CALIFORNIA AGRICULTURAL EXTENSION SERVICE CIRCULAR 73 MARCH, 1933 The Contour Check Method of Orchard Irrigation J. B. BROWN Cooperative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, and June 30, 1914. B. H. Crocheron, Director, California Agricultural Extension Service. THE COLLEGE OF AGRICULTURE UNIVERSITY OF CALIFORNIA BERKELEY, CALIFORNIA Digitized by the Internet Archive in 2011 with funding from University of California, Davis Libraries http://www.archive.org/details/contourcheckmeth73brow The Contour Check Method of Orchard Irrigation J. B. BEOWNi During the past few years, there has been an increasing interest in the irrigation of orchards by the contour check method. In the Yuba City and Gridley sections, the majority of the orchards are irrigated by this method at the present time, while in the Hollister and San Jose sections, its use is common and is increasing. The use of this method is slowly extending to other counties in the state. The use of contour checks as a method of irrigation is not new, but its application to orchard irrigation where the positions of contour levees are permanently marked by means of various painting schemes is a de- velopment of recent years. CONDITIONS FOR CONTOUR CHECK IRRIGATION The contour check method may be used in place of any of the common systems of flood irrigation, such as single basins, square checks contain- ing a number of trees, or strip checks, provided the available head of water is sufficient to fill the contour basins without excessive percolation during the process of filling. Contour checks usually contain several trees in each basin and cannot be economically irrigated with small streams, especially on sandy soils. With streams of 50 to 300 gallons per minute, single-tree basins or furrow distribution would give a more uniform application of water than the contour check method. With heads of sufficient size, the method may be used in furrow-irri- gated orchards where the grower thinks that the trees will not be dam- aged by water coming in contact with the trunks and where the grade does not exceed 2% feet per 100 feet of length. It is not applicable to foothill orchards where furrows are run down the steep grades. For new plantings in such locations, the orchard should be planted on grade con- tours and irrigated by means of contour furrows. 2 There is considerable 1 Extension Specialist in Irrigation. 2 Huberty, M. E., and J. B. Brown. Irrigation of orchards by contour furrows. California Agr. Ext. Cir. 16:1-16. 1928. (Revised, 1932.) 4 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClR. 73 flexibility in contour check systems, and it is entirely practicable to take care of the occasional swale through the orchard where slopes may ap- proach 5 feet per 100 feet. One orchard in Butte County had such a swale where the slope was 5.4 feet in 88 feet. In this case, the standard contour interval of 0.2 foot difference in elevation between levee bases could not be maintained. By dropping two intermediate contours, it was possible to carry the levees through on a 0.6 foot difference of elevation. With such differences of elevation, the contour checks have the appear- ance of broad furrows. The method is particularly adaptable to the irrigation of mature or- chards which were originally laid out with the idea that irrigation would not be necessary and in which little or no leveling and smoothing was done. ADVANTAGES OF CONTOUR CHECK IRRIGATION The advantages of this method are : a smaller amount of levee work is required in constructing the checks as compared with the rectangular check or basin method ; less leveling or smoothing is necessary than that required for furrow irrigation or for satisfactory basins on sloping land; and there is a great reduction in irrigation labor in applying water. The method permits the use of large heads of water under control of the irrigator at the entrance to a single check ; hence, it does not in- volve the adjustment of numerous small streams as in furrow irriga- tion, nor does it involve the large amount of shoveling necessary to con- trol water in basins containing only one tree. When the vertical interval between contours is small, the uniformity of distribution with such a system is probably better than distribution by means of furrows and only slightly poorer than distribution by level, single-tree basins. Distribution is better by this method than in single- tree basins on sloping ground where the slope is such that two or more contours would intersect the basin. DISADVANTAGES OF CONTOUR CHECK IRRIGATION The principal disadvantage of this method is the tendency to apply too much water in case the checks are large. The application of excessive amounts of water to large checks is controllable by proper design or layout, the size of the checks being adjusted to soil type and head of water available. Measurement of the depth of water in the contour basins after filling is not a measure of the total number of acre-inches per acre applied because of percolation of water into the soil during the process of filling. 