294 DEPAKTMENTAL REPORTS. 



if 



maturing of cultivated crops has required the diversion of enough 

 water to cover all the land irrigated to a depth of slightly more than 

 4 feet. Measured at the margin of fields, the water actually applied 

 has amounted on the average to a little more than a depth of 2 feet. 

 The greatest source of loss, therefore, is through leakage from canals, 

 and while this can not be wholly prevented, it is certain that in time 

 it can be largely reduced whenever the increasing value of water will 

 make it profitable to introduce betterments hitherto not regarded as 

 necessar}^ 



These imj)rovements will benefit irrigated agriculture in two direc- 

 tions. The water now lost through leakage from canals returns in 

 many instances to the surface on the lower-lying fields, converting 

 what were formerly productive areas into unsightly swamps and 

 marshes, which, for the time, are practically worthless. It will also 

 make it possible to apply to beneficial use a large percentage of the 

 water supply w^hicli is now lost through evaporation from these over- 

 irrigated areas. One of the next steps in irrigation development, 

 therefore, is the better construction and operation of canals, and one 

 of the leading lines of work in these investigations is the measure- 

 ment of losses from seepage and a stud}^ of the methods of canal con- 

 struction and operation by which it can be prevented. 



DRAINAGE SURVEYS AND INVESTIGATIONS. 



In all of the irrigated countries of Europe, drainage and irrigation 

 go hand in hand, and there is every reason to believe that this will 

 ultimately be the practice of this country. The irrigation code 

 recently formulated by the commission created for that purpose in 

 California has made the same board both a drainage and an irriga- 

 tion commission, and in the irrigation investigations of this Office it 

 has been found desirable to supplement the studies of seepage by 

 kindred studies of the problems of drainage, bj^ which the waters thus 

 lost can be made available and the areas rendered unproductive 

 brought again under cultivation. 



The drainage problems connected with irrigation differ in some 

 respects from those where the surplus watei- supply comes from rain- 

 fall. The water which leaks from canals, or sinks into the subsoil 

 from overirrigated fields, when it reappears, comes from below instead 

 of coming from above as in humid districts. In some instances com- 

 plete relief can not be obtained by providing channels for its removal. 

 The water lost from canals must be intercepted before it reaches the 

 surface, and this necessitates different engineering methods from 

 those prevailing in the East. What these methods must be is as yet 

 largely unknown. They can only be determined by careful stud3^ 



Because Eastern drainage methods will not answer, many of the 

 attempts thus far made have prbven failures and have led to the belief 

 that the drainage of irrigated lands is impossible. The lesson of these 

 failures is, however, as valuable as what has been taught by success 

 in other localities, and both are being studied by the agents of this 

 Ofiice. 



The benefits which are to come from drainage in the older irrigated 

 States, like Colorado and California, are not realized except by a few 

 who are familiar with the extent of the areas rendered unproductive 

 and with the growing encroachment of the surplus water supply on 

 the lands now being cultivated. In response to petitions which 

 embraced practically aU of the agricultural and horticultural interests 



