Evaluating the Hydrologic Control of Check Dam Systems under Combined Climate and Land-Use Change Scenarios in a Semi-arid Watershed, Iran

Abstract

Aims: This study aims to evaluate the hydrological impacts of check dam systems under climate and land-use change scenarios in an arid watershed, and to assess their role in enhancing water balance and resilience. Materials & Methods: The Soil and Water Assessment Tool (SWAT) was calibrated and validated with observed streamflow data from the Gharah Kahriz Watershed, Markazi Province, Iran. Four simulation scenarios were designed: (1) climate change without check dams, (2) climate change with check dams, (3) land-use change without check dams, and (4) land-use change with check dams. Future climate scenarios under RCP 2.6, 4.5, and 8.5 pathways were generated using the LARS-WG stochastic weather generator. The model was calibrated with observed daily data from 2005–2021 as the baseline period, and monthly change factors derived from bias-corrected GCM outputs were applied to simulate daily weather data for 2021–2098. Simulations were conducted for near (2021–2040), mid (2041–2070), and far (2071–2098) future periods, and the results were aggregated to assess long-term climatic trends. Land-use maps for 1990, 2000, 2010, and 2020 were generated from multi-temporal Landsat imagery. Supervised classification techniques were applied to distinguish major land-use categories, supported by ground truth data and accuracy assessment. The resulting maps provided a consistent spatial framework for analysing land-use dynamics and their impacts over the study period. Findings: In this study, the SWAT model was executed under two conditions—before and after the construction of check dams — using baseline period data, including the 2020 land-use map and existing climatic records. The results indicate that annual mean runoff increased by 17%, 24%, and 25% under RCP 2.6, RCP 4.5, and RCP 8.5 scenarios, respectively, compared to the baseline period. The mean monthly runoff in 2000 and 2010 was higher than in 1990 and 2020. The inclusion of check dams reduced annual runoff by 53.8 mm (43%), while increasing evapotranspiration by 35.4 mm (27%) and groundwater recharge by 18.4 mm (40%). Conclusion: Check dams substantially mitigate surface runoff while enhancing subsurface recharge and evapotranspiration, thereby improving watershed resilience under changing climatic and land-use conditions. These results highlight the importance of integrating check dam systems into watershed management strategies, especially for: optimizing water-harvesting and recharge programs in arid and semi-arid basins; designing adaptive land and water management policies that account for future climate uncertainty; and guiding investment priorities for nature- based solutions to sustain water resource management.