THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA DAVIS STATE OF CALIFORNIA DEPARTMENT OF PUBLIC WORKS DIVISION OF WATER RESOURCES EARL WARREN, Governor C. H. PURCELL, Director of Public AVorks EDWARD HYATT, State Engineer BULLETIN No. 51 IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 1945 printed in California state printing office TABLE OF CONTENTS ORGANIZATION, STATE DEPARTMENT OF PUBLIC WORKS ^^^ ^ Following Title Page ORGANIZATION, UNITED STATES DEPARTMENT OF AGRICULTURE Following Title Page LETTER OF TRANSMITTAL 5 ORGANIZATION 6 INTRODUCTION 7 DEFINITION OF TERMS 10 FACTORS AFFECTING THE NEED AND QUANTITY OF IRRIGATION WATER APPLIED IN PRACTICE 12 Climate 12 Soils 13 Soil characteristics affecting the use of water hy plants 13 Character of the plant 15 METHODS OF APPLYING IRRIGATION WATER 18 The furrow or corrugation method 18 The border method 19 The subirrigation method 20 The sprinkling method 20 Underground pipe system 20 SOUTH PACIFIC BASIN 22 Northern San Diego County 23 Irrigation requirements of citrus and avocados 24 Irrigation water applied 28 Santa Ana River Valley 29 Transpiration studies of citrus and walnut trees 31 Irrigation requirements of citrus and walnuts 40 Transpiration studies of deciduous fruit trees 43 San Fernando Valley, Los Angeles County 43 Irrigation requirements of citrus 43 Irrigation requirements of alfalfa 45 Water deliveries in San Fernando Valley 46 Irrigation of tomatoes in Los Angeles County 48 Beaumont Plains, Riverside County 48 Depths of irrigation water applied to deciduous fruits 49 San Jacinto Basin, Riverside County 50 Depths of irrigation water applied to citrus, walnut and apricot trees 52 GREAT BASIN DESERT AREA 61 Coachella Valley 61 Irrigation requirements of date palm trees 61 Irrigation requirements of vineyards 64 Imperial Valley 65 Irrigation of alfalfa 65 Irrigation of flax 65 Antelope Valley 67 Irrigation of pear trees 67 Irrigation of alfalfa 69 SAN JOAQUIN VALLEY 73 Description 73 Irrigation experiments with cotton at Shafter and at Firebaugh 74 Irrigation requirements of cotton 79 Miscellaneous estimates of consumptive use and depths of irrigation water applied to cotton in practice 80 Experimental treatments in irrigation of ajfalfa 80 Miscellaneous estimates of consumptive use and depths of irrigation water applied to alfalfa in practice 81 Irrigation of vineyards 84 (1) TABLE OF CONTENTS— Continued SAN JOAQUIN VALLEY— Continued Miscellaneous estimates of depths of irrigation water applied to beans in practice 85 Irrigation of sugar beets 86 Experimental irrigation of young peach trees near Delhi, California 87 Estimates of duty of water by peach trees 89 Irrigation of pastures 89 SACRAMENTO-SAN JOAQUIN DELTA 94 Experimental studies of consumptive use 94 Farm irrigation deliveries 96 SACRAMENTO VALLEY 99 Experiments in the use of water by crops at the University Farm, Davis 100 Irrigation of watermelons 100 Irrigation of alfalfa 101 Iri'igation of barley 104 Irrigation of wheat 105 Irrigation of oats 106 Irrigation of corn 107 Irrigation of dwarf milo maize 108 Irrigation of rice 109 Stream diversions serving a single crop type for irrigation 110 Water pumped from wells serving a single crop 112 Estimates of irrigation requirements of crops by various agencies 113 SUMMARY ^ 114 South Pacific Basin 115 Great Basin Desert Area 117 San Joaquin Valley 119 Sacramento-San Joaquin Delta 119 Sacramento Valley 122 LITERATURE CITED 124 (2) LIST OF TABLES Table Page 1. Some moisture relations of California soils 15 2. Root depths of vegetable plants 16 3. Relative tolerance of agricultural plants to different degrees of salinity in the soil solution 17 4. Border strip dimensions for three grades of soil 19 5. Summary of temperature, rainfall and length of growing season in northern San Diego County, California 24 G. Transpiration use of water by citrus and avacado trees in San Diego County, California, 1927 26 7. Summary of winter transpiration use of water by trees and cover crops, October 15, 1925 to April 1, 1926 in the vicinity of Escondido, Vista and Fallbrook, California 27 8. Irrigation water applied to mixed acreages of avocados and citrus, Vista Irri- gation District, 1937-43 2S 9. Irrigation water applied to 10 avocado groves, Vista Irrigation District, 1937-43 29 10. Summary of temperature, rainfall, and length of growing season in the Santa Ana River Valley, California 30 11. Locations and main characteristics of plots in interior zone, Riverside and San Bernardino counties, California. Seasons of 1930 to 1935 32 12. Transpiration use of water by citrus trees in the Anaheim, Tustin and Santa Ana areas in Orange County, California, 1028-29 34 13. Transpiration use of water by mature walnut trees, Orange County, California, 1928-29 35 14. Monthly transpiration use of water by citrus, and irrigation data for interior zone, Riverside and San Bernardino counties, California, April through October, 1930 36 15. Monthly transpiration use of water by citrus, and irrigation data for interior zone, Riverside and San Bernardino covmties, California, April through October, 1931 37 16. Monthly transpiration use of water by citrus, and irrigation data for interior zone, Riverside and San Bernardino counties, California, April through October, 1933 38 17. Monthly transpiration use of water by citrus, and irrigation data for interior zone. Riverside and San Bernardino counties, California, April through October, 1924-35 39 18. Estimated depth of maximum summer irrigation requirements for citrus trees in Orange County, California 40 19. Annual transpiration loss by mature citrus trees in Orange County, California 40 20. Ten-year average irrigation and yield for walnut trees in Orange County, California 41 21. Transpiration use of water by citrus trees with cover crop in the Ebert grove, near Azusa, California, 1929-30 42 22. Monthly temperature, rainfall and estimated transpiration use of water by citrus plots at Encino, San Fernando Valley, California, 1940 44 23. Summary of disposal of rainfall and irrigation in San Fernando Valley, Cali- fornia, September 23, 1939 to March 6, 1940 45 24. Use of irrigation water per acre, by principal irrigated crops in San Fernando Valley, California, by years, 1930 to 1937. Records furnished by Los Angeles Department of "Water and Power 47 25. Irrigation and yield of tomatoes grown in Los Angeles County, California, 1940 48 26. Mean monthly knd seasonal rainfall, 45-year record ending 1939, at Beaumont, California, elevation 2,558 feet. Authority United States Weather Bureau — 48 27. "Water applied for irrigation of deciduous fruits, Beaumont Irrigation District 50 28. Mean monthly and annual temperature and rainfall, San Jacinto, California, elevation 1,550 feet. Authority United States Weather Bureau 51 29. Water applied for irrigation of citrus near Hemet, San Jacinto Valley, Cali- fornia, 1930-37 54 30. Water applied for irrigation of walnut trees near Hemet, San Jacinto Valley, California, 1935-38 56 31. Water applied for irrigation of apricot trees near Hemet, San Jacinto Valley, California, 1939-40 57 32. Water applied for irrigation of citrus trees near Moreno, San Jacinto Valley, Riverside County, California 58 33. Water applied for irrigation of citrus trees near Moreno, San Jacinto Valley, Riverside County, California 59 34. Temperature, rainfall and transpiration use of water by date palms, Coachella Valley, California, 1936-38 63 35. Transpiration use of water bv Thompson seedless grapes in Coachella Valley, California, 1937-38 64 36. Irrigation and yield of alfalfa grown in Imperial Valley, California, 1943 65 37. Average depths of water applied in irrigation of flax in Imperial Valley, Cali- fornia, as reported by Imperial Irrigation District, 1941-42 66 38. Depth of water applied, yield and cost of water for irrigation of flax. Imperial Valley, California 66 (3) LIST OF TABLES— Continued Taile Page 39. Mean monthly temperature and rainfall at Palmdale, Antelope Valley, Cali- fornia, elevation 2,654 feet 67 40. Water applied for irrig-ation of pear trees, Littlerock Creek Irrigation District, Antelope Valley, California, 1934 68 41. Irrig-ation water applied to alfalfa in Antelope Valley, Los Angeles Countv, California, 1931 69 42. Water applied for irrigation of alfalfa on the Milaway Ranch, Lancaster, Antelope Valley, California, 1929-33, inclusive 70 43. Temperature and rainfall for each of the years 1927 to 1930 compared with the long term means. Bakersfleld, California 75 44. Depth of water transpired hy cotton, number of irrigations, depths of water applied and yields on plots undergoing different irrigation treatments. Shatter, California, 1927-1930 76 4.'). Temperatures and rainfall at Madera, California 77 46. Depths of consumptive use of water by cotton grown on plots of Panoche adobe soil near Pirebaugh, California. 1932-33 78 47. Temperature and rainfall at Turlock California 82 48. Irrigation water applied and crop yield of alfalfa grown on Oakley fine sand at Delhi, California 83 49. Irrigation and yield of Thompson seedless grapes grown in Kern Countv, Cali- fornia. 1930 85 50. Depth of water applied to young peach trees during the irrigation season, number of irrigations applied, and yield of peaches per tree near Delhi, California, 1923-28 88 51. Denths of water anpled to irrigated pastures on loam and sandy loam soils in Tulare County, California, 1940 91 52. Summary of estimated seasonal renuirements for irrigations water delivered at farm headgates, San .Toaquin Valley, California 92 53. Unit consumptive use of water by crops in Sacramento-San Joaquin Delta, California 95 54. Depths of water pumped to irrisrated crops in the Mokelumne area, obtained by the United States Geological Survey 97 55. Mean monthly temperature and annual rainfall at Davis, California 99 56. Irrigation annlied to watermelons and their yield at the University Farm, Davis, California 101 57. Irrigation water apnlied, rainfall, and crop yield of alfalfa at the University Farm. Davis, California 102 58. Irrigation water applied, rainfall, and crop yields of alfalfa grown on different soil types with different depths of irrigation water applied, Sacramento Valley, California 104 59. Comparison of yields of barlev after vears of light and heavy rainfall at the University Farm, Davis, California. 1910-1921 105 60. Irrigation water applied, rainfall, and crop yields of wheat grown under dif- ferent irrigation treatments at the Universitv Farm, Davis, California 106 61. Irrigation water applied, rainfall and crop yields of oats grown under different irrigation treatments at the University Farm, DaA'is, California 106 62. Summary of comnarisons of yields of corn given different irrigation treatments at the University Farm, Davis, California 108 63. Sumrnary of irrigation water applied, rainfall and crop yields of dwarf milo maize grown under different irrigation treatments at Davis, California 108 64. Summary, according to soil tyve. of net denths of irrigation water annlied and cron yields of rice grown on hea\'^' soils in Sacramento Valley, California 110 65. Monthly and total distribution of water diverted from streams to various single crops in per cent of its seasonal use in Sacramento-San Joaquin Valleys, 1935-42 111 66. Use of water pumped from wells to various single crop types in the vicinity of Suisun, Dixon, Woodland and Sacramento. California 112 67. Estimated water requirements per acre at farm headgate, Sacramento Vallev, California 113 68. Summary of irrisraion data applicable to the South Pacific Basin, California 116 69. Summary of irrigation data applicable to the Great Basin Desert Area, Cali- fornia 118 70. Summary of irrigation data applicable to the San Joaquin Valley, California 120 71. Summary of irrigation data applicable to the Sacramento-San Joaquin Delta, California 121 72. Summary of irrigation data applicable to the Sacramento Valley, California 123 LIST OP FIGURES Finure Page 1. South Pacific Basin 21 2. Great Basin Desert Area 60 3. San Joaquin Valley 72 4. Sacramento-San Joaquin Delta Area 93 5. Sacramento Valley 98 (4) LETTER OF TRANSMITTAL Mr. Edward Hyatt, State Engineer, Sacramento, California. Dear Sir : The material transmitted herewith for publication is a cooperative report on "Irrigation Requirements of California Crops." The report, prepared by Arthur A. Young, is a comprehensive com- pilation of data that have been published or made available from public and private files as well as unpublished findings resulting from our cooperative research studies pertaining to agricultural crops common to California. These data are of practical economic importance in determining the water supplies for and their uses in irrigation. The conservation and disposal of the water supplies of California for agriculture are based ultimately upon such information. Respectfully submitted. ^'^^, Chief, Division of Irrigation, Soil Conservation Service, United States Department of Agriculture. Berkeley, California, November 8, 1945. (5) ORGANIZATION STATE DEPARTMENT OF PUBLIC WORKS DIVISION OF WATER RESOURCES C. H. PuRCELL Director of Pullic Works Edwaed Hyatt State Engineer Harold Conkling Deputy State Engineer UNITED STATES DEPARTMENT OF AGRICULTURE, SOIL CONSERVATION SERVICE, DIVISION OF IRRIGATION Cooperating in Studies on Use of Water in Irrigation H. H. Bennett Chief of Service M. L. Nichols Assistant Chief of Service, Research W. W. McLaughlin Chief of Division This report was prepared by Arthur A. Young, Irrigation Engineer (6) Irrigation Requirements oF California Crops INTRODUCTION In California, as in all western States, water is the limiting factor in the expansion of irrigated areas. The increasing cost of new projects not only approaches the capital values that newly irrigated lands may profitably support but in many cases exceeds them and other benefits are evaluated to justify construction. Conservation of existing water sup- plies is therefore of the first importance in the economy of the irrigated west. Savings in irrigation seldom exist where water is plentiful but where it is scarce conserving methods are the rule, wasteful practices are avoided, and water is carefully applied. It is axiomatic that the most economical use prevails where there is a diminishing supply and water is high priced. Such conditions prevail in parts of California. Under these conditions economy in irrigation methods, involving a better understanding of the water requirements of agricultural plants, will benefit all irrigated areas. It is the purpose in this bulletin to make available in a single report existing data on the irrigation requirements of crops grown in the several physiographic subdivisions of the State. Not all the areas are included because for many localities irrigation data are lacking. In some areas high ground water makes available data of dubious value, and they are omitted. Practically all crops in California require irrigation in various amounts ranging from those that need but one or two irrigations to supplement a scanty rainfall, to high water requirement forage crops such as alfalfa and rice, which requires sub- mergence for a considerable part of the growing season. The irrigation data available throughout the State are divided into three groups. First, irrigation requirements for some of the principal crops have been determined through experimental studies by State and Government agencies, frequently in cooperation with the Division of Irrigation, Soil Conservation Service.^ Such data are based on soil moisture investigations, measurements of water applied in irrigation, estimation of rainfall stored in the soil that is used by the crop prior to the irrigation season, evaporation from soil after irrigation, and deter- mination of the efficiency with which irrigation water is applied. "With a knowledge of these items the irrigation requirement may be computed. Complete data for such computations, however, are seldom available in the published reports, which are the basis of this bulletin. The second group includes information on plant use of water as measured by soil moisture studies in determination of consumptive use or the transpiration use of water by crops. In Southern California nearly all investigators have taken soil samples below the three or four inches of dry surface soil, thus excluding soil evaporation losses, and the resulting measurement is one of transpiration use only, assuming that deep percolation losses are negligible. In Northern California soil samples generally have been obtained beginning at the soil surface so 1 Formerly Division of Irrigation, Bureau of Agricultural Engineering. (7) 8 DIVISION OF WATEE KESOURCES that the measurement of water consumed is consumptive use as it includes both transpiration by the plant and evaporation from the soil. In esti- mating the irrigation requirement of a crop it is necessary to have an understanding of the definitions of consumptive use and transpiration use in order that all the factors of soil moisture disposal may be taken into consideration. Definitions of terms appear later in this report. The third group of data includes records of depths of water applied in ordinary irrigation practice, estimated water requirements by engi- neers, appraisers and experienced water administrators. These data are less reliable than those obtained by intensive soil moisture investigations, but in the absence of investigational results they may be accepted as indicative, with the reservation that they generally exceed the actual requirements except where there is a definite scarcity of water for irri- gation use. Crops for which soil moisture studies have been made usually are those that are the most important in the areas in which they are grown. In Imperial Valley high ground water within the root zone causes a condition that makes it impossible to determine the consumptive use of many crops. For the South Coastal Basin, results of experimental studies in citrus and avocado orchards and in walnut groves are avail- able. In the San Joaquin Valley the consumptive use by cotton has been determined in the principal cotton producing areas. Consumptive use by the principal crops has been determined by experiments in the delta area ; and in the Sacramento Valley, at tlie University Farm and else- where, irrigation treatments of a number of the principal crops have been studied. Portions of the coastal area northward from Los Angeles County are intensively cultivated as an irrigated area. In the extreme northeastern part of the State several thousand acres are reported under irrigation but data on the irrigation requirements are not available. For the purpose of discussion the State has been divided into six general subdivisions representing the geographical distribution of water resources and agricultural lands. They are generally, although not always, separated by topographical features designating natural bound- aries and in most cases there are some climatic differences. Irrigation requirements are influenced bj^ various factors to be discussed later, but temperatures in the different sections of the State frequently control the choice of crops. Citrus trees can not be grown where subfreezing weather is usual and cotton does not grow unless summers are long and warm. Within these areas agriculture is successful only through the general practice of irrigation. The six subdivisions are as follows : 1. South Pacific Basin 2. Great Basin Desert Area 3. San Joaquin Valley 4. Sacramento-San Joaquin Delta 5. Sacramento Valley 6. Coastal Area north of Los Angeles County The South Pacific Basin includes northern San Diego County, the Santa Ana River Valley and its tributaries extending to Beaumont Plains and San Jacinto Basin ; the San Gabriel Valley, and the San Fernando Valley in Los Angeles County. In this area are a majority of all the IRRIGATION REQUIREMENTS OP CALIFORNIA CROPS \f citrus and subtropical fruits grown within the State. Tlie Great Basin Desert Area includes the irrigated sections of Imperial, Coachella and Antelope Valleys, occupying desert areas at low altitudes where the cli- mate is hot and the seasons long. Crops are principally alfalfa, vege- tables and cotton, with dates in the Coachella Valley. The San Joaquin Valley is the largest single farming area in the State. It grows a variety of crops including cotton, citrus, grapes, rice, potatoes, and many others. Its water suppl.y is derived partly from mountain streams and partly by pumping from underground basins. The Sacramento-San Joaquin Delta area is important agriculturally and its method of supplying water to crops by subirrigation differs from irrigation methods commonly used elsewhere. It is noted for its crops of potatoes, asparagus and celery. The delta differs also from the other areas mentioned in respect to its elevation at sea-level and its large acreage of peat soil which is extensively farmed. The Sacramento Valley grows alfalfa, peaches, grapes, rice, nnd grains. ' Because the University Farm and the California Agricul- tural Experiment Station are located in the valley, many of their irri- gation studies are the basis of the irrigation data used in this report. Portions of the coastal area lying north of Los Angeles County are impor- tant from an agricultural standpoint but they are not discussed here, as irrigation data are lacking. 