THE IRRIGATION AGE. 



371 



given, and it is most often the case that this is not 

 given. Consequently the form of expression now gen- 

 erally accepted as the best is the last one named. Of this 

 form of expression there can be no doubt and no mis- 

 understanding, for it means the same wherever it is 

 used. What adds further value to it is the fact that it 

 is the same form as that used for expressing rainfall, 

 and irrigation is simply artificial rainfall, applied in 

 the quantity and at the time best suited to the needs of 

 plant growth. 



As most generally considered, then, the duty of 

 water is the amount that is used in growing crops, ex- 

 pressed in the total deptli applied during the season. 

 It may be different with different soils, different rain- 

 fall, different crops, and different practice. 



Since 1899 the Office of Experiment Stations of 

 the United States Department of Agriculture has been 

 making measurements of the amount of water used un- 

 der different canals throughout the West. The measure- 

 ments since 1901 have not been grouped, but for the 



insignificant ; in others, they include as much as 75 per 

 cent or more of the water entering the headgates. While 

 engineers constructing canals must take these losses into 

 consideration, they really have nothing to do with the 

 duty of water, and to be a definite guide to farm prac- 

 tice, measurements should be made where the water is 

 used. A large number of measurements have been so 

 made by the Office of Experiment Stations. The aver- 

 age depth of water applied during 1899, 1900 and 1901 

 on some fifty farms in eight Western States was found 

 to be 3.98 feet, not including rainfall, the crops watered 

 ranging from alfalfa, which requires a considerable 

 amount of water, to oranges and lemons, which are suc- 

 cessfully grown with a much smaller supply. In 1899, 

 the average depth applied on five selected orange or- 

 chards at Riverside, Cal., ranged from 1.67 feet to 2.95 

 feet, including .47 foot rainfall. In 1901 the average 

 depth applied to twenty-one farms under Pioneer canal 

 on Tule river, also in California, most of the farms 

 being planted to citrus fruits, ranged from 1.26 feet to 



MEASURING A SMALL FLOW. 

 Measuring the duty ot water with a small weir board inserted in field ditch. 



water diverted by the many canals measured was each 

 three seasons of 1899, 1900 and 1901, the amount of 

 season sufficient to cover the land irrigated to an average 

 depth of 4.45 feet. In 1903 approximate data regard- 

 ing the amount of water diverted were collected from 

 twenty ditches in Northern Colorado, from thirty-two 

 ditches in Wyoming, and from five large ditches in 

 Western Nebraska. Expressed in depth over the surface 

 of the land irrigated, the average under the Colorado 

 ditches was 3.27 feet, under the Wyoming ditches, most 

 of which were small individual ditches, was 8.52 feet, 

 and under the Nebraska ditches was 3.60 feet. Under 

 one small ditch enough water was diverted to cover the 

 land irrigated under the ditch to a depth of 21 feet. 



Through seepage and other avoidable or unavoid- 

 able waste, much of the water entering canals is lost 

 before reaching the land to be irrigated. These losses 

 vary so greatly with different canals that no useful pur- 

 pose would be served by attempting to average them. 

 In some cases, as where canals are cement lined, they are 



4.83 feet, the mean for the twenty-one farms being 2.37 

 feet, including .37 foot rainfall. Measurements kept 

 during the four seasons 1898 to 1901 on twenty-five 

 farms at Lindsay, Cal., showed a mean depth of water 

 applied for the four seasons of 1.00 foot, 1.63 feet, 1.50 

 feet and 1.14 feet, respectively. This water was meas- 

 ured carefully, because it was pumped from wells and 

 paid for by quantity delivered. The rainfall for these 

 years was .47 foot, .60 foot, .85 foot and .84 foot, re- 

 spectively. In 1904 measurements of the amounts used 

 under sixty pumping plants in Santa Clara valley, Cal., 

 were made, an agent of the Office of Experiment Sta- 

 tions doing the work with a current meter, a carefully 

 constructed stationary weir, or a; small weir board in- 

 serted in the field ditch being measured. The average 

 depths of water being applied were found to range from 

 under one foot to nearly five feet, and averaged 1.13 

 feet, not including rainfall. With rainfall added the 

 depth was 2.00 feet. All of the land considered was 

 planted to deciduous fruits. The duty was high be- 



