Optimal Management Strategies for Cutback Furrow Irrigation

Abstract

The optimal management of a cutback‐furrow‐irrigation system with spatially variable infiltration based on an average intake function was analyzed. The problem was formulated as a cost‐minimization function subject to meeting a specified fraction of the irrigation requirement. Optimal solutions were examined in the context of developing a real‐time control system for furrow irrigation. Although total infiltration was adequately predicted with the average function, final water distribution was not. Consequently, the optimal policies resulted in actual requirement efficiencies less than the target value. Nonetheless, relative changes in performance as a function of the constraint were well predicted. The performance index was relatively insensitive near the optimum, and cutback time had the least impact on application efficiency and uniformity. Satisfactory performance was therefore still obtained by reducing the inflow after the final advance time. Similar values of application efficiency were generally computed with decreasing application depths, but smaller efficiency resulted when the optimized cutoff time was less than the final advance time. There were small performance differences between discrete and continuous‐time cutback functions.