1933] CONTOUR CHECK METHOD OF ORCHARD IRRIGATION A comparison of the times required to fill three adjoining checks con- taining 50, 50, and 150 trees respectively, gave times of 1 hour, 1 hour, and 5 hours, with the same head of water. The first two checks being of equal area received the same amount of water, but the third check, while only three times as large as either of the smaller checks, received 1% times as much water per unit of area as the smaller checks received. For all practical purposes uniformity in the total amount of water applied to each check can be secured by adjusting check sizes to heads of water and soil type. Fig. 1. — Contour check irrigation of peaches; Sutter County. DESCRIPTION OF THE METHOD Contour checks are irregular basins formed by small levees or ridges located on level contours (fig. 1). The usual interval in elevation be- tween contours is 0.2 foot or .2.4 inches. The ends of contour levees are joined at the boundary of the tract by an enclosing levee. When filled, the water in the basin will be deeper against the lower levee than against the upper levee by an amount equal to the vertical difference in eleva- tion between the bases of the respective contour ridges. A difference of 0.2 foot elevation between levees will give five levees for each foot differ- ence of elevation. A difference of 3 inches in vertical elevation which gives four contours per foot difference of elevation, is liable to be too great and lead to difficulties in constructing proper levees. CALIFORNIA AGRICULTURAL EXTENSION SERVICE [Cir. 73 The location of contour ridges is marked on adjacent trees at the time of layout by means of dashes or bands of paint of various colors, or by painted disks of tin nailed to the trunks of the trees. Adjacent trees on the upper side only of the contour are marked. The band of paint is usually 3 to 4 inches in width and should extend around the trunk of the tree far enough to be readily seen by the tractor man when approaching from either direction along the contour when constructing levees. Where two or more contour ridges pass between two trees, the marked tree is Fig. 2. — Typical contour levees; Sutter County. painted with two or more colors representing the corresponding contour ridges. The color representing the ridge of highest elevation is at the top of the series of color bands. Various color schemes are employed to mark the location of contour ridges. Some employ only three colors while others employ four. The use of four colors such as red, white, blue, and yellow is generally preferred, as the fourth color serves to make the sequence of various series of colors a little more pronounced. Using the colors red, white, blue, and yellow in ascending elevation, the lowest contour ridge would be indicated by red, the next above by white, the next by blue, and the highest by yellow. The contour next above the yellow would be indicated by red, and so on. In descending order from the high point of an orchard, the sequences would be yellow, blue, white, red, yellow, blue, etc. 1933] CONTOUR CHECK METHOD OF ORCHARD IRRIGATION 7 When tin disks are used to mark the position of contour ridges, the disks (can tops) are attached to the trees by shingle nails. Care in nail- ing should be exercised and no nail should be driven in tight against the tree, but should be left with % inch to % inch of head exposed. When nailed down tight, the growth of trees will pull the tin disk over the nail head. Contour ridges or levees are constructed by means of various types of ridgers which will be described in following paragraphs. Levee height should be from 12 inches to 14 inches above the general ground level. Soil in the ridge should be well pulverized in order to make a water-tight dam. This may necessitate going over the levee more than once with the ridging machine. Levees should have broad, rounded rather than sharp, peaked tops (fig. 2). With machines building large