10 DIVISION OF WATER RESOURCES DEFINITION OF TERMS _ Irrigation Requirement: The quantity of water, exclusive of pre- cipitation, that is required for crop production. It includes surface evaporation and other economically unavoidable wastes. Usually expressed in depth for given time (volume per unit area for given time) . (See also water requirement.) Water Bequirement : The quantity of water, regardless of its source, required by a crop in a given period of time, for its normal growth under field conditions. It includes surface evaporation and other economically unavoidable wastes. Usually expressed as depth (volume per unit area) for a given time. (See also irrigation requirement.) Consumptive Use (evapo-transpiration) : The sum of the volumes of water used by the vegetative growth of a given area in transpiration and building of plant tissue and that evaporated from adjacent soil, snow, or intercepted precipitation on the area in any specified time, divided by the given area. If the unit of time is small, such as a day or a week, the consumptive use is expressed in acre-inches per acre or depth in inches, whereas, if the unit of time is large, such as a crop grow- ing season or a 12-month period, the consumptive use is expressed as acre-feet per acre or depth in feet. Transpiration: The quantity of water absorbed by the crop and transpired and used directly in the building of plant tissue, in a specified time. It does not include soil evaporation. It is expressed as acre-feet or acre-inches per acre or as depth in feet or inches. Duty of Water: The quantity of irrigation water applied to a given area for the purpose of maturing its crop, expressed as acre-feet or acre- inches per acre or as depth in feet or inches. litigation Efficiency: The percentage of irrigation water delivered to the farm or field that is available in the soil for consumptive use by the crops. When measured at the farm headgate it is called farm irriga- tion efficiency and when measured at the field or plot it is designated as field irrigation efficiency. Field Capacity: The moisture percentage, on a dry weight basis, of a soil after rapid drainage has taken place following an application of water, provided there is no water table within capillary reach of the root zone. The moisture percentage usually is reached within two to four days after an ordinary irrigation, the time interval depending on the soil type. Permanent Wilting Percentage: The moisture content of a soil at which plants wilt and do not recover unless water is added. It is expressed as percentage of moisture based on the oven-dry weight of the soil. Moisture Equivalent: The quantity of water retained by a soil in a standardized apparatus (soil centrifuge) when the moisture content is raRIGATION REQUroEMENTS OF CALIFORNIA CROPS 11 reduced by means of a constant centrifugal force of 1,000 times gravity nntil brought into a state of equilibrium with the applied force. It is expressed as a percentage of the dry weight. It agrees closely with the field capacity of most of the fine textured soils but not of the sands. Available Moisture: The quantity of water in the soil that is avail- able for plant use, as limited by the field capacity and the permanent wilting percentage. It is expressed as percentage of the dry weight of the soil or as depth of water in inches per foot depth of soil. The desirable practice is to replenish the moisture before the wilting per- centage is reached. Moisture Percentage: The percentage of moisture in the soil based on the weight of the oven-dry material. Apparent Sjyecific Gravity (volume weight) : The ratio of the weight of a unit volume of oven-dry soil of undisturbed structure to that of an equal volume of water, under standard conditions. Soil Moisture: The water in unsaturated soil. It is expressed as a percentage on a dry weight basis, or in inches per foot depth of soil. Sub -irrigation: Irrigation by the application of water below the ground surface or by absorption from a high water table which may be controlled or fluctuated for this purpose ; colloquially termed ' ' subbing, ' ' 12 DIVISION OF WATER RESOURCES FACTORS AFFECTING THE NEED AND QUANTITY OF IRRIGATION WATER APPLIED IN PRACTICE CLIMATE Extremes in rainfall occur in different parts of California, ranging from three inches in Imperial Valley to 100 inches in the northwestern coastal area. Rainfall is deficient throughout the fertile interior valleys and along the slope of the southern coastal plain, with the greater part of the area receiving less than 20 inches annually and one-third receiving less than 10 inches. This precipitation, coupled with an almost com- plete absence of rain during the growing period forces the practice of irrigation for the satisfactory growing of crops. All the rain falling upon a field is not effective in promoting plant growth. A light rain, falling upon dry soil, will soon be dissipated by evaporation and no benefit will be derived by the plant. If a light rain precedes or follows a heavy rain within a few hours both storms combined will provide the plant with moisture. The effective rain- fall is designated in irrigation as one that becomes available for plant use and is not lost by evaporation into the atmosphere. Usually, effec- tive rains are those exceeding one-half inches falling within a few consecutive hours. Thus it is seldom advisable to accept a record of total rainfall as a measure of moisture available for plant growth. As a result of the winter rains, moisture stored in the soil is available for the plant during spring months, postponing the time of the first irrigation until the soil moisture is nearly depleted. This period varies according to the amount of soil storage and the seasonal demands of the crop but often irrigations are not required before April or May and sometimes as late as June. The equable temperatures of the coastal region are in sharp con- trast to the hot summers of the interior valleys. In Southern California Vaile (61)2 j^g^g drawn a distinction between coastal, intermediate, and interior climates in which the basis of the divisions is taken as the mean maximum temperature during the summer. On this basis the coastal zone includes most of Orange County and the Whittier and Pasadena sections of Los Angeles County, the intermediate zone includes the San Gabriel and Pomona Valleys, and the interior zone includes the San Fernando, Fillmore, Redlands, Highlands and Riverside districts. The mean monthly maximum temperature of the month of August in each zone was found to be : Coastal 87° F. Intermediate 91° F. Interior 94° F. (Tulare County) 98° F. All crops in these areas are irrigated except winter grains which are usually grown on a summer fallow rotation system, vineyards in western Riverside and San Bernardino Counties, and lima beans grown in the coastal area during years of sufficient rainfall. Improved production 2 Numbers in parenthesis refer to literature cited. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 13 of beans could be expected if rainfall was supplemented with irrigation, especially during years of rainfall deficiency. The frost-free period in valley areas decreases northward from 365 days per year at San Diego to an average of 273 days at Red Bluff in Sacramento Valley and shorter periods occur at higher elevations. The frost-free period is designated by the Weather Bureau as the period between days when temperatures of 32 degrees or lower are reported. Evaporation from water surfaces is nearly proportional to the irrigation requirement, but the absence of evaporation data in many areas prevents use of this criterion in this report. SOILS The agricultural soils of California fall mto one of three general classifications : the unweathered alluvial soils, weathered soils developed on unconsolidated materials, and the weathered soils developed on con- solidated rock. The first group consists of recent alluvial deposits that are deep, friable and productive. Some are still in process of accumu- lation. The second group represents progressive stages in weathering of the older sedimentary deposits of the valleys. They occupy stream and coastal terraces and more elevated valley plains now undergoing erosion. The third group has been developed on the sandstone, shale, granitic and volcanic bedrocks. The soils comprising it occupy hilly and mountainous areas which are susceptible of irrigation only in sections of the more favorable topography and water supply. In low-lying areas drainage and disposal of alkali salts involve problems limiting the number of crops to those that are tolerant of salinity. Salts carried in irrigation waters add to the salinity of the soil, and in order to maintain a satLsfactorj^ salt balance excess water is required in irrigation to carry accumulated salts below the reach of roots and maintain the soil in a satisfactory degree of productivity. In extreme conditions, salts render the soil unfit for cropping. Where irri- gation supplies are obtained from streams of doubtful character the water should be analyzed before use. Surface waters originating in low hilly areas are sometimes found to contain quantities of salts detrimental to agriculture. Waters originating in mountain areas and fed by snow melt are of good quality. Most of the agricultural sections of California have been mapped for soils by the U. S. Department of Agriculture and the California Agricultural Experiment Station (53) (68). Soil Characteristics Affecting the Use of Water by Plants The objective in irrigation is to maintain moisture in the soil, in an adequate amount, to enable the plant to reach maturity and produce a profitable crop. The measurement of soil moisture requires the sys- tematic collection of many soil samples taken at intervals within the limitations of root activity. For this purpose soil samples, usually one foot in length, are obtained by means of soil tubes driven by hand or by air-driven hammers. The samples are dried in an electric oven and the equivalent depth of water in the sample is computed by the formula D = ^^, in which D is the equivalent depth of water in inches held in the sample; P, the percentage of moisture in the sample; V, the apparent specific gravity (volume weight) of the soil in place; and d, 14 DIVISION OF WATER RESOURCES the depth of soil sample in inches. The depths to which samples should be taken depend on the deptlis to which roots go in search of moisture, and vary from four to as much as 18 feet ; the average depth usually is about six feet for most crops and six to 12 feet for alfalfa and wal- nut trees. The amount of soil moisture available for plant use depends upon a number of factors such as plant spacing, volume, porosity of soil occupied by the root system, and such characteristics as field capacity, wilting percentage (sometimes called wilting range) and readily available mois- ture. The depth and spread of root systems outlines the volume of soil from which the plant may extract moisture and greatly affects the total amount of water available. Wide spacing tends to prevent intermingling of roots with those of adjacent plants, but it also encourages evaporation from the soil owing to reduced shading. Permanent crops such as trees and alfalfa have deeply rooted systems that can draw moisture from full depth early in the season, if necessary, as compared with annuals which produce new roots each season, drawing moisture from shallow depths early in the year and at successively greater depths as the season advances. Thus deeper rooted crops are able to withstand early drouth when annuals can not survive. Field capacity is a measure of the water a soil will hold after it has been wetted and allowed to dry enough to work easily ; an interval usually of two to four days, depending on the soil texture and structure. The time interval is dependent on the percolation rate and on soil evaporation. In homogeneous soils the lowest percolation rates correspond to the high- est field capacities and the highest rates correspond to the lowest field capacities. Clay and adobe soils, which drain slowly, have the highest capacities ; sandy soils drain rapidly and have the lowest capacities, while loamy soils are intermediate. The moisture equivalent agrees closely with the field capacity of fine textured soils and often is used in place of it, but it does not agree well with the field capacity of sand. It is a standardized centrifuge method of estimating the amount of water a soil will hold shortly after it has been thoroughly wet and usually it has a slightly lower value than the field capacity. Both field capacity and moisture equivalent are expressed as a percentage of the dry weight of the soil (62). The wilting point, or permanent wilting percentage, indicates the moisture content of a soil at which plants can not obtain sufficient water and therefore wilt. The best method of measuring the wilting point is to allow growing plants to dry out the soil until they wilt. Usually dwarf sunflowers are used for this purpose. Since plants wilt gradually, it is not possible to determine their exact wilting point, and it is becoming customary to use the term "wilting range" to cover a narrow range of soil moisture within which wilting occurs. It is expressed as a percentage of the dry weight of the soil. Water available for plant use is the quantity between the field capacity and the wilting point. It varies for different soils, being less for sands than for fine grain materials. While plants are able to reduce soil moisture to approximately the wilting point it is unwise to permit so large a degree of extraction as danger of damage to the plant is increased. Among the better irrigators it is customary to irrigate when the soil moisture has reached a point about midway between field IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 15 capacity and wilting point, a method requiring more frequent irriga- tions but less water at each irrigation, as full replenishment of the soil volume is unnecessary. The water-holding capacity of the root zone of plants depends on the depth and volume of soil within which roots function, and on soil texture. Amounts vary for different soils but in general average sandy soils "will hold from one-half to one inch of available water per foot of depth, sandy loams from one to one and one-half inches, silt and clay loams from one and one-half to two inches, and some clays as high as three inches of water per foot of soil (37). For example, if a four-foot root zone in a sandy loam soil should dry down to the wilting point, it would require an irrigation of four to six acre-inches per acre to recharge it to field capacity. A few of the items of moisture relations of California soils, com- piled from various sources, are shown in Table 1. Variations occur for the same type of soils, as might be expected, because no two soils are exactly alike ; but in most cases the differences shown for the same soil types are not serious. SOME MOISTURE RELATIONS OF CALIFORNIA SOILS Soil type Depth of soil Moisture equiva- lent Wilting percentage Field capacity Depth of available water per foot of soil Litera- ture cited Feet Per cent Per cent Per cent Inches Ref. No. OaHpV finfi Rii.T\(\ 3.29 28.23 16.80 9.09 11.09 31.12 28.33 34.50 27.33 1.33 20.05 8.93 4.17 3.08 25.70 12.49 16.80 12.53 0.34 1.34 1.26 .80 1.31 .71 2.53 2.83 2.36 (38) Salinas fine sandy loam (38) (38) (38) (38) (38) Salinas silt clay loam . (38) Salinas clay (38) Yolo clay (38) 0- 6 0-15 0-5 0- 7 0- 6 0- 6 20.6 25.0 20.1 21.1 14.5 18.2 4.0 9.5 7.5 11.0 12.5 11.0 (20) (20) (20) (20) (20) (20) (13) 0- 6 0- 4 0- 6 0- 4 0- 5 (13) (13) (13) (13) 10.1 20.1 30.8 30.0 32.0 25.2 20.0 23.5 3.5 8.5 16.5 18.1 17.0 13.6 8.3 (12) (4) (4) (4) (4) (4) (4) (4) 26-32 (4) CHARACTER OF THE PLANT Characteristics of plant growth, such as length of growing season, rooting habits, age of trees, extent of aerial growth, and tolerance of plants to saline conditions, have separate effects on the water require- ment. Plants use water most rapidly when making the fastest growth, 2—53207 16 DIVISION OF WATER RESOURCES and alfalfa, which grows rapidly between the several cuttings per year, has a high irrigation requirement. Each cutting requires one or two irrigations in order to force new growth, and the total requirement is affected by the number of cuttings and the crop yield. Beans have a short growing season and a low water requirement. In some areas, beans may be planted as late as May or June. In the delta, the growing season appears to be June to September with a con- sumptive use of about 16 acre-inches per acre as compared with 38 acre- inches for alfalfa in the same area. In the cool, moist air of the coastal area of Southern California lima beans may be grown without irrigation, but they do not stand the heat of the interior. The irrigation requirements of trees, both citrus and deciduous, vary with age and extent of aerial growth, the water use increasing as the trees approach a mature size (10), (7). Citrus trees are relatively shallow rooted but roots of deciduous trees may extend to depths of 15 or 20 feet, thus providing a large volume of soil for storage of moisture. The absorption of water by trees has been found by Weaver (67) to occur throughout the depth of the rooting system, but to take place most actively at the root tips in the younger portions of the root system. In the older portions the roots are more of a woody nature that provide strength for anchorage against winds. Regardless of the maximum depths at which roots occur it has been found by soil sampling methods, that the actively working portion of the rooting system occurs at some medium depth below the surface and that the lower roots abstract but little moisture from the soil. This is a reasonable finding since the bulk of the roots occur in the middle section. Thus, for citrus trees as much as 80 per cent of the moisture absorbed is obtained from the upper three feet of soil while for walnut trees the most moisture appears to be absorbed in the upper six to eight feet of soil. The root depths of vegetables differ considerably according to variety, as is shown in Table 2. TABLE 2 ROOT DEPTHS OF VEGETABLE PLANTS (57) Shallow-rooted (2 ft.) Moderately deep-rooted (4 ft.) Deep-rooted (6 ft.) Broccoli, sprouting Beans, bush Artichokes Brussels sprouts Beans, pole Asparagus Cabbage Beets Beans, lima Cauliflower Carrots Cantaloupes Celery Chard Parsnips Corn, sweet Cucumbers Pumpkins Lettuce Eggplant Squash, winter Onions Mustard Potatoes, sweet ■ Potatoes, Irish Peas Tomatoes Radishes Peppers Watermelons Spinach Squash, summer Turnips Under normal soil and moisture conditions root development occurs to its full depth and spread, but local conditions may prevent normal action. For instance, a high water table limits the depth of growth to the water level, the roots are stunted and increase in length laterally rather than vertically. The same effect may be caused by shallow layers of hardpan or by coarse gravel which can not maintain sufficient moisture for plant use. Root development is stimulated by fertilization, and IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 17 concentration of roots have been fonnd (57) where organic matter was abundant, the soil in such areas drying out more rapidly than in zones fertilized more lightly. The relative sensitivity or toleraiice of agricultural plants to soluble salts in soils occupied by root systems is shown in Table 3 (40), (35). In assuming these classifications, it is presumed that the soil is not exceedingly sandy as sandy soils hold less water than fine grained soils, and in them a given percentage of salt produces a more concentrated solution. Such classifications are made on the basis of percentage of salts to the dry weight of the soil. In this table the relative tolerance of plants to salt constituents in the soil solution is in four groups, as follows: (1) sensitive crops that do well when the soil contains light concentrations between 0.1 and 0.4 per cent ; (2) medium sensitive plants that can produce profitably when the salinity is between 0.4 and 0.6 per cent; (3) medium tolerant plants that do reasonably well on a soil containing salts within the range 0.6 to 0.8 per cent; and (4) tolerant plants that are adapted to concentrations between 0.8 and 1.0 per cent. In reaching decisions as to which are the best crops to grow on saline land, it is necessary to know something about the kinds of salts and their degrees of concentration. White alkali salts in reasonably low concen- tration are not particularly dangerous to plant life although in the case of cereals, hay crops may be produced profitably when grain is unable to mature. Sodium carbonate or "black alkali" is detrimental to all plant life and any attempt at cropping on soil permeated with it will end in disappointment. A few crops are sensitive to an excess of boron, particularly lemon and walnut trees which are subject to injury when the concentration is more than 0.5 p.p.m. (47). TABLE 3 RELATIVE TOLERANCE OF AGRICULTURAL PLANTS TO DIFFERENT DEGREES OF SALINITY IN THE SOIL SOLUTION (40), (3 5) Sensitive crops able to stand salinity of 0.1 to 0.4 per cent Medium sensitive crops able to stand salinity of 0.4 to 0.6 per cent Medium tolerant crops able to stand salinity of 0.6 to 0.8 per cent Tolerant crops able to stand salinity of 0.8 to 1.0 per cent Peaches Com Beans Red clover Field peas Potatoes Horse bean Vetch Proso Oats, grain Emmer, grain Wheat, grain Alfalfa, young Onions Squash Carrots Ladino clover Sunflower Rice Rye, grain Barley, grain Oats, hay Wheat, hay Grain sorghum Foxtail nullet Strawberry clover Sweet clover Cowpeas Flax ■Barley, hay Tomatoes Cotton Alfalfa, mature Sorgo Kale Rape Meadow fescue Italian ryegrass Oested wheatgrass Slender wheatgrass Tall oatgrass Smooth bromegrass Western wheatgrass Bermuda grass Rhodes grass Sugar beets MUo Table beets Salt grass The tolerance of only a few of the crops listed above will be dis- cussed. Alfalfa, the most important forage crop in the west, has a medium tolerance of saline soils, except young growth, which is very sensitive. It is difficult to start, even on moderately saline soil, unless leaching prior to seeding or heavy rains carries the surface concentra- tions into the soil. If alfalfa roots are able to penetrate to some depth 18 DIVISION OF WATER RESOURCES before the salts again return to the surface, alfalfa may continue to grow even though sometimes surrounded by light deposits. Certain meadow and pasture grasses may be safely recommended for subirrigated bottom lands that contain salts up to 1 per cent, espe- cially as the customary heavy irrigation of pastures in California will leach out much of the salt content. Bermuda and Rhodes grasses are high in tolerance of salinity. Where leaching is not carried on exten- sively, fertilization of irrigated pastures is a worthy practice that will bring marked results when the pastures are several years of age. Sweetclover is a common weed in many localities, but it is valuable for pasturage and hay and useful as a green manure crop. It is tolerant of medium salinity. Of the cereals, rye is one of the most tolerant. Cotton and flax, both ranking crops in California, are tolerant of salinity, cotton being markedly so while flax is only moderately tolerant. Sugar beets are highly tolerant of salt concentrations but, as with alfalfa, diffi- culty is often experienced in obtaining a stand on saline soils although once well rooted it is possible for satisfactory yields to be obtained. However, as the salt concentration in the soil increases, the effect of the salt tends to decrease the sugar content. Date palms will stand some salinity, but citrus and deciduous fruit trees are sensitive to alkali in the soil. Apples, pears and peaches are very sensitive. Among citrus trees, lemons are the most sensitive, grape- fruit trees tolerate the most salt, and oranges are in between. Grapes are believed to be highly tolerant of salt. Of the garden vegetables and truck crops, wax beans are very sensi- tive, onions, carrots, and squashes are medium sensitive, tomatoes and asparagus are medium tolerant while table beets are most tolerant. Asparagus is grown extensively in the Sacramento-San Joaquin Delta area where in some cases it is believed to receive saline water by subirri- gation from tidal effects. METHODS OF APPLYING IRRIGATION WATER In planning a farm irrigation system, the farmer should have a knowledge of the slopes of his land, the quantity and time of delivery of his water supply, and a basic understanding of irrigation practices, in order that