93 



1. Methods of Irrigation. V 



The methods of irrigation given for alfalfa will apply to practically all 

 forage crops as clover, peas, etc. Because of the rolling character of most 

 of the irrigable land of British Columbia, the method best adapted to the 

 irrigation of alfalfa is the furrow method, almost universally used in the 

 Yakima Valley of eastern Washington, said often spoken of as the Yakima 

 or corrugation system. Another system adapted to rolling land and used 

 extensively in the Rocky Mountain states Colorado, Montana, Wyoming 

 and Utah is known as the flooding method. It consists in running small 

 parallel ditches through the fields, 50 feet to as much as 200 feet or more 

 apart, and running the water over the ban-k of the ditches down the slope 

 of the fields. This method requires an irrigating head of from 40 to 100 

 miners' inches or 1 to 2 y 2 cubic feet per second and is more wasteful than 

 the corrugation method. The other methods of irrigation commonly used 

 are known as the border method and the check method. These are adapted 

 only to comparatively level land and require large heads of water. Only 

 the first method will be described as it is the one best adapted to most of 

 the irrigable land of British Columbia. The other methods are fully 

 described in Farmers' Bulletin 373 on Irrigation of Alfalfa, which can be 

 obtained from the U. S. Department of Agriculture, at Washington, D. C. 

 Furrow method of alfalfa irrigation. 



The water is run in shallow furrows from which it spreads laterally 

 and moistens the soil on each side. The laying out of the head ditches or 

 flumes, the length and slope of the furrows, and the application of the water 

 is much the same as for orchards. The farmer often makes his furrows 

 too long in order to avoid many head ditches. This is poor practice for it 

 causes unequal distribution of water with a loss by percolation at the 

 upper end of the furrows. It is best to plan the distribution system so 



J2"* 12" flume 



"x &" Flume. 



350' 



S 



Z&O' 



LEGEND 



- -- F/ume 



Slope of La net 

 " ^~* Direction of F/ow /n Flume 



330' 



Fig-. 75. Distribution system for ten acre traet, Kenewiek, \Vnsh. 



(O. E. S. Bulletin 188, U. S. Dept. Agr.) 



