseding agreement had been in effect from the effective date of said previous agreement and that said previous agreement is hereby superseded by this superseding agreement with the same effect and result as would have been the case had the previous agreement provided for a total expenditure of Forty Thousand Dollars (#40,000.00), one-half from each party, for investigation and report upon both rivers. Department shall under no circumstances be obligated to expend for or on ac- count of the work provided for under this superseding agreement any sum in excess of the Forty Thousand Dollars (4140,000.00) as provided for in this superseding agreement, and in the event of inadequacy of funds shall be obligated to make only such investigation and re- port as funds available therefor shall permit. Upon completion of and final payment for the work provided for in this supersed- ing agreement, Department shall furnish to City a statement of all expenditures made under this superseding agreement and of any expenditures made on account of said work from State funds, if any, other than those allocated for said work from said Emergency Fund. If any balance shall remain of the sum of Forty Thousand Dollars ($40,000.00) as made available as aforesaid, there shall be returned to City one-half of said balance. ARTICLE III CONTINGENT UPON ALLOCATION Notwithstanding anything contained in this superseding agreement contrary hereto or in conflict herewith, this superseding agreement is made contingent upon the Director of Finance making the necessary allocation and re-allocation of funds to Department to meet its share of the cost of said work as provided for in this superseding agreement. This superseding agreement shall become effective only after said allocation and re- allocation is made. ARTICLE IV AVAILABILITY OF RECORDS All data and records pertaining to the work covered by this superseding agree- ment in the possession or control of City or Department shall be made fully available to the other for the due and proper accomplishment of the purposes and objects hereof. 180 I IN WITNESS WHEREOF, the parties have affixed their signatures and official seals, City on the 1st day of May, 1945, and Department on the 11th day of Hay, 1945- Approved: /s/ C. H. PURCELL THE CITY OF SAN DIEGO Director of Public Works (SEAL) By F. A. Rhodes City Manager Approved: James S. Dean Director of Finance Approved: DEPARTMENT OF PUBLIC WORKS OF THE STATE OF CALIFORNIA J. F. DuPaul City Attorney of San Diego (SEAL) Approved: By Edward .Hyatt State Engineer C. C« Carleton Chief Attorney, Department of Public Works Approval Recommended: Spencer Burroughs Principal Attorney, Division of Water Resources SUPPLEMENTAL AND AIIENDATORY AGREEMENT BETWEEN THE STATE DEPARTMENT OF PUBLIC WORKS ANl) THE CITY OF SAN DIEGO FOR THE INVESTIGATION OF AND REPORT UPON WATER RESOURCES OF THE SAN DIEGUITO RIVER AND THE SAN DIEGO RIVER. This agreement, executed in triplicate, entered into by and between the Depart- ment of Public Works of the State of California, acting by and through the State Engineer, hereinafter referred to as "Department" and the City of San Diego, hereinafter referred to as "City", WITNESSETH: WHEREAS, by agreement heretofore entered into by and between the parties hereto, executed by City on the 1st day of May, 1945, and by Department on the 11th day of May, 1945, the making by Department of an investigation of the water resources of the San Dieguito River and of the San Diego River and rendering a report thereon was provided for; and WHEREAS, additional funds are required to complete said investigation and re- port, and it is the desire of each party that an additional sum of Twenty-Five Thousand Dollars ($25,000.00) shall be provided, Twelve Thousand Five Hundred Dollars ($12,500.00) by each party; NOW THEREFORE, in consideration of the premises and of the several promises to be faithfully performed by each as hereinafter set forth, the parties do hereby mutually agree as follows: 1. City upon execution by it of this agreement shall forward to the Department the sum of Twelve Thousand Five Hundred Dollars ($12,500.00) which shall be deposited in the Water Resources Fund (also known as the Water Resources Revolving Fund) in the State Treasury for expenditure by Department for the making of an investigation of the water resources of the San Dieguito River and of the San Diego River and rendering a report thereon. L 181 2. Upon receipt of said sum of Twelve Thousand Five Hundred Dollars (#12,500.00) from City and deposit thereof into said fund, Department shall procure the deposit into said fund of state funds in equal amount which have been made available by Executive Order No. E-1974 dated March 2b, 1947, of Department of Finance. 3. Insofar as consistent herewith, all of the terms and provisions of said prior agreement to which this agreement is supplemental and amendatory are hereby confirmed, ratified and continued in effect. IN WITNESS IJHERSOF, the parties hereto have affixed their signatures and official seals. City on the 24th day of April, 1947, end Department on the 1st day of May, 1947. I Approved: C. H. PURCELL Director of Public Works (SEAL) By A. H. Henderson Deputy Director Approved: THE CITY OF SAN DIEGO F. A. Rhodes By City Manager DEPARTMENT OF PUBLIC WORKS OF THE STATE OF CALIFORNIA James S. Dean Director of Finance By A. D. Edmonston Assistant State Engineer Approved: City Attorney of San Diego Approved: C. C. Carleton Chief Attorney, Department of Public Works Approval Recommended: Spencer Burroughs Principal Attorney, Division of Water Resources LJH DEPARTMENT OF FINANCE APPROVED May 5, 1947 182 I APPENDIX B ESTIMATES 0? COST OF AC'^UISITION OF WATER RIGHTS REOTIRED FOR DETELGPHENT OF SAN DIEGUITO BASIN By G. E. Arnold, Director of Water Department, The City of San Diego April 22, 1948 183 THE CITY OF SAN DIEGO San Diego 1, California April 22, 1948 Edward Hyatt, State Engineer 401 Public Works Building Sacramento 5, California Attention; A. D. Edmonston Deputy State Engineer Dear Sir: The State Engineer in draft of a letter to City Manager dated Dec. 19, 1947 prepared for preliminary discussion indicated that the City should, in ac- cordance with contract under which investigations are being made, furnish estimated costs of certain water rights. A review has been made of the water rights obtained by the City's predeces- sors downstream from Hodges Dam. It is indicated that with full conservation of the runoff occurring above Hodges Reservoir by construction of Sutherland, Pamo and Super-Hodges Dams, j35,000 may be re4.uired to quiet legitimate claims from interference with water rights below Hodges Dam caused by the ad- ditional storage of water. A brief review has been made of the sources and dependability of the water supply of certain lands in Sections 23, 25, 26, 55, and 56, T. 12 S, R. 1 W, being that portion of San Pasqual Valley and the surrounding hills easterly of the Fenton lands. It is indicated that the total value of the property approaches ^500,000. (a) If either or both Sutherland and Pamo reservoirs were con- structed and operated to capacities of 56,500 and 47,500 acre feet, respectively, and only runoff that would be of no value to the lands in ques- tion were placed in storage and diverted to San Vicente reservoir, then it is deemed reasonable to suppose that there could be no legitimate claims against the City. In fact the lands would be substantially benefitted be- cause of the material reduction in damage from floods. (b) If both Sutherland and Pamo reservoirs were constructed and operated to capacities of 56,500 and 47,500 acre feet, respectively, and the maximum quantities of water impounded and diverted to San Vicente res- ervoir, it is deemed reasonable to suppose that the acquisition of the necessary water rights would cost about ^1400,000. (c) If Sutherland reservoir were constructed and operated to a capacity of 5t),500 acre feet and the maximum quantity of water impounded and diverted to San Vicente reservoir, it is deemed reasonable to suppose the acquisition of the necessary water rights would cost $250,000. Very truly yours, /s/ G. E. Arnold G. E. Arnold Director, Water Department FDP/f 185 I i I APPENDIX C 1 I ESTIMATES OF COST OF LAND ACQUISITION FOR LAKE HODGES AND MISSION GORGE RESERVOIRS By B. A. Etcheverry, Consulting Civil Engineer and G. F. Mellin, Consulting Land Appraiser Page No. Cost of Lands for Super-Hodges Reservoir, April 29, 1947 I89 Cost of Lands for Mission Gorge Reservoirs, May 28, 194? 192 187 B. A. ETCHEVERRY Consulting Civil Engineer Mr. Edward Hyatt, State Engineer 401 Public Uorks Building Sacramento 5» California Dear Sir: Subject: 12 Engineering Building Berkeley April 29, 1947 Cost of Lands for Super-Hodges Reservoir At your re^^uest we have estimated the present day market value of the lends and improvements in the proposed Super-Hodges Reservoir that would have to be purchased, and of the accompanying damages, for each of the four different water surface elevations that have been considered or proposed. We herewith submit a brief statement of the work done and a summary of our findings. For our work we had: (1) a good contour map of the reservoirs lands on which was transposed the property ownerships and soil types; (2) the Fairchild Aerial maps on which were shovn the proposed highwater lines and the boundaries of properties affected; (3) the basic date on the properties that would have to be purchased. This basic data included the descriptions and acreages of the properties, the county assessor's data for 1946 valuations, and the information on sales of properties in the proposed reservoir. In addition we had sales of other properties not in the reservoir but in the general vicinity. The County Assessor's information and data on each property is complete and de- pendable. It contains detailed data on all of the improvements. This information and data is far superior to that of any other County with which we are acquainted. Ve made an analysis of the sales made since 1941 and compar with the corresponding 1946 County Assessor's valuations. Ue used th sor's valuations because these were available for all the properties while the 1947 valuations had not been completed for all the properti parison of sales values with the corresponding 194b County valuations for the increase in market values from the dates of the sales to the that a very good estimate of the present day market values of all the could be obtained by using the following factors or ratios of market Assessor's valuations - a factor of 5 for all farm properties (includ provements) and a factor of b for all subdivision property in Campo D few properties on which improvements w=re made since 1946 County Asse made separate estimates of the value of these improvements. ed the sales values e 1946 County Asses- in the reservoir, es. From this com- and with allowance present we concluded properties involved value to 1946 County ing lands and im- el Dios. For the ssor's valuation we With all of this information and data, and the dependable ratio of market value to County Assessor's valuations it was possible to complete our work in the field in the three days, April 10, 11, and 12 that we were in San Diego, and to make our estimate of present day market values in a relatively short time. Our findings of the total present day market value of all the lands and improve- ments to be purchased including the accompanying damages and the cost of relocating the power and telephone circuits for each of the four proposed water surface elevations are summarized in the following tabulation. Elevation of Water Surface 1 568 582 396 416 Acres to be flooded {excluding city owned) 717 1,516 2,003 5,216 Acres to be purchased (excluding city owned) 1,222 2,422 4,148 4,871 Estimated Cost of: Lands ; 581,420 •5 565,250 1 846,600 $ 904,240 Improvements 547,040 584,190 752,960 785,690 Damages 96,870 202,700 115,600 120,550 TOTAL $1,025,530 #1,552,120 n, 715,160 11,810,480 189 We attach as part of this Report the accompanying statement of Procedure fol- lowed in estimating the right-of-way costs for Super-Hodges Reservoir, including a tabulation of the main items of costs. Mr. D. B. Willets collected and compiled in excellent shape the information and data used by us, he accompanied us on our trip to San Diego and gave us the benefit of his knowledge of local conditions. He made all the required computations in accordance with our instructions. His efficient and competent help is appreciated. Respectfully submitted. Enclosure: /s/ B. A» Etcheverry B. A. Etcheverry /s/ G. F. Mellin G. F. Mellin PROCEDURE FOLLOWED IN ESTIMATING RIGHT OF WAY COSTS FOR SUPER-HODGES RESERVOIRS April 25, 1947 Right of way costs were estimated for four different water surface elevations Max. W.S. Elevation U.S.G.S. datum Height, Dam to Spillway Feet Reservoir Capacity Safe Yield Acre-Feet Acre-Feet 368 382 396 416 150 165 180 2U0 104,464 157,300 224,800 340,000 20,200 24,000 26,800 29,300 