Climate changes and the unremitting overexploitation of groundwater in the Hamedan-Bahar Plain have raised concerns about the sustainability of groundwater resources. The current research focused on the development of an integrated system dynamics model to examine the long-term effects of employing five adaptation strategies on groundwater. The model was calibrated and validated using a 21-year historical data set, and the strategies were combined into 21 management and climate change scenarios (seven management scenarios in tandem with three climate change scenarios) to project groundwater levels for the period 2020– 2050. Future climatic conditions were projected by downscaling the data of the CanESM2 general circulation model under three representative concentration pathway scenarios (RCP2.6, RCP4.5, and RCP8.5). By applying the business-as-usual management scenario, the groundwater table change rates will be −0.37, −0.45, and −0.44 m/year under the RCP2.6, RCP4.5, and RCP8.5 scenarios, while the corresponding rates for the most efficient management scenario are +0.22, +0.11, and +0.13 m/year, respectively. The strategies have been ranked according to their effectiveness as follows: (i) reducing irrigated agriculture in favor of rainfed agriculture or fallow fields, (ii) applying an adaptive cropping pattern, (iii) developing early-maturing cultivars, (iv) practicing deficit irrigation, and (v) enhancing irrigation efficiency. The findings indicate that the local management strategies will play a greater role in future groundwater sustainability than global climate change.
