1- Semnan university
Abstract: (7 Views)
Introduction
In recent decades, climate change has emerged as one of the most critical threats to the sustainability of freshwater resources worldwide. This challenge has been particularly severe in semi-arid regions, where rapid population growth, economic development, and unsustainable resource exploitation have further disrupted the balance between water supply and demand. Shifts in precipitation patterns, rising temperatures, and increased evapotranspiration have significantly impacted hydrological processes, especially groundwater recharge. Additionally, land use changes and poor water management practices have intensified these effects. Numerous studies emphasize that the decline in water resources in Iran results from both climatic variability and anthropogenic pressures. In this context, applying General Circulation Models (GCMs) under different Shared Socioeconomic Pathways (SSPs), particularly SSP3.7 and SSP8.5, offers a more accurate projection of future water resource conditions. This study assesses the long-term impacts of climate change on groundwater resources in the Damghanroud watershed using updated climate projections from CMIP6 models and the Soil and Water Assessment Tool (SWAT), a robust hydrological simulation model. The Mann–Kendall trend test and Sen’s slope estimator are used to detect trends and their magnitude in hydrological time series. Furthermore, the Standardized Precipitation Index (SPI) and the Standardized Runoff Index (SRI) analyze meteorological and hydrological droughts under future climate scenarios. This research provides valuable insights into the annual-scale interactions between runoff, drought, and aquifer recharge, supporting improved water resource management in semi-arid environments.
Materials and Method: The SWAT (Soil and Water Assessment Tool) model was applied in a semi-arid watershed in central Iran to evaluate the future impacts of climate change on surface runoff and groundwater recharge. The model setup included the preparation of essential spatial and climatic input data, comprising topography, land use, soil properties, and daily meteorological records. After data preparation, the model was calibrated and validated to ensure reliable simulation performance. Future daily climate projections for the period 2030–2060 were obtained from selected CMIP6 models. To improve the accuracy of climate projections, bias correction techniques were applied, including the Quantile Mapping method to correct precipitation, and temperature data normalization. All input data were processed in the ArcSWAT interface, and the model was executed to simulate monthly values of runoff and groundwater recharge, which were then aggregated to annual time scales. To detect trends in the time series of hydrological and meteorological variables, the non-parametric Mann–Kendall test assessed the statistical significance of trends, while the Sen’s slope estimator measured the magnitude of changes. Additionally, two drought indices—Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI)—were calculated to analyze the frequency, intensity, and duration of meteorological and hydrological droughts under future climate conditions. All modeling and spatial analyses were conducted in ArcGIS, while statistical analyses were performed using R and Excel software.
Results and Discussion: The simulation results indicate a noticeable upward trend in mean annual temperature under the SSP3-7.0 and SSP5-8.5 scenarios. The projected increases are approximately 0.3°C and 0.35°C, respectively, suggesting a warmer future climate in the study area. In contrast, annual precipitation is expected to decline significantly, with reductions of about 35% under SSP3-7.0 and 40% under SSP5-8.5. This substantial decrease in precipitation will likely lead to a marked reduction in surface and groundwater availability. Annual surface runoff exhibits a decreasing trend, with negative rates of 0.1 mm/year and 0.15 mm/year for SSP3-7.0 and SSP5-8.5, respectively. Groundwater recharge also follows a declining trajectory, with an average decrease of 0.9 mm/year, indicating reduced infiltration and recharge efficiency under warmer and drier conditions. These findings underscore the sensitivity of hydrological processes to projected climate changes in semi-arid environments. Drought index analysis further reveals a significant increase in the frequency of meteorological and hydrological droughts during the 2030–2060 period, particularly between 2051 and 2056. While some years may show a temporary reduction in drought intensity, the overall number of drought events is projected to rise notably. This trend points to a growing risk of multi-year droughts, exerting additional stress on regional water resources. The combined impacts of reduced precipitation, elevated temperatures, declining groundwater recharge, and increased drought occurrence highlight the vulnerability of the Damghanroud watershed to future climate change. These results align with findings from other studies in arid and semi-arid regions, emphasizing the urgent need for adaptive water management strategies and integrated planning to mitigate long-term climate risks.
Conclusion: This study demonstrates that future climate changes, under moderate and severe scenarios, will have significant negative impacts on surface and groundwater resources in semi-arid regions. The findings indicate a considerable reduction in precipitation, runoff, and groundwater recharge, accompanied by increasing temperature and consecutive drought events. These changes will severely disrupt the hydrological balance of the region and have profound impacts on agriculture, potable water supply, and sustainable development. Although the overall trend of climate change points to increased climatic stress, the variability in drought intensity over the years suggests that adaptive measures must be dynamic, region-specific, and based on continuous monitoring. One key practical implication of this study is the need to integrate climate change scenarios into regional water resource policies, enhance artificial groundwater recharge measures, and reconsider irrigation and water consumption patterns. Furthermore, the uncertainty in climate model outputs and the spatial heterogeneity of hydrological responses are key challenges in decision-making that require further in-depth studies. Overall, this research emphasizes the necessity of adopting resilient and climate-adaptive strategies for water resource management, particularly in water-stressed regions. It provides a significant step toward developing science-based policies for sustainable water governance in the face of changing climatic conditions and offers valuable guidance for decision-makers and planners.