Basic data on property owners, property descriptions, assessed valuations, and recent sales were secured in the San Diego County Assessor's office. The Hodges Reservoir area for the purpose of the right of way study was divided into two general areas. All of the lands east of the westerly line of Rancho San Bernardo and comprising the Bernardo Region and San Pasqual Valley are shown on Fairchild Aerial map four inches to the mile. All of the remainder, being west of the westerly line of Rancho San Bernardo and including the Campo Del Dlos Subdivision, is shown on a Fairchild Aerial map one inch to 400 feet. On these maps property lines are shown in blue and the limits of San Diego City ownership are defined in red. Property is identified by a D.W.R. reference number. On the first mentioned map (4 inches to the mile) soil classifications have been imposed as well as data respecting recent property sales. On both maps the con- tours of the four proposed high water lines, elevations 3o8, 382, 396 and 4l6 are shown. For each parcel of property the flooded area at each of the four elevations was deter- mined by planimeter. A complete tabulation of all the property owners whose parcels would be affected at the 41b elevation was made. For identification purposes each parcel was assigned a D.W.R. reference number, there being 782 in all. This tabulation shows the D.V/.R. refer- ence number, property description, owner, area, assessed valuation of land and improve- ments, and for each of the four proposed water surface elevations the flooded area. A tabulation was made of sales since County Recorder. This tabulation shows the ge and revenue stamps on the deed. By selecting lowing for a reasonable increase in market val ratio of market value to 1946 assessed valuati is lands easterly of the westerly land of Ranc division, sales for 1946 and 19*7 were tabulat sessed valuation was 4.b for lots only and for It was decided to use a mean ratio of 6 for th 1941, based upon transcripts from the neral location of the sales, property owners, parcels within the proposed reservoir and al- ue between 1944 and 194-6, an over-all mean on was fixed at 5 for the farm property (that ho San Bernardo). In the Campo Del Dios Sub- ed. The ratio of market value to 19*6 as- lots with improvements the ratio was 5»6« is subdivision property. An inspection of the reservoir site and property to be evaluated was made by G. F. Mellin and B. A. Etcheverry accompanied by H. M. Crocker and the writer. During the course of the inspection, conversations were held with Crowell D. Eddy, County Assessor, 190 Mr. Robert Henrich and Mr. Charles Mendenhall of the Assessor's office, and Mr. Arthur Wade, Manager of the Del Dios Water Company. . As a result of their inspection, the fol- lowing decisions were made by Messrs. Etcheverry and Mellin: 1. That the valuations used by the County Assessor were sound and consistent and therefore could be used as a basis for right of way costs by applying a factor equal to the ratio of market value to County Assessor's valuations. 2. That for the farm property the factor of market value to 19*6 assessed valuation should be 5» 3. That for subdivision property in Campo Del Dios, the factor of market value to 19*6 assessed valuation should be 6. 4. The limits of the property to be purchased and the estimated damages to property severed. (Shown on maps) 5. That it would be necessary to purchase the entire Del Dios Subdivision at all elevations considered. This was based upon the fact that the water supply of the mutual water company would be flooded at elevation 3b8, that the main water line to the entire subdivision would also be flooded, and that nearly half of the property would be flooded at elevation 368, which in itself would greatly depreciate the remainder. 6. That wherever new improvements had been constructed after the 194-6 tax roll was made up, the 194? assessed valuations when available would apply. 7. That an estimate should be made of the cost of relocating power and tele- phone circuits. Improvements constructed subsequent to March 1946 were valued by using the 1947 assessment and the same factors as applied to 1946 assessment. This applied to four par- cels in the San Pasqual Valley and 12 lots in the Del Dios Subdivision. There were four new houses in Del Dios which had not been assessed for 1947. Values were estimated for these. Both the San Diego Gas and Electric and Pacific Telephone and Telegraph Company have circuits in or through the reservoir site. Mr. G. E. Jenner, of the San Diego Gas and Electric, was contacted for information regarding cost of relocating two feeder cir- cuits which would be affected. Mr. John A. Redlon, of the telephone company, was contacted regarding the toll circuit across Lake Hodges. Damages to each utility v/ere estimated by each company at approximately ^40,000 for the maximum water surface elevation. 1 nssmin man of nit ooss cuT-^a (i<.n-c:tx( cut oT Ud4 Ceal ef -,. TdMI Coat BLninc* y>e 0,1 mo. ud 669 i.iW 60 •1S9.900 • kS.O» soi.wo I 33.870 7J3,ao um ' ** " JJ.OOO 30,000 33.000 30,000 rvtUA 717 i.Tll • }41,l.23 •ft7,0(|0 196.870 •i,oas,»o nxtmoa m 3u r**qul «lHt .- U.IM U.JU »ift.710 69, 000 • 71,170 11,000 •1)6.700 • IM.SSO 100,000 I»l !»<>■ Ui w Ml.SW 502,020 7«,SW S« ruqwl Se&Mt Csclrle COWHT ° I " ' lil.OOO ».ooo JU,000 32.000 wtua 1,316 ixli •56S.IJ0 tSSt,15« iKx.rM to.5W.lW EtMWJCa 396 "• (1.95S 1 1 •SJft.oto W.ooo •w.sto 11,000 • U.MO • 819,620 100,000 Ml Km bs •o m.MO 5OI.0M T«.SW uul * ^ ** " )6.00o 16,000 J6.006 36,000 RTIlLS J.OOl l.,U.S KU.wo •TSS,960 ms.ooo |l.nS,160 ■I«»«T10» US au ruqui ».ii.. "*= IM« tw.T*l 09.000 n.ooo • JS.550 • »ab.t«io 100.000 tel taam 1|8 «a Wl.SW SOJ.OW TI3.ao 9m fMVMl auiMl o I.OOO t.oee -4 ° * c V>.ooo tio.ooe W.ooo bo.eoo ntua !.ii'' u.sn •Wt.JfcO t785.*W |i>e.S5o *1.B10JA> 191 B. A. ETCHEVERRY Consulting Civil Engineer Mr. Edvrard Hyatt, State Engineer 401 Public Works Building Sacramento 5i California Dear Sir: Subject: 12 Engineering Building Berkeley May 28, 1947 Cost of Lands for Mission Gorge Reservoirs At your re^iuest we have estimated the present day market value of the lands and improvements in the proposed Mission Gorge Reservoirs, including all properties (excepting the lands already city owned) up to contour 3^0 for dam sites No. 2 and No. Zero and to contour 331 for dam site No. 3. We li^rewith submit a brief statement of the work done and a summary of our findings. It was our understanding that the contours to be considered were 33I and 553« However, the map of Mission Gorge Reservoir Topography (Scale 400' = 1") prepared by Fairchild Aerial Surveys, Inc., had on it contours at 10-foot Intervals to 350, but not 333, and the slope of much of the land above 350 is so flat that contour 353 could not be extrapolated with any degree of accuracy. We therefore used contours 331 and 350. If it is important to extend our appraisal so as to include lands up to contour 353> this can be easily done by having Fairchild Aerial Surveys, Inc. locate this contour accurately on the topographic map. As commented upon later in this report, contour 350 seems to include all of, if not more than the properties which may have to be acquired. On the above stated topographic map the property ownership boundaries and the soil classification lines were transposed. For all the properties involved we also had all basic data, including: (a) Descriptions and acreages of the properties; and (b) County Assessor's data for 194b valuations. The records of the County Assessor's valuation give detailed dependable infor- mation on all of the improvements at the time of the valuation, and the valuations of lands and improvements are complete and consistent. As an indication of market value of properties, Mr. D. B. Willets of the Divi- sion of Water Resources had compiled for us the data and information on sales of properties within and adjacent to the proposed reservoir lands. These data were tabulated together with the corresponding 1946 County Assessor's valuations and we made an analysis of the re- lation of sales values to the 1946 Assessor's valuations, with proper allowances for the increase in market values from the dates of the sales to the present. This analysis showed that a very good estimate of present day market values of the properties involved would be obtained by using the following factors or ratios of market value to 1946 County Asses- sor's valuations: (1) a factor of 4 for all unimproved farm properties (2) a factor of 4 for the land and 6 for the improvements for all the improved properties. These are gener- ally small tracts with residential improvements; (3) a factor of 4 for the land and 5 for the improvements for the Scripps and Good Ranches. On these ranches the improvements are mostly in farm buildings. Our field survey showed there were I8 buildings either new or under construction below elevation 350» that had not yet been valued by the County Assessor. We estimated the market value of these buildings and found their total market value to be $60,000 - simi- larly we found four new buildings below elevation 331j with a total market value of $9200. We found that the County Poor Farm (known as Edgemore ) was so situated that only a flowage easement over it should be acquired, and we made a separate appraisal of this easement. This farm contains 472 acres, of which 383 acres are below elevation 350. The lowest land is at elevation 330. About 2/3 of the land is above elevation 340 which eleva- tion is subject to an average frequency of flooding of approximately once in ^^ years. The residential improvements are above elevation 3^8. These would be about 3 feet above ele- vation }^3 which has an average frequency of flooding of about once in 250 years. Because of these conditions we appraised the value of the flowage easement at 30 percent of the fee value of the 385 acres of land below elevation 350. 192 For all of the other properties and for both contours, JJl and 350, we esti- mated the fee values. Where these contours cut properties so as to damage the remainder of the property above the contours, we have estimated the damage. Our findings on the total present day market value of all the lands and im- provements, including the value of the flowage easement on the County Poor Farm, are summarized in the following tabulation: Dam sites No. Zero and No. 2 No. 3 High water elevation 350 331 Acres to be flooded (excluding City owned) 1915 1163 Acres to be purchased (excluding City owned) 2035 1202 Estimated cost of: Lands (J z ob 5 U o UJ < UJ < O z O -1 u. 2 o 60 10 20 30 40 50 PRODUCT OF MEAN MONTHLY TEMPERATURE TIMES PERCENT OF DAYLIGHT HOURS (ACCUMULATED TOTAL") RELATION BETWEEN OBSERVED CONSUMPTIVE USE BY NATIVE VEGETATION AND THE PRODUCT OF MEAN TEMPERATURE AND PERCENT OF DAYLIGHT HOURS (NEAR BONSALL, CALIF) 202 In table 3 the consumptive use has been computed for Escondldo temperature con- ditions based on the ratio found in Bonsall Basin. The normal annual consumptive use by dense vegetation at Escondido amounts to 56 inches {4.7 feet) as compared with 55 inches (4.D feet) in Bonsall Basin or on a percentage basis, 102 percent of the use in Bonsell Basin. This ratio is assumed to hold for all types of crops, including irrigated, dry farmed and native vegetation of different densities. 