Document Type

Full Issue

Publication Date

11-1922

Abstract

All information that will 'enable the irrigator to use water economically is valuable to arid-climate agriculture. In many arid-climate regions, including the western part of the United States, excessive waste of water occurs in the irrigation of highland porous soil areas, as a result of lack of information concerning the capacity of the soil to hold water. Following the waste of water on the uplands by excessive percolation through open soils, vast lowland areas are rendered partially or wholly nonproductive by water-logging. To illustrate, a gravelly bench soil four feet deep, if underlain by a coarse open gravel to a great depth, has the power to hold but a small amount of water. If, to such a soil, a large amount of water is applied in a single irrigation, then unnecessary waste through deep percolation inevitably follows. Furthermore, the wasted water slowly but surely finds its way to low-lying lands from which there is in adequate natural drainage, and water-logging results. It is doubtful if an acre of a typical upland soil, four feet deep, would retain more than three acre-inches of irrigation water. If therefore it took six hours adequately to cover an acre with a 2-second-foot stream, the total amount of water applied would be 12 acre-inches an acre, or four times what the soil could retain. Such excessive applications frequently result from the difficulty in getting the water spread uniformly over the surface. In the illustration given above it is clear that 9 acre-inches, of the 12 acre-inches applied to one acre, must be lost to the upland soil and added to the lowland soil, provided of course allowance is made for evaporation losses. The experiments reported in this bulletin were planned to measure the capacity of some soils to retain water, and thereby assist the irrigator better to determine the proper amount of water to apply to such soils in single irrigations.

 
 

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