he may design a system best suited to his needs. Methods of irrigating vary according to slope of the land, soil type, crop to be raised, and availability of the water supply. The principal methods used in California are the corrugation or furrow method, the border method and its modifications, subirrigation method, the sprinkling method, and methods adapted to the underground pipe system. A contour map of the area showing the elevation and slope of the land is one of the first requirements. THE FURROW OR CORRUGATION METHOD Cultivated crops are irrigated by means of small ditches between the rows, designated as furrows; when the furrows are small they are called corrugations. The spacing of furrows is regulated by the spacing of the crop rows. Corrugations are sometimes spaced to conform to soil characteristics, and on sandy soils the spacing is close. Steep slopes, likewise require the corrugation method of irrigation, as small streams of water will move down the slope with less danger of erosion than would larger flows. The length of furrows or corrugations should be governed IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 19 by soil conditions, the time rate of flow being sucli that water reaches the lower end of the furrow before the upper end receives more water than can be held in the root zone. Average lengths of 300 feet or less should be satisfactor.y for corrugations on steep slopes; the length of furrows should not exceed 400 to 600 feet in loam soils, while 1,000 feet may be satisfactory on moderate slopes of tight soils (37). THE BORDER METHOD The border, or controlled flooding method, is best adapted to irriga- tion of alfalfa, clover and grains, and can best be used where canals are able to deliver water to the borders in large heads. It is especially suit- able for light sandy soils as the use of a large stream confined within the border levees makes it possible to force water over the surface without excessive percolation losses. It consists of the division of a field to be irrigated into narrow strips or lands by low flat levees sufficiently smooth to permit operation of farm machinery over the levee without personal discomfort to the operator or damage to the equipment. The length and width of border strips can be determined experi- mentally for any head of water available. Assuming a given width, the length will be governed by the time rate of flow of the sheet of water contained in the border. At some point in the strip, the flow will show a slowing do-\^ai in its advance over the ground surface, this point indi- cating the distance from the head ditch at which the border should end. If the border strip extends beyond this point, seepage losses may become excessive. Widths vary from 20 feet on steeper slopes to 50 or 60 feet on flat slopes, and they also depend on the head of water available. At the upper end of the border strip for a distance equal to its width a flat area without slope will distribute the flow evenly and obtain complete coverage of the full border width. Careful leveling between levees pre- vents high or low spots and is essential for careful practice. The slope of the border, its length and width, and the head of water used are all factors in erosion or its prevention. A smooth surface hav- ing a slope of two to three inches per 100 feet may be adaptable to heads as high as eight to 10 cubic feet per second without damage to the sur- face. If the surface is exceptionally well leveled it is possible to make borders on minimum slopes of one inch per 100 feet ; maximum slopes of two feet per 100 feet are possible, but care should be taken on the steeper slopes that erosion does not occur. Large volumes of water can not be handled on steeper slopes. Lengths of border runs vary according to soil type and size of irri- gating stream, the shorter runs being most adaptable to open porous soils and the longer runs to heavy soils. The border dimensions of three grades of soil for different rates of flow are set out in Table 4 (28) . TABLE 4 BORDER STRIP DIMENSIONS FOR THREE GRADES OF SOIL (28) Head Sand Loam Clay Width Length Width Length Width Length Cubic feet per second l._. Feet 20- 30 30- 40 30- 40 40 Feet 200-300 300-400 440 440-600 Feet 30 30- 40 40 50 Feet 300-400 440-060 440-660 660-880 Feet 30 30- 40 50 50 Feet 440-660 1 to 2 660 2to4 660-800 4to8 880-1,320 20 DIVISION OF WATER RESOURCES THE SUBIRRIGATION METHOD Subirrigation is practiced in parts of the Sacramento-San Joaqiiin delta area on low lands which have a high water table. Crops grown are sugar beets, asparagus, potatoes, celery, and various short-rooted crops. Water is admitted to a given area from the river to raise the ground- water level to the height presumed to be required for the best welfare of the crop. Much of this area is peat formation and water tables are maintained at higher levels than would be permitted in other irrigated sections. After the irrigation, pumping removes excess water from the soil, thus preventing waterlogging of the lands during the winter months (52). THE SPRINKLING METHOD The sprinkling or spray method of applying water for irrigation has been used in California since approximately 1920 (19). Tlie early systems of permanent overhead sprinklers were expensive, costing from $300 to $500 per acre for installation, but the operation costs were negli- gible except for the cost of the water. Several years later, through the availability of quick-coupling pipe, portable sprinkling systems came into use and for these the initial cost was low but the cost of labor in moving the pipe over the fields was relatively high. At about tlie same time low head sprinklers set under orchard trees also came into use, most of these being portable, so as not to interfere with cultural practices. The overhead systems are used principally for irrigation of trees. Growers report them to be generally satisfactory where properly in- stalled and to use about the same amount of water that would be required by a furrow system of irrigation. Low-head portable sprinklers are also used in orchards. Portable sprinklers are popular in some districts for irrigation of field and truck crops to Avhich they are well adapted. They have been used on bean land, in Orange County, on truck crops, in the Salinas Valley, and on sugar-beets and other crops in the Delta area and the Sacramento Valley. In some cases sprinkling systems have been used for irrigation of lands unfit for surface irrigation because of lack of proper land preparation. In areas formerly subirrigated but where groundwater levels have since receded below the reach of root systems, sprinkling systems are applicable. UNDERGROUND PIPE SYSTEMS In southern California, and other areas where water is scarce and costs are high, underground pipe systems for irrigation are conserving of water. Use of such systems results in high irrigation efficiencies. Concrete pipe is used extensively in California, with risers from the buried pipe delivering water into surface ditches or borders, and where the pipe is under enough pressure water can be delivered to sprinklers. The cost of the first installation is high, but it is economical in the end, as it has a long life, is out of the way beneath the surface, does not encour- age the growth of weeds as do surface ditches, and does not interfere with farming operations. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 21 SOUTH PACIFIC BASIN Scale of miles 10 20 30 «o Fig. 1 22 DIVISION OP WATER RESOURCES SOUTH PACIFIC BASIN The South Pacific Basin includes the agricultural area adjacent to the Pacific Ocean between the westerly boundary of Ventura County on the northwest and the Mexican boundary on the south. Its northerly and easterly limitations are defined by the summits of San Gabriel, San Bernardino and San Jacinto Mountains, and the mountain ranges in San Diego County. It includes all of Orange County and those portions of Ventura, Los Angeles, San Bernardino, Riverside and San Diego Coun- ties in which the watersheds are tributary to the Pacific Ocean. The agri- cultural lands are principally in alluvial valleys, but in places crops are gro^vn at higher elevations. The total area capable of producing crops, including valley floors and marginal plains and foothills is in excess of 2,000,000 acres, of which 594,600 was irrigated in 1939, according to the 1940 census of agriculture (58). The South Pacific Basin (Fig. 1) has the most meager supply of surface run-off of any of the major subdivisions of the State. Torrential winter rains that sometimes occur in mountain regions create serious flood problems, but summer rains are inconsequential and in few instances do they provide surface flow in streams. Flow available for irrigation is thus limited to small streams emerging from the mountains during early summer months, to a sustained flow in the middle Santa Ana River and the San Gabriel River, and to storage in mountain reser- voirs. Even if the total flow were available for irrigation there would still be less than sufficient water for irrigated areas ; much of this insuffi- cient supply is lost into the ocean, or through evaporation and by seepage into underground basins. It is necessary, therefore, to supplement the surface supply with pumped water, and in portions of the south Coastal Basin as much as 75 per cent of the water pumped for irrigation comes from underground storage. Without irrigation few crops can be raised, as precipitation is insufficient during the growing season. Dry land farming is confined principally to the growing of grains on a summer fallow rotation in the interior valleys, wine grapes near Ontario, and beans in the coastal area. The principal irrigated crops are subtropical fruits and nuts, deciduous fruits, hay, truck crops, sugar-beets and beans. The climate of the South Pacific Basin is characterized by a long rainless summer extending from April to October or November. Sea- sonal rainfall along the coast varies from 10 to 20 inches with totals of 30 to 40 inches in mountain areas. Temperatures are moderate and freezing weather seldom occurs except inland, and then only for a few hours at night. Average frost-free periods usually are from February to late November and in man.v years frosts do not occur at all except in colder areas. Winter rains provide soil moisture for winter growth but not always in sufficient quantity to forestall the necessity of some winter irrigation. Uneven distribution of rainfall throughout the winter may, under conditions of cover cropping, require additional moisture by irri- gation. Individual irrigation methods and practices for the various crops and soil types found in the basin usually follow neighboring practices IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 23 and customs as regards distribution of water to crops, and where water deliveries are on regular rotation schedules the irrigation intervals depend on the time of delivery rather than on the supply of moisture in the soil available for plant use. Such practices often result in applications in excess of crop needs and cause over-irrigation and additional water costs. In this report efforts are made to estimate reasonable average irri- gation requirements for various crops and localities without estimating the irrigation intervals. Experimental work carried on for many j^ears by the Division of Irrigation, Soil Conservation Service, and the California Agricultural Experiment Station, either separately or cooperativel}", provides much of the basis on which many of the irrigation requirement values may be estimated. Such experiments include soil moisture studies throughout the growing season to discover the transpiration use of water by crop plants. With this value known, estimated irrigation requirements may be derived if data are available concerning moisture lost by evaporation, penetration of water below the zone of root activity, and waste of water at the ends of irrigation furrows. Such experiments usually are of sufficient duration to provide average values for the usual climatic varia- tions. Experiments on consumptive use of water may be conducted with tanks in which plants are grown with measured quantities of water applied according to adopted schedules. In tank studies the water used by the plants includes evaporation from the soil surface of the tank as well as transpiration from the leaves so that the total use becomes consumptive. For such studies it also is possible to estimate average irrigation requirements. In the South Pacific Basin, however, tank studies, other than for grasses, have not been undertaken. In localities where no experimental work has been undertaken the nearest approach to the requirements is through records of water applied, especially if pumped from wells, and irrigation requirements derived from soil moisture studies. In the South Pacific Basin experimental studies have been conducted by the Division of Irrigation or the California Agricultural Experiment Station on irrigation requirements of citrus, avocados, deciduous fruits, walnuts, and alfalfa in San Diego, Orange, Kiverside, San Bernardino and Los Angeles Counties. Depths of water applied in direct irrigation also are tabulated for various valleys and sub-basins. NORTHERN SAN DIEGO COUNTY Northern San Diego County includes portions of Escondido Creek, and the San Luis Rey and Santa Margarita River watersheds. The area is principally mountainous except for small interior valleys adjacent to a narrow coastal plain. "Within these watersheds lies a considerable acreage of arable land for which there is a limited water supply for irrigation. Most of the suppl}^ is dependent upon the storage of river flow although pumping from wells is also practiced. Irrigated crops include oranges, lemons, avocados and some grapes and vegetables. The principal farming localities within this area are those surround- ing the tovms of Escondido. Vista and Fallbrook, which lie generally within a zone ranging from ]00 to 1,000 feet above sea level. The prin- cipal soils of agricultural value are residual sandy loams with heavier 24 DIVISION OF WATER RESOURCES subsoils that grade into decomposed granitic bedrock at depths ranging from 30 to 60 inches. The surface is rolling hill land separated by nar- row valleys, which in spite of the shallow depths to bedrock produces profitable crops. Climatic conditions are extremely favorable for growth of citrus and subtropical trees, and crops grow throughout the year. The distribu- tion of rainfall varies according to location and ranges from an average of 10 inches at San Diego to about 20 inches at Fallbrook. A summary of temperature, rainfall and length of growing season, in Table 5, shows increases in rainfall according to elevation. Irrigation seldom is neces- sary before May or June and over a 25-year period the average time between effective rains was 236 days, ranging from a maximum of 332 days to a minimum of 130 days. Effective rainfall here is considered as being an amount that adds to the soil moisture supply. Usually rains of less than one-half inch are of no value to crops unless the soil has previously been moistened without opportunity to dry out. In order to provide for normal water requirements one winter irrigation in three years out of 10 and two winter irrigations in two years out of 10 have been found necessary. The average length of time between killing frosts at Escondido is 255 days, killing frosts being defined as temperatures at or below 32 °F. Frostfree periods vary from place to place and from year to year. As a rule frosts are not serious and frost protection is practiced less here than in some other areas in Southern California. The water supply for irrigation by the Escondido Mutual Water Co. and Vista Irrigation District comes from storage in Lake Henshaw, located on the upper waters of San Luis Rey River. The reservoir is owned by the San Diego County Water Company, which sells water on an acre-foot basis. In the Fallbrook area water is pumped by individual owners in addition to the Fallbrook Public Utility District supply which is pumped from wells in the sands and gravels of San Luis Rey River. Individual wells in the Fallbrook area frequently are limited in produc- tion because of their shallow depth which is controlled by bedrock forma- tion. SUMMARY OF TEMPERATURE, RAINFALL AND LENGTH OF GROWING SEASON IN NORTHERN SAN DIEGO COUNTY, CALIFORNIA •Location Elevation Climatic zone Mean annual temperature Mean annual rainfall Mean length of growing season' Sau Diego Feet 26 50 750 120 750 Coastal Coastal Intermediate Intermediate Intermediate "F. 61.4 61.4 61.0 Inches 10.30 14.25 16.60 16.64 20.08 Days 365 Oceanside,- Escondido _ 255 Vista Fallbrook ' Average number of days between the dates of the last killing frosts in the spring and the first killing frosts in the fall which are designated by the Weather Bureau as temperatures of 32° F. or less. Irrigation Requirements of Citrus and Avocados Cooperative studies of transpiration use of water by lemon, orange and avocado trees, including also water used by winter cover crops in IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 25 the groves, were undertaken in 1926 and 1927 by the Division of Irriga- tion and the California Agricultural Experiment Station (11). Soil sampling methods were employed to determine the depths of soil moisture used by the crops, the dry soil mulch being first removed before samples were taken. Determinations of moisture, therefore, were of transpira- tion use rather than consumptive use which includes soil evaporation. As a result of the studies the depths of moisture consumed from rain- fall, the depths used from irrigation deliveries, and the total depths tran- spired are shown in Table 6. The total transpiration use varied from 5.8 inches of depth to a maximum of 13.4 inches for the 6^-month irriga- tion period. The causes of these low values in northern San Diego County are a deficiency of water, a sliallow root zone overlying the parent rock, and the high cost of water. Average applications of water to six groves out of seven totaled 11.4 acre-inches per acre during the season. Cover cropping between trees during winter months is the usual practice in southern California, the crop being planted in the fall and disked under for green manure usually about ]\Iarch when the crop begins to compete with the trees for moisture. The effect of cover crops is to increase the winter water use of a grove, but as the crop is grown during the M'et season there is no additional demand upon irrigation require- ments provided disking is done while a sufficient amount of moisture from rainfall is retained in the soil. Table 7 shows transpiration losses from October 15, 1925 to April 1, 1926 for seven groves of citrus and avocado trees having cover crops. The different amounts of water con- sumed may be attributed in a large degree to the size of the trees and the growth and density of the cover crop. Comparison of this tabulation with the summer use by clean cultivated trees, shown in Table 6, indicates nearly 50 per cent higher average use of water per month during the rainy winter season than during the drv summer irrigation season. 26 DIVISION OF WATER RESOURCES jaa g-S aaj S'-Z-s OO CO O 00 CO 00 l>^ ■< I 9 P oO OS t.-a fill Q.B « ^o£ ^ ^ O CO OO C^ 00 M ^ CO t^ CO CO OS «5 OS ■^ OS b* CO cq T*< IC Oi '<*<■**' -rj* CD CO t* O 1-1 CO ic o -^ t^ -«J< C^ <-" (N CO M ^ O OS Oi-^ OOO lO CO i-( ■«»< c^ t^ lo cq Oi i-t ■^ CO ■^ oi CO OOCOOQOCOO O CO t- Tji t^ CO OS CO -H CO r^ »-i t o o o a^~ g a a a-S S S g OJ OJ o rt " ™ > I (M ^ *C Tt< (N a a §§ a ;^^ >,>>o I'^'S «^ ^"2 c3 ca T3T3 ea ,Ji ill :§x^— _m'c^ 3 CQfc>Q 03>-iCC ^ -o^ JJi C4 s c«^ ° £, ^2 s^ oooooooooooooooooooooo o "^ .3 .3 ^5 5 _3 _3 3 3 3 .3 .3 .3 .S ,3 ,3 ,3 .S ,3 ,3 _3 _S _3 3 o, ^ « ^ Ml WWOW>fafel*Wfc.WHb.febHbHHWWOOWWbH 3 Z 3 £ 3 s cr t t- c cr £ 3 O O CO CD CO "iO ,0 iiiimiiisssssSm^^siiSsi CO cc oi CO cc t/i c a a s a s i ^C^ CO CSI »-H c > &.S.S-S =SJ3 S-3-:3 i2 S rt 3:S'a s so • o • ^CC1I^5 a ::3 ::q "3 "a "O "O ^ 'a_r'j;''e'a s'e E^'a'aa a'e g COCOCOCOCD — .a 9 a^ CiiO c^ MO "5 OS cct^ lO S t J=-3 c •"I'm e<3 ci(N im' ra S3 " o o CO -1 oo ja ■3 M-W ooo CO a 1-5 nci (m' — '"' -^ Q 1 002 ■* . 1 0-* 1^ o t^ CO 1 ed S o t^ 115 s _I- (N-H '^ ''" " M 00 00 oo lOiO W3 1 O. ■g T °i CC-H c! << "'" " a a. o, "o .2 i o « M s O kl k> ■o-o oo 1 o •2 ■^ -Tj* S rt rt ss M(M •| a a t4 ^ 00 Ol CQ 00 Oi a IMCM V C ' 1 05 05 s Oi OS s IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 35 TABLE 13 TRANSPIRATION USE OF WATER BY MATURE WALNUT TREES, ORANGE COUNTY, CALIFORNIA, 1J28-29 Month Transpiration use Month Transpiration use Inches 0.50 4.07 3.82 6.38 August- Inches 5.35 3.22 October 1.68 July - - Total -- 25.02 Estimated seasonal irrigation requirement, inches. In the upper counties of Riverside and San Bernardino more exten- sive soil moisture studies were conducted on plots by the California Experiment Station and the Division of Irrigation (44) to determine transpiration losses by citrus trees during the years 1931 to 1935, inclu- sive. Location of the plots and their main characteristics are described in Table 11. Results of these investigations, reported in Table 14 to Table 17, show water transpired by months and total depth, depth of water applied in irrigation, and other irrigation data. Methods employed and water applied were according to the owner 's usual practice except that water was measured Avhere possible. Examination of the tabulations shows variation in the depth of water applied to different orchards in the same month, owing to differences in soils and personal management. In 1930 the maximum depth applied to a grove was 34.5 acre-inches per acre as compared with a minimum of 21.6 inches applied on another grove. Irrigation practices varied also in regard to the number of irrigations during a season. In 1930 the greatest transpiration loss was from a field which had eight irrigations while the least transpiration came from five irrigations. In the same year, the transpiration in July varied from 8.0 to 3.2 acre-inches per acre for different orchards. For all years, the average seasonal transpiration loss was nearly 21 acre-inches per acre, ranging from 18.8 to 23.5 inches. 36 DIVISION OF WATER RESOURCES £ « "4 o I. O as CO ^ CD oo OS f*5 »0 -H 1— ( ♦-. to *0 CO IM - ■^i-H.-HOQO'^ooeot^coc^c^ cococ^c^'-ic^weoco'»aotoc^cow3-^co c^co(NC^^'-tc^(Ncoc^(r)eONC^NOi30:DOOOCO toc-ioo C* -i CNJ ^ "H ^ M f— — ' -H (M 1-H C*j (>) r-l 1-. -g rt bog o o o o S » C8 > « J3 oo — e sss IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 37 H §? N S 9 « BS - W - H « z w » n o 5 < ^ < S? °§ |g g < -O Depth water applied 1 o h- m e^ -• TO «n o co«oo ^CS^Ot^-^-^O ^•wf Oi o9 CO « CO CO 0 a s t^xioot^«r^ot^ t~. CO 00 S) 'E fe: ^ O I. "tS — -Q C^ D. > s C^-* CO iiO-»'l«l-- O C-< cc -a "S \ 'o. 1 3 (MNlMCOlOt-COO CO CD CO COCOCOC^-'^CO"^^ Ti<'c> "3 •-5 -g •*0 — Ott — -^IM •^-e^co ■^•j;05 ■^ oaco CO'^'COCOCOCO^W ■ 85 1 -^ - C9 sar-o>o — -oooce S:a| 2% o-o 2| « .2 38 DIVISIOX OF WATER RESOURCES 5 ^ o s < X H O Q O 2 X 2 H < B ■^ '■*' t^ CQ -^ «D Oi ffO -^ ^ «• (M to CO CD «3 Cq eo « iCfM'**^ occic-^occ^co oo o »C O CO lO ^ CD t^ O »0 CD 5o. « s CO O O CO f— < 05 C^) 00 :D C^) O Cq C^ (N N i -^ .