levees, it is some- times impossible to build more than two levees between trees. Where levels indicate that more than two levees should be built between two trees, it becomes necessary to discontinue one contour ridge through such spaces. The dropped ridge is dead-ended against the adjacent up- stream ridge. In some cases three levees can be built in one tree row and four small levees have been constructed in a 24-foot row. This latter number would have been impractical with large, satisfactory levees. Various painting schemes have been devised to indicate dropped con- tours but such schemes are not discussed herein. LAYOUT OF CONTOUR CHECKS Before attempting any level work for the location of contour levees, the orchard should be disked and floated in two directions in order that minor irregularities of the ground surface may be eliminated. Orchards which have been plowed year after year to the trees or away from the trees should be. disked and floated crosswise to any ridges or depressions formed by such systems of cultivation. It is necessary that rod readings be indicative of the general elevation of the ground in the vicinity of each sight and not just the elevation of a local hump or hollow. The positions of contour ridges are determined by means of an engi- neer's level and target rod divided into feet and hundredths of a foot. With the target set at the proper reading for a given contour, the level- man directs the rodman to move up or down the slope until the cross wires of the level intersect the cross line of the target. The foot of the rod is then at the elevation of the required contour and the adjacent tree or trees on the upper side of the contour are indicated to the painter by the rodman, for marking. The rodman then moves along to the next 8 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [Cm. 73 space between trees. It is well to hold the rod in both the longitudinal and the cross tree rows. For determining positions of contours, it is only necessary that the cross hairs of the instrument intersect the crossline of the target to within % inch. A bright, clean target can be readily seen through rather thick foliage. A short tripod is sometimes an advantage as it allows the instrument to be set low enough to see under the branches of the trees. Such an arrangement may save considerable time by saving in the number of stations occupied by the instrument. The level should be in good adjustment. In some locations it is possible to set the level on a ditch bank or river levee in such a position as to be able to see over the tops of the trees. By using a long rod, work can be done much faster than by setting the in- strument in the orchard. Portable towers for setting the level above the tree tops have been used. INSTRUCTIONS FOR LEVELING AND NOTE KEEPING The following instructions may be of assistance to those farmers who wish to do their own surveying but who have had little experience in running a level or in keeping level notes. The elevations of all contours should be referred to a point of fixed elevation. Such a starting point for leveling surveys is known as a bench mark and is indicated in notes by the letters B.M. A bench mark may be the top of a fence post, a nail driven in the side of a tree, or any other immovable point on which the rod may be held. Its elevation is usually assumed at 100 feet. Set the tripod legs of the level firmly in the ground and level the in- strument. Sight on the rod held on the bench mark. Suppose the rod reading is 1.82 feet. This means that the elevation of the line of sight of the instrument is 1.82 feet higher than the bench mark. (See line 2, level notes.) Record 1.82 in column 2, line 2. Add 1.82 to 100.00 and record the sum, 101.82 in column 3, line 2. The column heading is H.I. which means height of instrument. Now, in order to determine the eleva- tion of any other point, it is necessary to read the rod held on that point and subtract the rod reading from the elevation of the line of sight or H.I. Line 3 shows that the rod reading (to the nearest 0.1 foot) at the high point in the orchard was 2.4 feet (line 3, column 4) . Then 101.82 ■ — 2.4 = 99.4 == elevation of high point (line 3, column 5) . Dropping down 0.2 foot (the contour interval), the elevation of the highest contour was fixed at 99.2 feet. The correct target setting to give an elevation of 99.2 feet with an H.I. of 101.82 feet is 2.62 feet. With the target set at 2.62 1933] CONTOUR CHECK METHOD OF ORCHARD IRRIGATION feet, locate the 