260 



THE IRRIGATION AGE. 



be on the flat slope and the short side on the steep slope. 

 A fall of 3 to 5 inches between adjacent checks is pref- 

 erable to either more or less. Usually the width of 

 checks can be so adjusted as to permit of this difference 

 in elevation. The length of each rectangle will depend 

 on the slope in that direction as well as the location of 

 the supply ditches. The field should be laid out in such a 

 way that the levees may be built with the least handling 

 of dirt. Rectangular checks possess many advantages 

 over irregular contour checks, but if much of the better 

 quality of surface soil has to be removed in order to build 

 the former, the advantages may be more than outweighed 

 by the damage caused by grading and 

 the extra cost. 



Figure 6 shows in outline the rect- 

 angular checks, supply ditches, and 

 check boxes on the farm of T. K. Beard, 

 east of Modesto, Cal. Mr. Beard plows 

 the land in the early spring to a depth 

 of 6 inches with a 4-gang plow. Dur- 

 ing the summer the checks and ditches 

 are built in a sort of rough way, no ef- 

 fort being made to level the floor of the 

 checks or to smooth the levees and 

 ditch banks. It is then heavily irrigated, 

 and after the soil is sufficiently dry 

 the floor of each check is carefully 

 leveled and the levees trimmed and 

 smoothed. For the latter purpose the 

 grader shown in figure 7 is preferred. 

 One passage of this grader across the 

 top of each levee and once along each 

 side reduces the levee to a base of 14 

 feet, and a height of 8 inches on the 

 high side. 



On the west side of the San Joa- 

 quin Valley the land to be seeded to 

 alfalfa is almost invariably formed into 

 contour checks. A common arrangement is that shown 

 in figure 8 Here the supply ditches are intended to be 

 about 600 feet apart, and levees are built midway between. 

 The sides of the checks conform in a measure, but not 

 exactly, to the natural contours, having a difference in 

 elevation of 0.3 to 0.4 foot. The average area of a check 

 is half an acre. In 1908 prices were obtained on the cost 

 of preparing land in contour checks and seeding to alfalfa. 

 The average cost on 2,067 acres of comparatively smooth 

 grain land was $11.46 per acre. Across the river in 

 Modesto and Turlock districts, where rectangular check- 

 ing is more common and where the natural surface is more 

 uneven, the cost was estimated at $17.50 for contour 

 checks and $19 for rectangular checks. These latter 

 figures included ditching, but excluded the cost of seed 

 and seeding. 



feet per second are available four checks may be irrigated 

 simultaneously. This head flowing on a check containing 

 1 acre would cover it to a depth of about 5 inches in one 

 hour. A part of the water so applied is always lost by 

 evaporation, but the balance percolates into the soil to 

 furnish moisture to the plants. The skillful irrigator be- 

 gins with the highest checks and works down for the 

 reason that all waters which escape through the gopher 

 holes or broken levees may be then applied to dry checks. 

 To reverse this rule might result in overirrigating the 

 lower checks. The average cost of irrigating for the 

 season where proper check boxes are inserted is about 



Fig. 9. Scraper. 



In the Modesto and Turlock irrigation districts the 

 feed ditches -are designed to carry large heads of 10 to 20 

 cubic feet per second. These large heads are used by 

 the farmers in turn for short periods of time, depending 

 upon the acreage served. In the smaller checks a head 

 of 5 cubic feet per second will suffice, and if 20 cubic 



Fig. &. Laying Out Contour Checks. 



60 cents an acre. 



On the west side of the San Joaquin River each of the 

 irregular compartments contains 1 to 3 acres, averaging 

 about 2 acres. Few permanent wooden check boxes are 

 used. The water is checked up by dams of coarse manure, 

 and an opening is made in the levee bank with a shovel 

 to admit the water. The lack of suitable boxes to control 

 the water passing from the feed ditch into each check and 

 the use of smaller heads greatly increase the cost of ir- 

 rigating over that of the Modesto and Turlock districts. 

 In the latter the cost for the season was estimated at 60 

 cents per acre, while in the former the estimate is 90 

 cents for each watering. 



The chief advantage of the check method is that 

 one man can attend to a large volume of water and can 

 irrigate 7 to 15 acres in ten hours, making the cost of 

 applying water less than by any other 

 method except- the border method. To 

 counterbalance this important gain, there 

 are several disadvantages which western 

 farmers ought to consider. These are 

 the removal of a considerable quantity 

 of surface soil to form the levees, which 

 frequently decreases the yield on the 

 graded spots; the extra cost of prepar- 

 ing the land; the damage done to farm 

 implements in crossing levees; and the 

 fact that this method is not well adapted 

 to a rotation of crops. 



The Flooding Method. 



Flooding from field ditches or 

 laterals is still the most common meth- 

 od of applying water to the arid lands of 

 western America. In the States of Colo- 

 rado, Montana, Wyoming, Utah, and to 

 a large extent in Idaho, alfalfa, clover, 

 native meadows, and grain are irrigated 

 in this way. This manner of wetting dry soil originated, 

 it is believed, in the mountain States, and the past half 

 century has witnessed a gradual evolution of this plan, 

 so that now it has not only become firmly established, 

 but is regarded as the best suited to the conditions under 

 which it is practiced. It can be profitably used on slopes 



