Computer application for optimization of turn assignment on a tree-structured irrigation network

Abstract

Most of the easier structural solutions for greater utilization of water resources have already been implemented. The principal objective of this paper is to develop a methodology for helping to produce irrigation scheduling policies for the deployment of water resources for agricultural use. We have, therefore, developed WISCHE (Water Irrigation Scheduling), a decision support system for irrigation scheduling in an arborescent network. Computational experience has been implemented with satisfactory results in La Comunidad de Regantes, Riegos de Levante, Canal 2nd, eastern Spain. Its irrigation area covers 2188 Hectares, with 2831 nodes distributed in 20 sectors. Irrigation is needed on a daily basis in five time periods. Network topology, periodical demands and historical consumptions are the inputs and scheduling the hydrants and turns are the output. Assignments must satisfy two types of constraints: the first one based on physical network limitations and the other one based on previous consumptions and demands. In order to deal with the first limitations, a mixed 0-1 separable quadratic program is proposed. Statistical information about previous consumptions on turns demanded and non-attended demands is used to assign a priority to hydrants. Thus, the system favours hydrants which used what they applied for and hydrants which could not be well attended previously.