99.2 Y (yellow) contour (line 4). When the 99.2 Y con- tour is run out to the boundaries of the orchard, raise the target 0.2 foot to 2.82 which is the correct setting for the next lower or 99.0 B con- tour. For each successive lower contour, raise the target 0.2 foot. Assume that the levelman could not see through the trees for the 98.0 W contour and that it could not be run out to the boundary (line 10) . This requires that the instrument be moved forward. Since it is neces- sary to carry elevations all the way through the survey, the rod is care- fully read on some fixed point such as a stake, and the elevation of its top determined. Such a point should be preserved during the survey as SAMPLE LEVEL NOTES (Left hand page of field book) JOHN DOE LAND COMPANY (Right hand page of field book) J. B. B.— Level May 11, 1932 E. F. S.— Rod S. M. D— Paint (1) (2) (3) (4) (5) Eleva- (6) (7) ' (1) Station + H.I. — tion Color Remarks (2) B.M. 1 82 101.82 100.00 Top of concrete stand, S.E. Cor.— assumed elevation (3) 2.4 99 4 Elevation high point in orchard (4) 2.62 99.2 Y Fixed elevation for highest contour. Letters in (5) 2 82 99 B column 6 indicate color of contour. Minus (6) 3 02 98.8 W sights to hundredths in column 4 are target (7) 3.22 98.6 R settings for various contours (8) 3.42 98.4 Y (9) 3.62 98.2 B (10) 3.82 98.0 W (ID T.P. 5 73 103.17 4 38 97.44 Stake on E. Boundary— 200' N. of S.E. corner (12) 5.17 98.0 W Continuation of 98.0 W. contour (13) 5.37 97.8 R (14) 5.57 97.6 Y it may be used several times. Points used for carrying levels forward are called turning points and are recorded as T.P. in the notes (column 1, line 11). Read the rod on the T.P. and record the reading, 4.38, in col- umn 4, line 11. Subtract reading from H.I., 101.82 — 4.38 = 97.44, which equals elevation of T.P. (column 5, line 11). Move the instrument and relevel. Sight on the rod held on the T.P. and record new reading, 5.73, in column 2, line 11. Treat as if starting from a new bench mark, that is, add reading to elevation of T.P. stake for a new H.I., 97.44 + 5 :73 = 103.17 (line 11, columns 2, 3, and 5) . Continuing the 98.0 W contour, the correct target setting for eleva- tion 98.0 from an H.I. of 103.17 is 5.17 feet (line 12, columns 4 and 5). For contours 97.8 R and 97.6 Y, the corresponding target settings are 5.37 and 5.57 (lines 13 and 14). 10 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [Cm. 73 The best time for locating contours is from late fall to early spring when the trees are bare. In evergreen orchards with dense foliage, such as citrus, it may be impossible to locate contour ridges directly in the field by moving from point to point on the contour with the rod. In such cases the construction of a contour map of the orchard first would be useful in locating contours, especially if the topography is regular and the slopes are slight. The location of contour levees in the field from a contour map is, in general, not to be recommended because the positions of contours on a map are usually interpolated from fewer level readings than are taken in the direct location of contours. Once the contours are located in the field and the trees marked, it is oftentimes of greatest help to the owner and irrigator for the engineer to locate the various contours on a map drawn on ordinary rectangular coordinate paper, the position of trees being indicated by the intersec- tions of cross lines. Such a map is a great help in locating the position of field ditches and cross levees where checks are too large to be irrigated as one unit. One or more permanent bench marks should be established for each field and during the process of surveying, turning-point stakes should be protected so that accurate elevation may be picked up anywhere in the orchard. All surveying should start at the high point of the orchard. If an engineer's level is not available, a farm level may be used pro- vided it is kept in good adjustment. The rods accompanying these cheaper types of levels are generally very poor and are usually divided into feet, inches, and fractions of an inch, making note keeping a very complicated process. Using such a rod, the contour interval should be fixed at 2% inches. "Work will be facilitated by the use of a rod graduated in feet and hundredths. DESIGN OF THE SYSTEM To make this a successful method of irrigation, other factors than ac- curate location of contour levees must be considered. This method is sub- ject to the same limitations in regard to sizes of checks in relation to