Water Quality in Irrigated Watersheds

Abstract

AbstractHistorically, attention to water quality in irrigated watersheds has been focused on irrigation waters and the relationships of their chemical composition to soil permeability and crop production. Recently, because of environmental concerns, it has become necessary to look beyond the quality of irrigation waters and consider also the quality of waters that drain from irrigated lands. Irrigation agriculture affects drainage‐water chemical composition. In turn, drainage waters can influence the quality of receiving waters which may have a variety of beneficial uses to be protected.The two types of drainage waters from irrigated lands, surface runoff and subsurface drainage or percolation water, are characteristically different in composition and chemical concentration. The pollution potential of subsurface drainage waters, with respect to nitrate and total soluble salts is of particular concern. Studies of individual field conditions are providing information that can be extrapolated to show the effects of watershed management on ultimate water quality in a receiving stream or ground water.A new concept has been developed concerning irrigation water management to minimize the quantity of salt discharged from irrigated lands and thereby help alleviate water quality degradation associated with disposal of salt‐laden subsurface drainage waters.