1/ The product of temperature times percent of daylight hours is slightly more at EscondTdo during the summer six months and slightly less during the winter six months than that in Bonsall Basin. The consumptive use of 5b inches for dense vegetation is for a normal year. To arrive at the uses for each individual year the temperatures at Escondldo were tabulated for the period 190b to 1944 from U. S. Weather Bureau records. The ratios of use, divid- ed by temperature times percent of daylight hours (Use/t x p) of 1.19 for the summer six- month period and 0.48 for the winter six-month period were then applied to each individual year. These computations are shown on table 4. The annual indices were then computed as a percentage of the long time average. It will be noted that there is very little varia- tion in the annual indices. The maximum is 104 percent and the minimum is 96 percent. Considering the accuracy by which consumptive use can be measured and by which vegetated areas can be mapped and classified the variation in annual use might be disregarded and the long time average unit uses applied to each individual year for which there is a crop survey. Table J - Observed and computed use of water by native vegetation at Bonsall Basin and Escondido, California Period Bonsall Basin Escondido 1 t X p* Observed consumptive use Use t X p* t X p* Computed consumptive use inches inches April through September 56.27 45 1.19 37.2 44.5 October through March 25.11 12 .48 24.5 11.8 Year 55 56.1 Temperature (t); percent of daylight hours (p), Attempts were made to incorporate the growing period as determined by U. S. Weather Bureau data on dates on which the last killing frost in the spring and the first killing frost in the fall occurred, but no correlation could be established. Rainfall varies considerably from year to year but for vegetation with a higli water table this will have little if any effect owing to the fact that the vegetation gets ample water for maxi- mum growth from the ground water sources. Irrigated crops, particularly citrus orchards, are given water as needed and the rainfall may have little effect on its total consumptive use. Possibly the greatest effect that variation in annual rainfall has on valley consump- tive use is in the distance to the water table. In wet years the water table may be higher than in others resulting in a more dense growth of vegetation. This should show up in the crop survey. The consumptive use of hillside vegetation varies to some extent with the seasonal total and distribution of rainfall. In years of subnormal precipitation the vegetation may suffer from lack of water and the consumptive use is lower than average. In wet years the vegetation may become more luxuriant as a result of more available water for a longer period. The consumptive use of vegetation which gets its entire water sup- ply from rainfall will not, however, vary as much as does the rainfall. In San Luis Key watershed it was estimated that the hillside vegetation used 1.3 feet per year and any rainfall exceeding this amount either ran off as surface flow or penetrated below the root zone. The average annual rainfall at Escondido is 16.60 inches which is undoubtedly ex- ceeded in the hifiier elevations of the San Pasqual watershed. Distribution of rainfall will affect the consumptive use by vegetation growing without irrigation or not underlain by a high water table. Usually this vegetation re- ceives water by direct rainfall starting in November or December and ending in April or May. The summer periods are always dry and the vegetation either dies or becomes dor- mant after the moisture from the last rain is extracted from the soil. A cooperative \J Although this relation may not hold exactly for irrigated areas, the use by these crops is small compared to the other classifications. More accurate results can be obtained by a field study of agricultural crops, if necessary. 20 J Table 4 - Temperature data and computed Index oT consumptive use at Eacondldo for period 1906 to 19hU as based on natlva vegetation study in Bonsall Basin, San Luis Rey Valley, Calif. (Table is based on San Luis Roy unit consumptive use for dense vegetation in Bonsall Basin as U.6 feet) yoar MASn Mnnt-V.1.. (Amni.T.a( a( Rfl«nn.11i1n April through September October Ju.ough Ilarch Yoar Percent or average Dates of killing froot at Escondldo Average tempera- ture (t) t IP 1/ 0. 2/ Average tempsra- ture(t} t xpi/ 0-i/ Last In spring First in autumn No. of days betwaon dates Jan. Feb. Mar. Apr. nay Juno July Aug. Sept. Oct. Nov. Doc. Annual 1906 U9.6 57,0 56.8 53.8 63. U 69. U 76.1( 72. 1( 69.2 61(.2 53.0 50.9 61.3 67.1* 37.5 1(1*. 6 55.3 2l(.6 11.8 56.1, 101 Apr 2 Oct 20 201 1907 U6.0 56.2 53.2 59.9 61.1( 65.8 73.2 70.1 63.6 60.8 56.6 52.1 60.1 65.7 36.5 U3.5 51*. 5 2l(.2 11.6 55.1 98 Apr 3 Nov 16 227 1908 51.U SO.U 55.0 58.9 59. 1( 6I(.7 72.6 72. 1( 69.0 58.0 5l(.o 1*8.0 59.5 06.2 36.8 1(3.6 52.6 23.5 11.3 55.1 98 May 16 Oct 23 160 1909 51.0 51.5 53.1 59.1( 62.2 67.8 71.2 7l(.7 70.0 6I4.I, 57.6 52.5 61.3 67.2 37.6 1(1(.7 55.1 2l(.5 11.8 56.5 101 Mar 13 Oct 30 231 1910 50.9 52.1 58.6 62.2 65.9 67. 1( 7l(.0 72.7 72.6 63.6 56.6 53.0 62.5 69.1 36.1* 1(5.7 55.8 2l*.6 11.9 57.6 103 Feb 18 Oct 12 236 1911 53.8 1(9.7 57.8 58.1 61.8 66. 1( 72.l( 72.8 68.2 62.9 56.8 1*8.0 60.9 66.6 37.0 hh.o 55.2 2U.5 11.8 55.8 99 Apr 15 Nov 25 221, 1912 5U.6 52.1( 53.2 56.2 63.l( 68.6 75.3 71.5 66.2 62.0 58.0 1*6.5 61.0 67.2 37.3 Uk.k 5l».8 21*. 3 11.7 50.1 100 Feb 26 Dec 6 281, 1913 1(6.9 51.8 53.6 58.9 61.6 66.8 72.6 7l(.3 73.0 62.8 55.l( U9.8 60.6 67.9 37.7 Uk.9 53.1* 23.7 ii.U 56.3 100 Mar 27 Doc 3 251 19m 52.0 53.5 59.6 61.0 61.8 68. 1( 72.8 72.8 69.6 65.0 61.1* 1(7.5 62.1 67.7 37.6 U*.7 56.5 25.1 12.0 56.7 101 Fob 8 Dec 15 310 1915 1(9.0 51. 2 57.1( 59.8 62.1 69.0 72. U 73.9 67.8 62. U 51(.5 SO.I 60.8 67.5 37.5 l*l*.6 5U.1 2l*.0 11.5 56.1 100 Jan 20 Nov 11 295 1916 1(7.7 53.8 58.8 60.3 62.1( 68.1, 72.1( 73.1 69.2 56.0 52.7 1(6.7 60.2 67.6 37.6 U*.7 53.0 23.5 11.3 56.0 100 Feb 2 Oct 30 271 1917 1(6.5 51.0 52.U 57.7 60. 1( 70.6 7l(.0 72.6 69.8 63. 1( 55.6 51.5 60.5 67.5 37.5 l*l*.6 53. U 23.7 ll.U 56.0 100 Apr 1 Nov 15 228 1918 51.2 52.8 55.8 58.5 60.2 71.6 71. U 72. 1( 72.1( 67.6 56.1 51. 1( 61.8 67.8 37.7 l*l*.9 55.6 2l*.8 11.9 56.8 101 Fab 17 Nov 8 26U 1919 53. U U8.U 52.0 58.2 62.3 68. U 71.2 71.2 68.0 60. 3 57.1( 55.0 60.5 66.6 37.0 l*l*.o 51..1* 2l(.2 11.6 55.6 99 Mar 15 Nov 28 258 1920 5I(.3 5I(.2 53.2 56.5 62.3 66.6 72.2 73. 1( 68.8 60.2 56.7 52.1 60.9 66.6 37.0 1*1*. 55.1 2l(.5 11.8 55.6 99 Mar 26 Dec 21 296 1921 51.7 53.5 56.8 56.6 58. 1( 66.0 72.6 71.8 68.5 65.2 29.6 56.9 61.5 65.6 36.5 1*3. U 57.3 25.5 12.2 55-6 99 Apr 17 Nov 18 215 1922 ua.9 50.2 51. U 53.9 62.1( 68.2 70.7 73-6 72.6 62.0 51*. 1* 5l(.5 00.2 66.9 37.2 1.1*. 3 53.6 23.8 ll.U 55.7 99 Apr 11 Nov U 207 1923 53.8 51.2 55.1 66.9 63. 1( 63.1 68.7 69. 1( 68.6 62.0 59.6 52.0 60.3 65.0 36.1 1*3.0 55.6 2l(.7 11.9 5U.9 98 Mar 10 Dec 12 271 192lt Si.l( 55.6 51.1 55.U 63.0 67.0 68.8 68.6 66.2 58.1* 59.2 51.3 59.6 65.2 36.2 U3.1 5U.5 24.2 11.6 51*. 7 98 Apr 17 Oct 12 176 1925 Sl.l( A-h 55.2 56.2 61.l( 66.6 72.6 69.8 65.8 60.2 55.0 Sk-k 60.2 65.1* 36.3 U3.2 55.1 2l(.5 11.6 55.0 96 Mar 13 Nov 6 236 1926 50.0 A.k 57.6 61. 1( 63. 1 68.1, 70.6 71.6 65.6 6U.1 61.2 1*9.6 61.5 66.8 37.1 hk.-L 56.2 25.0 12.0 56.1 100 Jan 28 Dec 15 321 1927 51.6 5U.0 52.9 56.5 62.0 65. u 72.2 71.1 66.7 63.7 61.2 51.6 60.7 05.6 36.5 1(3 .U 55.3 2l(.e 11.9 55.3 99 Har 20 Doc 8 263 1920 5I(.6 53.2 56.9 57.2 61(.3 66.3 69.9 70.0 69.5 61.8 56.8 53.0 61.1 66.2 36. B 1*3.6 56.1 2l(.9 12.0 55.8 99 Apr 5 Nov 30 239 1929 50.2 1(9.0 5l(.o 55.7 65.0 67.1( 73.1 76.3 70.l( 68.0 60.5 59.0 62.1* 68.0 37.6 1(5.0 56.8 25.2 12.1 57.1 102 Mar 25 Nov 21 2ia 1930 51.7 55.8 56.8 60.6 57.8 65.1( 72.6 72.8 66.1 63.6 61.2 51*.l* 61.6 65.9 30.6 1*3.6 57.2 2S.1( 12.2 55.8 99 Jan 9 Nov 19 311* 1931 53.9 5I(.7 58.8 62.6 67.0 69.6 76.0 76.2 70.5 66.2 55.0 50.1* 63.1* 70.3 39.1 1(6.5 56.5 25.1 12.0 58.5 10l( Mar 9 Nov 22 258 1932 Ue.l( 52.6 56.8 58.9 62.0 66.1 69.2 70.3 68.6 63.3 63.2 50.1 60.6 05.9 36.6 U3.6 55.7 2l(.7 11.9 55.5 99 Feb 1, Dee 15 315 1933 1(9.0 1(9.6 5U.5 55.6 55.9 63.8 70.1 71.I4 61(.6 65.0 61. U 53.1* 59.5 63.6 .35.1* 1(2.1 55.5 2l(.7 11.9 5l*.o 96 Mar 26 None 339 193l» 51(.o SS.8 61.1( 61.9 65.3 61(.2 72.1( 72.1 71.8 66.,7 59.0 56.0 63.5 68.1 37.8 1(5.0 58.6 26.1 12.5 57.5 102 Jan 12 None 353 1935 52.5 55.3 51. 1( 59.1 60.1( 66.l( 70.9 7l(.8 70.0 63.3 55.6 5I*.8 61.2 66.9 37.2 hh.3 55.5 2l(.7 12.9 57.2 102 Mar 23 Nov U 226 1936 5U.S 53.0 57.8 59.8 61(.o 68.0 73.7 73.0 69.3 65.0 60.8 53.8 62.7 68.0 37.8 1(5.0 57.5 25.5 12.2 57.2 102 Mar 26 Dec 2 251 1937 1(3.6 51.0 5l(.o 57.6 62.5 66.6 72.l( 72.2 71.I4 63. 1( 57.5 57.0 00. 6 67.1 37.3 U*.l* 51*.l* 2l(.2 11.6 50.0 100 Feb 27 Dec 22 298 1938 55.8 53.2 5l(.2 59.3 61.1( 66.0 70.1( 73.0 72.5 63.0 56.8 57.0 61.9 67.1 37.3 hh-h 56.7 25.2 12.1 56.5 101 Feb 11 Nov 9 269 1939 52.1 1(7.8 53.2 61.6 62.8 66.0 71.8 73.2 73.3 65.6 61.3 58.0 62.2 06.1 !7.e 1*5.0 56.1* 25.1 12.0 57.0 102 Mar 9 Dec 25 291 191*0 55.l( 5U.6 58.3 59.9 68.3 65.3 71.1 71.3 68.1( 65. 1( 56.8 57.3 62.8 67.7 37.6 1*1*. 7 58.0 25.8 12.1( 57.1 102 Mar 12 Nov 23 256 I9I1I 52.8 55.2 57.3 57.0 65.2 66.0 71.2 71.6 66.1( 63.1( 60.2 52.8 61.6 00.2 36.6 1*3.8 57.0 25.3 12.1 55.9 100 None Nov 22 326 19U2 Sl(.2 51.0 Sk-k 56.8 61.0 65.5 71.3 70.5 66.6 63.0 57.7 51*. 6 60. C 0..-,., 36.3 M.2 55. S aU.e 11.9 55.1 96 Mar 26 Dec 6 255 191(3 55.0 56.6 57. U 60.2 6l(.8 65.2 71.0 72.6 71.6 65.0 59.9 53.1* 02.7 C7.0 37.0 1*1*. 7 57.9 25.7 12.3 57.0 102 Feb 10 None 321* 19IA 53.0 50.1( 55.1( 56.2 61.8 62.7 67.1 71.2 69.8 61(.l( 55.5 5lt.6 60.2 ol*.8 36.0 1*2.8 55.6 2l(.7 11.9 51(.7 98 Feb 18 Doc 3 289 Av- orag from 50.6 0. 3 52.5 w. 55.2 3. 58.ll 62.5 67.5 72.0 72.3 69.0 62.9 57.3 52.1 61.1 67.0 37.2 111*. 3 55.1 2l(.5 11.6 56.1 100 Mor 9 Nov 25 261 = Percent daylight hours. 2/ U^ = = Annual consumptive Mat t X p X 1.19 = consumptive use, Apr. 1 to Sept. 30- i/ ^^^ = t x p x O.I4.6 = consumptive use, Oct. 1 to Mar, 3I. 204 report by the Division of Irrigationi/ indicates that the average date of the last effec- tive rain in the spring is April 9 and the first effective rain in the fall is November JO for Escondido. "Effective rain" as used in this publication is a rain of one-half inch or more. Rains of less than one-half inch are assumed to evaporate. In table 5, unit consumptive use values are shown for a normal year in San Pasqual Valley together with the probable monthly distribution of consumptive use. These values must be considered as preliminary and subject to change as more information becomes available on depth to ground water, evaporation, etc. Refinement of the preliminary unit uses may be made on the basis of a curve similar to that shown on figure 2. Inspection of the valley during the summer of 1945 indicates that a large portion of the consumptive use was a result of native vegetation supported by a high ground-water table. The curve on figure 2 was developed for San Luis Rey Valley after establishing four points by the use of tank data, diurnal fluctuations of the water table and depth of rainfall penetration. Because there is no distinct dividing line between the classifications of dense, medium and sparse growths the portions of the curve assigned to these classifications are shown as overlapping. Many observation wells would be required before such a curve could be constructed for San Pasqual Valley. The rate of evaporation from free water surfaces is often used as an indication of consumptive use rate. Its value lies chiefly in providing- a means of transferring data from one locality to another. There has been much work done in southern California on transpiration and consumptive use by irrigated crops and native vegetation and in most cases evaporation records were kept during the course of investigation. Because the evapo- ration rate differs in different type pans it is advisable to use a more or less standard type. Most of the available evaporation records are for a U. S. Weather Bureau type pan 4 feet in diameter and 10 inches deep. Table 5 - Preliminary estimate of unit consumptive use values for a normal year together with the monthly distribution for San Pasqual Valley, California Classification Annual consumptive use IRRIGATED Feet Alfalfa 3.4 Field crops 1.5 Orchard 2.4 DRY FARMED All crops 1.3 NATIVE VEGETATION Valley floor Grass, weeds, pasture 2.7 Swamp, tules, reeds 4.9 Brush, trees, grasses Dense growth 4.7 Medium growth 2.4 Sparse growth 1.5 Hillside lands Brush and grass 1.? MISCELLANEOUS Water surface 4.0 Farm lots 2.0 Wasteland-bare 0.7 Roads-surfaced 0.5 Monthly distribution of average annual valley consumptive use in percent Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year 3 3 4 9 12 13 16 15 13 6 3 3 100 1/ Beckett, S. H. , Blaney, Harry F., and Taylor, C. A., Bulletin No. 489, Irrigation Water Requirement Studies of Citrus and Avocado Trees in San Diego County, California- 192b and 1927. Univ. of Calif. Agri. Expt. Sta. 1930. 205 FIG. 2 CONSUMPTIVE USE - INCHES PER YEAR ) o o o o c . ., ^A ) \ \ ^ ,B V ^ V \ V \ DEN?? SPARS r 9, ^lEDIUI A » ( } 2 4 6 e 10 1 DEPTH TO GROUND WATER IN FEET 2 CURVE DEVELOPED FOR SAN LUIS REY VALLEY SHOWING RELATIONSHIP BETWEEN CONSUMPTIVE USE AND DEPTH OF GROUND WATER FOR NATIVE VEGETATION (FROM SAN LUIS REY REPORT) D.MUCKEL 206 COPY APPENDIX A February 8, 1946 Pomona, California MeDiorandum to Mr. Harry F. Blaney From: Dean C. Muckel Subject: San Pasqual Valley, California With reference to our telephone conversation of February 8, 194b regarding the evaporation rate from bare sands in San Pasqual Valley 1 have compiled available informa- tion we have in Pomona. It includes work done by Sleight in Colorado, Young at Santa Ana, Calif, and F. E. Green for the J. B. Lippincott Engineering Offices in connection with early investigations in San Pasqual Valley. Sleight tested the evaporation rate from 5 different soils with the water table at different depths and expressed it as the percent of evaporation from a free water sur- face. He shows that the evaporation rates for different soils vary, as would be expected, with the capillary rise. Following is a summary for the two types of river-bed material vriiich he tested and are more or less comparable, I believe, to the river-bed materials in San Pasqual Valley: Cherry Creek sands Water table depth 3 inches 6 inches 10-1 inches 24 inches Soil evaporation in percent 77.0 69. 64.5 57.7 11. 