heads of water available as is the method of square or rectangular checks. Considering the manner in which water is absorbed by different soil types, sandy soils are generally readily penetrated by water and have low water holding capacities while clay soils are usually difficult of pene- tration but have high water holding capacities. Since sandy soils usually are readily penetrated by water and have low water holding capacities, they require less water to wet them to a given depth than is required to wet clay soils to the same depth. This 1933] CONTOUR CHECK METHOD OF ORCHARD IRRIGATION 11 fact is commonly stated : light soils require light applications of water at frequent intervals ; heavy soils require heavy applications of water at longer intervals of time. A light application of water to any area is accomplished by running a relatively large stream of water for a short time on a small area ; a heavy application by running a small stream for a long time on a large area. A rule for size of checks, considering soil type and heads of water available, can be deduced from experience in other methods of irriga- tion. Successful experience in other sections indicates that the proper ratio of irrigating head, measured in cubic feet per second, to the area of check expressed in acres, should be 20 to 1 for sandy soils, and 2 to 1 for clay soils. For example, with a head of 20 cubic feet per second (9,000 gallons per minute or 1,000 southern California miner's inches) it would be possible to irrigate a check of 1 acre in sandy soil. The same area in clay soil could be properly handled with a head of 2 cubic feet per second (900 gallons per minute or 100 southern California miner's inches). In the orchard sections, most of the heads of water are small — from 300 to 1,400 gallons per minute. With sandy soil and 900 gallons per minute (2 cubic feet per second) the size of the check would be deter- mined from the above 20 :1 ratio as follows : 900 G.P.M. = 2 C.F.S. 20 2 1 area of check Area of check n= y 10 acre. Therefore, with sandy soils and a head of 900 gallons per minute, the area of the check should not exceed y 10 acre. For clay soils with 900 gallons per minute (2 cubic feet per second), it would be possible to use checks of 1 acre. A convenient way to determine areas is to count the number of trees in the check and compare that number with the number of trees per acre. For the number of trees per acre for various spacings for square and hexagonal plantings, see table 2. A check containing 19 trees square-planted 22 feet apart would con- tain x % of an acre or 0.21 acre. On a 22-foot hexagonal planting, the same number of trees would indicate an area of 1 %o3 acre or 0.184 acre. On lands with very slight slopes, a contour interval of 0.2 foot may enclose a check too large in area to be irrigated as a single basin. If. after applying the above tests as to area, soil type, and head of water, it is 12 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [Cm. 73 decided to divide the check into smaller areas, this division may be ac- complished by running cross levees between the upper and lower contour ridges. These cross levees may be marked by spotting trunks of adjacent trees with white crosses. When field ditches are run inside the orchard, TABLE 1 Sizes of Contour Checks Head of water delivered to a single check (measured in different units) Number of trees to a check* Gallons per minute Southern California miner's inches Statutory miner's inches Cubic feet per second Sandy soils Loams Clays 450 900 1,350 50 100 150 40 80 120 1 2 3 5 10 15 20 40 60 50 100 150 * Basis— 100 trees per acre. TABLE 2 Number of Trees per Acre for Square and Hexagonal Planting Distance apart, feet Square planting, number Hexagonal planting, number 18 134 154 20 109 125 21 99 114 22 90 103 24 75 86 25 70 80 30 48 55 35 36 41 40 27 31 45 22 25 50 17 19 60 12 14 their position may be spotted by double bars on the trunks of adjacent trees (see figs. 5, 6, 7). Field ditches are constructed by running paral- lel ridges at proper distances apart to carry the stream (fig. 3). On slopes too steep for ordinary field ditches where washing of the soil is a factor, the checks may have to be supplied by concrete pipe lines. Short lines of portable slip- joint pipe may be useful in reaching small checks on steep slopes. 