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<br />measured for each control strategy. Flna11y, the galns and losses from these <br />strategles are allocated among the varlous parties and conc1uslons are drawn <br /> <br />~ for public polley. <br />~ <br />I:) The site of the case study is the Grand Valley in western Colorado, where <br />~ <br />some 55,000 acres of crops are lrrigated from the Colorado River. The results <br />of the case study can llke1y be extended to other parts of the upper Basln. <br />Water dlverted for irrigation averages about 500 mg/l sa11nlty, whlch ls near <br /> <br />the salinity problem threshold. However, the qua11ty of return flows from the <br />aquifers underlying the Grand Valley was estimated by the U. S. Sol1 <br />Conservatlon Servlce (1977) to average 4,200 mg/1. Over one-half ml1l10n tons <br /> <br />of salts are dlscharged lnto the rlver annually from irrigatlon and natural <br /> <br />sources ln the Grand Valley reach (Inman, et a1.). Thls amounts to about 6~ of <br />the River's total salt load.3 <br /> <br />The Grand Yalley Model <br /> <br />The on-farm aspect of thesa11ne return flow problem derlves from <br />irrigation applications in excess of crop transplration requirements; the <br />excess then dralns lnto the aqulfer where it accumulates salt. Inefflclent <br />irrigation ls attributed to an lnexpenslve and p1entlfu1 water supply, so that <br />farmers have no incentlve to become more efflc lent. The solutlon then must <br /> <br />focus on control strategies that change the existing incentlves for excessive <br /> <br />water use. <br /> <br />A deterministic llnear programmlng model was formulated to slmu1ate crop <br />production decislons and the lrrlgation technology and management optlons <br />avallable to farm operators ln the Grand valley, and the salt dlscharges <br />associated wlth these options.4 The valley has a relatlvely short growlng <br /> <br />season and is far from major markets, so only a l1mlted range of products is <br /> <br />5 <br />