-I CO CO ^ w I -^ CO oo O W5 00 Oi 5 c4 C4 c, f= «« 2 ■«•«>■>»' — — 't*i a. O ^-T3 111 d ^ 00 — lO eg e »0 COTT a « s III 111 ■fc Q S g oc t^roocoo ent^oo fc fe: *-< O j^ «o 1=^ ■^ C3 o oo cooo -^ — 00 ifl od 05 00M — Qo'oi <: o z "3 f^ ^-r ro> c a- 2 •<>• C^-V C-> ■* ■«< o "£*§ a. "Sfe- S 00 W 00 t^ 00 t^ CO d •w t-.' r^ •*■ >-. a3-^ ^ ,^ O t. » ■c ■0" 00 CO 00 •a-oooo <,; o •z -§ ^ OCOOOOO O OOIO s COM N -• CO — £>< O ^ b* x> a f=, CO COCfl CD CO to en CO ^ 3 OOirt 00 oo 00 00 lO "S cococoe> s 00 00CMCspiration by alfalfa less than evaporation from the soil. Irrigation Requirements of Alfalfa Data obtained by the Division of Irrigation on the consumptive use of water by alfalfa in San Fernando Valley are listed below (15) : Month Consumptive use by alfalfa' Month Consumptive use bv alfalfa> mo January February March.. April May June Inchei 1.3 1.6 3.1 3.3 6.7 5.4 July .\ugust... September October November December Total for year Total, April 1 to October 31 Inches 7.8 4.2 5.6 4.4 3.1 1.3 47.8 37.4 ' Computed from soil moisture obeervations. 46 DIVISION OF WATER RESOURCES Water Deliveries in San Fernando Valley Water for irrigation of crops in San Fernando Valley is supplied by the Los Angeles Department of Water and Power throngh under- ground pipe systems, and all water delivered is measured through meters on a quantity basis. Thus the department has complete files of water delivered as well as crop acreages and is able to determine the water use per acre for many crops. The annual and average uses of water per acre for the principal irrigated crops grown in the valley for years 1930 to 1937, inclusive, together with the annual rainfall, are shown in Table 24 (26). The average values agree with similar data obtained for other areas in some instances and disagree in others. For instance, the aver- age depth of water delivered to alfalfa, 1.86 feet (22.3 inches) per acre is low, which may be because of high ground water in some sections from which alfalfa roots obtain a portion of their water supply, although no evi- dence is given that they do so. In some areas water is used sparingly where it is thought that crops may be affected by its quality. The average depth of water delivered to citrus trees agrees closely with similar data obtained elsewhere for the water requirement of the crop ; thus the depth of water delivered appears to be a fair value of the water requirement. Use of water by walnut trees, shown as 0.84 acre-feet per acre or 10 acre- inches, is considerably less than the requirement in Orange County, where it has been estimated (10) as 18 acre-inches per acre. Walnut trees have more extensive root systems than citrus and may have obtained a portion of their supply from ground water in some areas. The same may apply to deciduous trees, shown to have used 0.54 acre-feet per acre or 6.48 acre-inches, which is extremely low for such trees. For shallow rooted crops the data appear more consistent. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 47 < •J ^ O < « to fl 5 s '-' 5 Q "3 w « < < as "J 1-1 J ::i -a O a S 5 2 "" S » u < SJ^ »c: c^ ro t^ o ■<*' u3 ■»)* Ci r^ ^ CO CO M CO eo oD »« lO co-v »^ r^ 00 1ft o »c 00 r- CO -^ J r~ 00 r~ oo t^ t~ o o> oo — < > s c^ ^»« t^ r* r* ^- o to r>- O; CS oo C^ CO Oi c^ o ooo -H -^ w C^' (N ^ Cq C^ W '^' *c: Ci to o CO O C5 c^ :d i-« "C^ CS r>- Cs Ci Oi CO C^ Ci >!*< iC '<*" »o »o lO o ca CO CO :d Ci 00 to CO ^- C3 — O —' O js O 1— " o oc 0>-I^H,— ,,-. .-.,—1 .— (C- oc o ' WD »o us lO v2i CO ic C5 o uo ci OS o5 »— » OiOOCOCOi^^< CO OOOOOOOiOCO O^ <*-. O CD d Ci O COO GO ■* ^ csi 1— t OS O ca Oi '-• Ci OiO - X o CO :o oo cs t^ -^ oi ^^_„_H^C^J^ 1-HN si: t- o r^ M ii5 •* OQ r^ co 5^ t-^ 00 CS CO CO o »o -^ COO 0<-'C• W5 C^J GO OO CO CO U5 00 ^ »0 CO < 00 «-H O l>. CO t^ooco i-H C^ CO t^ »o O CO t^ COC^C<) W Ol C- » CO OOCOOOOOOO o ^ r^cot^-^osooio i-t 1-H CO ■* i-H (N 1-H ^ CVJ .-H T-H O W 1^- .co ococo w S t^OOCOOi-iOOCO t^CO'-HCOb-^OlCO owco-^^^oooooco O CO 'lO-^ i>-co O ■^ O Oi O O CO O Oi O ^ _>. IMC<>IM(N (M IMC> OOOO OOO J2 o o ■ ■ ' (S >. .« o o o— . -^_ooo d ■ 'co CO ca 1—1 1-5 a> s -« o o o -< —■OOO s >-. O CO CO Q "? ca £ u "S »^ W3 »o »Oir5 -^•g ^ .« 1 >H >clcoi--!od la J g:as 0S05 O: oa SSS IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 57 WATER APPLIED FOR IRRIGATION OF APRICOT TREES NEAR HEMET, SAN JACINTO VALLEY, CALIFORNIA, 1939-40 (50), (51) 1939 1940 Depth of Yield per Depth of Yield per water Yield per acre-inch of water Yield per acre-inch of applied acre water applied acre water per acre applied per acre applied Inches Tom Tons Inches Tons Tons 17.9 5.70 0.32 31.0 5.1 0.16 22.9 8.69 .38 42.0 5.0 .12 33.9 4.38 .13 29.3 4.5 .15 22.1 7.25 .33 27.9 9.3 .33 29.4 9.60 .33 33.4 5.5 .16 31.0 6.85 .22 24.7 8.8 .36 38.7 6.70 .17 35.8 5.2 .15 34.5 8.00 .23 49.9 4.9 .10 40.7 5.51 .14 35.3 3.6 .10 23.8 8.09 .34 26.0 2.6 .10 22.3 3.43 .15 26.9 5.0 .19 23.2 3.75 .16 40.3 4.3 .11 38.8 5.72 .15 20.7 3.6 .17 15.4 2.92 .19 23.2 6.9 .30 32.0 8.10 .25 27.6 2.27 .08 35.0 4.14 .12 Ma.ximum 40.7 9.60 .38 49.9 9.3 .36 Minimum 15.4 2.27 .OS 20.7 . 2.6 .10 Mean .'28.8 5.94 .22 =31.9 5.3 .18 1 Mean for 17 farms. ' Mean for 14 farms. 58 DIVISION OF WATER RESOURCES W3 00 CO 03 <£:> oo -^ CD >— < r~i o H g < z < 3 z OO CO — ' 00 t^ lO CD t^ t— t^ 00 OS CO ^ "t^ CO lO »0 ^ »0 »0 lO CO "^ « OOQOTf-Hao-— 'OS— '^H — 'QOU^ g CO-^^fTt^COiO^iOiO lOCOTT 00 00 -^ Ui CO lO OS >— ' .-. .— CO Oi COCO^C.coco-^eo co' t-^ r^" cooo»oc»3aocococo CO CO CO o t- U3 CO CO CO t^ to 00 ■^■^■^COCO-^CO'^"^ coco-^ O CO CO t^-t- X 3C -^ t^ -^ O C 0*0 lO ' ooooooooo ooo O O O O O O 00 O O 000*^ ooooooooo O-^C^C0^»f0C0t^C_ cocococococofocoeo ga 60 DIVISION OF WATER RESOUECES S A R N A R D I N O u o ^Indio ^Coachella < \ ^ kThermal V Niland _.x , ^Calipatra Westmoreland Brawlej/f • GREAT BASIN DESERT AREA Scale of miles 10 20 30 40 5C Fig. 2 IRRIGATION REQUIREMENTS OP CALIFORNIA CROPS 61 GREAT BASIN DESERT AREA Portions of the Desert area for which some irrigation requirement data are available are the Coachella and the Antelope Valleys. COACHELLA VALLEY Coachella Valley (Fig. 2), in Riverside County, is that portion of the desert depression occupied by the valley of the Whitewater drain- age. It lies in the northern end of the structural trough of which Salton Sea and Imperial Valley are a part. Indio, the principal town, has an elevation of 15 feet below sea level. The climate is typically desert with long summers, high temperatures and very low rainfall. Temperatures of 100 degrees are possible in nine out of 12 months and a maximum of 125 degrees has been recorded. Rainfall is negligible and the small amounts that occur during winter months are of no value to crops. The 63-year average at Indio is 3.28 inches. Seasonal extremes in past years have ranged from a minimum of 0.18 to a maximum of 11.50 inches for the season 1939-iO. Average monthly temperatures and rainfall are listed in Table 34. Average length of the frost-free period is 302 days between the dates of February 5th and December 4th. The agricultural soils of the valley are found in four distinct series of which the Coachella and Indio series are the most important on an agricultural basis (36). The Superstition series represents a some- what older deposit and is mostly located around the edges of the valley as delta cones at the mouths of canyons. Soils of the Woodrow series are low-lying, are highly alkaline and of little agricultural value. All irrigation, except in a few instances above Point Happy, is from wells. Rainfall on the valley floor is too limited to contribute to the ground water basins, but run-off from adjoining hills and mountains seeps into detrital cones, partly replenishing the groundwater, levels of which are, however, steadily receding. Near Salton Sea are a few flow- ing wells, but most wells have to be pumped. Hope for additional water is based upon eventual operation of the Coachella Branch of the All- American Canal. Because of the extreme aridity, crops can not be grown in Coachella Valley without irrigation, but a growing season that extends throughout the year, together with good soil and a water supply, make this a highly productive area. The net acreage cultivated probably is about 13,000 acres, although if double cropping be taken into account, the total cropped acreage is 19,000 acres. Principal crops are vegetables, citrus, dates, cotton and grapes. Irrigation Requirements of Date Palm Trees Observations on use of water by irrigation have been made by the California Agricultural Experiment Station cooperating with the Divi- sion of Irrigation, Soil Conservation Service. Transpirational use of water by date palms as recorded in the studies is summarized in Table 34 (43). Depth of moisture used by the trees was determined by soil sam- pling to depths of eight feet below the dry mulch. Although variations 62 DIVISION OF WATER RESOURCES occurred the average root activity was found to be 59 per cent in the upper two feet of soil, 30 per cent in the next two feet and only 2 per cent between the sixth and eighth foot. The average annual transpirational use of water by all plots was 72.4 acre-inches per acre and the average depth of water applied was 90.7 acre-inches. Cover crops on some plots increased the transpiration use. Transpiration data indicated in Table 34 include only records from plots where the soil moisture in the lower depths of six to eight feet was at or below the moisture equivalent, thus avoiding any data that included drainage loss. By measuring the depths of water applied and deter- mining the soil moisture increase it was found that the average irrigation efficienc}" was 80 per cent, a high value made possible only by basin flooding. Assuming that there is no unusual amount of deep percolation below the zone of root activity and with an 80 per cent irrigation efficiency, it may be presumed that the depth of water applied becomes also the water requirement of the crop. Thus a depth of 90 inches applied, including transpiration, evaporation, and a very limited deep percolation, may be assumed to be the average irrigation requirement of dates in the Coa- chella Valley. IRRIGATION REQUIREMENTS OP CALIFORNIA CROPS 63 H « "g StJ » 1 •«■ U5 00 00 lO O ^ C^ O COTr CC o •^ CT> o. -a a «- o ^1. w 1 — 1 O to ■<»< CO ■«< •» a'ai oioooiOMM Q§ •~. t^ I-, >,^ §3=i 1 t-. CO b- 00 Oi •— ' °o ^11 OlMCMC^SlO c o CO >. g §3g &." M 0> to O O lO fwr 11^ CO •— »0»0 CO »o C3O:00 t^coi« ■ t^ a a CJ -»^ j= 1 ^ -2 |g-a K I CO e^ 00 00 OiTj* CO ■*' lO t^ oj o ■«» & •S a .- o o"i3 j= 2 o 05 Tj< O « 05 CO g,'|.3 e^ CO ■<»< to t^ oc> Q i "-, £: >!-< §5=3 1 -HU5e> 3 §5'S t^O-HINo ci o> t-^ >o>otot~t~oo as i^ JS ' t« -^ I J3 O 1 1 3 2 S= >.« li a a < >-5 6:< 1^ -< »a; >-j 5—53207 64 DIVISION OF WATER RESOURCES Irrigation Requirement of Vineyards Transpiration losses by mature Thompson seedless grapes grown on a plot of Coachella fine sand in the Oasis district of Coachella Valley was determined (43) by soil moistnre sampling during 1937-38. Irriga- tion was by flooding within the plot although the rest of the vine3-ard was furrow irrigated. Root distribution was found to be 66 per cent in the upper three feet, 29 per cent in the next three feet and five per cent at depths from six to nine feet. Some deep penetration of water was deter- mined but not in unusual amounts. Table 35 shows monthly depths of transpiration and water applied. TRANSPIRATION USE OF WATER BY THOMPSON SEEDLESS GRAPES IN COACHELLA VALLEY, CALIFORNIA, 1937-3 8 (43) Month January. February March... April May June Depth of transpiration use Inches 0.4 .5 1.0 2.3 5.1 8.3 Depth of water applied Inches 0.5 .6 1.2 2.8 6.3 10.2 Month July August September. October November. December. Totals Depth of transpiration use Inches 7.4 4.7 43.6 Depth of water applied Inches 9.6 9.1 5.8 4.2 2.5 53.7 The seasonal depth of transpiration from April 1st to October 30th amounted to 39.0 acre-inches per acre as compared with 48.0 acre-inches of irrigation water applied. On this basis the average irrigation effi- ciency would be approximately 80 per cent, a high value that appears to have been obtained by use of the basin method of irrigation. Since rain- fall is not a factor in sui^plying crops with water in this area it may be assumed that, in ordinary irrigation practice where deep percolation is negligible and the irrigation efficiencies are 70 per cent or more, the irri- gation requirement closely approximates the depth of water applied. On this basis the requirement for grapes for the irrigation period April to October, inclusive, maj^ be assumed to be within the range of 36 to 40 acre- inches per acre. As compared with the requirements of wine grapes in Riverside and San Bernardino Counties, however, these values are high, as in these areas grapes are seldom irrigated unless there is a deficiency in the seasonal rainfall. IRRIGATION REQUIREAIEXTS OF OALIFORNIA CROPS 65 IMPERIAL VALLEY irrigation of Alfalfa Imperial Valley (Fip\ 2), during its long growing' season is subject to high temperatures which are conducive to a high water use for crops. In 1944 alfalfa was grown on 147,000 acres. High ground water exists over much of the area and any estimate of consumptive use of water should consider the possibility of the plant obtaining a portion of its supply from this source. The Imperial Irrigation District data show the average depth of water delivered to 72 farms totaling 7,600 acres of alfalfa during 1941 as 4.01 acre-feet per acre, the production area cover- ing all sections of the valley. The growing season is about 10 months and a high use may be expected. In 1943 the Agricultural Extension Service made a cost and efficiency analysis (69) of alfalfa in Imperial County in which depths of water applied to seven farms were compared with yield of crop. In Imperial Valley water is cheap and there is not the inducement to economize in irrigation that is usual elsewhere in southern California. Also because of the salts carried by irrigation water and their concentration in the soil solution, it is advisable to over-irrigate in order to prevent their accumulation. These factors tend toward the greater use of water by all crops in the valley. The alfalfa study showed depths of water applied ranging from 70 to 31 acre-inches per acre annually, as set out in Table 36. The highest yields were from 6.2 to 5.0 tons per acre, produced with 60 acre-inches of water applied as compared with an average of 48 acre-inches per acre as recorded for an area of 7,600 acres by the Imperial Irrigation District. TABLE 36 IRRIGATION AND YIELD OF ALFALFA GROWN IN IMPERIAL VALLEY, CALIFORNIA, 1943 (69) Age Depth of Cost of Yield Area of Cuttings Irrigations water water per stand applied per acre acre Acrei Years Number Number Inches Dollars Tons 80 1 5 16 70 4.24 4.3 60 1 7 16 60 3.75 6.2 40 2 5 16 60 3.75 5.8 20 2 14 60 3.75 5.0 30 3 12 56 3.50 4.9 100 1 5 12 41 2.25 3.8 40 1 4 16 31 1.95 3.5 Maximiinn . 100 3 7 16 70 4.24 6.2 Minimum.. . 20 1 4 12 31 1.95 3.8 Mean . 53 1.6 5 15 54 3.31 4.8 From these data and because of high ground water it is evident that no reliable estimate of the irrigation requirement of alfalfa can be made for Imperial Valley. Irrigation of Flax Flax in the Imperial Valley is a "svinter crop sown from October 15th to December 1st and harvested in the spring and early summer. It therefore has a relatively low irrigation requirement as compared with crops grown during the hot summer season. Records provided by the Imperial Irrigation District show the average depth of water delivered 66 DIVISION OF WATER RESOURCES to 160 farms covering a total of 16,018 acres of flax during the season 1941-42 was 2.11 feet, as set out in Table 37. All parts of the valley were included and there was little variation in the several divisions. AVERAGE DEPTHS OF WATER APPLIED IN IRRIGATION OF FLAX IN IMPERIAL VALLEY, CALIFORNIA, AS REPORTED BY IMPERIAL IRRIGATION DISTRICT, 1941-42 Division Farms Net area Depth of water applied Number 13 14 60 37 9 12 15 Acres 1,621 1,382 4,629 2,677 1,869 1,389 2,451 Feet 2 00 Holtville . . 2 19 ElCentro 2 07 1.89 2 19 2 38 2.20 Totals.. 160 16,018 Mean 2.11 Records obtained by the Agricultural Extension Service of the Uni- versity of California (54) show an average water application to 16 farms growing flax, over a period of five years, to be 25.2 acre-inches per acre, which is almost the figure obtained by the district for the larger acreage. A total of 73 out of 85 fields M^ere preirrigated before the planting in order to provide moisture for germination. In Imperial Valley rainfall is negligible, averaging 2.7 inches annually over a 30-year period, and pre- irrigation was generally necessary. Usually five irrigations were applied during the season in addition to the preirrigations. The yields averaged 25.8 bushels per acre of field-run seed of which about two bushels per acre were dockage. Irrigation data for these tests are shown in Table 38. TABLE 38 DEPTH OF WATER APPLIED, YIELD AND COST OF WATER FOR IRRIGATION OF FLAX, IMPERIAL VALLEY, CALIFORNIA (54) Year Farms cooperat- ing Total area Average yield of field-run seed Irriga- tions after plant- ing Average depth of water per irrigation Total depth of water applied Cost of water per' Rainfall at Acres Ac-ft. Brawley 1935 Number 16 20 17 17 15 85 Acres 2,743 3,620 3,197 2,340 1,882 13,782 Bushels 24.7 21.8 24.5 27.5 30.7 25.8 Number 4 5 5 5 5 5 Inches 4.4 4.2 4.5 4.5 4.0 4.3 Inches 22.0 25.0 27.0 27.0 24.5 25.1 Do 2.61 2.52 3.96 2.87 3.08 3.01 lars 1.43 1.21 1.76 1.28 1.51 1.44 Inches 3.4 1936 1.1 1937 .8 1938 1.4 1939 .. Totals «2.7 1 Includes $0.50 per acre-foot plus gate charges of $0.25 per day. Does not include assessments. ' Thirty-year average. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 67 ANTELOPE VALLEY The irrigated portions of Antelope Valley (Fij?. 1), in the Mojave Desert comprise about 25,500 acres of alfalfa, 3,500 acres of grain, and 3,000 acres of orchards in the northeastern part of Los Angeles County north of the San Gabriel Mountains. The principal towns are Palmdale and Lancaster. Soils are open and porous on the northern slopes and less permeable toward the center of the valley where they sometimes are impregnated with alkali. Climate is of the desert variety, with long hot summers, no rain during the irrigation season, an average of seven to 10 inches of rain during winter months, and low humidity. Frost-free period at Mojave averages 264 days between February 27th and November 18th. Frost occurrence, however, is erratic and killing frosts have been recorded early in April and late in September. Such variations are of decided economic importance, as warm spring days force fruit trees into blossom, and sudden changes in temperature accompanied by killing frosts can do much damage. It is said that on December 30. 1895 the temperature fell to six degrees above zero near Lancaster. Mean monthly tempera- ture and rainfall at Palmdale are listed in Table 39. The valley is a closed basin and the only water supply comes from drainage of the surrounding slopes, most of it sinking beneath the surface within short distances. Some storage is effected on Little Kock Creek for irrigation of the Little Eock Creek Irrigation District and additional water comes from the perennial flow in Eock Creek, most of which sinks into the coarse alluvial deposits near the southern edge of the valley. In the central area water for irrigation derives mostly from pumped wells although there formerly were a few flowing wells. For several years there has been a drop in ground water levels, estimated at four to five feet annually in some areas. Possibility of any considerable recharge, beyond that now being effected, appears unlikely. TABLE 39 MEAN MONTHLY TEMPERATURE AND RAINFALL AT PALMDALE, ANTELOPE VALLEY, CALIFORNIA, ELEVATION 2,654 FEET Month Mean monthly temperature Mean monthly rainfall Month Mean monthly temperature Mean monthly rainfall 44.2 46.7 52.8 58.5 65.7 73.2 Inches 1.70 2.12 1.95 .52 .17 .04 July 'F. 81.7 80.8 72.9 63.3 52.8 46.1 Inches 0.00 .\ugust .. .44 .32 .43 May November .20 2.34 Total 10.23 Mean 61.6 Irrigation of Pear Trees Little Eock Creek Irrigation District occupies about 2,500 acres at the foot of the northern slope of the San Gabriel ]\Iountains with about 1,100 acres irrigated, including 600 acres of deciduous trees, 270 acres of alfalfa, and 200 acres in vegetables and nursery stock. The water supply 68 DIVISION OF WATER RESOURCES for irrigation of this area comes from storage in Little Rock Creek Reser- voir and the quantity of water available depends entirely upon the sea- sonal rainfall. In years of low precipitation there is a deficiency that is overcome to some extent by supplementing storage with a small quantity of pumped water. Water applied to 26 pear orchards in 1934, a drought year with a total rainfall of six inches, is listed in Table 40 (14). The average irrigations were 17.2 acre-inches per acre from March through October, the maximum for the group being 26.9 inches. The orchards were less thrifty than some observed elsewhere, and showed effects of irrigation deficiency. Reports from the district in 1942 indicate an average duty of water for the entire area including the 270 acres of alfalfa, which has a higher requirement than deciduous trees, of 35.0 acre-inches per acre. Rainfall for this year was 14 inches ; hence it may be presumed that no soil deficiency existed at the beginning of the irrigation season and that water was used more lavishly than during years of low rainfall when storage was less than the amount required for full irrigation demands. Inadequacy of the data prevents any definite estimate of the irriga- tion requirement for pear orchards in this area, but it may be presumed from experience under similar conditions elsewhere that 17 inches of water applied seasonally is too low and 35 inches is somewhat above nor- mal requirement. It is believed that from 24 to 30 inches applied during the irrigation season in Little Rock Creek Irrigation District will, under good management, produce profitable crops of pears. Variations will depend on differences in soil t.vpe, methods of irrigation, and personal farm management. TABLE 40 WATER APPLIED FOR IRRIGATION OF PEAR TREES, LITTLEROCK CREEK IRRIGATION DISTRICT, ANTELOPE VALLEY, CALIFORNIA, 1934 (14) Area irrigated Acres 10 20 18 10 10 5 9 20 10 10 10 20 17 10 10 4 8 20 10 10 10 12 10 10 10 10 Maximum Minimum Mean Irriga- tions Number 5 3 5 4 6 5 4 3 6 4 5 5 3 3 4 5 5 5 3 5 S 5 4 7 3 5 7 3 4.5 Depth'of water applied per acre March Inches 0.0 3.84 3.84 3.84 4.80 3.84 3.84 .