Modelling optimum water release for agricultural lands using goal programming approch

Abstract

The agricultural sector is one of the main sectors which benefits from several sources of water supply. This sector faces several challenges in securing water supply for its respective crops. Since the demand for water is increasing due to several factors, including population growth and an increased level of water dependent activities, and changes to crop selection influenced by various factors, including ever changing demand, the need for optimal use of water is identified as a priority for the rural agriculture sector in Sri Lanka. Past inflow data was used to obtain inflow values from the Udawalawa reservoir by using a forecasting model and the seasonal ARIMA model which was a statistical forecasting model used to forecast the inflow using RStudio software. In this respect water reservoir management is a crucial factor for allocating water for agricultural crops for study, a Goal programming model was formulated to determine the optimum water release for agricultural lands in Udawalawa region. Six main agricultural land divisions of the Udawalawa irrigation scheme were selected, and two of them received water from the right bank canal while the other four received water from the left bank canal of the Udawalawa reservoir. A Goal programming model with a 246 number of variables, 72 equality constraints, and 138 inequality constraints is solved using the MATLAB programming language and results show that water allocation from each reservoir can be used to fulfill the water demand throughout the year by using the water flow and allocation for each crop according to the priorities. In this case, it was assumed that 60% of the farming land used to cultivate paddy while the remaining 40% of the farming land used to cultivate other crops. These findings can be used by the stakeholders when making decisions on water allocation, not just based on the demand but also meeting a balance of crop selection. Key words: Water Release Optimization, Goal Programming, Forecasting