3 of that from free water South Platte graded river-bed material Water table depth 3 inches 12 inches Soil evaporation in percent 66.0 24.2 of that from free water In State Bulletin No. 44 of the South Coastal Basin Investigation Young gives the evaporation from Hanford fine sandy loam near Santa Ana, Calif, for water table depths of 2 and 3 feet. In percent of evaporation from a free water surface these amount to ap- proximately 5 and 9 percent respectively. Capillary rise in this soil will be greater than in a river-bed material consisting of sands and gravels. F. E. Green made tests in San Pasqual Valley, Calif, in 1924 for the J. B. Lippincott Engineering Offices. Materials used were described as delta sanda formed by the junction of Santa Maria Creek and Bernardo River in San Pasqual Valley and as being somewhat finer than that in the active channel of the main river. I have only the curve drawn by Green and it is included on the accompanying diagram. It is notable that for a shallow water table (the surface soil being saturated) the rate of evaporation from the soil was greater than from a free water surface. Fortier in some of his early work on irrigation got similar results. The curves on the diagram indicate that the evaporation from river-bed material is negligible when the water table is 3 feet or more below the ground surface. In finer soils with greater capillary rise there would undoubtedly be evaporation losses with a 3-foot water table. In the units set up in our preliminary report on San Pasqual we gave a figure of 0.7 feet for bare sands. This figure includes losses after rains only and does not in- clude any losses by capillary rise from the water table. If it is found that the water table is less than 3 feet I would suggest using Green's curve modified so that when the water table is at the ground surface the evaporation rate is 100 percent of that from a free water surface. I have shown this suggested curve on the diagram. In most valleys the river channel is alternately dry and wet-dry in the summer and has flowing water in the winter. This occurred in San Luis Rey Valley and we did not attempt to set up one definite unit to apply the year round. The consumptive use for these areas was computed in two parts- one for the winter period based on evaporation from a free water surface and the other based on the evaporation from bare sands during the summer. This method requires that an estimate be made of the length of time the channel or sands have a wet surface. 207 120 100 z O o tr < UJ Ll Q. cr ?^ -I a: UJ $ oc < UJ o ^ cr z o oc o < > UJ 80 60 O OC u. 40 20 \ GREENS CURVE WITH SAN PASQUAL VALLEY SANDS SUGGESTED CURVE FOR USE WITH RIVER-BED MATERIAL IN SAN PASQUAL VALLEY SLEIGHTS CURVE WITh\ CHERRY CREEK SANDS YOUNGS RESULT WITH HANFORD FINE SANDY LOAM 12 3 4 DISTANCE OF WATER TABLE BELOW GROUND SURFACE IN FEET RELATION OF EVAPORATION RATE FROM SOILS WITH DEPTH TO WATER TABLE 208 APPENDIX E MONTHLY PRECIPITATION RECORDS AT STATIONS REPRESENTATIVE OF SAN DIEGUITO BASIN 209 MONTHLY PRECIPITATION RECORDS AT STATIONS REPRESENTATIVE OF S.-iN DIEGUITO BASIN Precioltation records from the follov.lng stations have heretofore been publish- ed es indicated^ and, althoueh utilized in connection vith the present investigation, are not repeated herein: Index Number Period of Record Location of Bulletin No. -i8 Station to July 1, 1948 Published Record 23 San Felipe 1911-1924* Bulletin Ko. 48 28 Matagual 1911-191^ II tt n 29 Volcan Mountain 1911-1924 ri 't II 30 Santa Ysabel-'/arner Divide 1913-1916 II ti It 32 Damrons 1911-1922 M M t' 36 Amago 1912-1944 U. S. Veather Bureau Bulletins 39 Santa Ysabel Ranch 1900-I916 Bulletin No. 48 41 Witch Creek 1909-1916 11 II It 43 Rose Glen 1911-1916 11 It II 44 Pamo Camp 1914-1923* n tt II 47 Valley Center #1 1872-1903 11 II It 48 Valley Center #2 1911-1924* II ri 11 30 Rockwood Ranch 1893-1915 II II II 51 Ramona #1 (Verlaque) 1896-1916 II 11 II 52 Ramona #2 (Sentinel) 1911-1931 II II n 53 Ramona #3 1927-1948 U. S. Weather Bureau Bulletins 53 Escondido #1 1918-1948 II II II 11 56 Esccndido ^2 1894-1935 II " II II 56 Escondido f'} 1887-1897 Bulletin No. 48 57 Twin Oaks 1875-1887 II It 11 62 Santa Fe Ranch 1912-1915 II H II 63 Powa y 1878-1909* U. S. X'eather Bureau Bulletins 69 San Diego 1850-1948 M 11 ri II 101 Julian 1879-1948* It 11 II It * Broken record Note: "Bulletin No. 48" refers to "Bulletin No. 48, San Diego County Investiga- tion", Division of Water Resources, State Department of Public Works, 1935" In general, the fcllcwing precipitation records are published herein for the first time. For many stations these records are in ccntinuetlon of data for seasons prior to 1933-34 published in Bulletin No. 48. In a few instances the present records reflect changes in prior published data, based upon revised or more authoritative information. 211 PRECIPITATION in Inches Precipitation Station Location: Sec- 10, T. S.3.B.4M. Hen Shaw Dam 11 S. , R. 2 E- Elevation: 2,702 feet Authority: San Diego County Water Company and Vista Irrigation District Index No. 33 Bulletin No. 48 Sea- Season July Aup. Sept. Oct. Nov. Dec. Jan. Feb. Har. Apr. May June sonal Total 19J3-5* 0.22 0.58 3.55 2.81 3.14 O.Ob u.lB 0.32 10.86 1934-35 O.Ofa 0.08 0.38 2.01 1.27 6.22 5.41 4.12 3.92 2.64 0.20 26.31 1935-36 2.48 0.37 0.21 0.66 0.68 0.48 12.38 i.-^^ 2.08 0.05 23.70 193b-37 0.74 O.bl 0.02 3.38 0.b4 15.64 6.96 14.14 8.42 1.54 0.28 38.78 1937-38 0.20 0.14 4.21 3.36 9.79 18.30 1.97 0.81 1938-39 0.49 0.38 0.10 7.76 4.85 5.09 3.26 1.82 23.75 1939-10 7.09 0.40 1.01 1.29 6.55 7.13 0.38 5.45 0.06 29.14 1940-41 0.05 2.29 0.55 12.90 2.25 6.67 10.82 6.80 0.62 0.07 45.02 1941-*2 1.25 0.13 3.32 • 5.46 7.39 1.20 5.45 5.39 2.60 0.02 28.21 19'.2--5 0.18 0.72 0.33 2.81 13.04 4.73 5.52 3.07 0.19 30.59 1943-44 0.56 0.96 6.41 2.30 10.01 2.47 2.10 0.30 0.12 25.25 19-4-45 7.52 1.24 0.80 4.20 9.48 0.57 25.81 1945-46 4.54 0.05 0.12 0.46 10.23 0.72 2.28 5.10 0.96 0.14 24.60 1946-4'; 0.28 0.01 2.45 7.73 2.53 1.92 0.94 2.04 1.26 0.83 19.97 1947-48 0.05 1.31 0.08 0.29 0.90 4.37 0.10 3.99 4.24 1.75 0.05 0.28 17.41 Additional record published in Bulletin No. 4-8. Precipitation Station: Mesa Grande {.'^gels) Location: Sec. 21, T. 11 S. , H- 2 E. , S.B.B.*M. Elevation: 3,450 feet Index No. M Authority: C. H. Angel and San Diego County Water Company Bulletin No- 48 Sea- Season July Aug. Sept. Oct. Kov. Deo. Jan. Feb. Ker. Apr. flay June sonal Total 1911-12 M n M M n M 1.50 0.07 15.88 5.50 2.03 « K 1912-15 0.50 0.91 M 5.55 1.56 9.81 8.57 3.65 1.57 0.78 0.67 51.15 1913-14 0.26 1.10 5.45 2.89 12.47 7.50 2.70 5.48 0.16 0.88 56.89 1914-15 1.64 1.50 4.98 9.44 11.88 M 4.15 M K M I915-I0 0.25 0.17 1.80 5.44 55.60 2.45 2.86 0.47 0.72 47.76 1916-17 0.52 0.50 3.98 0.20 4.54 6.82 6.75 1.16 5. 06 4.50 33.63 1917-18 0.17 1.26 5.19 5.46 13.45 0.51 1.61 0.20 25.63 1918-19 0.12 1.10 3.19 1.60 0.52 5.85 4.72 0.76 0.50 18.36 1919-20 0.70 O.oO 0.60 2.50 3.00 1.44 1.50 3.50 7.85 1.70 0.63 29.00 1920-21 2.51 1.12 2.04 5.26 2.05 5.41 0.92 6.17 25.46 1921-22 0.95 4.45 0.60 20.50 6.95 7.25 4.01 2.14 1.37 48.02 1922-23 0.56 0.15 1.00 4.57 8.50 0.80 5.50 1.40 5.62 0.12 0.55 24.57 1923-24 0.10 1.25 1.80 5.11 0.52 9.25 4.19 20.02 1924-25 1.01 3.70 8.70 0.75 2.28 4.04 6.60 0.54 2.65 30.07 1925-26 v 6.70 2.57 2.50 2.85 7.28 1.55 16.25 0.57 40.05 1926-27 0.06 4.07 5.98 7.30 1.70 25.72 5.55 1.84 2.27 0.27 48.78 1927-28 4.00 5.00 5.70 3.19 3.96 0.36 1.57 0.16 25.72 1928-29 .47 0.28 3.14 5.92 5. 60 5.61 5.65 4.77 0.06 51.20 1929-50 ° 0.76 11.80 5.51 6.56 1.72 7.95 52.18 1950-51 1.84 5.69 5.24 5.79 0.35 6.55 2.15 0.15 25.56 1951-52 0.19 0.40 3.25 5.53 11.59 4.27 16.50 1.02 1.85 0.47 1.05 45.88 1952-55 0.25 2.65 0.50 7.58 8.20 0.42 0.12 5.46 5.20 0.16 28.54 1933-34 u 0.75 U.65 4.54 2.65 4.67 0.64 0.85 1.09 15.82 1934-55 0.15 1.24 0.44 2.53 b.95 4.56 5.54 3.81 5.60 0.56 29.18 1955-36 0.6u O.lo 0.52 0.81 1.20 0.56 19.17 4.51 5.10 0.12 50.95 193&-57 0.55 0.50 0.50 5.67 1.10 15.55 5.90 15.10 8.62 1.55 1.62 54.50 1937-58 1938-59 0.29 6.56 2.88 14.92 15.87 2.82 1.85 45.17 0.68 0.27 9.05 5.44 5.47 5.10 5.59 0.27 29.67 1959-40 7.52 1.05 2.14 2.00 8.84 8.34 5.20 5.40 0.05 . 58.52 1940-41 3.17 0.90 13.66 3.62 8.74 15.47 8.56 1.55 0.40 54.07 1941-42 1.00 0.25 4.40 "•57 8.47 1.08 4.75 4.00 5.12 0.16 55.80 1942-45 0.45 1.58 1.28 5.44 11.72 5.14 7.11 4.50 0.70 55.92 1945-44 0.31 1.47 0.12 8.27 2.80 9.98 4.20 5.12 0.40 1.28 31.95 1944-45 8.45 1.55 0.55 5.00 12.90 1.10 0.47 29.82 1945-46 2.58 0.15 0.39 1.29 14.56 1.94 1.d7 22.18 1946-47 0.50 3.36 11.54 4.50 2.10 0.55 5.54 0.95 0.14 20.74 1947-48 1.55 4.74 0.25 5.58 5.15 3.90 0.60 19.77 Record missing. 212 PRECIPITATION (continued) in Inches Precipitation Station: Mesa Grande Location: Sec. 3i T. 12 S. , R. 2 S. S.B.B.tH. Kleretlon: },550 feet Authority: E* R* Davis and Cleason Ambler Index No. 38 Bulletin No. 48 Season July Auf . Sept. Oct. Not. Dec. Jan. Feb. Mar. Apr. May June Sea- sonal Total 19JO-J7 1937-58 1938-59 1959-40 M r. K n 7.05 M M 1.02 0.88 M 1.70 15.88 B.OO 9.25 2.04 5.65 4.25 5.27 7.79 21.00 12.65 5.78 9.59 9.00 14.62 4.26 0.96 1.88 2.25 1.82 6.88 0.88 0.50 0.22 H 40.25 M 56.85 1940-41 1941-42 1942-45 1945-44 1944-45 1.75 K M 0.92 5.75 5.35 1.00 1.52 1.30 4.40 O.bO 9.11 12.24 8.12 2.94 9.69 2.05 5.8b 2.60 13.35 4.05 M 9.61 4.62 5.97 11.69 6.49 13.73 4.02 6.97 5.11 13.95 10.66 4.89 5.85 5.46 1.17 0.55 0.61 r 1.02 « M 58.07 K 1945-4b 194b-47 1947-46 4.05 u 0.45 1.59 4,18 1.00 1.34 9.87 1.97 14.62 2.95 5.37 1.62 2.37 2.25 1.75 5.77 6.50 3.75 5.57 0.71 1.60 2.95 1.00 1.04 52.50 27.84 25-47 Additional record published in Bulletin No. PI - Record missing. Precipitation Station: Location: Sec. 21, T. S.B-B.4M. Santa Ysabel Store 12 S., R. 3 E., 48 and by U. S. Veather Bureau. Elevation: 2,983 feet Authority: San Diego County Water Company and Santa Ysabel Store Index No. 40 Bulletin Ho- 48 1 Sea- Season July Au^. Sept. Oct. Not. Dec. Jan. Feb. Mar. Apr. May June sonal Total 1911-12 M K M r. M 2.05 1.15 13.97 4.12 2.00 0.35 K 1912-15 0.60 5.90 1.55 M M 5.24 M 1915-14 M 0.54 0.29 5.51 2.03 8.48 6.25 1.51 5.05 0.52 0.80 n 1914-15 K n M 1.59 1.28 4.70 8.65 9.48 2.68 5.43 4.99 ?! 1915-1° 0.75 2.22 4.73 29.41 2.19 3.29 0.08 0.54 43.21 191b-17 1917-18 0.20 0.10 0.25 3.03 4.31 4.80 4.82 0.81 3.35 1.77 23.44 0.93 2.58 3.61 10.72 0.09 1.28 0.13 19.54 1918-19 0.8b 1.11 2.92 5.54 0.20 5.20 4.44 0.94 0.26 19.27 1919-20 O.bb O.bl 2.16 4.41 1.80 1.48 7.43 8.58 1.82 26.95 1920-21 0.65 0.07 2.45 0.34 2.18 4.68 1.86 3.52 0.97 5'5i 22.20 1921-22 5.51 0.42 20.46 6.12 7.21 3.26 2.27 1.78 44.83 1922-25 0.25 0.81 1.30 7.42 3.90 3.15 2.44 3.22 0.37 22.84 1923-24 0.25 0.95 0.87 6.85 0.77 7.66 3.37 17.59 1924-25 0.75 1.50 0.66 1.81 3.81 5.17 0.23 2.07 22.85 1925-26 5.89 2.99 1.72 0.95 6.48 0.78 12.46 0.37 31.62 1926-27 1927-28 1928-29 0.25 2.86 9.64 1.73 21.01 5.20 1.90 2.15 0.16 44.90 0.45 1-33 1.87 6.67 1.10 2.81 2.46 0.38 0.99 18.04 0.60 1.62 5.88 4.53 z'.&l 4.92 2.91 22.19 1929-30 0.27 1.14 1.91 0.02 11.41 4.81 2.02 5.83 1.31 29.59 1930-51 O.lo 0.65 1.05 4.86 5.56 5.97 0.32 4.25 1.21 21.85 1931-32 0.30 0.44 2.31 4.83 8.12 5.55 15.06 0.70 1.86 0.22 0.85 58.04 1932-53 0.42 5.97 6.79 7.64 1.84 0.71 4.44 3.22 0.12 29.15 1955-54 0.15 0.57 0.41 4.50 1.56 4.40 0.99 0.44 0.96 14.08 1934-35 0.12 0.44 0.85 2.05 4.17 4.84 5.8b 4.40 3.72 0.40 26.85 1935-56 0.18 Q.81 0.33 0.25 0.59 1.54 0.65 12.94 4.49 2.01 23.57 1936-37 0.55 0.48 2.57 0.84 12.66 4.71 12.45 6.78 1.15 0.65 42.64 1957-58 1958-59 0.27 0.08 5.97 5.46 9.00 15.28 2.28 1.25 33.59 0.48 0.61 0.17 9.23 5.84 4.90 2.90 1.37 0.24 25.74 1959-40 5.18 2.14 1.35 5.80 8.26 0.12 5.46 23.31 1940-41 3.19 1.14 10.01 5.25 5.79 11.24 7.80 0.72 0.49 43.63 1941-42 1.95 0.48 3.72 2.52 5.57 2.25 3.51 3.11 3.57 26.46 1942-4J 0.64 0.85 0.90 2.47 10.10 2.63 5.06 4.62 0.15 27.42 1945-44 0.85 b.ll 7.79 8.86 5.57 1.73 0.65 24.56 1944-45 7.64 1.74 0.45 4.76 9.79 24.38 1945-4= 0.97 3.12 1.58 8.10 3.3b 4.52 0.62 22.07 1940-47 1947-48 0.95 4.12 4.51 5.85 1.15 1.15 2.54 1.25 0.35 19.87 0.40 0.51 0.76 0.58 4.22 5.89 4.56 l.b9 1.16 17.17 K - Record missing. 213 PRECIPITATION (continued) In Inches Precipitation Station: Location: Sec. Jl, T. S.B.B.*M. Escondido Ditcb Head #1 10 S., R. IE., Elevation: Authority: 1,7>5 feet Escondido Mutual Water Company Index No. Bulletin No. 46 48 Sea- Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June sonal Total l895-9b fl M K 0.25 M 0.25 3.37 M 5.00 0.25 K M M 1896-97 M M M 2.75 1.17 2.10 7.60 7.02 4.55 M M 1897-98 1898-99 M M M 1.60 0.25 1.25 5.80 0.70 2.42 0.10 K M M « M n M 0.26 1.45 3.15 1.80 2.92 0.40 0.35 n 1899-00 PI K M 0.85 2.00 1.70 2.60 M 1.30 2.72 1.92 M M 1900-01 M M M K 4.97 3.70 7.05 1.55 0.25 M « M 1901-02 M n M V. H M M M f M K K M 1902-03 K M V K 3.19 3.40 2.10 5.60 4.40 5.15 f. M 1903-04 M M M H M M M r. K K M M M 1904-05 M n K 1.25 M K M M 9.55 1.40 4.25 M M 1905-06 H M n M 5.45 M 2.30 7.51 21.15 M K r. M 1906-07 1907-OB 1908-09 n M M 0.10 2.75 4.35 6.25 1.70 6.00 1.15 0.35 f r. M M 5.45 0.90 1.00 6.65 5.55 2.30 1.25 0.75 r M M 1.00 1.35 0.55 0.80 1.48 10.90 6.75 4.26 0.13 0.17 M M Record missing. Precipitation Station: Escondido Ditch Head ^2 Elevation; Location: Sec. 5» T. 11 S. , R. IE., Authority: S.B.B.iM. 1,770 feet Escondido Mutual Water Company Index No. 46a Not listed in Bulletin No. 48 Sea- Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June sonal Total 1909-10 M 0.12 n M 4.83 8.8} 4.05 0.45 5. 