Planning the Optimum Crop Pattern Considering Surface and Groundwater Resources Interaction by Coupling SWAT, MODFLOW and PSO

In arid regions, excessive use without proper management put water resources under immense pressure and multiple stresses. Finding a good strategy for water resources management is essential to preserve sustainability in such regions. This study aimed at optimizing the water use for the agricultural crops in the Eshtehard watershed in Iran, where the aquifer is a strategic resource for irrigated agriculture and is facing intensive drawdown due to over extraction. A hydro-agronomic simulation-optimization approach is used for surface and groundwater modeling in which the agricultural production and water level variation are simulated by linking SWAT and MODFLOW and the optimal crops pattern is searched for by the PSO algorithm. The crops’ area and their irrigation water consumption are the decision variables with the objective of maximizing the net benefit gained from the crops’ yield while the groundwater drawdown is limited to a pre-defined stability level. Results showed that in the optimum state, irreparable damage to groundwater depletion is reduced. To this result, a part of area cultivated by winter wheat and cotton must be replaced by winter barley which results in reduction of the groundwater extraction for winter wheat, winter barley and cotton by 45%, 7%, and 10%, respectively. Also, after the application of these changes, the profit from winter wheat and cotton crops decreased by 35% and 13%, respectively, and that for barley increased by 49%, which generally increased the production profit of irrigation products by 4%.