1933] CONTOUR CHECK METHOD OF ORCHARD IRRIGATION 13 WATER APPLICATION AND IRRIGATION RATES In applying water to soil, a knowledge of the amount of water neces- sary to wet different types of soil to various depths will aid in determin- ing the total amount of water to apply. A convenient "rule of thumb" is the following : An acre-inch per acre of water, or 1 inch in depth over a given area, will wet clay soils 4 to 5 inches in depth ; loam soils, 6 to 10 inches ; and sandy soils 12 inches or more. Fig. 3. — Field ditch formed by parallel levees; Sutter County. Irrigation by means of contour checks should start at the upper check and continue successively to the lower ones. This is necessary to protect the orchard from serious washing in case of breaks in levees. Starting at the top, there are always empty checks below to hold the water in case of a break. The whole head should be turned into each check in turn, cutting off each check as it is filled. This individual filling of checks is the principal departure from rice irrigation where water is spilled from upper to lower checks. Irrigation by spilling from one check to another would re- sult, in most orchard soils, in the upper checks receiving very much more water than the lower ones. 14 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ Cl R- 73 Comparisons of the amounts of water applied to various areas are readily made by means of simple calculations. The following formulas are useful in computing amounts of water applied : 1. Water measured in cubic feet per second: Number of second feet X hours run acre-inches per acre Number of acres ~~ or inches of depth applied 2. Water measured in statutory miner's inches: Number miner's inches X hours run acre-inches per acre 40 X number of acres or inches of depth applied 3. Water measured in common or southern California miner's inches: Number of miner's inches X hours run acre-inches per acre 50 X number of acres ~~ or inches of depth applied 4. Water measured in gallon per minute: Number of gallons per minute X hours run _ acre-inches per acre 450 X number of acres ~" or inches of depth applied Calculations of Amounts of Water Applied. — How many acre-inches per acre of water are applied to a check containing 24 trees planted 22 feet apart on hexagonal system in 70 minutes by a pump throwing 640 gallons per minute ? 22-foot hexagonal planting — 103 trees per acre. 24/ 103 — 0.233 acre. 70 minutes = 1.17 hours. G.P.M. X hours 640 X 1.17 450 X acres 450 X 0.233 7.1 acre-inches per acre. For other units of water measurement, select the proper formula above. TYPES OF RIDGERS There are many types of ridgers in common use. Any type may be selected as long as a proper ridge is constructed, that is, water tight, of sufficient height, and with a broad, rounded crown. The common types of ridgers are as follows : Blade or Open V-ridger. — This type of ridger has steel or wooden blades joined together in the shape of an open-ended letter V. It is drawn with the larger opening forward. Such a ridger may be used in light soils but the resulting levee is liable to be too low and too peaked at the top. Single Disk Ridgers. — These ridgers are of the wheel type with two large single disks set to throw to the middle. Some tools are constructed 1933] CONTOUR CHECK METHOD OF ORCHARD IRRIGATION 15 only for use as ridgers while others have tool bars to which the disk mountings are attached and to which other tools for various orchard operations may be attached. Implements with tool bars provide ready adjustment of distance between disks, while tools constructed only as ridgers are not so readily adjustable. The single disk ridgers are satis- factory in light and medium soils but do not work up heavier soils into fine enough particles to make good levees in a single operation. By going over levees more than once, levees are settled and pulverized. Fig. 4. — Eidging using front half of orchard disk; Sutter County. Multiple Disk Types. — One type of ridger is a special tool constructed in local machine shops consisting of sets of three disks of varying sizes attached to heavy plate metal frames. Each set of disks is composed of 26-inch, 22-inch, and 18-inch disks set with the largest disk to the inside. These ridgers are heavy and rather wide. They are not readily adjust- able. They make a satisfactory levee in heavy soils as the smaller disks behind the large inner disks work the soil into sufficiently fine particles. The front half of an ordinary heavy orchard disk also makes a satis- factory ridging tool. The disks are set to throw inward and upward. In heavy soils, the tool must be weighted (see fig. 4). With this tool, it is necessary to go over levees twice and in some cases in heavy soils, three times in order to get a compact, water-tight levee of sufficient height. Orchard disks are readily adjusted in pitch and angle. 