60 0.95 0.05 M M 1910-11 0.06 M K 0.70 l.b3 0.33 0.87 6.97 4.48 1.43 0.05 M « 1911-12 M « 0.88 0.31 2.44 0.60 M 12.80 4.80 2.25 M M 1912-13 0.25 0.80 « 2.85 2.15 2.90 5.75 1.50 1.02 0.55 0.41 « 1913-14 0.25 « M M M 2.10 10.70 10.40 2.70 2.45 0.28 0.40 « 1914-15 n M K M M 4.96 8.85 9.40 2.52 5.28 3.44 0.05 M 1915-16 M M M M M M H M M M fl « M 1916-17 1917-18 191S-19 0.17 n M M M 4.35 6.00 3.90 0.80 6.30 2.10 M M n 0.80 K K M M 4.00 2.75 9.15 M 1.1} 1.30 M H M M M M 3.50 O.bO 5.46 4.92 1.15 1.00 n M 1919-20 0.65 M M 1.10 2.90 2.38 1.17 8.95 7.71 M M n M 1920-21 M M M n « M M H 2.90 0.33 5.60 M M 1921-22 K M M M M M M M M M n M M 1922-23 M M M M 3.25 4.05 3.95 2.05 2.40 3.31 0.30 M M 1923-24 K M M M « M M M M M M M M 1924-25 n M n n M 9.12 0.89 1.75 3.50 3.75 1.87 3.00 n 1925-26 M n M 5.25 M 1.25 3.00 9.10 3.S8 14.15 0.25 M H 1926-27 1927-28 2.88 6.65 1.00 15.75 1.50 1.25 0.25 33.14 2.00 2.00 4.54 1.20 3.25 1.95 0.20 0.75 15.89 Record missing. 214 PRECIPITATION (oontlnuod) in Inches Precipitation Stotlon: Location: Sec. 55, T. S.B.B.*K. Sscondldo Ditch Head ^3 10 S., R. 1 E. , Elevation: 1,850 feet Authority: Escondido Mutual Water Company Index No. 4 6b Not listed in Bulletin No. 48 Sea- Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June sonal Total 1929-50 M 0.09 1.27 8.49 i.50 4.55 2.67 7.25 M 1930-51 1.15 5.00 2.96 4.60 0.50 5-55 1.15 18.49 1951-52 0.72 « M M 4.56 14.55 1.58 2.38 0.90 0.67 M 1952-55 H « 6.96 8.29 0.57 0.39 *-i2 1.96 M 1935-5* H M M 4.57 1.97 5.22 0.73 0.88 0.96 M 195*-55 0.55 M M 3.20 5.27 5.75 4.40 2.84 2.44 0.30 M 1955-56 2.95 1.02 0.91 0.45 4.28 10.22 5.59 1.01 0.4} 20.38 1956-37 0.26 0.10 0.19 M 0.17 11.56 9.85 8.09 1.58 1.51 M 1957-58 1958-59 0.15 0.11 5.98 5.85 8.0b 12.15 2.42 0.94 51.64 0.25 0.35 0.19 6.66 4.70 5.55 5.59 1.50 0.80 21.59 1959-*0 5.45 0.45 1.25 1.15 6.74 6.26 4.04 2.44 25.74 1940-*1 2.74 0.84 9.09 1.96 0.29 10.29 6.75 1.73 O.bO 40.29 19*1-12 0.85 0.4b 0.15 5.52 5.50 5.85 0.37 5.10 5.44 5.51 0.07 26.80 1912-A5 0.21 0.58 0.06 2.19 9.63 5.55 4.75 5.75 0.16 24.64 1945-14 0.06 0.81 0.06 7.75 1.55 9.05 5.06 1.50 0.59 1.06 25.07 1944-45 7.74 1.15 0.62 5.67 7.75 0.89 0.12 0.62 22.54 1945-46 1.80 0.81 6.71 0.91 1.65 4.54 2.64 1.12 20.18 1946-47 1.09 6.90 2.90 0.92 1.29 1.91 1.31 0.30 0.07 16.69 1947-48 c 0.53 0.55 0.88 5.65 0.10 2.56 3.56 1.75 0.12 13.66 K - Record missing. Precipitation Station: Valley Center #3 Location: Sec. 5, T. 11 S., R. 1 W. , S.B.B.tM. Elevation: Authority: 1,550 feet H. U. Lake Index No. 48a Not listed In Bulletin No. 48 Sea- Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June sonal Total 1924-25 0.4fa 0.03 }.61 0.69 0.57 2.47 2.18 0.24 0.80 11.05 1925-26 5.40 2.30 1.30 1.75 3.84 0.74 10.04 0.10 0,07 25.54 1926-27 1927-28 1928-29 0.05 2.02 4.97 0.44 14.08 5.65 1.01 0.79 0.19 27.18 0.04 2.95 0.18 5.02 0.87 3.25 1.35 0.19 0.71 0.06 14.60 0.60 1.45 5.48 2.55 2.20 2.51 1.97 14.76 1929-30 0.65 8.06 1.08 3.85 2.57 4.29 0.02 20.50 1930-31 0.72 1.50 2.11 2.26 5.45 0.19 3.28 0.80 16.29 1931-52 0.68 0.03 1.32 3.57 7.59 5.47 10.60 0.39 0.42 0.07 0.31 28.25 1932-33 2.51 4.79 6.34 0.14 0.18 2.65 1.20 0.11 17.72 1935-54 0.17 0.19 5.57 0.95 5.15 0.61 0.29 0.88 9.79 1954-55 0.15 0.60 1.72 2.11 4.89 4.}4 3.81 2.92 2.04 0.57 23.15 1955-56 1.40 0.25 0.95 0.52 0.59 7.76 2.71 0.88 0.11 0.05 15.22 1936-37 1957-58 1938-39 0.16 0.04 0.04 5.46 0.15 9.05 4.}b 9.14 6.97 0.95 1.00 0.02 57.52 0.24 0.1} 2.51 5.09 4.77 12.42 1.56 0.36 0.05 24.95 0.32 b.56 5.90 3.05 2.54 1.28 0.55 18.18 1939-40 4.76 0.30 0.85 0.79 5.40 4.66 2.79 1.27 0.14 0.24 21.20 1940-41 0.08 1.84 0.68 9.06 1.76 6.72 10.50 6.26 0.10 0.07 37.67 1941-42 M M 0.19 2.82 5.07 4.01 0.78 3.79 2.63 3.00 2.83 0.05 H 1942-4} M 0.25 0.55 0.55 1.91 8.48 3.75 2.25 0.18 0.25 K 1943-44 M M M M 7.55 0.97 6.12 1.69 0.90 0,18 0.68 K 1944-45 M M M 4.56 1.12 0.29 1.85 4.67 0.30 0.13 0.34 K 1945-4b 0.06 2.98 0.43 b.bO Record 1 discon -inued Record missing. 215 PRECIPITATION (oontlnued) in Inches Precipitation Station: Uohlford Lake Location: Sec. 53, T. 11 S. , R. 1 U. , S.B.B.iK. Elevation; Authority: 1,510 feet Escondido Mutual Water Company Index No- Bulletin No. 49 48 Sea- Seasor. July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. Kay June sonal Total 1926-27 1927-28 1928-29 2.72 5.81 0.99 16.66 5.42 0.97 1.45 0.14 32.16 1.55 2.65 5.64 0.77 2.75 1.15 0.10 0.60 15.01 0.02 0.59 1.68 4.72 2.88 2.90 2.61 2.63 17.83 1929-50 0.22 0.80 7.80 1.33 5.56 0.94 7.05 21.48 1930-51 0.06 0.05 0.85 2.56 M 7.23 0.13 3.40 0.99 M 1951-32 0.45 1.55 4.21 7.b4 2.22 11.75 0.55 1.01 0.11 0.52 29.59 1952-33 2.04 4.69 6.57 0.24 0.32 2.74 1.57 0.07 18.04 1955-54 0.54 5.44 2.27 3.55 1.55 0.25 0.04 0.66 11.90 1954-55 0.56 1.50 2.60 5.67 5.69 4.04 2.72 2.24 0.21 23.25 1955-56 0.28 0.53 0.52 9.56 2.22 1.12 0.12 14.15 1956-57 1957-58 1958-39 0.05 4.14 0.45 4.21 4.09 8.05 5.97 0.83 0.68 28.45 0.10 0.20 2.12 2.36 7.73 10.95 1.56 0.27 25.29 0.30 0.20 0.11 6.71 3.21 3.52 5.07 1.71 0.25 19.08 1939-40 5.05 0.55 0.75 0.75 5.75 5.43 0.41 4.29 20.98 1940-41 0.05 0.92 0.61 10.00 4.07 5.80 9.56 5.96 0.95 0.17 58.07 1941-42 0.09 0.45 0.19 2.b6 2.86 5.68 0.91 4.41 2.24 5.56 0.06 25.11 1942-45 0.48 0.61 0.54 1.80 8.38 3.58 4.74 2.55 0.15 0.18 22.99 1943-44 O.lB 0.41 0.06 6.32 1.55 6.57 1.98 1.18 0.61 0.78 19.44 1944-45 0.03 5.22 1.64 0.28 5.69 6.45 0.58 0.12 0.38 18.19 1945-46 0.05 2.51 0.04 0.57 7.76 0.69 l.o2 4.75 0.75 0.51 19.25 1946-47 1.62 6.64 2.02 0.59 0.64 3. 06 0.56 0.18 0.02 15.55 1947-48 0.80 5.62 0.04 1.88 1.32 2.77 0.65 11.08 M - Record missing. Precipitation Station: Location: Sec. 15, T. S.B.B.4M. Ramona #4 15 S., R. 1 E., Elevation: 1,450 feet Authority: U. C. Upjohn Index No. 55A Not listed in Bulletin No. 48 Season July Aug. Sept. Oct. Nov. Deo. Jan. Feb. Mar. Apr. May June Sea- sonal Total 1942-43 1943-44 1944-45 1945-46 1946-47 1947-46 0.13 0.03 1.57 0.09 0.41 0.15 0.23 0.50 0.52 1.45 0.44 0.46 0.05 5.31 0.50 5.72 0.52 2.25 5.54 1.24 6.76 1.63 2.96 5.96 2.06 0.16 0.82 0.51 0.05 2.77 5.82 2.58 1.05 0.69 2.02 5.96 2.59 5.44 2.79 1.96 2.45 0.21 1.18 0.29 0.75 0.44 0.90 0.59 0.10 0.16 0.15 0.03 0.24 0.11 0.05 0.60 18.24 18.58 15.06 14,51 10.60 10.27 Precipitation Station: Location: Sec. 10, T. S.B.B.*M. Bernardo Bridge 15 S., R. 2 W. , Elevation: Authority: 550 feet City of San Diego Index No. 58 Bulletin No. 48 Sea- Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June sonal Total 1955-54 0.10 0.26 0.45 2.55 0.46 2.47 0.87 0.02 0.45 7.41 1954-55 0.19 1.22 2.00 4.55 5.27 4.65 2.10 1.54 0.10 19.60 1935-36 0.14 0.98 0.91 0.78 6.48 2.52 0.57 0.58 12.18 1956-57 4.96 0.50 9.65 3.44 9.17 5.54 0.24 33.86 1957-58 0.10 0.14 2.21 2.10 4.48 6.00 1.00 0.19 0.05 16.27 1958-59 0.10 0.10 6.56 3.55 1.87 0.90 0.85 0.08 15.57 1959-40 5.75 0.50 0.54 0.67 4.69 4.70 0.11 4.14 19.10 1940-41 1.97 0.53 6.71 4.69 4.16 7.67 5.76 0.69 52.18 1941-42 0.04 0.04 0.13 2.Dl 2.67 5.98 0.95 2.04 1.90 2.52 0.04 18.90 1942-45 0.17 0.51 0.19 1.81 D.59 1.72 4.2b 1.82 17.07 16.58 1943-44 0.50 O.Oo 6.94 1.10 5.01 1.58 1.51 0.18 0.10 1944-45 5.58 1.57 0.13 2.42 5.66 0.15 0.02 0.08 15.61 1945-46 0.03 1.56 0.15 0.4b 5.51 0.75 0.81 2.80 0.55 0.04 12.66 1946-47 0.05 0.81 5.85 1.55 0.50 0.55 2.b9 0.25 9.81 1947-48 0.05 0.60 1.47 5.16 0.02 1.85 2.41 0.54 0.56 10.44 Additional record published in Bulletin No. 48 216 PRECIPITATION (continued) in Inches Precipitation Station: Hodges Dam Location: Sec. l8, T. 15 S. , R. 2 U. S.B.3.4M. Elevation: Authority: 550 feet City of San Diego Index No. 60 Bulletin No. 48 Sea- Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June sonal Total 1955-34 0.15 0.17 0.42 2.44 1.19 2.82 0.75 0.08 0.80 8.80 1954-55 0.14 0.51 1.56 2.45 4.18 5.07 4.15 2.15 1.52 0.24 19.57 1955-56 0.20 0.04 0.22 O.B4 0.87 0.71 6.28 1.85 0.56 0.05 0.03 11.0} 1956-57 1957-56 1958-59 0.05 0.06 4.95 0.51 9.18 5.08 e.69 5.16 0.58 0.66 52.92 0.12 0.10 2.11 1.34 5.67 6.99 0.86 0.34 0.11 17.64 1S.O9 0.05 4.97 0.08 5.35 3.31 1.68 1.79 0.85 0.05 1959-40 3.35 0.51 0.29 0.52 4.80 5.25 0.32 5.15 18.19 1940-41 0.04 1.17 0.38 5.60 1.94 4.96 6.74 5.22 0.80 26.85 1941-42 0.02 0.15 2.99 2.57 6.29 0.78 2.16 1.53 2.51 0.08 19.08 1942-43 0.12 0.46 0.25 1.9B 7.24 1.62 3.20 1.82 0.03 0.13 16.85 1945-44 0.02 0.26 0.05 7.76 1.04 4.28 1.34 0.89 0.12 0.4} 16.17 1944-45 0.05 5.35 1.4o 0.06 2.47 5.21 0.10 0.08 14.76 1945-4 ■> 1.96 0.10 0.39 4.99 1.00 1.06 3.05 0.46 0.08 13.09 1940-47 1947-46 1.0b 3.92 1.62 0.50 0.59 2.53 0.42 0.09 10.55 0.07 0.41 1.21 2.58 1.33 2.66 0.77 0.33 9.16 Additional record published in Bulletin No. 48. Precipitation Station; Location: Sec. 16, T. S.B.B.4M. San Dieguito Dam 13 S., R. 5 W., Elevation: Authority: 250 feet City of San Diego Index No. 6l Bulletin No. 48 Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June Sea- sonal Total 1933-34 1934-35 0.13 0.44 0.09 1.25 0.42 2.05 2.30 3.85 0.75 5.09 2.45 4.79 1.17 2.09 0.15 1.52 0.21 0.85 8.27 19.09 1935-36 1956-37 1937-58 1958-59 1959-40 0.10 0.08 0.24 0.05 0.04 0.03 0.03 2.41 0.25 5.66 0.05 0.32 0.83 0.54 0.03 0.01 0.27 0.86 8.13 1.85 4.49 0.50 0.86 2.69 1.04 2.61 3.40 6.59 6.28 5.56 1.46 5.16 1.41 5.23 5.71 1.61 0.25 0.47 0.54 0.72 0.50 5.21 0.05 0.51 0.32 0.07 0.04 0.16 11.59 27.80 15.27 10.84 15.50 1940-41 1941-42 1942-43 1943-44 1944-45 0.02 C 0.06 0.02 0.17 0.03 O.Oo 1.04 2.72 0.46 0.32 1.76 2.41 0.26 0.04 5.10 5.45 5.85 1.25 7.79 1.52 2.16 0.70 6.1} 1.54 0.04 4.55 2.71 1.27 3.85 2.03 6.46 1.54 2.23 1.29 4.2} 4.94 1.78 1.80 0.93 0.06 0.60 0.05 0.07 0.07 0.20 0.31 0.10 26.78 17.75 15.66 16.15 15.21 1945-46 1940-47 1947-48 1.41 0.09 0.02 0.15 0.11 0.52 0.30 0.71 4.47 0.64 4.80 1.85 2.31 0.71 0.48 0.90 0.64 1.23 2.55 1.88 2.08 0.59 0.17 0.71 0.14 0.07 0.01 0.40 11.81 10.11 7.82 Additional record published in Bulletin No. 48. 217 PRECIPITATION (continued) in Inches Precipitation Station: Miramar Location: Sec. 5i T. 15 S. , R. 2 S.B.B.tM. Elevation: 660 feet Authority: G. A. Riley, S. G. Erro and B. E. Hendrii Index No. Bulletin No. 64 48 Season July Aug. Sept. Oct. Not. Dec. Jan. Feb. Mar. Apr. May June Sea- sonal Total 1954-55 c o.eo 1.81 4.85 2.94 5.bb 2.34 1.78 20.18 1955-56 1956-37 1957-58 1958-39 1939-40 0.15 5.55 5.17 0.15 1.10 2.15 0.50 0.20 0.85 7.29 2.35 4.70 u.d5 1.25 2.76 1.95 3.52 5.75 7.75 6.70 5.75 2.50 4.78 1.69 4.45 5.60 2.00 2.10 0.54 1.47 0.70 0.45 0.80 0.56 14.70 26.54 16.48 12.97 18.93 1940-41 1941-42 1942-43 194J-44 1944-45 0.32 1.65 3.10 0.80 0.75 2.10 1.80 4.05 6.15 5.67 1.42 7.85 1.65 1.85 0.85 6.10 0.75 0.65 4.90 5.50 2.70 5.05 2.60 7.70 1.50 5.15 1.60 4.20 6.75 0.75 2.45 1.10 0.25 0.15 29.75 15.79 17.62 17.40 15.50 1945-46 1946-47 1947-48 1.40 u 1.55 0.74 0.d5 3.27 1.48 5.50 1.40 4.18 1.05 0.63 5.55 0.23 l.b5 5.30 1.06 1.89 0.48 0.50 0.04 0.20 15.75 8.14 10.08 Additional record published in Bulletin No. 46. Precipitation Station: Diverting Dam Location: Sec. 11, T. 14 S., R. 2 E. , S.B.B.ftM. Elevation: 840 feet Authority: La Mesa, Lemon Grove end Sprinp Valley Irrigation District Index No. Bulletin No. 96 48 Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June Sea- sonal Total 1935-54 1954-55 1955-36 1956-57 1957-38 1938-59 Record dis 0.16 0.07 continued 0.25 0.18 0.18 0.09 0.15 0.22 0.41 0.10 1.84 0.28 0.69 1.03 0.80 0.41 0.04 2.51 2.42 0.76 7.96 2.14 6.85 0.81 5.04 0.57 4.59 2.25 5.52 2.28 5.70 8.65 8.68 5.95 2.96 0.80 2.71 5.45 4.38 7.15 1.94 0.08 2.66 1.25 0.71 1.18 0.47 0.41 0.12 0.30 7.69 1S.O6 15.72 28.71 19.11 16.34 Additional record published in Bulletin No. 48. Precipitation Station: Location: Sec. 22, T. S.B.B.4M. Holdredge Ranch 11 S., R. 2 E., Elevation: 3,480 feet Authority: F. E. Holdredge Index No. 152 Not listed in Bulletin No. 48 Sea- Season July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June sonal Total 1954-55 M M M M M M b.lO 5.78 4.9b 4.42 0.25 M 1955-56 1956-57 1957-58 1958-59 1959-40 1.18 1.50 7.-^2 0.58 4.27 0.98 1.18 0.10 0.55 0.64 1.71 2.12 17.97 6.6b 10.87 1.74 0.77 7.90 4.49 6.70 8.43 20.57 18.24 13.75 6.57 8.59 5.5b 9.89 15.43 4.82 0.90 3.46 2.38 2.58 2.58 2.61 1.41 2.69 0.10 56. b7 62.16 44.15 52.08 52.28 1940-41 1941-42 1942-45 1943-44 1944-45 5.59 4.95 1.15 1.21 0.12 4.09 1.25 9.21 18.06 5.17 6.26 2.18 5.50 0.73 13.58 5.29 1.72 10.64 5.18 4.78 12.24 4.96 9.68 3.70 7.65 4.16 15.09 8.93 3.82 5.18 2.87 1.08 0.67 0.41 0.16 0.95 0.68 56.95 40.51 56.54 55.59 53.08 1945-46 1946-47 1947-48 4.05 D 1.03 O.bb 0.58 5.17 0.65 5.22 9.64 1.56 15.42 5.25 5.24 5.68 2.45 0.17 0.61 1.67 4.81 5. 61 3.59 5.97 1.17 1.57 2.81 1.05 0.92 0.03 0.09 0.76 55.17 27.54 22.64 Record missing. 