A NONLINEAR MIXED-INTEGER PROGRAM MODEL FOR EVALUATING RUNOFF IMPOUNDMENTS FOR SUPPLEMENTAL IRRIGATION

On-farm runoff collection through small impoundments (ponds) is a pote ntial irrigation water source. This study evaluates the economic feasi bility of such impoundments for supplemental irrigation in the Blackla nds region of Texas. This is done using a risk sensitive model which s imultaneously considers water supply, irrigation system investment, ir rigation scheduling, and crop mix selection. A two-stage, mixed intege r, nonlinear mathematical programming model under uncertainty, was use d to formulate the problem and solved with Benders' decomposition. Pon d-based supplemental irrigation is found to be both risk reducing and net income increasing in the study area. The model results also show o ff-farm water needs to be worth more than $100 per acre foot to make i mpoundments undesirable.