\pril Inches 3.84 4.00 3.84 4.27 3.84 3.84 3.84 3.67 1.92 3.60 3.84 3.84 3.84 3.84 3.84 3.84 3.84 4.27 2.44 May Inches 3.94 3.84 4.26 3.84 1.92 3.84 4.27 3.84 3.84 3.84 3.84 3.95 3.60 4.80 3.84 3.84 3.84 3.84 7.68 3.84 3.84 3.84 7.68 3.39 June Inches 3.84 3.84 4.00 3.84 3.84 3.84 3.84 3.84 3.84 3.84 1.92 7.68 3.60 4.80 3.84 3.84 3.84 3.84 3.84 3.84 3.84 3.84 7.68 3.36 July Inches 3.84 3.84 3.73 3.84 3.84 3.84 4.27 3.84 3.84 3.84 3.84 3.95 1.92 3.84 3.00 4.80 3.84 3.84 3.84 3.84 3.84 3.84 3.84 3.84 4.80 3.51 Aug. Inches 3.84 3.84 3.84 3.84 3.84 3.84 3.84 3.84 3.84 3.84 3.84 1.48 Sept. Inches 0.0 4.26 3.84 4.27 3.84 3.84 3.60 4.80 3.84 3.84 3.84 3.84 4.80 1.68 Oct. Inches 0.0 3.84 3.84 3.84 3.84 .44 Total Inches 19.2 11.5 20.2 15.4 21.1 19.2 17.1 11.5 23.0 15.4 19.2 19.2 11.6 5.8 15.4 18.0 24.0 19.2 11.5 19.2 19.2 19.2 15.4 26.9 11.5 19.2 26.9 5.8 17.2 IRRIGATIOX REQUIREMENTS OF CALIFORNIA CROPS 69 Irrigation of Alfalfa Alfalfa is the principal crop of the Antelope Valley -which has been called the ' ' milkshed of Los Anji'eles, ' ' and uses more water than any other crop groAvn in the area. Records obtained from 14 ^rowers by the Agricul- tnral Extension Service, University of California, for 1931. presented in Table 41. show the average depth of water applied to have been 6.05 acre-feet per acre for sand and sandy loam soils, with a minimum of 2.20 and a maximum of 9.62 feet (24). Yields varied from 4.8 to 7.9 tons per acre while yields per acre-foot of water applied varied from 0.50 to 2.68 tons, with 1.16 tons as an average for the farms nnder obser- vation. TABLE 41 IRRIGATION WATER APPLIED TO ALFALFA IN ANTELOPE VALLEY, LOS ANGELES COUNTY, CALIFORNIA, 1931 (24) Soil type Depth of water applied Yield per acre Yield per acre- foot of water applied 72 45 45 60 25 24 4 75 60 33 38 35 10 153 Rosamond fine sand Hesperia loamy sand Hesperia loamy sand Rosamond sand Rosamond sand Rosamond fine sandy loam Rosamond sand Rosamond sand Hesperia sand (heavy) Hesperia loamy sand Rosamond fine sandy loam Rosamond sand Sunrise fine sandy loam Maximum Minimum Mean Feet 5.81 4.40 4.50 7.78 9.62 5.47 2.20 5.77 6.78 8.36 8.20 4.60 5.19 6.03 9.62 2.20 6.05 Tons 6.65 5.66 7.90 5.79 4.80 7.18 5.90 5.91 6.43 5.94 7.05 6.97 4.80 5.26 7.90 4.80 6.16 Tom 1.15 1.29 1.75 .75 .50 1.30 2.68 1.02 .95 .71 .86 1.51 .93 .87 2.68 .50 1.16 Depths of water applied to alfalfa on the Milaway Ranch near Lan- caster during the years 1929 to 1933, inclusive, are presented by months in Table 42. After 1929, which was the first year for this crop, the varia- tions in total water applied were small. The mean value was 6.83 acre- feet per acre which agrees favorably with the average depths of water applied to 14 farms as shown in Table 41. Values of irrigation requirements for alfalfa have not been deter- mined for this area but may be estimated by comparison with consump- tive use by alfalfa in the San Fernando Valley and converted to the irriga- tion requirement in Antelope Valley through the following procedure as used by Blaney (16) : 70 DIVISION OF WATER RESOURCES ^ OcOkOOOS OOOO **• 00 CO CD CO CD OO CO CO ■^ O .-I "S (M_^^»-«l^ C^ CO *2 "^ ^ o . ■^eoOcoo -"tf^pceo ic "5 •^OOCQO "tP o <— I '« O 00 »M C so (N oca coO i-H >^5 ■ S COOO 00 t^OO 00 c s ^ CCOJlOrHWS lO --I »-* oofcOOecN cooo"«t* — « 1— I OO 05 iC O O O OO O lO OS O -^ ■^ -^ CD ^*< O oi C^ CO CC CO C^ CO C^ (M OlO»-<'7: q2 a K ^, 'S c S ■^ iO-^f W5CD fe C35 »C W3 O (M* CD t^ t^ t^t^ a. ter inted as il ture ;ase J iDC^I iCiCO .=« 2 b 2.2 c 1 (M-^J* (M uOOi fe g£ " S " 1 B-S ja > ■1 '^ "^. ""! ^ ^ J3 g t^ iCtJi t^-*^ o. Q o s (MC^ICqOCO 3 ■-5 •-1 co(Ncqcoc^ >, 2 OO -H O 1-H ca "C S c ^ 2 C^ ■«*< Tj* -^ji Tf cc CO CO CO CO l-Hl— iCMCSf-",-.^,-),-!^,-. '-Hco'OOcDt--iC'-Ht>-a;co ^ C^ CD W3 O CO «0 b* W t^ 00 W5 g T-i rt C^ C9 CO '-"-H M (N COCOOCOOsiOC*^OOt>-(Md COTpCOCO"^'^C^C < 6 H z ■" S M < ■-) e$ 2 o u < ■S B a^ i eS 2 " = ocscoooect^ooccooo -^ oaca o t^-^ c«-* _ OS o — O-HOOOOOOOOOOO o — ,— .a — c^ — OO— • — '3-^ — O C^ Cb »5 O O t^ ^*90 »o C; o »o o>oias^oocioooo««05:oo O to 00 =0 ^*^**oc>oociCi _ X c ^o oE2'SSo"£ 3 3 7—53207 96 DIVISION OF WATER RESOURCES of the area. In Table 53 the water used during non-crop months, indi- cated by italic figures, show consumptive use caused by soil evaporation and use of water by weed growth. During crop periods weeds may be allowed to grow with the crop, thus increasing the consumptive use. These cases are shown in the table by stars (*). A more complete description of the investigation of use of water by crops grown in tanks in the delta area has been presented in the State Division of Water Resources, Bulletin No. 23 (52). The net consumptive use of water by crops grown in tanks as shown in Table 53 can not be converted into irrigation requirement values for field grown crops because tank conditions differ from actual field con- ditions in this area in regard to sources of the water supply. In a tank all water received is under control and is replenished by measured amounts. Under open field conditions in much of the delta area a meas- ureable part of the water supply is received from regular irrigation sources, but another part comes from an upward pressure movement of water into the root zone and these amounts are not measureable. The total quantity of water used by the crop should be approximately the same regardless of the source, whether the crop be grown in a tank or in the open field. Consumptive use by tank growth is equivalent to its irrigation requirement because there are no losses by deep percolation or waste such as occur under field conditions, but the irrigation require- ment of field growths is less than that of tank growths because a part of consumptive use by field growths is derived from ground-water sources. Farm Irrigation Deliveries The average delivery of water to farms in the East Contra Costa Irrigation District through the long period 1922 to 1942 have been tabu- lated (27) as follows: Crop Acre-feet per acre Alfalfa 1.67 Trees ... .. 1.28 1.78 .80 Trees and vegetables . . . 1.56 1.02 Trees and alfalfa^ . 1.12 Flaxs 1.14 1 Average of 17 years. 2 Average of 7 years. 3 One year, 40 acres. A record of river diversion to fields devoted exclusively to sugar beets in the East Contra Costa Irrigation District, as reported by the Sacramento-San Joaquin Water Supervisor (17), shows a rate of 1.1 acre-feet per acre for a field of 109 acres in 1942. This irrigation dis- trict is normally one of low irrigation requirement principally because of high ground water conditions requiring drainage. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 97 Records of 73 piinipiiig- plants which served only one type of crop in the Mokelnmne area, obtained from unpublished records of the U. S. Geoloo'ical Survey, are shown in Table 54 for a period of several years. TABLE 54 DEPTHS OF WATER PUMPED TO IRRIGATED CROPS IN THE MOKELUMNE AREA, OBTAINED BY THE U. S. GEOLOGICAL SURVEY (27) Crop Period of record Average area irrigated Depth of water applied Years 1927-33 1927-33 1929-33 1928-32 Acres 661 1,993 144 144 Inches 20.9 21.9 Alfalfa 39.2 22.3 98 DIVISION OF WATER RESOURCES SACRAMENTO VALLEY Scale of miles 10 20 30 40 50 I I I I Fig. 5 SACRAMENTO VALLEY The northern part of the Great Central Valley of California, occupy- ing the drainage basin of the Sacramento River System, has available for its many uses the greatest volume of water of any single river system within the State. Only by storage, however, will there be adequate distribution of the total flow necessary for the monthly needs of irrigation, power, salinity control, municipal and industrial uses, flood control and navigation. Shasta Dam permits control of flood wastes and provides a better use of existing supplies. The agricultural portion of the valley extends from Mount Shasta on the north to the Sacramento-San Joaquin Delta on the south in a valley separating the Sierra Nevada and Cascade Range on the east from Coast Range on the west. This is an area about 150 miles long and about 30 miles wide. (Fig. 5.) The mean run-oflP of the Sacramento River at Red Bluff, approxi- mately at the upper end of the main body of agricultural lands, is about 10,000.000 acre-feet annually. The annual flow has been as high as 22.7 million acre-feet and in years of deficiency as low as 3,000,000 acre-feet, the difference of nearly 20.000,000 acre-feet indicating the necessity of a great storage capacity. The principal tributaries of the Sacramento River are the Pit and McCloud Rivers above Red Bluff, the Feather, Yuba, Bear, and American Rivers entering from the east, and Stony, Cache, and Putah Creeks from the west. The climate is variable according to altitude and latitude. Records of rainfall available for the City of Sacramento since 1849, show an aver- age of about 18 inches annually with extremes marked by a minimum of seven and a maximum of 35 inches. At Red Bluff the average rainfall is increased to 23 inches and at Nevada City (elevation 2,580 feet), a 60-year record shows an annual precipitation of 53 inches. The long term mean temperature and the annual rainfall at Davis, Calif., for 1934-35 and 38 are presented in Table 55. The frost-free period decreases northward from Sacramento where it averages 306 days between killing frosts, so tliat at Red Bluff it is but 273 days. The difference may account for selection of crops. TABLE 5 5 MEAN MONTHLY TEMPERATURE AND ANNUAL RAINFALL AT DAVIS, CALIFORNIA Month Long term mean tem- perature Rainfall Month Long term mean tem- perature Rainfall 1934 1935 1938 1934 1935 1938 'F. 46.5 50.9 55.1 59.5 65.9 72.7 Inches 1.16 3.21 .10 .35 .25 .44 Inchet 4.87 .83 2.88 4.40 T Inehtt 3.49 8.87 4.26 1.11 .38 T July - "F. 76.2 74.0 71.7 63.6 54.3 47.4 Inchu T T .65 2.51 2.57 Inches T T 1.03 1.05 1.51 Inches .09 .76 May .60 1.08 61.5 11.24 16.57 Totals 20.64 (99) 100 DIVISION OF WATER RESOURCES Various classifications have been given the soils of the Sacramento Valley, but of greatest importance are the Class 1 lands north of the delta. These comprise about 1,735,000 acres for which the soil texture, alkali, or topography does not materially limit the feasibility of irrigation. Mountain valleys are in different categories by reason of altitude and climatic differences that increase the depth of precipitation and at the same time shorten the growing season. For such areas the irrigation requirements of crops will be less than for lower elevations on the val- ley floors. Practically every crop grown in the State may be found in some degree in the Sacramento Valley. Citrus is grown to a limited extent in the north central portion of the valley. Deciduous fruits, including figs and nuts, are well distributed. The largest peach growing area is in Sutter, Butte and Yuba Counties. Grapes are grown throughout the valley. Rice does well on some of the heavy soils north of Sacramento. Alfalfa is one of the general crops that may be found in most localities and sugar beets, vegetable and truck crops, small grains and beans are grown in several localities. EXPERIMENTS IN USE OF WATER BY CROPS AT THE UNIVERSITY FARM AT DAVIS Experiments in the use of water by a number of crops have been con- ducted at the University Farm at Davis, for many years. Among these crops are watermelons, alfalfa, small grains, corn and milo maize, each of which will be discussed in relation to its consumptive use losses which were obtained as a result of soil moisture studies by the personnel of the station. Each study and its results have been described in publications of the California Agricultural Experiment Station but, because the objec- tive was usually the relation of plant response to different irrigation treat- ments, quantitive determination of irrigation requirements for indi- vidual crops was not usually reported by the investigators. It is pre- sumed that in the process of obtaining records of the consumptive use losses sufficient data were made available to the investigators for calcu- lation of the irrigation requirements for profitable crop production, but in the absence of complete published data no attempt will be made here to arrive at the irrigation requirements for the different crops listed. Irrigation of Watermelons Irrigation of watermelons was studied by the California Agricultural Experiment Station at the University Farm, for a three-year period to determine the effects of different irrigation treatments on yields (22). The soil was a fine sandy loam which could be filled to field capacity within the limits of root activity in years in which seasonal rainfall amounted to 16 inches or more. Nevertheless all plots were flooded before being seeded to insure a uniform distribution of soil moisture to the depth desired at the beginning of the season. Four irrigation treatments were established. Treatment A did not provide an irrigation after germination so that the only water applied was in preirrigation. Treatment B involved irrigation often enough to maintain the soil moisture well above the permanent wilting percentage, the number of irrigations ranging from four applications totaling 13.7 acre-inches per acre to seven applications amounting to only 7.05 acre- IRRIGATIOX REQUIREMENTS OF CALIFORNIA CROPS 101 inches. Treatment C provided a sinjrle irrigation Avlieii soil to the depth of root activity reached the wilting point. Depth of water applied ranged from 2.6.1 acre-inches per acre to 9.13 inches regardless of the depth of rainfall during the previous winter and spring. Treatment D was the same as Treatment B except that there was no irrigation during the blossoming period. This treatment occurred only during the last year of the experiment and provided two irrigations for a total of 7.9 acre- inches applied. During the first year irrigations were applied by means of furrows spaced nine feet apart, a distance that was insufficient to moisten all the soil between the furrows ; but thereafter irrigation was by flooding which permitted a better distribution of the moisture in the soil. The number of irrigations, depth of water applied, and fruit yield per plant are listed in Table 56. TABLE 5 6 IRRIG.\TION APPLIED TO WATERMELONS AND THEIR YIELD AT THE UNIVERSITY FARM, DAVIS, CALIFORNIA (22) Year Treatment Irrigations Irrigation method Depth of irrigation RainfaU January 1 to October 30 Yield per plant 1934 A B C A B C A B C D Number 7 1 5 1 4 1 2 Inches 0.0 7.05 2.65 .0 18.95 9.13 .0 13.70 4.50 7.90 Inches 6.16 6.16 6.16 14.01 14.01 14.01 18.96 18.96 18.96 18.96 Lbs. 70.2 1934 Furrow- Furrow 69.4 1934_ 58.2 1935 36.7 19.35 Flooding Flooding 38.2 1935 - - 47.4 1938 26.1 1938 Flooding Flooding Flooding 30.4 1938 30.4 1938 28.2 Yields fluctuated widely with the highest — 70 pounds of fruit per plant — occurring in 1934 on soil that had no irrigation other than that prior to seeding. In this year rainfall was below normal, amounting to 6.16 inches between January 1st and October 30th. Nearly the same yield was received from Treatment B in the same year with seven irriga- tions totaling 7.05 acre-inches per acre. In the following year and with the same Treatment B, five irrigations totaling 18.95 acre-inches, resulted in a yield of 38.2 pounds per plant, a decrease of nearly 50 per cent. This was a year of nearly normal rainfall. The best yields were obtained with application of a small depth of irrigation but the data do not defi- nitely indicate the best amounts to apply. In another paper (38), how- ever, two of the original authors stated that a total of seven to eight acre-inches of irrigation was needed to produce a maximum crop of watermelons on Yolo sandy loam at the University Farm. Irrigation of Alfalfa Investigations of the irrigation of alfalfa in the Sacramento Valley were carried on through cooperative studies from 1910 to 1915 by the California Agricultural Experiment Station, the Office of Experiment Stations (including the present Division of Irrigation, Soil Conserva- tion Service), and the State Department of Engineering of California, 102 DIVISION OF WATER RESOURCES at the University Farm at Davis, California. In 1913 the scope of the work was increased to include similar studies on a number of repre- sentative alfalfa farms of different soil types in several parts of the Valley. Results of the investigations are contained in several publica- tions (1), (2), (8), (9). Alfalfa is one of the important crops of the Sacramento Valley, as it is in other parts of the State ; but in percentage of total area cropped it is less than in some other areas. From the data available it appears that this crop occupies somewhat more than 10 per cent of the entire irrigated acreage of the valley. The purpose of the investigations was to obtain information on the duty of water in order that alfalfa growers might have a better under- standing of the proper number of irrigations, the intervals between them, the depths of water to apply at each irrigation, and the total quantity of irrigation necessary for the production of the best yields. These values differ with variations in soil type and also in different localities, according to several factors of which altitude, precipitation, and tem- perature are the most important. A summary of the observations at Davis from 1910 to 1925 is presented in Table 57, which shows the rela- tion of different irrigation treatments and total depths of water applied to crop yields. No attempts were made to determine the actual irri- gation requirement of the crop. TABLE 57 IRRIGATION WATER APPLIED, RAINFALL, AND CROP YIELD OF ALFALFA AT THE UNIVERSITY FARM, DAVIS, CALIFORNIA (9) Year Area irrigated' Irrigations Depth of each irrigation Depth of irrigation Annual rainfall Yield per acre 1910-15.. Acres Plots Plots Plots Plots Plots Plots Plots 0.61 .61 .61 .61 .59 .54 .68 .68 .68 .82 .77 .71 Number 2 3 2 3 4 6 8 12 2 3 4 6 8 12 Inches 6 6 6 rii 9 12 15 15 10 7J^ 5 214 15 10 7H 5 2H Inches 12 18 24 30 36 48 60 30 30 30 30 30 30 30 30 30 30 30 30 Inches 16.9 16.9 16.9 16.9 16.9 16.9 16.9 15.0 15.0 15.0 15.0 15.0 15.0 14.6 14.6 14.6 14.6 14.6 14.6 Tons 5.63 1910-15 6.80 1910-15 7.92 1910-15 8.98 1910-15 9.27 1910-15 9.02 1910-15 8.42 1918-21... 8.24 1918-21 8.41 1918-21... 7.57 1918-21 8.72 1918-21 8.79 1918-21 9.42 1921-25 8.33 1921-25 8.29 1921-25 7.36 1921-25 8.61 1921-25 8.47 1921-25 9.20 ' Soil was Yolo loam. During the 1910-15 period the total depth of water applied was varied at six-inch intervals from 12 to 60 acre-inches per acre. Appli- cation of 36 inches of irrigation water resulted in the highest yield, but the difference in yield between this and that obtained from 30 inches was too small to be significant. For applications greater than 36 inches seasonally there was a decrease in yield ; hence it may be assumed that under conditions existing at Davis for this particular period in which the rainfall averaged about 17 inches, 30 inches of irrigation water was IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 103 the most economical depth. This was obtained by means of four irriga- tions of seven and one-half inches each. The reported depths of root zone showed little variation for the different irrigation treatments. Two-thirds or more of the root activity, as evidenced by extraction of moisture from soil, occurred in the upper two feet of soil, while at depths of six feet the average extraction was about two per cent. The soil was fine sandy loam shading into fine sand at about four feet in depth. It has long been a popular belief that alfalfa is a deeply rooted plant, the roots extending to depths of 20, 40, and even 60 feet. This may occur under favorable conditions with long established stands, but where stands are reseeded every few years and depth of root activity has been determined by soil moisture sampling, the majority of cases indicate that 95 per cent or more of the roots exist in the upper five or six feet of soil (60), (57), (9). This may be due to the fact that irriga-- tion water in the soil is consumed by the plant before it can penetrate to depth, and that beyond the depth of penetration the soil is too dry for root activity. If the soil is moist below the six-foot depth and the upper soil has dried out through lack of irrigation, for a time, at least, greater activity will occur at greater depths. In further tests at Davis, from 1918 to 1925, variations in the number of irrigations and the depths applied at each irrigation resulted in total applications of 30 acre-inches of water. The number of irriga- tions varied from two to twelve without changing the total application. The best yields resulted from 12 irrigations of 2.5 acre-inches each, but this increased yield probably would not pay for the extra labor involved in the large number of irrigations. On loam soils in the Sacramento Valley it appears that 30 inches of water applied in three to six irriga- tions represents good irrigation practice. In 1913-14 the alfalfa studies by the California Agricultural Experi- ment Station were extended to a number of other soil types throughout the length of the Sacramento Valley from Woodland to Willows (1), (2), (8). The soils included silt and clay loams, silty clay loam and coarse gravelly loam. Between 40 and 50 representative farms were under observation. "WHiile the purpose of the study included measure- ment and analysis of the amounts of water applied to the crop, in those cases where large amounts of water were applied it became also a study of the underground distribution of the irrigation water and observation of the capacity of the variou>s soils to maintain the moisture necessary for the best crop yields. A summary of the data is given in Table 58, as the complete data are too voluminous for this report. The table shows great variations in the depth of water applied, ranging from 61.8 acre-inches per acre to 22.0 inches. Where plenty of water was available it was applied wastefully and for these cases the records are not representative of actual irrigation requirements. This appears to be the case for those farms that were under observation at Orland and Los Molinos where an abundance of water was reported available for irrigation. In the Willows area the soil was compact, sticky when wet, and .subject to baking when dry. Penetration of irrigation water was difficult and in some cases reached depths of only a foot or so below the surface. Where local drainage was poor, rain water stood in the field, creating some damage to the crops. These conditions are 104 DIVISION OF WATER RESOURCES reflected in the low use of water and the low yields tabulated for this area. The best yields appear to have resulted from the application of approximately 30 inches of irrigation water during years when rainfall amounted to about 18 to 20 inches. TABLE 5 8 IRRIGATION WATER APPLIED, RAINFALL, AND CROP YIELDS OF ALFALFA GROWN ON DIFFERENT SOIL TYPES WITH DIFFERENT DEPTHS OF IRRIGATION WATER APPLIED, SACRAMENTO VALLEY, CALIFORNIA (1), (2), (8) Year Location of tests Soils Fields included Total area Irriga- tion Annual rainfall Yield per acre 1913 Gridley- Los Molinos Orland WiUows Woodland Number 14 12 7 3 12 6 Acres 284 130 214 28 295 207 Inches 39.7 61.8 55.9 22.0 28.0 35.3 Inches 17.9 20.0 20.0 22.2 20.0 17.9 Tons 6.19 1913-14 6.01 1913-14 Coarse, gravelly Silty clay loam Siltv loam . 