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o <::I ~, ~, salt discharges for various crops ana irr1gat1on techn1~ues .ou'~ be 1mpractical. Thus the tax approaCh 15 shewn as a hypothetical alternat~ve to the other strateg1es. The estimated response to is salt tax 1s approached ind1rectly. The salt constrafnt 1n the 11near program was reduced parametrically to show changes 1n the optimal solution. The shadow prfce on a ton of salt d1scharge 1s equivalent to the effluent ta:.:: wh1ch would opt1mize salt d1scnarges at each level of pollution by charging the full value of the right to put salt into the river. Tr.ese effluent tax change points are shown 1n-the first column of part B of table 2. A tax as 10'" as SO cents per ton of salt could discourage over 40,000 tens of salt discharge. In the S4.50 to S5.50 range, Ue use of short sets and gated pipe with manual cutback would allo~ savings in salt loads of up to 90,000 tons. Additional reductions would be gained with taxes around $1.00. $11.00 and $13.00 per ton. The net social cost for any level of reduction in salt discharges beyond the first increment 15 much less than for irrigatfon system subsidies. However, a marginal tax rate which is less than even our revised estimate of do'ftinstream marginal damages avoided drives net ~ll- _ rents into negative terr1tory. The results in part 8 of table 2 should be interpreted ~1th cauticn. ~ore extreme changes in farming practices might occur beyond the levels constra1ned by the model. As the salt tax increases, strong 1ncenthes might t:e exerted to replace unprofitable crops (1.e., barley and pasture) with higher valued crops (1.9., com and pinto beans). Retiring the IOOst marginally product1ve lands might also occur. Economic motives would also hasten the adoption of rr.ore efficient means of controlling salt d1schar;es. Thus total salt Cl1scharges 12