218 APPENDIX F ESTIMA.TED OR MEASURED ACTUAL MONTHLY RUNOFF AT KEY GAGING STATIONS IN SAN DIEGUITO BASIN 1912-13 to 1947-48, Inolualve 219 ESTIMATED OR MEASURED ACTUAL MONTHLY RUNOFF AT KEY GAGING STATIONS IN SAN DIEGUITO BASIN 1912-13 to 1947-48, Inclusive in Acre-Feet Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 1912-13 1915-16 Oct. 193^ 2d4 % Nov. 100^ 142 12 Dec. llo^ 232 12 Jan. 369 472 12 Feb. 866 1,350 310 Mar- 1,450 1,780 1,390 Apr. 708 916 320 May- 436 442 8 June 213 155 3 July 40 12 Aug. 9 b Sept. 4 11 Totals 4,524 5,782 2,067 Oct. 130 169 °b Nov. 220 360 Ok 441^ Dec. 438 750 Jan. 66.400 104,000 257,000 Feb. 11,600 19,800 24,800 Mar 7,810 11,200 16,300 Apr. 4,090 fa, 070 6,720 May 2,140 3,340 3,320 June 1,140 1,680 1,200 July 592 916 290 Aug. 268 64b Sept. 420 512 Totals 95,248 149,443 310,071 1913-14 1916-17 b Oct. 15 b Nov. 105 198 Dec. 207 279 2 Jan. 3,090 5,070 4,390 Feb. 5,550 8,500 12,765 Mar. 1,450 2,490 2,400 Apr. 964 1,620 1,200 May. 695 1,100 695 June 314 522 24 July 46 20 Aug. 3 6 Sept. 11 6 Totals 10,450 19,817 21,480 Oct. 484 1,040 1,590 Nov. 383 762 666 Dec. 701 1,860 3,060 Jan. 1,880 3,540 7,620 Feb. 3,450 7,220 8,330 Mar. 2,510 3, 640 4,650 Apr. 1,580 2,760 3,520 May 1,320 2,020 2,020 June 774 791 552 July 337 348 Aug. 167 164 Sept. 134 187 Totals 13,720 24,332 32,008 1914-15 1917-18 Oct. 48 35 " Nov. 76 125 Dec. 270 397 Jan. 2,230 4,320 6,509 Feb. 8,b60 14,400 26,296 Mar. 4,910 7,500 9,b44 Apr. 2,640 4,860 8,687 May 9,220 13,bOO 20,557 June 2,050 2,800 1,760 July 615 959 54 Aug. 232 569 53 Sept. 183 232 Totals 31,134 49,797 73,560 Oct. 74 152 Nov. 155 305 6 Dec. 128 311 9 Jan. 221 738 261 Feb. 349 905 1,100 Mar. 3,990 7,810 22,400 Apr. 988 1,240 1,570 May 744 614 212 June 425 138 14 July 96 87 Aug. 98 77 Sept. 87 fa6 Totals 7,355 12,443 25,572 221 SSTIMATED OR MEASURED ACTUAL MONTHLY RUNOFF AT KEY GAGING STATIONS IN SAN DIEGUITO BASIN (continued) 1912-15 to 1947-48, Inclusive in Acre-Feet Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 2 b No. 33 Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 1918-19 1921-22 Oct. 127 175 Nov. 327 446 111 Dec. 560 738 117 Jan. 358 483 93 Feb. 928 961 989 Mar. 1,440 1,690 1,689 Apr. '643 839 380 May 312 443 23 June 60 57 July 12 5 Aug. 9 6 25 Sept. 56 25 7 Totals 4,812 5,868 3,434 Oct. 65 59 12 Nov. 54 39 41 Dec. 11,400 20,300 55,918 Jan. 5,550 9,410 15,240 Feb. 10,400 17,100 27,485 Mar. 9,280 15,300 24,557 Apr. 5,570 9,100 10,665 May 2,940 5,150 4,678 June 1,510 1,980 1,550 July 500 818 525 Aug. 215 294 68 Sept. 97 14 9 240 Totals 47,159 79,659 118,557 1919-20 1922-25 Oct. 64 28 50 Nov. 261 175 55 Dec. 458 558 48 Jan. 251 285 44 Feb. 1,570 2,540 8,285 Mar. 5,040 7,190 Apr. 2,980 4,770 5,838 May 1,570 1,750 495 June 'V, 54 6 2 July 98 59 Aug. 255 42 57 Sept. 50 14 Totals 12,519 17,554 14,547 Oct. 129 248 175 Nov. 517 581 209 Dec. 1,580 2,390 2,665 Jan. 824 1,540 1,862 Feb. 2,420 5,870° 4,815 Mar. 1,650 2,640° 5,047 Apr. 1,610 2,576° 2,248 May 719 1,150° 440 June 552 530° 177 July 90 140° 210 Aug. 50 80° 186 Sept. 58 60° 78 Totals 9,559 15,805 lb, 110 1920-21 1925-24 Oct. 102 71 39 Nov. 168 150 58 Dec. 251 287 51 Jan. 454 652 155 Feb. 415 528 91 Mar. 64 6 1,010 697 Apr. 518 555 104 May 596 795 227 June 242 215 July 19 10 56 Aug. 10 Sept. 19 Totals 5,171 4,071 1,485 Oct. 74 ° 118 24 Nov. 122 195 65 Dec. 250 568 85 Jan. 261 418 92 Feb. 159 222 102 Mar. 861 1,578 2,056 Apr. 791 1,26b 1,674 May 227 565 149 June 56 58 101 July 256 Aug. 171 Sept. Totals 2,741 4,586 4,751 222 ESTIMATED OR MEASURED ACTUAL MONTHLY RUNOFF AT KEY GAGING STATIONS IN SAN DIEGUITO BASIN (continued) 1912-13 to 1947-48, Inclusive in Acre-Feet Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 1924-25 I927-2B Oct. 6 ° 10 39 Nov. 71 114 Dec. 615 984 200 Jan. 316 506 72 88 Feb. 265 424 Mar. 386 618 Apr. 1,100 1,760 1,122 May 363 581 105 June 336 538 18 July 11 18 Aug. Sept. Totals 3,469 5,553 1,731 Oct. 185 296 29 Nov. 210 33b 67 Dec. 566 906 1,752 Jan. 507 811 1,553 Feb. 785 1,256 3,496 Mar. 617 987 1,552 Apr. 402 643 277 May 281 450 144 June 71 114 July a Aug. 13 Sept. 21 Totals 3,624 5,799 8,904 1925-26 1928-29 Oct. lb3 °261 71 Nov. 178 285 29 Dec. 201 322 45 Jan. 167 267 Feb. 1,190 1,904 2,498 Mar. 402 643 331 Apr. 11,300 18,080 30,139 May 1,290 2,064 1,147 June 3bl 578 July 74 118 5 Aug. 12 19 83 Sept. 3 5 Totals 15,341 24,546 34,348 a c Oct. Nov. 204 326 Dec. 188 301 271 Jan. 430 688 269 Feb. 797 1,275 1,824 Mar. 1,075 1,720 2,252 Apr. 1,537 2,459 3,531 May 434 694 239 June 165 264 July 13 21 102 Aug. 10 Sept. 47 75 Totals 4,890 7,823 8,498 1926-27 1929-30 Oct. 25 c 40 Nov. 114 182 Dec. 2,070 3,312 1,210 Jan. 866 1,386 864 Feb. 30,800 49,280 126,630 Mar. 8,200 13,120 15,167 Apr. 3,680 5,888 8,196 May. 2,050 3,280 3,801 June 1,140 1,824 831 July 248 397 Aug. 147 235 Sept. 207 331 Totals 49,547 79,275 156,699 Oct. « 8 ' 13 Nov. 26 42 Dec. 27 43 26 Jan. 1,026 1,642 1,021 Feb. 561 898 749 Mar. 1,938 3,101 5,054 Apr. 1,031 1,650 837 May 2,650 4,240 7,704 June 563 901 76 July 14 5 232 Aug. 30 48 Sept. 8 13 Totals 8,013 12,823 15,467 223 ESTIMATED OR MEASURED ACTUAL MONTHLY RUNOFF AT KEY GAGING STATIONS IN SAN DIEGUITO BASIN (continued) 1912-13 to 1947-48, Inclusive in Acre-Feet Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 1930-31 1933-34 Oct. ^ 64 ° 102 Nov. 278 445 Dec. 183 296 Jan. 278 1,368 443 198 Feb. 2,221 3,826 Mar. 350 560 ^i^ Apr. 281 450 285 May 230 400 176 June 20 32 July Aug. Sept. Totals 3,094 4,951 4,811 Oct. " 12 C 19 36 Nov. 23 40 40 Dec. 200 320 414 Jan. 313 301 269 Feb. 252 403 505 Mar. 235 408 201 Apr. 116 186 13 May 3 5 June 72 July Aug. Sept. Totals 1,176 1,882 1,330 1931-32 1934-33 Oct. s 8 °13 ^ Nov. 104 166 1 Dec. 1,348 2,157 4,078 Jan. 1,132 1,843 2,873 Feb. 21,283 34,033 49,870 Mar. 3,979 6,366 10,092 Apr. 1,599 2,358 2,594 May 976 1,562 1,637 June 353 885 171 July 194 5i° Aug. 53 83 Sept. 30 48 Totals 31,279 50,046 71,316 Oct. « ° 258 Nov. 71 114 276 Dec. 290 464 768 Jan. 824 1,318 680 Feb. 922 1,475 3,040 Mar. 1,400 2,240 2,400 Apr. 750 1,200 970 May 330 528 129 June 51 82 July Aug. Sept. Totals 4,638 7,421 8,521 1932-33 1935-36 Oct. ^ 101 ° 162 88 Nov. 64 102 41 Dec. 354 5bb 1,261 Jan. 2,003 3,205 7,375 Feb. 1,537 2,491 3,821 Mar. 879 1,406 702 Apr. 702 1,123 1,231 May 1,307 2,091 2,649 June 490 784 113 July 103 168 Aug. 27 43 Sept. 14 22 Totals 7,603 12,lb3 17,281 Oct. " ° Nov. 77 Dec. 20 32 120 Jan. 96 154 99 Feb. 2,609 4,174 3,160 Mar. 92b 1,482 1,560 Apr. 1,981 3,170 3,930 May 516 826 30 June 64 102 July 96 134 77 Aug. 19 30 Sept. 6 10 Totals 6,333 10,134 11,053 224 ESTIMATED OR MEASURED ACTUAL MONTHLY RUNOFF AT KEY GAGING STATIONS IN SAN DIEGUITO BASIN (continued) 1912-15 to 1947-48, Inclusive in Acre-Feet Season At At At Season At At At Sutherland Pamo Hodges Sutherland Pamo Hodges and Dam Site Dam Site Dam and Dam Site Dam Site Dam Station Station Station Station Station Station Month No. 25 No. 26 No. 55 Month No. 23 No. 26 No. 33 1956-57 1939-40 Oct. ° 1,110 Nov. 50 48 66 Dec. 2,010 5,216 6,740 Jan. 5,610 5,776 10,200 Feb. 22,550 55,760 72,160 Mar. 10,880 17,408 47,560 Apr. 5,010 8,01b 18,100 May 2,220 5,552 5,100 June 985 1,575 1,850 July 548 557 Aug. 92 147 Sept. 57 59 Totals 47,570 76,112 162,866 Oct. 90 ° 144 55 Nov. 150 208 57 Deo. 161 258 158 Jan. 681 1,090 2,080 Feb. 1,890 5,024 6,550 Mar. 1,040 1,664 2,550 Apr. 2,560 5,776 6,400 May 497 795 281 June 119 190 July 9 14 Aug. Sept. Totals 6,977 11,163 18,071 1957-58 Oct. 51 ° 82 Nov. 85 153 46 Dec. 537 559 425 Jan. 461 758 1,070 Feb. 1,960 3,136 8,050 Mar. 20,310 52,496 70,600 Apr. 3,190 5,104 6,550 May 1,920 5,072 5,850 June 861 1,578 854 July 517 507 25 Aug. 102 165 81 Sept. 45 69 30 Totals 29,655 47,417 91,561 1940-41 Oct. 55 ° 56 56 Nov. 99 158 55 Dec. 2,470 5,952 10,260 Jan. 1,270 2,052 6,090 Feb. 5,910 6,256 17,220 Mar. 15,100 24,160 56,350 Apr. 15,850 22,128 56,020 May 5,760 6,016 22,120 June 1,420 2,272 10,400 July 596 954 604 Aug. 558 541 84 Sept. 186 298 15 Totals 43,014 68,825 179,252 1958-55 Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. 88 129 864 1,070 4,010 2,100 1,490 706 215 49 1 125 ° 141 206 1,582 1,712 6,416 3,560 2,384 1,130 344 78 2 200 19 4,951 5,046 15,662 8,906 4,432 680 41 408 Totals 10,847 17,555 40,145 1941-42 Oct. 454 ° 726 1,460 Nov. 465 744 2,800 Dec. 960 1,556 10,020 Jan. 1,770 2,832 8,950 Feb. 1,210 1,956 4,850 Mar. 1,670 2,672 6,960 Apr. 1,560 2,176 3,250 May 857 1,571 1,150 June 308 495 146 July 60 96 Aug. 2 5 Sept. Totals 9,116 14,585 59,566 225 ESTIMATED OR MEASURED ACTUAL MONTHLY RUNOFF AT KEY GAGING STATIONS IN SAN DIEGUITO BASIN (continued) 1912-13 to 1947-48, Inclusive in Acre-Feet Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 Season At At At Sutherland Pamo Hodges and Dam Site Dam Site Dam Station Station Station Month No. 23 No. 26 No. 33 1942-43 1945-46 Oct. 34 C 54 4b Nov. 86 138 21 Dec. 198 317 268 Jan. 2,870 4,592 10,470 Feb. 1,880 5,008 4,440 Mar. 5,620 8,992 19.610 Apr. 5,080 8,128 10,020 May 1,500 2,400 1,660 June 586 938 162 July 140 224 Aug. 2c 42 Sept. 1 2 2 Totals 18,021 28,855 46,699 Oct. 57 b^ Nov. 107 126 Dec. 5,380 5,280 9,920 Jan. 980 1,280 1,830 Feb. 571 795 1,230 Mar. 853 1,160 1,750 Apr. 854 1,500 1,650 May 332 476 June 30 59 July Aug. Sept. 22 57 Totals 7,166 10,529 16,457 1945-44 1946-47 Oct. 42 54 27 Nov. 87 124 4 Dec. 495 708 1,150 Jan. 499 758 1,360 Feb. 3,760 6,160 9,600 Mar. 4,680 6,970 5,650 Apr. 1,700 2,510 3,250 May 964 1,270 880 June 558 841 259 July 111 197 Aug. 12 20 Sept. 5 15 Totals 12,90b 19,597 22,175 Oct. 45 50 « 18 Nov. 739 1,030 457 Dec. 564 579 339 Jan. 321 481 145 Feb. 319 446 324 Mar. 442 668 1,035 Apr. 222 405 104 May 36 68 - 164 June 5 8 - 226 July - 256 Aug. - 199 Sept. - 153 Totals 2,493 3,713 1,444 1944-43 1947-48 Oct. 3 12 Nov. 493 802 899 Dec. 305 424 584 Jan. 277 453 b02 Feb. 764 1,250 1,940 Mar. 4,540 6,880 10,740 Apr. 2,010 2,760 2,760 May 756 988 257 June 373 487 6 July ^i 64 Aug. 198 211 Sept. 64 62 Totals 9,654 14,373 17,788 e Oct. - 104 Nov. 8 3 - 56 Dec. 127 145 308 Jan. 71 105 - 69 Feb. 243 377 37 Mar. 339 455 106 Apr. 341 405 - 72 May 52 86 - 60 June 23 28 - 57 July - 77 Aug. - 120 Sept. - Ill Totals 1,204 1,604 - 275 226 NOTES Runoff at Pamo dam site for the period February 1923 to September 1943, inclusive, is estimated by the Division of Water Resources. Remaining values are from records of the United States Geological Survey, except as noted: a - Observed or estimated by F. E. Green, City of San Diego. b - Runoff between Bernardo and Hodges Dam estimated by Division of Water Resources, and added to Bernardo runoff. c - Estimated by Division of Water Resources. d - Corrected by Division of Water Resources for rainfall on reservoir surface, as was done by United States Geological Survey for remaining seasons. e - Notation by United States Geological Survey, "For months when inflow to the reservoir was small and other elements were large, negative or discordant figures of runoff may appear. To the extent that such discrepancies may be attributed to changes in reservoir capacity since the time of the rating used, or to uncertantles in the rating, quan- tities too small for periods of falling stage in the reservoir are compensated by quantities too large for periods of corresponding rising stage." 227 APPENDIX G DATA REGARDING SPECIAL CENSUS Page No. Letter, Regional Director, United States Department of Commerce, March 29, 1949 231 Extracts from "Instructions to Enumerators for Special Censuses, Bureau of tlie Census, United States Department of Commerce 232 229 UNITED STATES DEPARTMEOT OF COMMERCE San Francisco Office 307 Customhouse Regional Office March 29, 19*9 Mr. Edward Hyatt, State Engineer, Division of Water Resources, Public Works Building, P. 0. Box 1079, Sacramento 5» California Attention: Mr. P. H. Van Etten, Principal Hydraulic Engineer Dear Mr. Hyatt: In further reference to your letter of March 7 and our reply of March 14, we now have a letter from the Bureau of the Census (Howard G. Brunsman, Chief, Population Division), Washington, reading as follows: "In special censuses, the military and naval personnel stationed in the area is included in its population, in ac- cordance with the marked paragraphs of the enclosed instruc- tions to Enumerators for Special Censuses. This practice is similar to the procedure followed in the 194-0 decennial census. Therefore, the population figure of 362,658 does include mem- bers of the armed forces stationed in San Diego on the census date. The separate population of the military establishments in the city, according to the special census was 72,209. This figure comprises only those persons living in such establishments. We are unable to furnish figures for members of the armed forces living off post." We are enclosing the release, "Instructions to Enumerators for Special Censuses", mentioned above. If you could take off the data you need from it and return it for our files, it would be very much appreciated. Very truly yours, /s/ John J. Judge, John J. Judge, Regional Director. 231 Extracts from "Instructions to Enumerators for Special Censuses" " Uho Is to be enumerated . — The persons to be enumerated in each dwelling unit include all persons whether civilian or members of the armed forces, who were living in this dwelling unit at the time of the interview, except that babies born after 12.01 A.M. of the census day should be omitted and persons dying after this time should be included in the census." " Enumeration of members of the armed forces . --Persons who are in the Army, Navy, Marine Corps, or Coast Guard are to be counted as now living in this dwelling unit only if they are stationed in this area and living off post in this dwelling unit." " Absent persons who are not to be enumerated as now living in the dwelling unit. --Below are listed certain types of persons whom the respondent may consider as still being members of his household but who are actually not to be enumerated as now living in this dwelling unit: (a) Do not include men and women now stationed elsewhere with the armed forces (Army, Navy, Coast Guard, or the Marine Corps) even though home on leave, furlough, or pass at the time of the enumeration." 