204 



IRRIGATION PRACTICE 



land; if the slope is great, the lower levee must be made 

 too high for practical purposes. A large head is always 

 necessary; for, if the head is small, the land, especially if 

 sandy, is likely to absorb the water so fast at the upper 



FIG. 43. Rectangular check method of irrigation. 



end that the lower end receives only a small part of the 

 water intended to cover the whole check. The flow of 

 water should be from 5 to 10 second-feet in order to make 

 the method thoroughly successful. In the older countries, 

 the checks are usually small. In America, the checks are 

 often very large from 10 to 20 or more acres. The 

 check method of irrigation, to be really successful, must 

 be practised with small checks, at the most from 1 to 3 

 acres in area. 



The compartments may be laid off in various ways. 

 If the land does not slope too much, the whole farm is 

 laid off into square or rectangular checks, into which the 

 water is admitted in succession. Where the land is uneven, 

 or the slope steep, the checks are made to conform to 

 the contour of the land. In either case, water must be 

 admitted at the highest point and be brought rapidly into 

 the compartment so that the ground may be covered 

 thoroughly and in a short time. At times a depression is 



