Assessment of the climate change impacts on the watershed-scale optimal crop pattern using a surface-groundwater interaction hydro-agronomic model

In arid regions, water resources are under immense pressure and multiple stresses. Excessive use of water resources without proper management occurs in the present situation, and it will be intensified under future climate change conditions. Finding a good strategy for water resources management is essential to preserve sustainability in such watersheds. In this study, the first purpose is to optimize 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 because of over-extraction. A hydro-agronomic simulation-optimization approach is used for agronomy and groundwater management 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. For the following purpose, the climate change impact on the optimal crop pattern across the watershed under two representative concentration pathways scenarios (RCPs 2.6 and 8.5) downscaled by the data of the HadGEM2-ES General Circulation Model for the near future is evaluated. Results show that irreparable damage to groundwater depletion is reduced in the optimum state, and lower stress is imposed on the aquifer under the climate change impacts by executing the optimum crop pattern. To see this, a part of the winter wheat and cotton crops’ area must be replaced by winter barley. Also, the crop’s irrigation amount must be decreased for winter wheat, winter barley and cotton by 45%, 7%, and 10%, respectively, which reduces groundwater extraction in the optimum situation. •A hydro-agronomic simulation-optimization approach for agronomy-groundwater management by linking SWAT and MODFLOW and PSO.•Evaluating the climate change impact on the optimal crop pattern across the watershed under two RCPs for the near future.•Decreasing the irreparable damage for groundwater depletion by using the optimized pattern in the climate change condition.•Reducing groundwater extraction by replacing a part of winter wheat and cotton crops’ area with winter barley.