14 



1. Diversion works. 



2. The main canal, with its structures, such as tunnels, 



siphons, flumes, spillways, bridges, culverts, etc. Tun- 

 nels and siphons are the most expensive structures, 

 but the number of these for this region appears to be 

 small, consequently the cost of the canal should not 

 be high. 



3. The field laterals. 



4. The preparation of the irrigated area to receive water, 



such as leveling, furrowing or checking. 



The major portion of the losses in an irrigation system occurs 

 in the small laterals and in the irrigated field, generally due to the 

 fact that the carrying capacity of the field laterals is too small and 

 that consequently the water, instead of covering the area which it is 

 intended to irrigate, sinks into %e ground at the upper end of the 

 lateral and leaves the lower end with a deficient supply. Furthermore, 

 the land must be prepared very carefully for irrigation. A little time 

 and money devoted in the beginning to a proper preparation of the 

 land will be more than repaid in the saving of the water and the ease 

 and cheapness with which it can be applied. Land once properly 

 prepared can always be cheaply and easily maintained in the best 

 condition. Where land is properly prepared one man can quickly 

 and thoroughly handle water on 10 acres; whereas, two or three men 

 will not produce as satisfactory results on the same area poorly graded 

 and prepared. 



Where water is to be applied by the flooding method great care 

 should be taken to produce a perfectly uniform slope and surface. 

 This should be done by the use of some of the grading tools which are 

 now on the market, in connection with levels taken to determine 

 within an inch or two as maximum limits the slope of the land. If 

 the surface is particularly uniform, deep ploughing followed by 

 harrowing and then dragging over the surface a heavy log or beam or 

 some other device for leveling the land will suffice. At other times 

 the slope may be too great to permit of irrigation by flooding, because 

 it would produce such a velocity as to cause erosion of the soil. This 

 is to be corrected by grading the soil so as to form checks or in 

 extreme cases by terracing, which is jjut an exaggerated form of check. 

 If the surface is uneven the water will stand about in pools, so that cer- 

 tain portions of the land will receive too much and become supersat- 

 urated while other places will be high and di-y. It is only, therefore, 

 by the creation of a uniform surface that water can be satisfactorily 

 applied by the flooding method. 



Where the soil is to be prepared for irrigation by furrows, and 

 especially where these furrows are to be small and narrow, even greater 

 care must be taken than in the flooding method in pi-oducing the 

 proper slope and surface level. If the slope of the land is loo steep 

 the furrows will, because of the velocity of the water, be rapidly 

 eroded. If the slope is too slight the water may take so long in flowing 

 across the fields as to be ail evaporated or absorbed before it reaches 

 the further end. Too steep slopes may be lectified by running small 

 ditches or flumes down the slope of the ground and inserting falls in 

 them to overcome excess of slope, and by turning the water from 

 these into lateral furrows and drills which i-un at such an angle as 

 procures the proper fall. 



