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measured for each control strategy. F1nally. the gafns ane losses from these o c;> "'" s'trat~fes are allocatee among the varfous partfes and conclusions are dra.n ,.. '-" for publIc polley. The s1te of the case study 1s the Grand Valley 1n "estern Colorado. where some 55.000 acres of crops are frrfga'ted from the Colorado Rfver. The results of the case study can likely be extended to other parts of the upper 8as1n. Water dfverted for frrfgatfon averages about. 500 mg/l sa11n1ty, which fs near the salfnity problem threshold. However, the qualfty of return flolfs from the aquffers underlyfng the Grand Valley was est1mated by the U. S. 5011 Conservatfcn Servfce (1,77) to average 4,200 mg/l. Over one-half m111fon tons of salts are C:fscharged fnto the river annually from irrigation anc natural sources fn the Grand Valley reach (Inman. et al.). Th1s amcunts to about 6~ of the R1ver's total salt load.3 The Grand Yalley Model The on-farm aspect of the sa11ne return flolf problem derfves from frrfgatfon applicatfons in excess of crop 'transpfratfon requfrements; the excess then drafns fnto the aquifer where ft accurr.ulates salt. Inefffc1ent frrfgatfon fs at'trfbuted to an ineJl:pensfve and plentiful water supply, so that farmers have no fncentive to become more efficient. The solution then must focus on control strat~fes 'that change the exfst1ng fncent1ves for excessive water use. A determinist1c l1near programmfng model was formulated to simu1ate crop production decisions and the irrigatfon technology and management options available to farm operators in the Grand valley, and the salt dfscnar;es assoc fated w fth these opt f ons. 4 The valley has a relat1vely short growfng season and 1s far from major markets. so on1y a limited range of prodl.lcts 1s 5