In recent decades, climate change has emerged as one of the most critical threats to the sustainability of freshwater resources worldwide. This challenge has been particularly severe in semi-arid regions, where rapid population growth, economic development, and unsustainable resource exploitation have further disrupted the balance between water supply and demand. Shifts in precipitation patterns, rising temperatures, and increased evapotranspiration have significantly impacted hydrological processes, especially groundwater recharge. Additionally, land use changes and poor water management practices have intensified these effects. Numerous studies emphasize that the decline in water resources in Iran results from both climatic variability and anthropogenic pressures. In this context, applying General Circulation Models (GCMs) under different Shared Socioeconomic Pathways (SSPs), particularly SSP3.7 and SSP8.5, offers a more accurate projection of future water resource conditions. This study assesses the long-term impacts of climate change on groundwater resources in the Damghanroud watershed using updated climate projections from CMIP6 models and the Soil and Water Assessment Tool (SWAT), a robust hydrological simulation model. The Mann–Kendall trend test and Sen’s slope estimator are used to detect trends and their magnitude in hydrological time series. Furthermore, the Standardized Precipitation Index (SPI) and the Standardized Runoff Index (SRI) analyze meteorological and hydrological droughts under future climate scenarios. This research provides valuable insights into the annual-scale interactions between runoff, drought, and aquifer recharge, supporting improved water resource management in semi-arid environments.
Materials and Method: The SWAT (Soil and Water Assessment Tool) model was applied in a semi-arid watershed in central Iran to evaluate the future impacts of climate change on surface runoff and groundwater recharge. The model setup included the preparation of essential spatial and climatic input data, comprising topography, land use, soil properties, and daily meteorological records. After data preparation, the model was calibrated and validated to ensure reliable simulation performance. Future daily climate projections for the period 2030–2060 were obtained from selected CMIP6 models. To improve the accuracy of climate projections, bias correction techniques were applied, including the Quantile Mapping method to correct precipitation, and temperature data normalization. All input data were processed in the ArcSWAT interface, and the model was executed to simulate monthly values of runoff and groundwater recharge, which were then aggregated to annual time scales. To detect trends in the time series of hydrological and meteorological variables, the non-parametric Mann–Kendall test assessed the statistical significance of trends, while the Sen’s slope estimator measured the magnitude of changes. Additionally, two drought indices—Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI)—were calculated to analyze the frequency, intensity, and duration of meteorological and hydrological droughts under future climate conditions. All modeling and spatial analyses were conducted in ArcGIS, while statistical analyses were performed using R and Excel software.
Results and Discussion: The simulation results indicate a noticeable upward trend in mean annual temperature under the SSP3-7.0 and SSP5-8.5 scenarios. The projected increases are approximately 0.3°C and 0.35°C, respectively, suggesting a warmer future climate in the study area. In contrast, annual precipitation is expected to decline significantly, with reductions of about 35% under SSP3-7.0 and 40% under SSP5-8.5. This substantial decrease in precipitation will likely lead to a marked reduction in surface and groundwater availability. Annual surface runoff exhibits a decreasing trend, with negative rates of 0.1 mm/year and 0.15 mm/year for SSP3-7.0 and SSP5-8.5, respectively. Groundwater recharge also follows a declining trajectory, with an average decrease of 0.9 mm/year, indicating reduced infiltration and recharge efficiency under warmer and drier conditions. These findings underscore the sensitivity of hydrological processes to projected climate changes in semi-arid environments. Drought index analysis further reveals a significant increase in the frequency of meteorological and hydrological droughts during the 2030–2060 period, particularly between 2051 and 2056. While some years may show a temporary reduction in drought intensity, the overall number of drought events is projected to rise notably. This trend points to a growing risk of multi-year droughts, exerting additional stress on regional water resources. The combined impacts of reduced precipitation, elevated temperatures, declining groundwater recharge, and increased drought occurrence highlight the vulnerability of the Damghanroud watershed to future climate change. These results align with findings from other studies in arid and semi-arid regions, emphasizing the urgent need for adaptive water management strategies and integrated planning to mitigate long-term climate risks.
Conclusion: This study demonstrates that future climate changes, under moderate and severe scenarios, will have significant negative impacts on surface and groundwater resources in semi-arid regions. The findings indicate a considerable reduction in precipitation, runoff, and groundwater recharge, accompanied by increasing temperature and consecutive drought events. These changes will severely disrupt the hydrological balance of the region and have profound impacts on agriculture, potable water supply, and sustainable development. Although the overall trend of climate change points to increased climatic stress, the variability in drought intensity over the years suggests that adaptive measures must be dynamic, region-specific, and based on continuous monitoring. One key practical implication of this study is the need to integrate climate change scenarios into regional water resource policies, enhance artificial groundwater recharge measures, and reconsider irrigation and water consumption patterns. Furthermore, the uncertainty in climate model outputs and the spatial heterogeneity of hydrological responses are key challenges in decision-making that require further in-depth studies. Overall, this research emphasizes the necessity of adopting resilient and climate-adaptive strategies for water resource management, particularly in water-stressed regions. It provides a significant step toward developing science-based policies for sustainable water governance in the face of changing climatic conditions and offers valuable guidance for decision-makers and planners.
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