358 IRRIGATION PRACTICE 



water flowing into the canal and its laterals has been 

 carefully measured, there yet remains the perplexing and 

 important problem of the proper distribution of the canal 

 or reservoir water to the numerous farms of various sizes, 

 growing different crops. Each irrigator must receive water 

 in a quantity proportional to his interests in the canal, and 

 at such a time as will each year insure him a good crop. 

 The irrigator, the owner of the water-right, knows only 

 one test of the efficiency of the canal management does 

 he have an ample supply of water whenever needed by his 

 crops? The success of an irrigation enterprise depends on 

 the success with which this test is answered; that is, upon 

 the system of distribution of water under the canal. 



216. Methods of distribution. There are three gen- 

 eral methods of distributing irrigation water among 

 farmers. First, a continuous flow of water to the farm 

 during the whole irrigating season. Second, an inter- 

 mittent flow, which means that the farmer gets a certain 

 flow of water for a definite length of time at certain inter- 

 vals. Third, the delivery of water to the farmer as he 

 applies for it. 



Under reservoirs, with an ample supply of stored 

 water, any one of these three methods may be used. 

 Where canals are taken directly from the rivers the first 

 two methods may be used but the third method is prac- 

 tically impossible. 



The method chosen for the distribution of water may 

 affect greatly the duty of water under the system, for it 

 may determine the crops to be grown and the areas to be 

 devoted to each. 



217. Continuous flow. Irrigation is not successful 

 unless the head or volume of the irrigation stream is 

 sufficiently large to cover quickly a suitable area of land. 



