Crop and Water Allocation in Andean Community Irrigation Systems: An Optimization Framework for Sustainable Irrigation Planning from a Social-Ecological Perspective

Community-managed irrigation systems in Andean mountain catchments often operate with limited hydrometric information, complicating crop- and water-allocation planning. This study developed a reproducible annual linear-programming framework for the Santul Irrigation System, Ecuador, combining census data from all 46 registered irrigators with documented agronomic, climatic, economic, phenological, and irrigation-efficiency parameters. Three allocation configurations were compared: an economic-only benchmark, a maximum-share diversification model, and a hypothetical crop-specific four-crop diversification scenario. Survey-informed proxy annual water budgets were derived from the reported nominal flow and self-reported irrigation intensity. Under the reference specification, all nine baseline cases used the complete 15.945 ha modeled-crop domain; the land constraint was binding, whereas the water constraint was non-binding. Annual gross output values were USD 129,634, USD 79,845, and USD 76,412, while annual modeled supplemental irrigation requirements were 9007, 8445, and 7740 m3/year, respectively. Under maximum planting-month demand, water became binding and modeled land use declined to 69.6%, 81.5%, and 80.0%. Of 328 baseline and robustness runs, 324 were feasible. The framework is a diagnostic decision-support tool whose outputs are interpreted from a social-ecological perspective; it does not directly optimize social-ecological outcomes or prescribe a crop plan.