Regional allocation of irrigation water in a rice paddy area with water-saving practices

A multiobjective optimization model has been presented for allocating irrigation waters in a rice paddy area. Water-saving practices conducted on the field-plot basis are considered and expressed in the optimal water allocation problem in the regional scale. Irrigation water allocated to the blocks of paddy fields is divided into two components of a basic amount and a safety margin in order to mitigate the effect of hydrological and hydraulic uncertainties on the study area. Four competing management objectives with regard to total rice yield, total water-saving cost, equity of water allocation, and safety of water supply are defined in the linear programming formulation so that noninferior solutions can be procured which are informative and persuasive in decision-making. Applicability of the optimization model is examined using water allocation problems for a hypothetical irrigation system. It is demonstrated that the optimization model can provide satisficing solutions where the four objectives are harmonized under substantial variations of total water supply to the irrigation system.