6.26 1914 4.82 1913-14 6.45 1913 -. Clay loam 6.76 As a result of the studies it was the conclusion of the investigators (8) that the depth of irrigation water required per annum to produce the best yields of alfalfa on medium loam soils in the Sacramento Valley was 30 to 36 acre-inches per acre, depending on rainfall, and that the desirable depth of each irrigation was six to nine inches applied in three to five irrigations. For gravelly or sandy soils the depth of irrigation required per annum was estimated at 48 to 60 acre-inches per acre applied in two or three irrigations per cutting in depths of three to four inches per irrigation. Where clay or clay loam soils were cropped it appeared that 30 to 36 acre-inches per acre would produce the best yields if applied in two or three irrigations per cutting in amounts of two to four acre-inches at each irrigation. Variations in normal rainfall would advance or retard the date of the first irrigation according to the amount of soil moisture available for the crop in the spring months. Irrigation of Barley From 1910 to 1921, inclusive, experiments on irrigation of barley were made on Yolo fine sandy loam soil by the California Agricultural Experiment Station at the University Farm, Davis, California (9). Barley is an early crop, sown in the fall and harvested in late spring so that it obtains the greatest benefit from winter rains. This practice makes irrigation a minor requirement except in years of low rainfall or poor distribution of rains during winter months. From 1910 to 1916, inclusive, one plot did not receive any irriga- tion, one was irrigated once and a third plot was irrigated twice, as indicated by crop needs. During the second period of experimentation, 1913 to 1921. one of the plots was without irrigation; of the other two, one was fall irrigated once before seeding and another was summer irrigated, also once before seeding. No apparent difference in j'ield was noted as a result of summer or fall irrigations. These studies were carried on during periods of both light and heavy rainfall which has a long time seasonal average for this locality of about 17.0 inches. The IRRIGATION' REQUIREMENTS OF CALIFORNIA CROPS 105 best yields were obtained from a total moisture supply of about 11 inches of irrigation plus 11.7 inches of rainfall. In Table 59 are shown irrigation data, rainfall and crop yields obtained under the different treatments. During years of high rainfall — 22 inches — application of 10.5 acre-inches of irrigation water did not increase the jield. Irrigation of Wheat Irrigation of wheat was studied at the University Farm during 1912- 1914 with one or two irrigations applied each spring according to crop needs (9). The years 1912 and 1913 were years of deficient rainfall — less than 10 inches — so that one or two irrigations amounting to six to 10 inches were needed to produce the best yields, depending on the rain- fall distribution. In 1914, which was a year of high rainfall (28.7 inches), the best yield was obtained without irrigation. For plots where irrigation was applied the yields decreased as the number of irrigations was increased, indicating that irrigation was unnecessary. Depths of irrigation Avater applied, rainfall, and yields of grain wheat orown under different irrigation treatments are presented in Table 60 (9). TABLE 59 COMPARISON OF YIELDS OF BARLEY AFTER YEARS OF LIGHT AND HEAVY RAINFALL AT THE UNIVERSITY FARM, DAVIS, CALIFORNIA, 1910-1921 (9) Years Irrigations Depths of irrigation and seasonal rainfall Irriga- tion Rain- fall Total Yield per acrei Seasons of deficient rainfall 1910, 1912 and 1913 1913, 1917, 1918, 1920 and 1921 Seasons of abundant rainfall 1911, 1914, 1915, and 1916— 1914, 1915, 1916, and 1919 Number I-Fall 1-Sum- mer Inches 0.0 6.7 12.2 .0 10.8 10.8 .0 5.2 7.0 .0 10.5 10.5 Inches 10.07 10.07 10.07 11.69 11.69 11.69 23.20 23.20 23.20 22.26 22.26 22.26 Inches 10.07 16.77 22.27 11.69 22.49 22.49 23.20 28.40 30.20 22.26 32.76 32.76 Bushels 17.5 34.1 44.1 16.1 46.0 43.8 31.7 37.1 37.7 34.8 32.4 34.2 ' Weight of barle)':= 48 lbs. per bushel. 106 DIVISION OF WATER RESOURCES TABLE 60 IRRIGATION WATER APPLIED, RAINFALL, AND CROP YIELDS OF WHEAT GROWN UNDER DIFFERENT IRRIGATION TREATMENTS AT THE UNIVERSITY FARM, DAVIS, CALIFORNIA (9) Year Area irrigated' Irriga- tions Depths of irrigation and seasonal rainfall Yield per Irriga- tion Rain- fall Total acre^ 1912 Plot Number 1 2 1 1 2 2 2 2 2 1 2 1 2 3 4 5 Inches 0.0 10.0 17. R .0 2.0 4.0 6.0 8.0 10.0 12.0 15.0 .0 6.8 13.0 .0 4.0 8.0 12.0 16.0 20.0 Inches 9.5 9.5 9.5 8.7 8.7 8.7 8.7 8.7 8.7 8.7 8.7 8.7 8.7 8.7 28.7 28.7 28.7 28.7 28.7 28.7 Inches 9.5 19.5 27.1 8.7 10.7 12.7 14.7 16.7 18.7 20.7 23.7 8.7 15.5 21.7 28.7 32.7 36.7 40.7 44.7 48.7 Bushels 9.4 1912 Plot . 20.2 1912 Plot - 32.2 1913 Plot 2.1 1913 Plot - - 9.4 1913 Plot 21.9 1913 Plot 26.7 1913 Plot. 27.2 1913 Plot -- 29.9 1913 Plot 26.8 1913 Plot 20.7 1913 Plot 22.6 1913 Plot- 28.8 1913 Plot 31.2 1914 Plot 20.4 1914 Plot 15.8 1914 Plot 15.2 1914 Plot 14.2 1914 Plot - - 13.6 1914 Plot 12.9 1 Yolo fine sandy loam. 2 Sixty lbs. per bushel. Irrigation of Oats Variations in number and depth of irrigation applied to oats grown at the University Farm during two years of rainfall of less than 10 inches also were studied in relation to yields. In three sets of treat- ments one plot was not irrigated, one was given one irrigation, and a third was given two irrigations, each applied during the spring accord- ing to crop needs. Without irrigation the yield ranged from complete failure to 13.6 bushels per acre while one irrigation of 8.1 acre-inches per acre produced 31.7 bushels, one irrigation of 13.2 acre-inches plus 9.5 inches of rainfall produced 45.9 bushels of grain, and two irriga- tions of 21.8 acre-inches plus 9.5 inches of rain resulted in a yield of 64.2 bushels per acre. These data are shown in Table 61. TABLE 61 IRRIGATION WATER APPLIED, RAINFALL AND CROP YIELDS OF OATS GROWN UNDER DIFFERENT IRRIGATION TREATMENTS AT THE UNIVERSITY FARM, DAVIS, CALIFORNIA (9) Area irrigated* Irriga- tions Depths of irrigation and seasonal rainfall Yield per Year Irriga- tion Rain- fall Total acre2 1912 Plot Number 1 2 1 2 Inches 0.0 13.2 21.8 .0 8.1 15.8 Inches 9.5 9.5 9.5 8.7 8.7 8.7 Inches 9.5 22.7 31.3 8.7 16.8 24.5 Bushels 13.6 1912 Plot . 45.9 1912 Plot 64.2 1913 Plot . . .0 1913 Plot . 31.7 1913 Plot... 47.1 1 Yolo fine sandy loam. 2 Thirty-two lbs. per bushel. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 107 It was the conclusion of the experimenters (9) that for the Sac- ramento Valley with normal rainfall normally distributed, the increase in o-rain yields did not warrant the cost and labor involved in irriga- tion, and that in years of low rainfall small grains can profitably be produced with irrigation. In 1910, 1912, and 1918, which were years of extreme rainfall deficiency, it was suggested that : ' ' Two irrigations of four to six acre-inches per acre should be suf- ficient to produce normal yields. Under conditions of partial drought, especially where a deficiency of rainfall occurs in the late winter and early spring (March or April), satisfactory yields may be obtained through one irrigation. In years of heavy rainfall irrigation may produce a decrease in yield. However, if this rain- fall should be unequally distributed, with a deficiency during March and April, irrigation water may be applied with advantage. Irri- gation of grain land before seeding (either in the summer or in the fall just prior to seeding) produces no increase in yields in years of normal rainfall. In years of deficient rainfall, normal yields will be produced by this method of irrigation. In years of drought the average yield produced by this method was one-third greater than the average yields produced in years of normal rainfall. "According to the results obtained in the eight years covered by these experiments, there have been six years of the past 18 years (1909-1926), at the University Farm, Davis, when irrigation would probably have produced no material increase in yields ; six years in which the distribution and amount of rainfall was such that one spring irrigation could have been applied with advantage ; and six years in which two irrigations would have been required for full production." Irrigation of Corn A longer study of the irrigation needs of corn was undertaken by the California Agricultural Experiment Station at the University Farm between 1910 and 1922 (9). The number of irrigations varied each year from none to four with depths of water applied ranging from zero to 15.8 acre-inches per acre by means of furrow irrigation. The aver- age seasonal rainfall varied from 10 to 22 inches with an over-all aver- age of 17 inches seasonally. Kecords of average depths of irrigation water applied, seasonal rainfall and crop yield are listed in Table 62, which is divided into three groups : viz, the dry years, in which rainfall was below normal; the wet years with above normal rainfall, and the average of all years of experimentation. In both the wet and the dry years the bast yields were obtained with three irrigations totaling 10.5 acre-inches regardless of the depth of seasonal rainfall. However, the increase in rainfall from the dry to the wet period resulted in a corre- sponding increase in yield amounting to about 40 per cent. 108 DIVISION OF WATER RESOURCES SUMMARY OF COMPARISONS OF YIELDS OF CORN GIVEN DIFFERENT IRRIGATION TREATMENTS AT THE UNIVERSITY FARM, DAVIS, CALIFORNIA (9) Years Irriga- tions Average depths of irrigation and seasonal rainfall Irriga- tion Rain- fall Total Yield of ensilage per acre Dry years— 1910, 1912, 1913, Wet years— 1911, 1914, 1915, 1922. Average of all years— 1910-15, 1922. Number 1 2 3 1 2 3 4 1 2 3 4 Inches 0.0 3.4 6.6 10.5 .0 3.6 6.8 10.6 15.8 .0 3.5 6.7 10.6 14.6 Inches 10.0 10.0 10.0 10.0 22.1 22.1 22.1 22.1 22.1 17.0 17.0 17.0 17.0 17.0 Inches 10.0 13.4 16.6 20.5 22.1 25.7 28.9 32.7 37.9 17.0 20.5 23.7 27.6 31.6 Tons 4.04 5.73 6.40 7.36 3.91 6.77 8.96 10.35 9.90 3.98 6.33 7.86 9.07 8.85 ' Soil was Yolo fine sandy loam. Irrigation of Dwarf Milo Maize Studies of irrigation treatments of dwarf milo maize by the Agri- cultural Experiment Station at Davis, between 1910 and 1922 (9) indi- cate the value of additional water applied at the proper intervals in increasing the yield of the crop, the variable factors being the frequency and depth of irrigation. Each variation in the increased number of irrigations and greater depths of water applied produced a greater yield. A summary of data regarding this experiment is shown in Table 63. TABLE 63 SUMMARY OF IRRIGATION WATER APPLIED, RAINFALL AND CROP YIELDS OF DWARF MILO MAIZE GROWN UNDER DI.pFERENT IRRIGATION TREATMENTS AT DAVIS, CALIFORNIA (9) Years 1910, 1911,1913,1922. 1910, 1911,1913, 1922 1910, 1911,1913,1922. 1910, 1911,1913,1922. Irrigations ■Number 1 2 3 Average depths of irrigation and seasonal rainfall Irrigation Inches 0.0 3.0 5.8 Rainfall Inches 15.1 15.1 15.1 15.1 Total Inches 15.1 18.1 20.9 23.7 Yield per acre' Lbs. 1,548 2,192 2,741 2,893 1 Soil was Yolo fine sandy loam. As a result of the studies with corn en.silage and milo maize the experimenters have concluded (9) that in years of normal rainfall in the Sacramento Valley not more than three irrigations totaling not to exceed 12 acre-inches per acre will produce the best crop. In years of mRIQATION REQUIREMENTS OF CALIFORNIA CROPS 109 deficient rainfall not more than fonr irrigations not exceeding 18 acre- inches per acre should be applied. For these crops fnrrow irrigations ■will give the best results and fonr acre-inches per irrigation shonld be applied for each irrigation. In years when there is insufficient mois- ture in the soil for germination of the seed a preirrigation will be necessary. Irrigation of Rice The growing of rice is adapted to the heavj^ clay, clay adobe and adobe soils of the Sacramento Valley and according to the agricultural census of 1940 (58) in excess of 90,000 acres was under irrigation there during the previous year. The soil that is the most satisfactory for rice is one that is most impervious to water, so that it will have the least percolation and require the least water for irrigation. Pervious soils permit water to pass through beyond the needs of the plant, thus increas- ing the danger of creating a drainage problem. It is probable that perviousness of the soil has a greater effect in promoting a high water requirement than all other factors combined. Irrigation of rice differs materially from irrigation of other crops in that rice is first alternately flooded and drained in order to keep the soil moist for germination of the seed, this period being followed by continued submergence to a depth of about six inches until it becomes necessary to drain the fields so that they may be dried out for harvesting. Kice must have a sufficiently large head of water to permit an initial flooding five to 10 inches deep followed by several shallow floodings to maintain a moisture supply at the soil surface. Heads of two to five cubic feet per second will be necessary depending on the area of the field. Rice fields require drainage ditches around the outside of the field to prevent a rise in the water table that would make the soil too wet for the use of harvesting machinery. Evaporation from the submerged areas and the growth of water grasses and rice weeds increase the irrigation requirement of the crop. It has been estimated (3) that evaporation disposes of about one-third of the net depth of water required. By net depth is meant the differ- ence between the total depth of water applied to the field for germina- tion and submergence and the depths of water drained from the field following submergence periods. Alkali in the soils of rice fields requires the circulation of water through the area between contour levees, thus increasing the head of water needed although not necessarily the net water requirement. Cooperative experiments in irrigation of rice in the Sacramento Valley made by the California Agricultural Experiment Station, in various years between 1914 and 1927, determined the best depths of submergence, the time of irrigation and the net depths of Avater neces- sary for production of the highest yields on different soil types. On 16 farms totaling 4,395 acres of clay adobe soil the net use of 5.13 acre- feet per acre produced an average of 36 saete of paddy rice. Eleven farms with a combined acreage of 6,226 acres of clay soil had a net use of 5.39 acre-feet per acre in producing 32 sacks of rice per acre. On the more open loam soil a total of 122 acres required 9.38 acre-feet per acre 110 DIVISION OF WATER RESOURCES to produce 43 sacks per acre (3), (46), (23). These data are listed in Table 64. TABLE 64 SUMMARY, ACCORDING TO SOIL TYPE, OF NET DEPTHS OF IRRIGATION WATER APPLIED AND CROP YIELDS OF RICE GROWN ON HEAVY SOILS IN SACRAMENTO VALLEY, CALIFORNIA (3), (46), (23) Year 1916 1916-17, 1924 1916-17, 1924 1916-17 Fields Area Number Acres 2 268 16 4,395 11 6,226 2 122 Soil type Clay loam and clay Clay adobe Clay Loam Average yield per acre Sacks 1 1 Sacks of rice average 100 pounds in weight. Results of four years of measurements of the use of water by rice on 40 acres of Stockton clay loam near Biggs, show the average net depth of water applied to be 4.53 acre-feet per acre, producing an average of 46 sacks of paddy rice of approximately 100 pounds per sack. The full irrigation season averaged from the middle to late April to about the first of October. It would appear that a net irrigation requirement of five acre-feet per acre on clay or clay adobe soils would produce 30 to 35 sacks of paddy rice under favorable conditions of growth. More open soils increase the water requirement through percolation losses. Rank growths of water grasses and weeds reduce the yield. STREAM DIVERSIONS SERVING A SINGLE CROP TYPE FOR IRRIGATION Table 65 summarizes the monthly average distribution of use of stream diversions and the total average depth of water delivered to about 22,000 acres of various single crops in the Sacramento and San Joaquin Valleys for the years 1935 to 1942 (17). In making this table only those diversions which served a single crop were tabulated. These are gross diversions which include waste, transmission losses, evaporation and possible deep percolation ; nevertheless the average depths of water delivered to the crops are not greatly in excess of depths of irrigation determined through experimentation. It will be observed that the monthly percentage of irrigation applied varies greatly for individual crops, a condition previouSily discussed in regard to cropping in the Sacramento-San Joaquin Delta. Thus the monthly ratio of use of water by corn in June is about 16 per cent of the seasonal total as compared with 33 per cent for beets in the same month. Eighty-three per cent of the water diverted to hops occurred during June and July while only 49 per cent was diverted to beans during the same period. Such data indicate the peak diversions of water required during the hot summer months. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 111 O mi O w ^ iJ N 5 « B5 ■* < 5 NO ^ l-J ►J ^ n « ^ 2. << S ^ S < 6 w w S< (d ^ H <« O D z O H s 5 H M Q >-) < H O H Q Z < >< >j X H Z o J= o & i< *" a -o 1 -a p 1 OO-^OOO'-O^OCC >o '^Tf«-^'^00*CCO'*<-^ "rt CO^'MC^^'-"MCr. » 8 t^OCOC'^'MC3lOeOO o 'B CJ!N(MCQ'^'^CO'M. "k 1 >> 8 C -^ O O -^ I- CJC oo o O S fe ■" '■" ^ ^^ — ' a. c 'E .^ (M — COC-iC^^-^MfM M o; a. J3 e u OCO--^OOC^OO — . 1 t t f 1 • cJ 3 1 3 1 1 ! 1 1 ! ! 1 fcD 1 1 1 ,-T3 1 ' « ] 1'^ 8—53207 112 DIVISION OF WATER RESOURCES WATER PUMPED FROM WELLS FOR IRRIGATION OF A SINGLE CROP TYPE The g'l'oss amount of water pumped from wells for deliver}^ to 15,000 acres of various single crops in the vicinity of Suisun, Dixon, Woodland and Sacramento, as reported by the State Engineer's Office, is presented in Table 66 (17). The average depth of water pumped per acre of cropped land shown in this table is considerably in excess of the acreage diverted from streams as listed in Table 65, although in most cases there is little difference for individual crops. The principal dif- ference lies in irrigation of beets which received 30 inches of irrigation from wells avS compared with 24 acre-inches diverted from streams and the addition to the list of Ladino clover using 52.8 acre-inches per acre which from reports on the use of irrigated pastures appears to be a heavy user of water. TABLE 6(, USE OF WATER PUMPED FROM WELLS TO VARIOUS SINGLE CROP TYPES IN THE VICINITY OF SUISUN, OIXON, WOODLAND AND SACRAMENTO, CALIFORNIA (17) Crop Wells i^rea irrigated Depth of water dehvered by pump Alfalfa Number 114 1 68 6 19 4 32 38 6 Acres 5,280 ■ 51 6,180 58 543 188 1,020 1,480 434 Inches 36.0 14.4 Beets - _ 30.0 33.6 Grapes 25.2 12.0 52.8 Orchard ....... ...... ... 26.4 26.4 Totals 288 15,234 Mean 32.4 IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 113 ESTIMATES OF IRRIGATION REQUIREMENTS OF CROPS BY VARIOUS AGENCIES Irrig'ation requirements of a number of crops grown in the Sacra- mento Valley, as estimated by the U. S. Bureau of Agricultural Eco- nomics, the Bureau of Reclamation, and the State of California, are listed in Table 67 (49). They are based upon the results of various experimental studies by the California Agricultural Experiment Sta- tion supplemented by irrigation experience and information from other areas and are considered liberal. They are not necessarily in agreement with the more exact data obtained from consumptive use determinations on small areas for which water was under close control by trained observers, as the data in this tabulation include losses in transit between the farm headgate and the point of application whereas the former did not. TABLE 67 ESTIMATED WATER REQUIREMENTS PER ACRE AT FARM HEADGATE, SACRAMENTO VALLEY, CALIFORNIA (49) Crop or other use Pasture: Ladino or mixed clover and grasses Pasture: Irrigated native Alfalfa—. Sudan grass Oats and vetch hay Field crops Sorghum — for grain or silage Corn or corn silage Sugar beets Tomatoes Peas, winter Beans Hops Small grains Rice Asparagus Truck crops Deciduous fruit Olives Citrus Walnuts Almonds Grapes Pre-irrigat ion Gun clubs Water requirements at farm headgate estimated by Bureau of Agricultural Economics Inches 54.0 18.0 236.0 15.0 9.0 is'o 15.0 27.0 21.0 9.0 415.0 18.0 9.0 84.0 24.0 21.0 21.0 21.0 24.0 24.0 15.0 15.0 6.0 18.0 Bureau of Reclamation! Inches 53.9 19.3 36.8 18. G 12.8 13.1 25.8 18.8 8.0 13.8 586.8 i8'2 23"8 State of California (64) Inches 15.0 336.0 36.0 12.0 72.0 24" 21.0 24.0 30.0 «18.0 ■Sullivan, A. B. Memorandum Report — Irrigation Requirements of Sacramento Valley Crops. February, 1941. Sacramento Valley Investigations. Bureau ."Agricultural Economics (unpublished). (55) - Also for deep medium textured soils, GO inches. 3 On gravelly soil, 60 inches deep. * For beans doubled cropped after grain hay or peas, 24.0 inches. 