200 IRRIGATION FARMING. 



shown by Fig. 59, the water enters the distributing 

 ditches at the upper left-hand corner, and, dividing, 

 flows through these into the still smaller ditches, from 

 which it is turned laterally into furrows. Little dams 

 or temporary obstru<5lions of earth check its flow from 

 point to point. After water flows out upon a field, 

 any surplus can be caught by small trenches shown in 

 the figure as trending diagonally toward the right-hand 

 lower comer. From these trenches the water can be 

 turned upon the lower fields, so that the excess or 

 seepage is not wasted, but is employed on the less ele- 

 vated tradls. In cases of inadvertent pitch, as some- 

 times occurs in furrows for street irrigation, the danger 

 of washing can be controverted by putting in perma- 

 nent sunken sluices. When it is necessary to irrigate 

 a tree along such a sluiceway the water can be led out 

 in a sufficient quantity by boring an auger-hole in the 

 bottom of the sluice two feet or so above the tree. 

 When water is not needed to irrigate the tree in this 

 way the hole can be plugged. 



Backsetting. — In Western Kansas a primitive 

 system of subirrigation by damming a stream in a flat 

 country and forcing the water through the adjacent 

 lands by percolation is somewhat relied upon, but will 

 not become generally adopted. The water is dammed 

 and simply forced out through the banks into the 

 ground, and in this way subterranean moisture is 

 afforded the surface soil to produce good crops. The 

 plan is rather too expensive in dam building to make 

 it very popular, and the operator having no control 

 over the seepage tide would soon find his ground water- 

 logged and too wet for ordinary farm crops. 



