440 IRRIGATION FARMING. 



some sinks into the soil below the reach of plants. 

 The amount of water which sinks below the roots of 

 the irrigated crops depends upon various conditions. 

 Observations in many secftions show that usually this 

 water sinks diredlly downward with very little side- 

 flow till it reaches a stratum of rock or clay so compadl 

 that it can go no farther. Then as other sinking 

 water is added, the surface of the underground reser- 

 voir rises, filling all the pores and spaces in the soil till 

 it reaches a layer of gravel or sand, through which it 

 slowly percolates until it finds outlet into the river 

 from which it was originally taken, or it may appear in 

 some arroyo, branch, or draw which leads into the 

 river — in any event, it finally finds its way back to the 

 parent stream. This is why the water-table in the 

 wells of an irrigated country rises many feet nearer the 

 surface than before irrigation was practiced, and even 

 springs often burst out at the foot of hills below irri- 

 gated fields or mesas. The deeper this seepage water 

 has to sink before finding an impervious layer to form 

 the bottom of its underground reservoir, the longer 

 will it be before the detrimental effedls of over-irrigation 

 will show themselves and the looser the layer through 

 which it flows, and the greater the slope of such layer the 

 more rapid will be the underflow of the seepage water. 

 This underflow may come out tjpon a lower lying 

 field, and as said previously tend to convert it into a 

 marsh, establishing water-sick land, or it may bring 

 up a solution of alkali to ruin the soil of such fields. 

 In either case, suits for damages may follow. Such 

 results are becoming alarmingly apparent in the irri- 

 gated districts of Colorado and elsewhere throughout 