5 Includes 6.0 acre-inches for flooding. • On shallow soil 21.0 inches. The setting up of such values assumes an average skill in irrigating and they apply to avei'age climatic conditions. Variations in the require- ments depend on changes in soil conditions, weather, drainage condi- tions, and skill and experience of the irrigator in making the most effi- cient use of the water applied. Under unfavorable conditions it is possible that tabulated requirements may be increased as much as 10 to 25 per cent. SUMMARY Irrigation requirements of crops vary with such climatic factors as temperature, rainfall, evaporation, and length of growing season; the quantity and cost of the available irrigation supply; the efficiency of irrigation ; with crop characteristics such as rate of growth and rooting habits ; and according to soil type. High temperatures, a long growing season and evaporation increase the requirement while low temperatures and effective rainfall decrease it. Expensive water used for irrigation promotes high irrigation efficiencies by deterring overirrigation and other wasteful practices. Both fast-growing and shallow-rooted crops require excess water and mature trees use more water than young trees. Sandy soils ijeed irrigation more frequently than the heavier types. Ground water, close enough to the surface to supply capillary moisture to plant roots, decreases the irrigation requirement and adequate drainage increases it. These are important factors controlling the selection of crops and the depths of irrigation required for their satisfactory pro- duction. Adequate determination of the irrigation requirement, as it has previously been defined, has not been attempted in this report, generally owing to the lack of soil moisture data on which to base satisfactory estimates. Wherever it has been possible, transpiration use or consump- tive use has been tabulated as presenting the best evidence available of plant requirements ; and where neither of these values is available, depth of water applied in irrigation has been listed as next in value. Where an irrigation requirement value has been listed it usually has been the estimate of the original investigator who is presumed to have had more adequate data on which to base an analysis than has been available to the author of this report. In such cases it is probable that the investi- gator 's estimate is as close a value as may be ascertained and it may be accepted with a reasonable degree of assurance. The availability of a supply of rainfall stored in the soil within the root zone at the beginning of the growing season is an item in the determination of the irrigation requirement. As long as roots draw on an adequate moisture supply in storage the first irrigation may be delayed, usually until May, and the irrigation season shortened. In California the rainy season occurs during winter months and, if the season is a normal one, the first few feet of soil will be filled with moisture until it is depleted by root action. The quantity of moisture extracted by the plant prior to the irrigation season, when deducted from the seasonal consumptive use, provides a closer approach to the irrigation requirement, but the net seasonal irrigation requirement may not be determined accurately until losses in transmission through farm laterals, by percolation beyond the depth of root activity and by waste, are known. Upon these latter values are based the irrigation efficiency percentage. Federal and State investigations of the use of water for irrigation of crops in California have been conducted principally in the southern coastal areas, San Joaquin Valley, the delta area, and Sacramento (114) IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 115 Valley. In these areas, including also portions of the Mojave Desert in Antelope, Coachella and Imperial Valleys, are found the greatest percentage of irrigated lands in the State. Elsewhere, and particularly along the coast northerly from Los Angeles and in the extreme north- easterly portion including Lassen and Modoc Counties, there is a definite lack of information on irrigation of crops. In certain districts climate or soil appears to be best suited for pro- duction of specific crops although from year to year there may be a shift of crop from one valley to another. Thus, for a time, cotton was one of the principal crops of the Imperial Valley. Later a decline in the pro- duction of cotton in Imperial Valley was accompanied by a large increase of its gro^vth in southern San Joaquin Valley. Large acreages of south- ern California have climate and soil suitable for growing citrus and other subtropical fruits which cannot be grown elsewhere except in a few limited areas not affected by freezing. Alfalfa is one of the prin- cipal crops and is grown generally throughout the State. Rice is a product of Imperial, San Joaquin and Sacramento Valleys where it is grown on impermeable soils. Grain is a winter crop often grown on summer fallow rotation mthout irrigation but in years of rainfall defi- ciency better yields may be obtained by one or two irrigations. The irrigation requirements of crops are closely associated with the length of time between planting and maturity and the time of year in which they are produced, although there are other factors of importance. For most crops the principal growing period in which irrigation in Cali- fornia is required is from April through October, although transpira- tion loss and consumptive use are actiA^e for longer periods. Grain, being a winter crop, receives most of its moisture from winter rains. Beans are generally a short season crop, and in coastal areas where cli- mate is cool and moist, may be grown without irrigation although yields may be improved by use of additional water. In the interior valleys beans definitely require irrigation. Alfalfa has a long growing season. Because it grows rapidly following each of its several cuttings, it has a high irrigation requirement that does not differ greatly in the interior valleys. In the southern part of the State the coastal influence is a considerable factor in reducing the water requirements of crops, whereas in the interior valleys the warmer summers increase the requirements. In reports of experimental studies the absence of recorded yields is detrimental to the estimation of the irrigation requirements. SOUTH PACIFIC BASIN Citrus, avocados and walnuts are the principal crops in this area for which experimental studies have been conducted to determine the best use of water by irrigation. In northern San Diego County irriga- tion is characterized by a limited water supply often not exceeding 12 inches during the irrigation season, April to October. In the lower Santa Ana River Valley in Orange Count}' the supply is larger. An irrigation requirement of 18 inches appears to be applicable to both areas. For young citrus trees 12 to 14 years old an irrigation require- ment of 12 acre-inches per acre appears to be satisfactory. ]\Iature wal- nuts require 18 inches seasonally during the summer period. These areas are in the coastal region, where sandy loam soils predominate. A sum- mary of irrigation data applicable to the area appears in Table 68. 116 DIVISION OF WATER RESOURCES c> 1 2 (Ut3 ^ ' ^ — — O^-r-^-^-^rcrcici^iC^c^lc^) — corcCi^r]occcc<)'MC^c^»0 c — 1 § . ^^T-*-^-^ — ^„„l, t- ;£::c — :ci^^^l-I-I-r ' TO — ■ « o 3 d tC -i -i -j: 3C ^ m t^ t- 3-. CM e-) (M C^ (M TO — CJTO c^ic^e^TO cq iI:S cc ooousoggggg ojgog^o 'S'c p. 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" c OCQH = 03 a ill £ '■ he's Si 3 C g IRRIGATION REQUIREIMENTS OF CALIFORNIA CROPS 117 Less definite information exists regarding]: tlie reqnirements of citrus in the npper Santa Ana River Valley in Riverside and San Bernardino Counties, but the interior climate is warmer, humidity is less than along the coast, and the water use is increased. Without more definite infor- mation it seems safe to assume an irrifration requirement of 24 to 26 acre-inches per acre for mature citrus trees grown in this area under reasonably good methods of irrigation practice where water is delivered through pipe systems and efforts are made to avoid waste. Transpiration use of water by peaches grown on sand near Ontario amounted to 27.3 acre-inches per acre during the summer irrigation season and an additional 6.5 acre-inches during the winter months Octo- ber to April. This land was clean cultivated so that the winter los.s was principally because of evaporation from soil after rains. An irri- gation requirement of 31 acre-inches per acre has been estimated. Irri- gation water applied to deciduous fruits in the Beaumont area at eleva- tions of 2.500 to 3.000 feet depended entirely upon the quantity of water available and in some years the supply was deficient. Trees were in better shape with applications of 18 inches than when nine inches was applied. It may be assumed that 18 inches was the lowest irrigation requirement possible for adequate growth of the trees and satisfactory yields of fruit. In the Hemet area where the average elevation is about 1,000 feet lower than at Beaumont and the water supply is more plenti- ful. 30 acre-inches per acre was applied to apricots. This appears to be normal practice in the Hemet area. Consumptive use by alfalfa grown in San Fernando Valley amounted to 37.4 acre-inches per acre between April and October. Few data exist on the use of water by cover crops grown in citrus groves, but two cases may be cited from soil moisture records. In San Fernando Valley the transpiration use by trees and cover crop from November to ]\Iarch, inclusive, was 9.2 acre-inches per acre and in north- ern San Diego County the average for five groves was 10.4 inches. This loss does not include soil evaporation which depends upon the amount and distribution of rainfall during the winter months and in Southern California has been determined to be approximately one-half acre-inch per acre (13) after each rain storm. In general the least irrigation requirement for mature citrus, wal- nuts and avocados as based upon soil moisture studies in Southern Cali- fornia appears to be about 18 acre-inches per acre between April and October, inclusive, and the most from 24 to 26 acre-inches. Moisture received from rainfall, and irrigation water applied during early spring or late fall, will bring the total water requirement as distinguished from the irrigation requirement to approximately 30 acre-inches per acre annu- ally for the best production. GREAT BASIN DESERT AREA Table 69 shows a summary of some irrigation data applicable to the desert area of Southern California. The irrigation requirement of alfalfa in the Antelope Valley is estimated as 52 acre-inches per acre from April to October, inclusive. This estimate is based upon a com- ])arison with consumptive use values for alfalfa grown in San Fernando Valley. From records of the Imperial Irrigation District it is shown that the average depth of water delivered to 7,600 acres of alfalfa has 118 DIVISION OP WATER RESOURCES fe >- lU ^ rJl-fllosCOC •^ -^ g ■ -•« o "5- C^ ,-1 CO Til ■<)< lOrt a tti 1 (S ■u 3 6 — i(M to ■* lO r- 00 O e2^ ■^ ^^ CO CO CO CO CO ^* , .il^ «0 O o Irrig tior requii ment dept e §2 CO ■>i< a a 1 - i '3 o H o ■ •1 ; != m 1 2 ? Q) c^ 00 1 oo 1 q3 t- f^ « ■>i< 1 in 1 - 3 J > g g S-g rt fl-s S§l QQQOSSO P ^■si 1 c: 03 O 1 ■*o jd 22§ -a 1 i. ca 1 "o o O """ 1 •""S oo «300t-U5eO-H(M *2— ea o, cJoo>ra>nt^ ^i- ■■^ ■c -c i c c rt ^ s _o — o o >> 'o "D TO -o-o c a C S9 rf'TS Gj'^ " " c c c >.>.«(C « E E S>>S g g c ^ c: J jS>£ a 5 o t^ ■« o ^^ CS o. g >2.245-^ 2 S rt g 5^.^ !■ >■ >. 3? i capoopqa -< ■< HH UO 1— < 1 I IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 119 been 48 acre-inches per acre, but there is a possibility here that some additional water may have been received from existing high ground Avater. Date palms are heavy users of water and it has been shown by experiment (43) that the requirement for the trees is as much as 72 acre-inches per acre for a 12-month year in which 90.7 inches is applied. Coachella Vallej^ is the principal date producing area in the United States. Flax, grown in Imperial Valley, is a winter crop that is harvested in the spring or early summer and its irrigation requirement is less than that of crops growing during the warmer periods. The average depths of water applied in irrigation of flax groAvn in Imperial Valley is 25 acre- inches per acre. Pear trees in Antelope Valley, during years of rainfall deficiency, receive less water for irrigation than is to the best interest of the crop but in years of normal rainfall the water supply appears to be sufficient. It is estimated that 24 to 30 acre-inches per acre is a satisfactory irriga- tion requirement. SAN JOAQUIN VALLEY Lack of experimental studies prevents adequate summarization of the irrigation requirements of many of the crops grown in San Joaquin Valley. Cotton is an exception, as satisfactory information on its require- ments is available. Studies by the California Experiment Station indi- cate an irrigation requirement of 30 to 36 acre-inches per acre on sandy soil at the U. S. Cotton Field Station at Sh after and 34 inches on adobe soil on the west side of the valley, farther north. A summary of irri- gation data applicable to the San Joaquin Valley comprises Table 70. The best yields of alfalfa grown at Delhi were obtained \vith irriga- tions amounting to 42 acre-inches per acre, but six inches less water resulted in a decrease of one-half ton per acre. It is estimated that the best irrigation requirement lies between 36 and 42 acre-inches per acre applied during the months April to October. More irrigation results in less yield. Irrigated pastures are of increasing importance because of their expanding acreage and their large use of water for irrigation. No figures are available for an irrigation requirement but the average depth of water applied to 22 farms in Tulare County amounted to 76 acre-inches per acre. Soils were shallow and the number of irrigations were high. SACRAMENTO-SAN JOAQUIN DELTA Consumptive use of water data for the delta region are based mostly on tank and field experiments by the Division of Irrigation, in coopera- tion with the State Division of Water Resources, on both peat and sedi- mentary soils. These data have been adopted by the State Engineer for estimating total quantities of water required for irrigation of large areas in the vicinity of the Sacramento and San Joaquin Rivers. On account of high ground water in the delta and its upward recharge it is not possible to estimate the irrigation requirements within a reasonable degree of accuracy, and no attempt is made to do so for this area. Con- sumptive use varies with the crop and the length of the irrigating season. Alfalfa on sedimentary land in areas where roots do not reach to a water table would require irrigation amounting to 30 to 36 inches in depth, 120 DIVISION OP WATER RESOURCES a Q £ J,^ 2 " l-rt* -^ (^ Oi C •^eoeOOOGOOOOOOOO^O'— I M (N (M CS»(M ; o o o o o o CO :oo as 0>0'-:*'t-C30000Dt^lOCO ooocoooo ^ >> ^^ ^ ^ X ^ o.J3^ aa a q. a < S S < -ii -i: -ii -^ ^ S •^ fl^ 5000000100 3 ^ -Tt^ CO CO (N t rt ' =3 a c c a 3'^-o S S S S ^ >^ S o o o=:=:z:i:=: »- ii os O O O >> 1 c ;■& ;c ! = , c ) b 1 « ! c ,'C 1 2 c c * ; ;J 1 1* a> 1 * Q J o O 2 c C c- L. I SJ « rt S !5 S Sj° § rt,,?^ rt a rt ffl ^c-O 122 DIVISION OF WATER RESOURCES but these conditions are not usually found on the low-lying delta lands. In the Contra Costa Irrigation District where irrigation requirements are noticeably less than elsewhere, possibly because of poor drainage conditions, 20 inches of water is applied for irrigation of alfalfa. Consumptive use by crops varies from 14.4 acre-inches per acre for celery to 32.3 acre-inches for asparagus which has a longer growing sea- son. Con>sumptive use for other crops lies between these values as is shown in a summary of irrigation data applicable to the delta area listed in Table 71. The values presented are for the growing season of each separate crop, but consumptive use occurs from the same area before and after the crop is planted and harvested because of the use of water by considerable weed growth that flourishes by reason of moisture sup- plied by high ground water levels. SACRAMENTO VALLEY Irrigation investigations in the Sacramento Valley at the Univer- sity Farm and elsewhere, under the supervision of the California Agri- cultural Experiment Station, have included such crops as watermelons, alfalfa, grains, and rice, and were made for the purpose of determining the duty of water and the methods of applying it to obtain maximum returns. Irrigation requirements were obtained only through correla- tion with maximum yields. On this basis seven to eight inches of irriga- tion water applied to watermelons produced 69 pounds of fruit per plant, a greater yield than was obtained from other irrigation treatments. Likewise, maximum yields of alfalfa were obtained with 30 to 36 acre-inches of irrigation water for several soil types in different parts of the Sacramento Valley. These and other values are listed in Table 72. For small grains, as barley, wheat and oats, grown on sandy loam soil, the irrigation requirement is dependent upon the amount and distri- bution of winter rainfall. In years of normal rainfall, about 17 inches, normally distributed, grains may be grown without irrigation. In years of deficient rainfall normal yields may be obtained by preirrigation and in years of heavy rainfall irrigation may result in a decrease in yield. In drouth years tAvo irrigations of four to six acre-inches per acre should produce satisfactory yields if properly distributed. On the basis of these investigations it may be assumed that the irrigation requirement of grains in the Sacramento Valley varies from zero to 12 acre-inches per acre. Corn grown for ensilage is a summer crop and needs irrigation regardless of the amount of winter rains, but investigations show that better yield are obtained in years of abundant rainfall. In two studies each applying 10.5 acre-inches of water per acre, the yield was 7.4 tons in a year of deficient rain and 10.4 tons in a year of above normal rain- fall. It appears safe to assume that the irrigation requirement is in the neighborhood of 12 acre-inches per acre for the Sacramento Valley. Rice requires a large amount of water for its production as the fields are flooded during a part of the growing season. Losses occur by evapo- ration and seepage. Considerably more water is applied to the field than is actually consumed by the crop, as in addition to the actual crop use water is drained from the flooded field prior to harvest. In general, it appears that the best yields are obtained by a net irrigation require- ment of about 60 acre-inches per acre. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 123 \o'3 a o. -3 i a? CC QOOC 30 OO - . - - CO NWC^ C^ ; a; c; cs CO CC ro CO coi:ot'*aoooooooosciOsa60000»-H.-ic«cieo^*^''^ 3COCOCOCOCOCO— ' — — ■^^— '-^'-' — -J'-^ — ^-— '^^^^ cccoeococoeo'«-''»'«'«'*»*°'*''*»"' -3 o o o o o : = =: O O-^ i i =^ : -T7 — L_, c_, I— I rt rj Tji'r^^^xn ^X^p2iXi,^P^X,X,X^Xl ''-^CQCOCOCVICO'MO'" ■< (N ec CO TT TJ« 0005C>-OOCOC^QOOOCOOOOOOOOiOCO:0«Dt^eO-<*< eocccoc^c^co^H,-.e £ E S H a s cs a _c_o_o_o 5 = 3 _=^p^^. =^=555=^>i>>>i>.s; ^.S^ E a e a = c = -°^°° = a c :: c^ ^ a-r: a o a a a a a a a a a^ "2 -3 -g — ' >.— ' >ll^a)oo"a■a■a-Oooo^ao>>>^'3>^ ^ ■- —Ji^;ii aflccaaccccccGsaasa <2>5i2.2.2>>>>>>. sag a s3 a SSSESSE3H _ ■g'lg'I'I'I'Ig'E'EE'e e III a'H'5 '" ~ a S o ■s Jl^ c -3 13 a a J a 3 fi ^ ^ b« a 3 H S" ft kM ■?^ c > q u M "o i: ^ g r^ -^ c- ^ a c H M iS LITERATURE CITED (1) Adams, Frank 1915. Progress Report of Cooperative Investigations in California, 1912-1914. California Department of Engineering Bulletin No. 1, 74 pp., illus. (2) Adams, Frank, Robertson, Ralph D., Beckett, Samuel H., Hutchins, Wells A., and Israelsen, O. W. 1917. Investigations of Economical Duty of Water for Alfalfa in Sacramento Valley, California, 1910-1915. California Department of Engineering Bulletin No. 3, 78 pp., illus. (3) Adams, Frank 1920. Rice Irrigation Measurements and Experiments in Sacramento Valley, 1914-1919. University of California Experiment Station Bulletin No. 325, pp. 44-68. (4) Adams, Frank, Veihmeyer, F. J., and Brown, Lloyd 1942. Cotton Irrigation Investigations in San Joaquin Valley, California, 1926 to 1935. University of California Agricultural Experiment Station Bul- letin No. 668, 93 pp., illus. (5) Althouse, Irvin H. 1942. Report on the Water Requirements of Tulare County, California, as Related to the Central Valley Project. 127 pp., mimeo. (6) Bailey, Paul 1923. Irrigation Requirements of California Lands. California Department of Public Works, Division of Engineering and Irrigation Bulletin No. 6, 196 pp. (7) Batcheler, L. D. 1936. Walnut Culture in California. University of California Agricultural Experiment Station Bulletin No. 379, 109 pp., illus. (8) Beckett, S. H., and Robertson, R. D. 1917. The Economical Irrigation of Alfalfa in Sacramento Valley. University of California Agricultural Experiment Station Bulletin No. 280, pp. 271-294. (9) Beckett, S. H., and Huberty, M. R. 1928. Irrigation Investigations with Field Crops at Davis and at Delhi, Cali- fornia, 1909-25. University of California Agricultural Experiment Sta- tion Bulletin No. 450, 24 pp., illus. (10) Beckett, S. H. 1930. Irrigation Requirements in Southern California. California Department of Public Works, Division of Water Resources, Bulletin No. 32, pp. 57-60. (11) Beckett, S. H., Blaney, Harry F., and Taylor, Colin A. 1930. Irrigation Water Requirement Studies of Citrus and Avocado Trees in San Diego County, California, 1926 and 1927. University of California Agricultural Experiment Station Bulletin No. 489, 51 pp. (12) Beckett, S. H., and Dunshee, Carroll F. 1932. Water Requirements of Cotton on Sandy Loam Soils in Southern San Joaquin Valley. University of California Agricultural Experiment Sta- tion Bulletin No. 537, 48 pp., illus. (13) Blaney, Harry F., Taylor, C. A., and Young. A. A. 1930. Rainfall Penetration and Consumptive Use of Water in the Santa Ana Valley and Coastal Plain. California Department of Public Works, Divi- sion of Water Resources, Bulletin No. 33, 162 pp., illus. (14) Blaney, Harry F., and Ewing, Paul A. 1935. Utilization of the Waters of Mojave River, California. United States Department of Agriculture, Division of Irrigation, 142 pp., mimeo. (124) IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 125 (1")) P.Ianoy. Harry F., and Stockwi'll. Hoiikm- J. 1040. Second Progress Report on Cooperative Re.searcli Studies on Water Ionization, San Fernando Valley, California. Irrigation Season of 1940. United States Department of Agriculture, Division of Irrigation, Soil Conservation Service. Unpublished. (IG) Blaney, Harry F. 1945. Estimated Consumptive Use and Irrigation Re(|uirements for Alfalfa in Antelope Valley, California, Based on Climatological Data. Unpublished. (17) Blote, Martin H. 1943. Report of Sacramento-San Joaquin Water Supervision for Year 1942. California Department of Public Works, 299 pp., mimeo. (18) Burlingame, Burt B. 1930. Second Annual Summary, Grape Efficiency Study, Kern County, Cali- fornia. University of California Agricultural Extension Service, 12 pp., mimeo. (19) Christiansen, J. E. 1942. Irrigation by Sprinkling. University of California Agricultural Experi- ment Station, Bulletin No. 670, 124 pp., illus. (20) Conkling, Harold (Chapter VI, Rainfall Penetration, by Blaney, Harry F.) 1933. Ventura County Investigations. California Department of Public Works, Division of Water Resources, Bulletin No. 46, 244 pp.. illus. with maps. (21) Division of Operation and Maintenance 1939. Farmer's Irrigation Guide. United States Department of the Interior, Bureau of Reclamation and Conservation, Bulletin No. 2, 40 pp., illus. (22) Doneen, L. D., Porter, D. R., and MacGillivray, John H. 1939. Irrigation Studies with Watermelons. American Society of Horticul- tural Science, Proc. 37, pp. 821-824. (23) Dunshee, Carroll F. 1928. Rice Experiments in Sacramento Valley, 1922-1927. University of Cali- fornia Agricultural Experiment Station Bulletin No. 454, 14 pp., illus. (24) Ernst, F. H. 1932. First Annual Report Alfalfa Enterprise Efficiency Study, Los Angeles County. University of California Agricultural Extension Service, 14 pp., mimeo. (25) Etcheverry, B. A., Haehl, H. L., Herrmann, F. C, and Wiley, A. J. 1928. Kern River Water Storage District. Report to State Engineer on Feasi- bility of Project. Vol. 1, Pt. II. (26) Ewing, Paul A. 1939. The Agricultural Situation in San Fernando Valley, California. Bureau of Agricultural Engineering, Division of Irrigation, 128 pp., illus., offset. (27) Ewing, Paul A. 1944. Water Requirements of San Joaquin Valley, United States Department of Agriculture S. C. S., Division of Irrigation, 38 pp. Unpublished. (28) Fortier, Samuel 1930. Irrigation Practices in Growing Alfalfa. United States Department of Agriculture, F. B. No. 1G30, 26 pp., illus. (29) Fortier, Samuel, and Young, Arthur A. 1933. Irrigation Requirements of Arid and Semiarid Lands of the Pacific Slope Basins. United States Department of Agriculture, Technical Bulletin No. 379, 66 pp. (30) Gillette, A. F. 1940. Tomato Production Costs with Five-year Summaries. 