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<br />l\) <br />-1 <br />t.."".J <br />~, <br /> <br />,:<>"; <br /> <br />6 <br /> <br />REUSE OF AGRICULTURAL <br />DRAINAGE WATER TO MAXIMIZE THE <br />BENEFICIAL USE OF MULTIPLE <br />WATER SUPPLIES FOR IRRIGATION <br /> <br />James D. Rhoades, U.S. Salinity Laboratory and <br />Ariel Dinar, University of California, Riverside and <br />San Joaquin Valley Drainage Program <br /> <br />ABSTRACT <br /> <br />This chapter provides ronceptual arguments and empirical evidence to show that the <br />blending approach typically used for water quality protection can result in economic losses <br />to the agricultural community as a whole. A better strategy is suggested for dealing with <br />the "disposal" of saline agricultural drainage waters which provides greater practical <br />benefit to be derived from the tOlal water supply than blending does. In this strategy the <br />drainage water is intercepted, isolated from lhe good-quality water, and reused for the <br />irrigation of suitably salt. tolerant crops in the same project. Ultimately, a greatly reduced <br />volume olsecondary drainage water is disposed of or treated in some manner Olher than <br />blending. <br /> <br />INTRODUCTION <br /> <br />The return of agricultural drainage to freshwater supplies is often claimed <br />to be beneficial as a means to conserve water and increase water use efficiency <br />in crop production (Davenport and Hagan, 1982). Water quality agencies <br />commonly implement regulatory policies which permit agricultural drainage <br />to be returned toa majorwatersupply after ithas been diluted with good quality <br />water to a concentration level where lhe contaminate in the blend does not <br />exceed a certain value (the so-called safe limit) deemed allowable. Such claims <br />and regulatory policies do not recognize the potential deleterious eflectthat <br />such blending can have on the usability of the total receiving water supply. <br /> <br />- <br /> <br />qq <br />