A practical planning software program for desalination in agriculture - SPARE:WATERopt

Water shortage limits agricultural production worldwide, and irrigation leads to a rapid depletion of water resources. Using desalinated water for irrigation reduces pressure on local resources but it is expensive. An economically viable utilization for using desalinated water in agriculture is only possible through the optimal planning and management of cropland and irrigation scheduling management. We developed a software program aiming to maximize the gross margin (GM) by optimizing cropping patterns using a site-specific crop water requirement model. We used the simplex algorithm under the boundary conditions of limited water (temporal scale) and available land (spatial scale). In a proof of concept, we tested the software for a desalination plant in Saudi Arabia that produces 60,000m3day−1. A cropping pattern for 4278ha was derived that maximizes GM (92 Mio US$ yr−1) and uses most (97%) of the constant water supply to the plant. An optimal cropping pattern (4023ha) solely maximizing GM yields a higher outcome (125 Mio US$ yr−1) and requires even less water for irrigation. This surplus water can be used for leaching soils or other purposes. Both cropping patterns are dominated by cucumber and tomatoes, covering the largest fractions of cropland at 74% and 88%, respectively.