1936-1940, Los Angeles County. University of California Agricultural Extension Serv- ice, 9 pp., mimeo. (31) Harding, S. T. 1920. Water Resources of the Kern River and Adjacent Streams and Their Utilization. California State Department of Engineering, Bulletin No. 9. 126 DIVISION OP WATER RESOURCES (32) Harding, S. T. !1922. Water Resources of Tulare County and Their Utilization. California Department of Public Works, Division of Engineering and Irrigation, Bulletin No. 3, 155 pp., illus. (33) Hendrickson, A. H., Veihmeyer, F. J., and Nichols, P. F. 1929. I. Irrigation Experiments with Peaches in California. II. Canning Quality of Irrigated Peaches. University of California Agricultural Experiment Station Bulletin No. 479, 63 pp., illus. (34) Jones, Burle J., and Brown, J. B. 1942. Irrigated Pastures in California. University of California Agricultural Extension Service Circular No. 125, 47 pp., illus. (35) Kearney, T. H., and Scofield, C. S. 1936. The Choice of Crops for Saline Land. United States Department of Agriculture Circular No. 404, 24 pp. (36) Kocher, A. E., and Harper, W. G. 1928. Soil Survey of the Coachella Valley Area, California. United States Department of Agriculture, Bureau of Soils, Series 1923, No. 16. (37) Lewis, M. R. 1943. Practical Irrigation. United States Department of Agriculture, Farm Bulletin No. 1922, 69 pp., illus. (38) MacGillivray, John H., and Doneen, L. D. 1942. Soil Moisture Conditions as Related to the Irrigation of Truck Crops on Mineral Soils. American Society of Horticultural Science Proc. No. 40, pp. 483-492. (39) MacGillivray, John H., Shultis Arthur, Michelbacher, A. B., Minges, P. A., and Doneen, L. D. 1943. Labor and Material Requirements of California Vegetables. University of California Experiment Station Pamphlet, 15 pp. (40) Magistad, O. C, and Christiansen, J. E. 1944. Saline Soils, Their Nature and Management. United States Department of Agriculture Circular No. 707, 32 pp., illus. (41) Matthew, Raymond 1931. Variation and Control of Salinity in Sacramento-San Joaquin Delta and Upper San Francisco Bay. California Department of Public Works, Division of Water Resources, Bulletin No. 27, 440 pp., illus. (42) Meikle, R. V., and Adams, F. 1938. Water Charges, Central Valley Project. United States Department of the Interior, Bureau of Reclamation. (43) Pillsbury, Arthur F. 1941. Observations on the Use of Irrigation Water in Coachella Valley, Cali- fornia. University of California Agricultural Experiment Station Bul- letin No. 649, 48 pp., illus. (44) Pillsbury, Arthur F., Compton, O. C, and Picker, W. E. 1944. Irrigation Water Requirements of Citrus ift the South Coastal Basin of California. University of California Agricultural Experiment Station Bulletin No. 686, 19 pp. (45) Bobbins, W. W., and Price, Charles 1936. Sugar Beet Production in California. University of California Agricul- tural Extension Service Circular No. 95, 78 pp., illus. (46) Robertson, Ralph D. 1917. Irrigation of Rice in California. University of California Agricultural Experiment Station Bulletin No. 279, pp. 254-270. (47) Scofield, Carl S., and Wilcox, L. V. 1931. Boron in Irrigation Waters. United States Department of Agriculture Technical Bulletin No. 264, 65 pp. IRRIGATION REQUIREMENTS OF CALIFORNIA CROPS 127 (48) Sdby, H. E. 1944. San Joaquin Valloy Water InvoslifAations. Af^ricultural Asiiocts. A Report to the War Department, United States Ensineer Office, Sacra- mento District. United States Department of Asriculture. Bureau of Agricultural Economics, 2.^!) pp., mimeo. (49) Selby, H. E. 1944. Sacramento Valley 'N^'ater Investigations, Agricultural Aspects. A Report to the War Department, United States Engineer Office, Sacra- mento District. United States Department of Agriculture. Bureau of Agricultural Economics, 109 pp., mimeo. (50) Shultis, Arthur 1939. Riverside County Apricot Enterprise Efficiency Study. Second Annual Report, Crop Year, 1939. T'niversity of California Agricultural Exten- sion Service in Cooperation with Hemet Valley Apricot Growers, 10 pp., mimeo. (51) Shultis, Arthur 1940. Riverside County Apricot Enterprise Efficiency Study. Third Annual Report, Crop Year, 1940. University of California Agricultural Exten- sion Service in Cooperation with Hemet Valley Apricot Growers, 11 pp., mimeo. (52) Stafford, Harlowe M. 1930. Report of Sacramento-San Joaquin Water Supervisor. California Depart- ment of Public Works, Division of Water Resources, Bulletin No. 23, 413 pp., illus. (53) Storie, R. Earl 1933. An Index for Rating the Agricultural Value of Soils. University of California Agricultural Experiment Station Bulletin No. 556, 44 pp., illus. (54) Sullivan, Wallace, Landerman. H. Lee, and Carpenter, G. A. 1940. Flax-Management Practices in Imperial Valley, with W^orld Statistics. University of California Agricultural Experiment Station Bulletin No. 641, 38 pp. (55) Sullivan, A. B. 1941. Memorandum Report — Irrigation Investigations of Sacramento Valley Crops. United States Bureau of Reclamation, Sacramento Valley Inves- tigations. Unpublished. (56) Taylor, C. A. 1941. Irrigation Problems in Citrus Orchards. United States Department of Agriculture, Farmers' Bulletin No. 1876, 34 pp. illus. (57) Turville, E. S., Hitch, Donald L., et al. 1944. Irrigating in Arizona. University of Arizona Agricultural Extension Service Circular No. 123, 60 pp., illus. (58) United States Department of Commerce, Bureau of the Census 1940. Sixteenth Census of the United States, 1940. (59) United States Department of Commerce, Weather Bureau 1944. Climatological Data, California Section. (60) United States Department of the Interior 1939. Farmers' Irrigation Guide. Bureau of Reclamation, 40 pp., illus. (61) A'aile, Roland S. 1924. A Survey of Orchard Practices in the Citrus Industry of Southern Cali- fornia. University of California Agricultural Experiment Station Bul- letin No. 374, 40 pp. (62) Veihmeyer, F. J., and Hendrickson, A. H. 1938. Essentials of Irrigation and Cultivation of Orchards. University of California Agricultural Extension Service Circular No. 50, 23 pp. (63) Vista Irrigation District, California 1937 to 1943. Annual Reports and Financial Statement. 9—53207 128 DIVISION OF WATER RESOURCES (64) Waddell, T. B. 1931. Sacrameuto River Basin. California Department of Public Works Bul- letin No. 26, 583 pp., illus. (65) AVahlberg, Harold E. 1938. Walnut Production Co.st Analysis Orange County, California. Ten-Year Summary, 1929-1938. University of California Agricultural Extension Service, 17 pp., mimeo. (66) Water Utilization Planning Service 1943. A Wartime Water Facilities Plan, Southern Portion of Central Valley, California. United States Department of Agriculture, Bureau of Agri- cultural Economics. (67) Weaver, John E. 1926. Root Developments of Field Crops. McGraw-Hill Book Co.. New York, 291 pp., illus. (68) Weir, Walter, and Storie, R. Earl 1936. A Rating of California Soils. University of California Agricultural Experiment Station Bulletin No. 599, 157 pp., with maps. (69) Winright, George L. 1943. Alfalfa Production, Cost and Efficiency Analysis, Imperial County. University of California Agricultural Extension Service, 5 pp., mimeo. (70) Wooley, W. F. 1943. Financial Statement of Secretary and Annual Report of Chief Engineer. West Stanislaus Irrigation District, 34 pp. (71) Worrell. Ralph L. 1940. Fifth Annual Study of Enterprise Efficiency Study — Irrigated Pastures for Tulare County with Five-Year Summary of Results, 10 pp., mimeo. (72) Young, Arthur A., Ewing, Paul A., and Blaney, Harry F. 1941. Utilization of the Waters of Beaumont Plains and San Jacinto Basin, California. United States Department of Agriculture, Soil Conservation Service, Division of Irrigation, 336 pp., mimeo. PUBLICATIONS DIVISION OF WATER RESOURCES PUBLICATIONS OF THE DIVISION OF WATER RESOURCES DEPARTMENT OF PUBLIC WORKS STATE OF CALIFORNIA When the Department of Public Works was created in July, 1921, the State Water Commission was succeeded by the Division of Water Rights, and the Depart- ment of Engineering was succeeded by the Division of Engineering and Irrigation in all duties except those pertaining to State Architect. Both the Division of Water Rights and the Division of Engineering and Irrigation functioned until August, 1929, when they were consolidated to form the Division of Water Resources. The Water Project Authority was created by the Central Valley Project Act of 1933. STATE WATER COMMISSION *First Report, State Water Commission, March 24 to November 1, 1912. *Seconcl Report, State Water Commission, November 1, 1912, to April 1, 1914. *Biennial Report, State Water Commission, Marcli 1, 1915, to December 1, 1916. *Biennial Report, State Water Commission, December 1, 191G, to September 1, 1918. 'Biennial Report, State Water Commission, September 1, 1918, to September 1, 1920. DIVISION OF WATER RIGHTS *Bulletin No. 1 — Hydrographic Investigation of San Joaquin River, 1920-1923. 'Bulletin No. 2 — Kings River Investigation, "Water Master's Report, 1918-1923. 'Bulletin No. 3 — Proceedings First Sacramento-San Joaquin River Problems Confer- ence, 1924. 'Bulletin No. 4 — Proceedings Second Sacraniento-San Joaquin River Problems Con- ference, and Water Supervisors' Report, 1924. No. 5 — San Gabriel Investigation — Basic Data, 1923-1926. No. 6 — San Gabriel Investigation — Basic Data, 1926-19 2S. No. 7 — San Gabriel Investigation — Analysis and Conclusions, 1929. Report, Division of Water Rights, 1920-1922. Report, Division of Water Rights, 1922-1924. Report, Division of Water Rights, 1924-1926. RciJort, Division of Water Rights, 1926-1928. 'Bulletin Bulletin Bulletin 'Biennial 'Biennial Biennial Biennial 'Bulletin 'Bulletin Bulletin •Bulletin 'Bulletin 'Bulletin Bulletin 'Bulletin Bulletin 'Biennial 'Biennial 'Biennial 'Biennial 'Biennial 'Biennial 'Biennial IncI 'Bulletin 'Bulletin Bulletin Bulletin Bulletin Bulletin 'Bulletin 'Bulletin Bulletin 'Bulletin Bulletin Bulletin DEPARTMENT OF ENGINEERING No. 1 — Cooijerative Irrigation Investigations in California, 1912-1914. No. 2 — Irrigation Districts in California, 1887-1915. No. 3 — Investigations of Economic Duty of Water for Alfalfa in Sacramento Valley, California, 1915 No. 4 — Preliminary Report on Conservation and Control of Flood Waters in Coachella Valley, California, 1917. No. 5 — Report on the Utilization of Mojave River for Irrigation in Victor Valley, California, 1918. No. 6 — California Irrigation District Laws, 1919 (now^ obsolete). No. 7 — Use of Water from Kings River, California, 1918. No. S — Flood Problems of the Calaveras River, 1919. No. 9 — Water Resources of Kern River and Adjacent Streams and Their Utilization, 1920. Report, Department of Engineering, 1907-1908. Report, Department of Engineering, 1908-1910. Report, Department of Engineering, 1910-1912. Report, Department of Engineering, 1912-1914. Report, Department of Engineering, 1914-1916. Report, Department of Engineering, 1916-1918. Report, Department of Engineering, 1918-1920. DIVISION OF WATER RESOURCES Reports of the Former Division of Engineering and Irrigation — California Irrigation District Laws, 1921 (now obsolete). — Formation of Irrigation Districts, Issuance of Bonds, etc., 1922. — Water Resources of Tulare County and Their Utilization, 1922. — Water Resources of California, 1923. — Flow in California Streams, 1923. — Irrigation Recjuirements of California Lands, 1923. — California Irrigation District Laws, 1923 (now obsolete). — Cost of Water to Irrigators in California, 1925. — Supplemental Report on Water Resources of California, 1925. — California Irrigation District Laws, 1925 (now obsolete). — Ground Water Resources of Southern San Joaquin Valley, 1927. Summary Report on the Water Resources of California and a Coor- dinated Plan for Their Development, 1927. uding No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. No. No. 10 No. 11 No. 12 * Reports and Bullelins out nf print. State Library at Sacramento, California. Tliese may be borrowed by your local lil)rary from tlie California ( i:^o ) PUBLIC ATIOXS — DIVISION OF WATER RESOURCES 131 Bulletin Xo. 10 — The Development of the Upper Sacramento River, containing U. S. R. S. Cooperative Report on Iron Canyon Project, 1927. Uulletin Xo. 14 — The Control of FloocLs by Reserxoirs, 192S. "Bulletin No. 18 — California Irrisation Di.strict Laws, 1927, Revision. ♦Bulletin No. 18-A — California Irrig-ation Di.strict Laws, 1929 Revision. Bulletin Xo. IS-B — California Irrigation District Laws, 1931 Revision. Bulletin Xo. Is-C — California Irrigation District Laws, 1933 Revision. Bulletin Xo. IS-D — California Irrigation District Laws, 1935 Revision. Bulletin Xo. IS-E — California Irrigation Di.strict Laws, 1937 Revision. ♦Bulletin Xu. l^-F — Califurnia Irrigation District Laws, 1939 Revision. Bulletin Xo. IS-G — Califurnia Irrigation District Laws, 1941 Revision. *Bullt:-tin Xo. IS-H — Water Code, Divisions 10 and 11, Irrigation District Laws 1943. Bulletin Xo. 19 — Santa Ana Investigation, Flood Control and Conservation (with packet of maps), 192S. Bulletin Xo. 20— Kennett Reservoir Development, an Analysis of Methods and E.xtent of Financing by Electric Power Revenue, 1929. Bulletin X'o. 21-^Irrigation Districts in California, 1929. Bulletin Xo. 21-A — Report on Irrigation Districts in California for the year 1929. Bulletin Xo. 21-B — Report on Irrigation Districts in California for the year 1930. Bulletin Xo. 21-C — Report on Irrigation Districts in California for the year 1931. *Bulletin Xo. 21-D — Report on Irrigation Districts in California for the year 1932. Bulletin Xo. 21-E — Report on Irrigation Districts in California for the year 1933. Bulletin Xo. 21-F — Report on Irrigation Districts in California for the year 1934. Bulletin Xo. 21-G — Report on Irrigation Districts in California for the year 1935. Bulletin X'o. 21-H — Report on Irrigation Districts in California for the year 1936. Biilletin Xo. 21-1 — Report on Irrigation Districts in California for the year 1937. Bulletin Xo. 21-.I — Report on Irrigation Districts in California for the year 1938. Bulletin X'o. 21-K — Report on Irrigation Districts in California for the year 1939. Bulletin Xo. 21-L — Report on Irrigation Districts in California for the year 1940. Bulletin Xo. 21-iI — Report on Irrigation Districts in California for the year 1941. Bulletin Xo. 21-X" — Report on Irrigation Districts in California for the year 1942. Bulletin X'o. 21-0 — Report on Irrigation Districts in California for the year 1943. Bulletin Xo. 22 — Report on Salt Water Barrier (two volumes). 1929. Bulletin X'o. 23 — Report on Sacramento-San Joaquin Water Supervisor, 1924-1928. Bulletin Xo. 24 — A Proposed Major Development on American River, 1929. Bulletin X'o. 2-5 — Report to Legislature of 1931 on State Water Plan, 1930. Bulletin Xo. 26 — Sacramento River Basin, 1931. Bulletin X'o. 27 — Variation and Control of Salinity in Sacramento-San Joaquin Delta and Upper San Francisco Bay, 1931. Bulletin Xo. 2S — Economic Aspects of a Salt Water Barrier Below Confluence of Sacramento and San Joaquin Rivers, 1931. Bulletin Xo. 2S-A — Industrial Survey of Upper San Francisco Bay Area, 1930. Bulletin Xo. 29 — San Joaquin River Basin, 1931. Bulletin X'o. 31 — Santa Ana River Basin, 1930. Bulletin Xo. .^2 — South Coastal Basin, a Cooperative Symposium, 1930. Bulletin Xo. 33 — Rainfall Penetration and Consumptive Use of Water in Santa Ana River Valley and Coastal Plain, 1930. Bulletin X'o. 34 — Permissible Annual Charges for Irrigation Water in Upper San Joaquin Valley, 19 30. Bulletin Xo. 3.3 — Permissible Economic Rate of Irrigation Development in California, 1930. Bulletin X'o. 3t5 — Cost of Irrigation Water in California, 1930. Bulletin Xo. 37 — Financial and General Data Pertaining to Irrigation, Reclamation and Other Public Districts in California, 1930. Bulletin X'o. 3S — Report of Kings River Water Master for tlie Period 1918-1930. Bulletin Xo. 39 — South Coastal Basin Investigation, Records of Ground Water Levels at Wells, 1932. Bulletin X'o. 39-A — Records of Ground Water Levels at Wells for the Year 1932, Seasonal Precipitation Records to and including 1931-32. (Mimeographed.) Bulletin Xo. 39-B — Records of Ground Water Levels at Wells for the Year 1933, Precipitation Records for the Season 1932-33. (Mimeographed.) Bulletin X'o. 39-C — Records of Ground Water Levels at Wells for the Year 1934, Precipitation Records for the Season 1933-34. (Mimeographed.) Bulletin Xo. 39-D — Records of Ground Water Levels at Wells for the Year 1935, Precipitation Records for the Season 1934-35. (Mimeographed.) Bulletin Xo. 39-E — Records of Ground Water Levels at Wells for the Year 1936, Precipitation Records for the Season 1935-36. (Mimeographed.) Bulletin X'o. 39-F — Records of Ground Water Levels at Wells for the Year 1937, Precipitation Records for the Season 1936-37. (Mimeographed.) Bulletin Xo. 39-G — Records of Ground Water Levels at Wells for the Year 1938, Precipitation Records for the Sea.son 1937-38. (Mimeographed.) Bulletin X'o. 39-H — Records of Ground Water Levels at Wells for the Year 1939, Precipitation Records for the Season 1938-39. (Mimeographed.) Bulletin Xo. 39-1 — Records of Ground Water Levels at Wells for the Year 1940, Precipitation Records for the St-ason 1939-40. (Mimeographed.) 'Bulletin Xo. 39-J — Records of Ground Water Levels at Wells for the year 1941; including San Jacinto and Antelope Valleys from beginning of record. Precipitation records for the Season 1940-41. Bulletin Xo. 30-K — Records of Ground Water Levels at Wells for the Year 1942. Precipitation Records for the Season 1941-42. Bulletin Xo. :;9-L — Records of Ground Water Levels at Wells for the Year 1943. Precipitation Records for the Season 1942-43. * Reports .iiid Bulletins out of print. Tiie^i- may he borrowed by your local library from the California State Library at Sacramento. California. 132 PUBLICATIONS — DIVISION' OF WATER RESOURCES Bulletin No. 40 — South Coastal Basin Investigation, Quality of Irrigation Waters, 1933. ♦Bulletin No. 40-A — South Coastal Basin Investigation, Detailed Analyses Showing Quality of Ii-rigation Waters, 1933. Bulletin No. 41 — Pit River Investigation, 1933. Bulletin No. 42 — Santa Clara Investigation, 1933. Bulletin No. 43- — Value and Cost of Water for Irrigation in Coastal Plain of Southern California, 1933. Bulletin No. 44- — Water Losses Lender Natural Conditions from Wet Area.s in Southern California, 1933. Bulletin No. 45 — South Coastal Basin Investigation, Geology and Ground Water Storage Capacity of Valley Fill, 1934. Bulletin No. 46 — Ventura County Investigation, 1933. Bulletin No. 46-A — Ventura County Investigation, Basic Data for the Pc-riod 1927 to 1932, inclusive. (Mimeographed.) Bulletin No. 47 — Mojave River Investigation, 1934. (Mimeographed.) ♦Bulletin No. 4 8 — San Diego County Investigation, 1935. (Mimeographed.) Bulletin No. 4S-A — San Luis Rey River Investigation, 193G. (Mimeographed.) Bulletin No. 49 — Kaweah River — Flows, Diversions and Service Area.-^, 1940. Bulletin No. 50 — Use of Water by Native Vegetation, 1942. Bulletin No. 51 — Irrigation Requirements of California Crops, 1945. Biennial Report, Division of Engineering and Irrigation, 1920-1922. Biennial Report, Division of Engineering and Irrigation, 1922-1924. Biennial Report, Division of Engineering and Irrigation, 1924-1926. Biennial Report, Division of Engineering and Irrigation, 1926-1928. PAMPHLETS Dams Under Jurisdiction of the State of California, 1941. Water Code, 1943. W'ater Rights, Divisions 1, 2 and 4 of Water Code, 1943. Supervision of Dams, Division 3 of Water Code, 1943. State Water Plan, Authorities and Boards, Division 6 of Water Code, 1943. California Administrative Code, Title 23, Waters. Rules and Regulations Pertaining to Supervision of Dams in California, 1946. Rules, Regulations and Information Pertaining to Appropriation of Water in California, 1946. Rules, Regulations and Information Pertaining to Determination Rights to the Use of Water in California, 1946. Rules and Regulations Pertaining to Protests and Hearings, 1946. COOPERATIVE AND MISCELLANEOUS REPORTS *Report of the Conservation Commission of California, 1912. ♦Irrigation Resources of California and Their Utilization (Bull. 251. ufRce of Exp. U. S. D. A.), 1913. *Report, State Water Problems (Conference, November 25, 1916. ♦Report on Pit River Ba'^in, April, 1915. ♦Report on Lower Pit River Project, July, 1915. ♦Report on Iron Canyon Project, California, 1914. ♦Report on Iron Canyon Project, California, May, 1920. ♦Sacramento Flood Control Project (Revised Plans), 1925. Report of Commission Appointed to Investigate (Causes Leading to the Failure of St. Francis Dam, 1928. Report of the California Joint Federal-State Water Resources Commission, 1930. Conclusions and Recommendations of the Report of the California Irrigation and Reclamation Financing and Refinancing Commission, 1930. ♦Report of California "Water Resources Commission to the Governor of California on State Water Plan, 1932. ♦Booklet of Information on California and the State Water Plan Prepared for United States House of Representatives' Subconimittee on Appropria- tions, 1931. ♦Bulletin on Great Central Valley Project of State Water Plan of California Prepared for United States Senate Committee on Irrigation and Reclama- tion, 1932. WATER PROJECT AUTHORITY Bulletin No. 1 — Publicly Operated Electric Utilities in Northern California, 1941. ♦Report on Kennett Power System of Central Valley Project, 1935. ♦Report on the Programming of Additional Electric Power Facilities to Provide for Absorption of Output of Shasta Power Plant in Northern California Market, 1938. The Story of the Central Valley Project of California, 1940. ♦Electric Power Features of the State Water Plan in the Great Central Vallev Basin of California, 1941. Auxiliary Electric Power Facilities Required for Central Valley Project. 1942. ♦ Reports and Bulletins out of print. These may be borrowed by your local libiary from the California State Library at Sacramento, California. 53207 1-46 2M ill t( " ^ ^ h -' '^•>'*■»^ LANDS WITH IRRIGATION SERVICE FROM KAWEAH RIVER 4^ THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW i ^ BOOKS REQUESTED BY ANOTHER BORROWER ARE SUBJECT TO IMMEDIATE RECALL -y t V ^- i 100^ DEC 2 19«S PHYS SCI UBRATTi u: II D1 M APR 5 199; A JUfj 18 1993 ^ Ptfecll« FEB 2 6 1930 OCT Q 1993 RECEIVED FEb 1 ■• ^:.j06I1j PHY SC! LIBRARY PHYSICAL SCS. LIBRARY NOV 12 199 NOV 8 199G«^i; W zd 1999 R[ CO RECEIVED 'MAY 2 'i 1999 RECEIVED ,, . PSL Nu LlBRAftY,S0NiyBRS1tY'OF CALIFORNIA, DAVIS Book Slip-Series 458 PHYSICAL SCIENCES LIBRARY •* -^'■^^•-^i LIBRARY UNIVERSITY OF CALIFORNIA DAVIS 110990