16 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClR. 73 Ordinarily, levees are left up for more than one irrigation. If the soil is such that much cracking takes place, it is necessary to run over the levees once with a disk before each succeeding irrigation. PAINTS AND PAINTING A good quality paint should be used. One with a small amount of var- nish or enamel to give a somewhat glossy surface is better than flat- drying paints. Paint manufacturers are now furnishing "Contour Paint." Retail prices of paints in small lots will approximate $3.50 per gallon. In larger quantities at wholesale the price would approximate $2.50 per gallon. A brush 1% inches in width is a convenient size. A small box with a leather handle and arranged to hold four pint fruit jars containing various colored paints is handy for use in spotting trees. Use a separate brush for each color. Brushes should be cleaned after each day's work. COST OF LAYOUTS Surveying costs vary considerably, being influenced largely by topog- raphy of the ground. One widely experienced engineer using a four-man party charges $4.00 per hour in addition to the cost of paint which is charged for at the rate of $2.75 per gallon. The work includes spotting of all contours and location of cross levees and field ditches. The follow- ing are some orchard layout costs : 1. 100 acres — four years old. Surveying $122, paint $22 ; total $144 or $1.44 per acre. 2. 17 acres — 12-14 years old, rough. Surveying $48, paint $12.75; total $60.75 or $3.58 per acre. 3. 10 acres — 12 years old. Surveying only $14. Owner furnished paint. 4. 40 acres— 6-7 years old. Surveying $87, paint $14.90; total $101.90 or $2.55 per acre. 5. 48 acres— 8-10 years old. Surveying $136, paint $47.10 (17% gallons at $2.75) . Bough, many dropped contours, heavy slopes. Total $183.10 or $3.82 per acre. 6. 50 acres— 8-10 years old. Surveying $144, paint $36.10 (13% gallons at $2.75). Rough, slow job. Total, $180.10 or $3.60 per acre. There was an additional charge of $56 for locating ditches on the last two fields. A combined charge for the two pieces would be as follows : 98 acres — surveying $336, paint $83.20; total $419 or $4.27 per acre. Other methods of charging for surveying are $2.00 per acre where the engineer furnishes one man in addition to himself and where the owner furnishes a man to do the painting and provides paint and brushes. Some charges have been as low as $1.75 per acre on the same arrange- ment where the slopes were light and not many contours required. 1933] CONTOUR CHECK METHOD OF ORCHARD IRRIGATION 17 Grade high point''] Fig. 5. — Typical layout for loam soils with head of water of 900 gallons per minute and a limit of 40 trees to a check. Order of contours in increasing eleva- tions: red, white, blue, and yellow. 18 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [Cir. 73 o o» o o o o olojo o ol o o \ o O o o o i o 1 o o O O J o 1 1 1 O O 0\0|0 o ol o o[o o o o O 1 o 1 o o o o Vo o Vo o o \ o \o O O O OlO o o o O 1 O 1 O o I o o o\o o\o O OVpVJO o o o • o o o o OlO >o o X N X BLW / o\o o o\o oXo O VO \o O O OlO o o X \ — X \ \ I I o o\o o o\o o o\oA o\ o Vo o \o o o d\o o 6\o o o\ o o\o 6 N , oVo °\i o \ o o\o O o o o o o\p o\pv^p o\o Ql o o\\o\o <}\ o 3* "»-£&> X^Bjue \ X \ o o o\ s Ow/p o o\b_o s \o o o*\o o^ o* o \o o o Op.o o\o o o o\o\ o o o o^jio, oio\ o o o o\oo o\o o o\o o o\o o \o Q o o oXo^ p o o\o o o "o\ o o o\o o\o^o X.YeJfc^ V X \ V -- ^ o o^o o\o o o\o o o o\o o o\o o o Vo o\ o O 0\ o o | o o | o o o o \o OlO O 4) O ' \ - iO o\ O _ o o N xo Voao N ^\v^ o o "§\o o o\o o o o\ o o 6\ o o o\o o ovv oX\o High point Grade Low point on pipe line- Fig. 6. — Typical layout for loam soils with a swale through the middle of the land. There are no dropped contours. It is planned for a head of water of 900 gallons per 1933] CONTOUR CHECK METHOD OF ORCHARD IRRIGATION 19 Pipe line- o o o o oy o o y ''o o o oto o o o o o"*\o o\o o o ; I „ v> ;^^>_-— ^ O O Oy O O , O Oyf O O O OJO 0)0 oj o o oj' o o o~ 0X0 o^'o to Jo /o/ o o 0/0 O O y'O o * •' / ,^ r.-. <^-^— — * * o o o 0/0 o o o ^ -' Yello w O Oy' OOOO 0000 n K *-Cross levee O J 0* w O O Q O White Fig. 7. — Typical layout for steep slopes on light soils, showing dropped contours. It is planned for a head of water of 900 gallons per minute, and a limit of 10 trees to a check. 14m-4,'33