2J2 APPENDIX H ESTIMATES OF COSTS Page No. Estimated Costs of Completing Sutherland Reservoir 235 Estimated Costs of Sutherland-San Vicente Pipe Line 236 Estimated Costs of Pamo Reservoir with Storage Capacity of 163,400 Acre-feet. . . 237 Estimated Costs of Pamo Conduit to Accommodate Reservoir of 163»400 Acre-foot Capacity 238 Estimated Costs of Lake Hodges with Storage Capacity of 310,000 Acre-feet .... 239 Estimated Costs of Pumping Water from Lake Hodges to a Point 2i Miles Southeast of Hodges Dam at Elevation 65O Feet. 240 Estimated Costs of Mission Gorge Reservoir No. Zero 241 Estimated Costs of Mission Gorge Reservoir No. 2 242 Estimated Costs of Mission Gorge Reservoir No. 3j with Concrete Gravity Dam at Lower Site 243 Estimated Costs of Mission Gorge Reservoir No. 3. with Concrete Variable-Radius Arch Dam at Lower Site 244 Estimated Costs of Enlargement of San Vicente Reservoir 245 233 ESTIMATED COSTS OF COMPLETING SUTHERLAND RESERVOIR (Based upon Prices Prevailing in April 1947) Elevation of crest of dam: 2,074 feet, U.S.G.S. datum. Elevation of crest of fixed spillway: 2,056 feet. Height of dam to crest of drum gates, above streambed: I58 feet. Capacity of reservoir to crest of drum gates (elevation 2,070 feet): 36,724 acre-feet. Capacity of spillway: 57,000 second-feet. Item Quantity Unit Price Cost Dam (including spillway) Diversion and care of river i Lump sum $ 2,000 Excavation Spillway, rock 22,000 cu. yds. 4.00 88,000 Cutoff, rock 1,000 cu.yds. 8.00 8,000 Concrete, reinforced Cutoff 2,200 cu.yds. 30.00 66,000 Buttresses 15,600 cu. yds. 21.00 327,600 Arches 11,800 cu. yds. 30.00 354,000 Bridge and struts 3,115 cu.yds. 60.00 186,900 Spillway structure and walls 3,600 cu.yds. 50.00 180,000 Spillway paving 1,700 cu.yds. 27.00 45,900 Reinforcing steel 3,360,000 lbs. 0.11 369,600 Drum gates, 13 x 50 feet 3 each 32,000 96,000 |1 ,724,000 Outlet Works Concrete Mass, in pipe anchors and pipes 100 cu.yds. 20.00 2,000 Reinforced 356 cu. yds. 60.00 21,400 Trash rack bars 32,000 lbs. 0.15 4,800 Structural steel 10,000 lbs. 0.20 2,000 Tractor gate and hoist 2 each 8,000 16,000 Tube valve, 48-inoh diameter 1 each 15,000 15,000 Steel pipe, 48-inoh diameter 42,000 lbs. 0.25 10,500 71,700 Reservoir Land and Improvements 360 acres 2,500 Clearing reservoir lands 660 acres 30.00 19,800 22,300 diiVit /-^+ fi 1 _ ________ $1 818,000 181,800 0UDT>0\/{1A ____________ Administration and engineering 10% (0.10 X 1,818 ,000) Contingencies 15f. (0.15 X 1,818 ,000) 272,700 Interest during construction 1 year at 3% 70,300 rpriT AT i2 342,800 iUiAJj --_--________- ANNUAL COST (based on capital cost to complete dam only) Interest 3% i 70,300 Amortization 50-year sinking fund at 3% (0 .00886) 20,700 Depreciation, dam 100-year life, 3% sinking fund basis (0. 10165) 3,700 Depreciation, outlet works 50-year life, 3% sinking fund basis (0.00886) 800 Operation and maintenance 10,000 TOT^ilT - $ 105,500 i J i K±. -_-_-______-_- 235 ESTIMATED COSTS OF SUTHERLAND-SAN VICENTE PIPE LINE (Based upon Prices Prevailing in April 1947) Length: 13.5 miles. Capacity: 4^ second-feet. From To Length in Type of Cost Mile Nile Miles Construct ion Per Mile Total 0.0 2.40 2.40 2.90 2.40 0.50 36-inch diameter, concrete pipe 6.5-foot diameter reinforced , concrete- $ 57,000 528,000 $136,800 264,000 lined tunnel 2.90 3.25 0.35 36-inoh diameter, concrete pipe reinforced 57,000 20,000 3.25 3.55 0.30 30-inch diameter, concrete pipe reinforced 45,000 13,500 3.55 4.55 1.00 30-inch diameter, concrete pipe reinforced 41,000 41,000 4.55 5.00 0.45 36-inch diameter, concrete pipe reinforced 54,000 24,300 5.00 7.50 2.50 36-inch diameter, cylinder pipe concrete 72,000 180,000 7.50 13.50 6.00 36-inch diameter, concrete pipe reinforced 54,000 324,000 Struo tures e Subtota nd valve 1 - - s 33,000 *1 ,036,600 Admin istrati on and e ngineering lOf. 103,600 Conti ngencie s 1^1 155,500 Inter est dur mg cons truction 1 ye ar at 3% 38,900 TOTAL - n 334,600 ANNUA In L COST terest 3f. $ 40,000 Am DTtizat ion 50-year sinking fund at ?f. (0.00886) 11,800 De preoiat ion 80-year life, 3fo sinking f und basis (O.OO312) 4,200 Op sration and maintenance 0.15% 2,000 rOTAL - $ 58,000 236 Elevation of crest of dam: 1,104 feet, U.S.G.S. datum. Elevation of crest of spilJway: 1,084 feet. Height of dam to spillway crest, above strearted: 224 feet. ESTIMATED COSTS OF PA«0 RESERVOIR WITH STORAGE CAPACITY OF 163,400 ACRE-FEET (Based upon Prices Prevailing in April 1947) Capacity of reservoir to crest of spillway: l6},400 aore-feet. Capacity of spillway with 5-foot freeboard: 44,000 second-feet. Item iuantlty Unit Price Cost Dam Diversion and care of river * lump sum i 6,000 Stripping and preparation of foundation Right abutment 264,000 cu.yds. 0.60 158,500 Left abutment 68,600 cu.yds. 0.70 48,000 Channel 54 3,000 cu.yds- 0.70 240,000 Excavation, common From strip borrow 434,000 cu.yds. 0.30 130,000 From borrow pits 7,226,208 cu.yds. 0.40 2,890,500 Excavation, rock, from quarry 119,170 cu.yds. 3.00 359,000 Embankment, compacted, from stockpile 262,000 cu.yds. 0.20 52,400 Embankment, compacted, from borrow pits and spillway (earth-fill) 6,487,000 cu.yds. 0.15 972,000 ♦4,856 400 Spillway Excavation Common 48,600 cu.yds. 0,50 24,300 Disintegrated rock 212,200 cu.yds. 0.75 159,000 Rock 116,330 cu.yds. 3.00 490,000 Rock, cutoff 1,275 cu.yds. 6.00 5,600 Backfill 2,600 cu.yds. 0.40 1,000 Concrete Mass Ogee weir 8,140 cu.yds. 11.00 89,500 Retaining walls 6,348 cu.yds. 11.00 69,900 Reinforced Spillway cutoff structure 1,801 cu.yds. 45.00 81,000 Channel bottom paving 6,635 cu.yds. 25.00 165,500 Channel side lining 1,700 cu.ydir. 30.00 51,000 Cutoff at ogee weir 1,275 cu.yds. 30.00 38,200 Bridge 576 cu.yds. 50.00 28,80c Drains lump sum 14,700 Pressure grouting 4,700 cu.yds. 2.00 9,400 1,227 900 Diversion Tunnel Excavation Common, open cut 13,300 cu.yds. 0.50 6,600 Disintegrated rock, open cut 58,000 cu.yds. 0.75 43,500 Rock, open cut 23,800 cu.yds. 3.00 71,400 Tunnel 20,700 cu.yds. 15.00 310,500 Concrete Mass, tunnel portals 610 cu.yds. 20.00 12,200 Tunnel lining 4,770 cu.yds. 30.00 143,000 587 ,200 Outlet Works Excavation, rock 250 cu.yds. 6.00 1,500 Concrete, for tower, reinforced 1,200 cu.yds- 60.00 72,000 Concrete, for tunnel plug and connection 800 cu.yds. 25.00 20,000 Cast iron, saucer valves and pipes 186,800 lbs. 0.25 46,700 Miscellaneous iron and metal 15,000 lbs. 0.30 4,500 Welded steel pipe, Jo-inch diameter 406,000 lbs. 0.15 60,900 205 ,600 Reservoir Land and improvements 2,483 acres 128,000 Relocating roads 3.25 miles 30,000 97,500 Relocating truck trails 3.85 miles 15,000 57,800 Glearinr reservoir lands QiiH ♦■ r^ *- Q 1 _ _____ ___ __ 2,150 acres. 25.00 53.700 357 000 J7,214 100 OUDljO^aX- — — — — — — — — — — ___ — — _ — Administration and engineering lOt (0.10 X 7,21* 100) 721 400 Contingencies on construction items 15i (0.15 X 7,086 100) 1,062 900 Interest during construction 1 year at 3% 270 000 TOTAL _-----_---_-------- _ - _ _ v9,268 400 ANTiTJAl COST Interest 3* i 278 100 Amortization 50-year sinking fund at }i (0.00886) 82 100 Depreciation 100-year life, 3% sinking fund basis (0. 00165) 14 600 Operation and maintenance 14 500 TOTAL ----------___--__-_ * 389 300 237 ESTIMATED COSTS OF PAMO CONDUIT TO ACCOMMODATE RESERVOIR OF 163,4-00 ACHE-FOOT CAPACITY Length: 36»3 miles. (Based upon Prices Prevailing in April 1947) Capacity: 30 second-feet. From To Length Type of Cost Mile Mile Miles Construction Per mile Total From Pamo R 3servoir to filtration plant site: 19.6 miles 0.0 12.1 11.1 39-inch diameter, concrete pipe reinforced $ 63,190 1701,400 6.2 6.5 0.3 39-inch diameter, cylinder pipe concrete 83,660 25,100 8.4 9.1 0.7 J9-inch diameter, cylinder pipe concrete 91,670 64,200 12.1 12.9 0.8 6.3-foot diameter lined tunnel , concrete- 528,000 422,400 12.9 19.6 6.2 39-inch diameter, cylinder pipe concrete 82,770 513,200 13.7 14.2 0.5 39-inch diameter, cylinder pipe concrete 104,580 •52,300 Struc tures < and valve s 48,900 $1 ,827,500 From filtrai Dion plan t site to Chesterton Tank: 12.6 mi les 0.0 0.9 0.9 36-inch diameter, cylinder pipe concrete 93,500 84,200 0.9 1.7 0.8 36-inch diameter, cylinder pipe concrete 139,000 111,200 1.7 3.8 4.1 36-inch diameter, cylinder pipe concrete 93,500 383,300 5.8 6.5 0.7 36-inch diameter, cylinder pipe concrete 139,000 97,300 6.5 16.7 10.2 36-inch diameter, cylinder pipe concrete 84,500 861,900 Struc tures £ Subtots nd valve 1 - _ - s 40,000 1 $3 ,577,900 ,405,400 Admin istrat: on and e ngineering 10% 340,500 Contli igencie s 15f. 510,800 rOTAL - $4 ,256,700 ANNUA] . COST In-t ,erest 3% 1 127,700 Amc )rtizat ion 50-year sinking fund at 3% (0.00886) 37,900 Def jreciat ion 80-year life, J>% sinkin g fund basis (O.OO312) 13,200 Op« 'ration and maintenance 0.10% 4,200 1 'OTAL - 9 183,000 238 ESTmATED COSTS OF LAKE HODGES WITH STORAGE CAPACITY OF 310,000 ACRE-FEET (Based upon Prices Prevailing in April 19*7) Elevation of crest of dam: 410 feet, U.S.G.S. datum. Elevation of crest of spillway: 395 feet. Height of dam to spillway crest, above streambed: 195 feet. Capacity of reservoir to crest of spillway: 310,000 acre-feet. Capacity of spillway: 88,000 second-feet. Item Quantity Unit Price Cost Dam (including spillway) Diversion and care of river Excavation, rock Concrete Mass Spillway training walls and piers Bridge and rail Reinforcing steel Grouting, drainage and seals ^ lump sum 133,500 cu.yds. 3-50 425,000 cu.yds. 10. 50 2,920 cu.yds. 35.00 570 cu.yds. 50.00 302,000 lbs. 0.10 1,015 ft. of dam 150.00 i 25,000 467,300 4,462,500 102,200 28,500 30,200 152,200 $5,267,900 Outlets Reinforced concrete Trash rack steel 36-inch dieuneter steel pipe 42-inch diameter steel pipe Double disc valves, 36-inch diameter Slide gate, 3.5 x 3.5 feet Needle valve, 56-inch diameter Reinforcing steel Reservoir Land Relocating county and state roads Clearing reservoir lands 100 cu.yds. 55,000 lbs. 43,000 lbs. 35,000 lbs. 6 each 1 each 1 each 15,000 lbs. 12 miles 2,000 acres 60.00 0.15 0.20 0.20 3,500 10,000 8,000 0.10 Subtotal Administration and engineering Contingencies on construction items Interest during construction 10% (0.10 X 7,419,900) 15% (0.15 X 5,657,900) I5 years at 3% 6,000 8,300 8,600 6,600 21,000 10,000 8,000 1,500 70,000 1,782,000 20,000 240,000 30.00 60,000 2,082,000 $7,419,900 742,000 845,700 424,400 TOTAL $9,432,000 ANNUAL COST Interest Amortization Depreciation, dam Depreciation, outlet works Operation and maintenance 3% $ 50-year sinking fund at 3% (O.OO886) 100-year life, 3% sinking fund basis (0.00165) 50-year life, 3% sinking fund basis (O.OO886) 282,900 83,600 11,400 800 14,500 TOTAL $ 393,200 259 ESTIMATED COSTS OF PUMPING WATER FBOH LAJtE HODGES TO A POINT 2j MILES SOUTHEAST OF HODGES DAM AT ELEVATION 650 FEET (Based upon Prices Prevailing in April 19i+7 ) Lake Hodges Operated Al one Lake Hodges Operated with Sutherland Reservol for Secon dary Yield for 1917-36 Firm Yield from 3u therland from Sutherland 1 Storage capacity of lOlt.500 157,300 22lt,eoo 31+0,700 10l+,500 157.300 22l+,800 277,800 10l+, 500 157,300 22l+,800 Lake Hodges, in acre- feet Average seasonal 1917-36 20,200 2l+,000 26,800 29,300 12,800 ll+,800 16,200 16,800 13,000 16,1+00 17,800 firm yield from Lake Hodgesa, in acre-feet Average seasonal 1917-36 12,000 15,800 18,600 21,100 l+,600 6,600 8,000 8,600 l+,800 8,200 9,600 firm yield to City of San Diego from Lake Hodges, In acre-feet Maximum demand^, in 20.14. 26.8 31.5 35.8 7.8 11.2 13.6 li+.6 8.2 13.9 16.3 second-feet Installed pump capacity. 25.5 33.5 39.1+ 1+1+.7 9.7 ll+.O 17.0 18.2 10.3 17.1+ 20.1+ in second-feet Maximum pumping head. 1+23 1+16 1+08 1+12 1+32 1+27 1+20 1+23 1+26 1+21 1+15 in feet Average pumping head. 3ia 327 313 296 351 335 321 311 31*9 331+ 318 Theoretical capacity'^, 1.397 1.809 2,088 2,392 Sl+7 775 925 1,001 563 950 1,096 in horsepower Installed capacity. 