optimizing Temporal Water Allocation by Irrigation Ditch Companies

ABSTRACT Adynamic programming (DP) algorithm is presented for allocation of irrigation water over time by ditch companies. The algorithm optimizes weekly deliveries of water to farmers and uses a single state variable, total storage in reservoirs at the beginning of each week. The DP objective is minimization of the sum of squared shortages over the irrigation season. The DP solution consists of optimal operating rules in the form of tables which indicate optimal target end-of-week storage as a function of beginning-of-week storage. One table is obtained for each week of the season. Stochastic treatment of crop water demand is compared against deterministic treatment using a case study ditch company near Fort Collins, CO. In repetitive simulations, stochastic DP always outperformed deterministic DP in terms of average sum of squared shortages, even when only two years of historical weather data were available for characterizing the reference E^ process.