Use and Waste of Water 



219 



ditch can be used for the preHniinary irrigation and possibly for the 

 first irrigation after planting, after which the gronnd will become 

 settled and packed and the ditch can be leveled off and planted 

 also. In the case of fnrrow irrigation, double heads can be run in 

 alternate furrows and subdivided about two-thirds of the way down 

 the field. Later, the intervening furrows can be treated the same 

 way, and thus the proportion of water received by the lower end 

 is increased. Another ])ractice is to turn a large head down each 

 furrow at first, and. when the water reaches the lower end, to re- 



Fig. 7. — An alfalfa field in Navajo County, irrigated by the corrugation 

 method. The corrugations are about three inches deep, are spaced at intervals 

 of about tliirty inches, and run down the steepest slope. This method is advan- 

 tageous particularly where the soil is heavy and tends to bake on the surface 

 if flooded. 



duce the head to such an amount as will continue just to reach 

 the lower end. 



Good control over the division of the stream of water into fur- 

 row streams or into separate heads for the lands is essential. Some- 

 times it is well to divide the stream into two, three, or more parts 

 by means of a division box. Then each part can be more readily 

 divided into furrow-heads. Spiles, made of laths or of narrow 

 boards, are effective in the final distribution. The spiles are set in 

 the ditch bank at the natural ground surface. Sometimes the w^ater 

 is let into forebavs and then distributed thru spiles. Wooden 



