10 SUGGESTIONS TO SETTLERS IN COLUMBIA RIVER VALLEY. 



Every irrigator should endeavor to learn just how much water is 

 required to fill his soil. For most of the soils of this region from 2^ 

 to 4 inches will be sulhcient for each irrigation if quickly applied. 

 To use more water than the soil will hold is the prevalent tentlenOy 

 and practice. This fact is plainly evidenced by the presence of ponds 

 of water and the need of drainage in some of the irrigated districts 

 along the Columbia River. This seepage water is largely due to 

 excessive irrigation. As the water percolates through the soil it 

 doubtless carries in solution nitrogen and other essential plant food 

 that it will cost time and money to replace. Where pumping plants 

 are used the raising of more water than is required also causes a 

 heavy loss. If overirrigation continues to be practiced, expensive 

 drainage systems will have to be constructed sooner or later to 

 carry the water back to the river." 



CHECKING LOSSES OF WATER. 



Water is mainly lost in two ways, viz, by percolation into the sub- 

 soil and by evaporation from the surface of the ground. 



Frequent light irrigation materially reduces the loss from percola- 

 tion, but increases the loss by evaporation. Loss from percolation 

 may also be reduced by increasing the water-holding capacity of 

 the soil. This is done by plowing under green manure and cover 

 crops and by heavy applications of stable manure. 



With a fine firm soil, thorough cultivation as soon as possible 

 after irrigating is the most effective way of checking evaporation. 

 Where the soil is light and sandy, however, clean cultivation keeps 

 it too loose and subjects it to the danger of drifting. Under these 

 conditions mulches of stable manure, straw, and other litter will 

 be found very beneficial in checking evaporation. 



DISTRIBUTION OF WATER. 



The amount of water which most irrigation companies agree to 

 deliver to the farmer is 1 cubic foot per second for each 160 acres of 

 land. During the irrigating season of seven months (April 1 to No- 

 vember 1) this amounts to about 32 inches in depth. Since little 

 irrigation is ordinarily done after October 1, 27 inches would be ap- 

 proximately the amount supplied. Up to the present time, with but 

 a small percentage of the land under the various irrigation systems in 

 cultivation, the companies have quite generally supplied more water 

 than their contracts required them to deliver. But as the acreage of 

 cultivated land increases from year to year and the demand for water 



«For records of the amount of water used on various crops at Kennewick, Wash., 

 in 1906, see Bulletin 188, Office of Experiment Stations, U. S. Dept. of Agriculture, 

 entitled "Irrigation in the Yakima Valley, Washington." 

 [Cir. 60] 



