IRRIGATION 



131 



Fig. 70. Flooding- method of irrigation. 

 (Sep. 514, U. S. Dept. of Agr.) 



ground, the crops grown, the amount of water available, kind 

 of soil, and other conditions. 



The Flooding Method. One of the more general methods 

 of application is known 

 as the flooding system. 

 It is generally used on 

 land when it is first re- 

 claimed, even though 

 another method is in- 

 tended to be used later. 

 Preparing the ground 

 for flooding consists in 

 leveling, grading, and smoothing, so that the water will 

 flow readily over it in sheets. To distribute the water, small 

 field ditches, or laterals, are located along the best routes. 

 These small ditches are usually from 50 to 100 feet apart, 

 and they generally follow grade lines, or contours. Where 



little care is used to control the flow 

 of the water, the practice is said to be 

 "wild flooding." The small ditches 

 are made with a double moldboard 

 plow, which turns a furrow on either 

 side. To cause the water to overflow 

 from the ditch to the side, a dam 

 must be put in place. This con- 

 sists usually of a piece of canvas 

 nailed along one edge to a strip of 

 wood. In other cases, the ditch may 

 be dammed by simply building up a 

 small ridge of earth across the ditch. 

 The Check Method. The check method of applying 

 water consists in dividing the fields into sections each having 

 a comparatively level surface and bordered on all sides by 



OPENING e"xs" 



Fig. 71. A canvas dam. 

 This dam has an opening 

 to divide an irrigating 

 stream. (Bui. 203, Office 

 of Experiment Stations.) 