1,750 2,260 2,610 2.990 560 970 1,160 1,250 700 1,190 1,370 in horsepower Pipe line"^ $263,800 $31+0,500 $1+35,100 $1+35,100 $180,000 $201+, 600 $236,000 $236,000 $160,000 $236,000 $263,800 Pumping plant Pumps 11,200 11,800 12,300 12,700 6,1+00 8,800 9,700 10,000 6,900 10,500 10,300 Fittings, valves and meters Motors 21,000 10,500 2I+.300 13,200 25,800 ll+,900 27,200 16,800 7,800 l+,600 12,000 6,500 ll+,600 7,500 16,000 8,000 8,500 5,100 ll+,900 7,700 17,600 8,700 Switchboards, controls, meters Building 10,500 29,000 10,500 32,000 10,500 35,000 10,500 38,000 10,500 17,000 10,500 20,000 10,500 23 , 000 10,500 26,000 10,500 17,000 10,500 23,000 10,500 27,000 Bouse and grounds 12,000 12,000 12,000 12,000 12,000 12,000 12,000 12,000 12,0110 12,000 12,000 Engineering and administra- tion, 10? Contingencies, 15/6 9,1+00 ll+,100 10,1+00 15,500 11,100 16,600 11,700 17,500 5,800 8,700 7,000 10,500 7,700 11,600 8,200 12,1+00 6,000 9,000 7,900 11,800 8,600 12,900 TOTALS t381,600 41+76,300 $573,300 $561,600 ♦252,600 $291,900 $332,600 $339,100 $255, 000 »33l+,300 $371,1+00 ANNUAL COSTS Pipe lineS } 12,200 $ 16,100 $ 20,300 $ 20,300 $ 8 , 100 $ 9,500 $ 10,800 $ 10,800 $ 8,100 $ 10,800 $ 12,200 Pumping plant® 13,1+00 ll+,200 ll+,800 15,1+00 10,200 11,600 12,300 12,000 10,600 12,500 13,200 Energy cost*" 50,600 63,700 71,700 75,300 20,600 27,800 31,200 33,1+00 21,300 3l+,200 36,000 Power demand charge 10,100 12,200 13,500 ll+,200 l+,800 6,300 7,100 7,300 5,000 7,1+00 6,100 TOTALS $ 86,300 $106,200 $120,300 $126,200 $ l+3,_700 $ 55,200 $ 61,1+00 $ 61+,300 $ 1+5,000 $ 61+, 900 $ 71,500 Annual costs per acre-foot Annual costs per acre-foot per foot of pumping head « 7.19 .021 $ 6.72 .021 $ 6.1+6 .021 $ 5.98 .020 $ 9.51 .027 $ 8.37 .025 $ 7.58 .021+ $ 7.1+8 .021+ $ 9.36 .027 $ 7.91 .021+ $ 7.1+1+ .023 a - Baaed on preliminary yield studies, which differ slightly fro:n final results, b - Haximuin demand assumed as average rate during July. July total equals lO.l+lj. per cent of aeaaonal. c - Overall plant efflcienty assumed as 70 per cent. d - Includes engineering and administration item of 10 per cent, and 1$ per cent for contingencies. e - Includes interest at 3 per cent, and charges for amortization, depreciation, operation and maintenance f - Based on rats schedule P-2, with oil at $1.1+5 pei' barrel. 240 ESTIMATED COSTS OF MISSION GORGE RESERVOIR NO. ZERO (Based upon Prices Prevailing in April 1947) Elevation of crest of dam: 353 feet, U.S.G.S. datum. Elevation of crest of spillway: 33t> feet. Height of dam to spillway crest, above streambed: 58 feet. Capacity of reservoir to crest of spillway: 23,700 acre-feet. Capacity of spillway: 116,500 second-feet. Item ^uant ity Unit Price Cost Concrete Gravity Dam (including spi llway) Diversion and care of river * lump sum i 25,000 Excavation Common 26,000 ou.yds. 1.50 39,000 Hock, stripping 31,700 cu.yds. 3.00 95,100 Cutoff trenches 3,300 cu.yds. 8.00 26,400 Concrete Mass 69,200 ou.yds. 10.50 726,600 Reinforced Gate house pier 130 cu.yds. 30.00 3,900 Spillway training walls 240 cu.yds. 30.00 7,200 Intake tower and gate hou se 140 cu. yds. 60.00 8,400 Reinforcing steel 44,000 lbs. 0.10 4,400 Grouting, drainage and seals 850 lin. ft. of dam 125.00 106,300 $1 042,300 Earth Fill Dam Excavation Common, stripping 28,900 cu.yds. 1.00 28,900 Borrow pit, and haul 116,500 ou.yds. 0.45 52,400 Embankment 101,300 ou.yds. 0.15 15,200 Riprap Rock 13,263 ou.yds. 2.00 26,500 Gravel 2,738 cu.yds. 2.00 5,500 128,500 Outlets Steel pipe, 30-inch diameter 310 lin. ft. 15.00 4,600 Slide valves in pipes, 30-lnc ti diameter 3 each 2,800 8,400 Slide valves in tower, 30-ino h diameter 3 each 2,800 8,400 Trash rack hoist 1 each 700.00 700 Trash rack and guides 6,400 lbs. 0.15 1,000 23,100 Reservoir Land and improvements 2,268 acres 911,700 Relocating roads 3.9 miles 167,500 Relocating pipe line 5-93 miles 90,000 353,700 Clearing reservoir lands 480 acres 30.00 14,400 1 ,447,300 q.iVv-i-,^ + c 1 _ _ $2 ,641,200 264,100 Administration and engineering lOf. (0.10 X 2,641,200) Contingencies on construction items 15f. (0.15 X 1,729,500) 259,400 Interest during construction 9 months at 3fo 72,800 THTAT _____-_-__ $3 ,237,500 luiiijj — — — — — — — — — — ANNUAL COST Interest 3% $ 97,000 Amortization 50- year sinking fund at 3% (C .00886) 28,700 Depreciation, dam lOC -year life, 3% sinking fund basis (O.OOI65) 2,500 Depreciation, outlet works 50- year life, 3% sinking fund basis (C .00886) 300 Operation and maintenance 7,600 TflTuT __---_---- $ 136,100 iKjLaij — — — — — — — — — — 241 ESTIMATED COSTS OF MISSION GORGE RESERVOIR NO. 2 (Based upon Prices Prevailing in April 19^7) Elevation of crest of dam: 353 feet, U.S.G.S. datum. Elevation of crest of spillway: 336 feet. Height of dam to spillway crest, above streambed: 92 feet. Capacity of reservoir to crest of spillway: 29,200 acre-feet. Capacity of spillway: lib, 500 second-feet. Item ^uant ity Unit Price Cost Concrete Gravity Dam (including spillway) Diversion and care of river i lump sum i 25,000 Excavation Common 14,160 cu.yds 1.50 21,200 Rock, stripping 30,130 cu.yds 3.00 90,400 Cutoff trenches 3,920 cu.yds 8.00 31,400 Outlet tunnel 90 cu.yds 20.00 1,800 Concrete Mass In dam 85,950 cu.yds 10.50 902,500 Outlet tunnel backfill 70 cu.yds 20.00 1,400 Reinforced Spillway walls 330 cu. yds . 35.00 11,500 Spillway lining 1,010 cu. yds 31.00 31,300 Gate tower and house 100 cu.yds . 60.00 6,000 Gate house pier 140 cu.yds • 30.00 4,200 Reinforcing steel 151,000 lbs. 0.10 15,100 Grouting, drainage and seals 640 ft. of iam 150.00 96,000 Backfill 4,100 cu.yds . 0.50 2,100 $1 ,239,900 Outlets Steel pipe, 30-inch diameter 460 lin. ft. 15.00 6,900 Trash racks and guides 6,400 lbs. 0.15 1,000 Slide valves in pipes, 30-inch diameter 3 each 2,800 8,400 Slide valves in tower, 30-inch diameter 3 each 2,800 8,400 Trash rack hoist 1 each 700.00 700 25,400 Reservoir Land and improvements 2,268 acres 911,700 Relocating roads 5.0 miles 297,000 Relocating pipe line 4.48 miles 90,000 403,200 Clearing land 5OQ acres 30.00 15,000 1 ,626,900 <^iihtnfnT -_---___ $2 ,892,200 QUU ou Laj. — — — _ _ _ _ Administration and engineering 10% (0.10 X 2,892 200) 289,200 Contingencies on construction Items 15% (0.15 z 1,980 ,500) 297,100 Interest during construction 1 jrear at 3% 107,600 TDTAT --________ J3 586,100 ± ui. Ai- ANNUAL COST Interest n i 107,600 Amortization 50- year sinking fund at J>% (0. 00886) 31,800 Depreciation, dam lOO-year 1 ife, 3% sinking fund basis (0 .00165) 2,600 Depreciation, outlet works 50- year life, 37= s: nking fund basis (0. 00886) 300 Operation and maintenance 7,700 TOT AT -_-_____ i 150,000 1\J1j±Lj —- — — _____ 242 ESTIMATED COSTS OF MISSION GORGE RESERVOIR NO. 3 With Concrete Gravity Dam at Lower Site (Based upon Prices Prevailing in April 194-7) Elevation of crest of dam: 331 feet, U.S.G.S. datum. Elevation of crest of spillway 31fa feet. Height of dam to spillway crest, above streambed: 21b feet. Capacity of reservoir to crest of spillway: 29,200 acre-feet. Capacity of spillway, 131,000 second-feet. Item Quantity Unit Price Cost Concrete Gravity Dam (includin g spillway) Diversion and care of river J lump sum $ 25,000 Excavation Common 46,200 cu.yds 1.50 69,300 Rock, stripping 93,500 cu.yds 3-00 280,500 Cutoff trenches 4,100 cu.yds 8.00 32,800 Concrete Mass, dam 279,900 cu.yds 10.00 2,799,000 Reinforced Spillway walls 230 cu.yds 35.00 8,100 Spillway lining 6,270 cu.yds 30.00 188,100 Reinforcing steel 517,700 lbs. 0.10 51,800 Grouting, drainage and seals 900 ft. of dam 150.00 135,000 Backfill 8,250 cu.yds 0.50 4,100 $3 ,595,700 Outlets Excavation, outlet tunnel 450 cu.yds 20.00 9,000 Concrete Mass, outlet tunnel backfi 11 370 cu.yds 20.00 7,400 Reinforced Gate tower and house 370 cu.yds 60.00 22,200 Gate house pier 200 cu.yds 30.00 6,000 Reinforcing steel 104,100 lbs. 0.10 10,400 Trash rack and guides 19,500 lbs. 0.15 2,900 Slide valves in pipes, 30-inch diameter 3 each 2,800 8,400 Slide valves in tower, 30-lnch diameter 5 each 2,800 14,000 Trash rack hoist 1 each 700.00 700 Steel pipe, 30-inch diameter 800 lin. ft. 15.00 12,000 93,000 Reservoir Land and improvements 1,202 acres 211,200 Relocating roads 6.35 miles 341,500 Relocating pipe line 6.00 miles 90,000 540,000 Clearing land 800 acres 30.00 24,000 1 ,116,700 o.ihtntnl ________ $4 ,803,400 480,300 OLlULUbaX ________ Administration and engineering 10% (0.10 X 4,805 ,400) Contingencies on construction items 15% (0.15 X 4,592 ,200) 688,800 Interest during construction 1 year at }% 184,700 fpflTAT __________ $6 157,200 LULRAj ________ — - ANNUAL COST Interest }% 1 184,700 Amortization 50-year sinking fund at 3% (O.OO886) 54,600 Depreciation, dam 100-year life, ii sinking fund basis (0 .00165) 7,600 Depreciation, outlet works 50-year life, 3% si nking fund basis (0. 00886) 1,100 Operation and maintenance 11,000 m Am AT __________ * 259,000 iUiAij -___-_---_ 243 estimatM' costs of nission gorge reservoir no. 3 With Concrete Variable-Radius Arc!' Dam at Lower Site (Based upon Prices Prevailing in April 1947) Elevation of crest of dam: 331 feet, U.S.G.S. datum. Elevation of crest of spillway: 31b feet. Height of dam to spillv;sy crest, above streambed: 21b feet. Capacity of reservoir to crest of spillway: 29,200 acre-feet. Capacity of spillway: 151,000 second-feet. Item ^iuantity Unit Price Cost Concrete Arch Dam (including spi llway _)_ *, lump sum i 25,000 Diversion and care of river Excavation Rock, strippin£ 98,600 cu.yds. 3.00 295,800 Spillway apron cutoff 1,200 cu.yds. 8.00 9,600 Concrete Arch, pravity section and thrust block 135,000 cu.yds. lb. 00 ?, 128, 000 Spillway apron 14,800 cu.yds. 15.00 222,000 Spillway apron cutoff 1,200 cu.yds. 20.00 24,000 Training walls 700 cu.yds. 35.00 24,500 Parapet wall 150 cu.yds. 33.00 5,000 Reinforcing steel 80,000 lbs. 0.10 8,000 Metal water stops, adjustment joints 12,100 lbs. 1.50 18,200 Sliding joint Service sheet lb, 000 s^.ft. 0.30 4,800 Metal water stop 3b0 lin.ft. 4.00 1,400 Grouting 1,000 ft. of dam I5O.OO 150,000 {2 ,916 500 Outlets Excavation, rock 150 cu.yds. 8.00 1,200 Concrete Manifold casing 150 cu.yds. 40.00 6,000 Trench 110 cu.yds. 25.00 2,700 Reinforcing steel 20,000 lbs. 0.10 2,000 Trash racks , 10,000 lbs. 0.20 2,000 Gate valve, 36-inch diameter 1 each 3,000 3,000 Hydraulically operated valves, 5 each 6,000 30,000 JO-inch diameter Steel pipe, 36-inch diameter 560 lin.ft. 16.00 5,800 Copper pipe, 3/4-inch diameter 3,500 lin.ft. 0.60 5,500 Gate houses 2 each lump sum 4,000 60 ,000 Reservoir Lend and improvements 1,202 acres 211,200 Relocating roads 6.35 miles 541,500 Relocating pipe line 6.00 miles 90,000 540,000 Clearing land 800 acres 30.00 24,000 1 ,116 700 Q , , >, 4. -. * Q 1 il ,095 000 oUDLOtai. --------- Administration and engineering lot, (0.10 X 4,093,000) 409 500 Contingencies on construction it ems 15% (0.15 X 3,881,800) 582 300 Interest during construction 1 ye ar at 3f. 157 500 THTAT __--__-__-- *5 ,241 900 i U i Kij —------ — — -- ANOTJAL COST Interest n * 157 500 Amortization 50- year sinking fund at 3f„ (0. 0088b) 46 400 Depreciation, dam 10c -year life, 3fo sinking 'und basis (0.00165) 4 800 Depreciation, outlet works 50- year life, 37« sinking fund basis (0.0088b) 500 Operation and maintenance 11, 000 mnrpAT __-_-_--___ $ 220, 000 lUliLLj — — — — — — — — — — — 244 ESTIMATED COSTS OF ENLARGEMENT OF SAN VICENTE RESERVOIR To Capacity of 250,000 Acre-feet (Based upon Prices Prevailing in April 1947) Elevation of crest of dam: 777 feet, U.S.G.S. datum. Elevation of crest of spillway: 7b8 feet. Height of dam to spillway crest, above streambed: 308 feet. Capacity of reservoir to crest of spillway: 250,000 aore-feet. Capacity of spillway: 42,000 second feet. Item ;iuantity Unit Price Cost Concrete Gravity Dam Enlargement Temporary outlet works i lump sum } 5,000 Excavation Common 22,000 cu.yds. 1.50 33,000 Rock, stripping 46,000 cu.yds. 3.00 138,000 Preparation of foundation for conore te 9,900 sq.yds. 2.00 19,800 Concrete Mass 620,000 cu.yds. 10.00 6 ,200,000 Reinforced Outlet tower and house 252 cu.yds. 60.00 15,100 Spillway training walls JIO cu.yds. 35.00 10,900 Crest parapet walls 300 cu.yds. 30.00 9,000 Reinforcine steel 109,000 lbs. 0.10 10,900 Preparation of surface of existing dam 16,000 sq.yds. 4.00 64,000 Removal of existing concrete 5,000 Grouting, drainage and seals Percussion grout holes 500 lin.ft. 1.00 500 Rotary grout holes 1,000 lin.ft. 3.00 3,000 Grout 500 cu.ft. 2.00 1,000 Copper water seals 3,400 lin.ft. 2.00 6,800 Vertical and inclined drains 23,000 lin.ft. 1.00 23,000 Rotary drain holes 900 lin.ft. 3.00 2,700 46 ,547 700 Outlets Cast iron pipe, Jb-inch diameter 300 lin.ft. 18.00 5,400 Saucer valves 25,000 lbs. 0.20 5,000 Miscellaneous metal work 20,000 lbs. 0.50 10,000 Valve house reconstruction lump sum 5,000 25 400 Reservoir Clearing reservoir land 490 acres 30.00 14,700 14 700 C!nV,*-^*-al ________ J6 ,587 800 OUU LO bdX ______ — — Administration and engineering lOf. (0.10 X 6,587,800) 658 800 Contingencies on construction items 15t (0.15 X 6,587,800) 988 200 Interest during construction 1 ye ar at 3fo 254 700 TflTAT __________ ?8 489 500 i U 1 H^ __________ ANNUAL COST Interest 3f. 254, 700 Amortization 50-year sinking fund at 3% (0. 00886) 74 200 Depreciation, dam 100-year life, 'i% sinking fund basis (0.00165) 10, 800 Depreciation, outlet works 50-year life , 3% sinking fund basis (0.00886) 200 Operation and maintenance 12, 700 TOTAT __________ $ 352, 600 IVJliiXi — _ _ — _ 245 « THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO 50 CENTS ON THE FOURTH DAY AND TO $1.00 ON THE SEVENTH DAY OVERDUE. PHYSICAL SCIENCES LIBRARY Ae LIBRARY tTNrVERSITY OF CALIFORNIA DA\rs 111614