1- Department of Combating Desertification, Faculty of Desert Studies, Semnan University, Semnan, Iran
2- Department of Arid Areas Management, Faculty of Desert Studies, Semnan University, Semnan, Iran
2- Department of Arid Areas Management, Faculty of Desert Studies, Semnan University, Semnan, Iran
Abstract: (491 Views)
Extended Abstract
Background: In recent decades, climate change has emerged as one of the most serious threats to the sustainability of freshwater resources worldwide. This challenge is particularly severe in semi-arid regions, where rapid population growth, economic development, and unsustainable resource exploitation have increasingly disrupted the balance between water supply and demand. Changes in precipitation patterns, rising temperatures, and increased evapotranspiration have significantly affected hydrological processes, especially groundwater recharge. In addition, land use changes and poor water management practices have further exacerbated these impacts. Numerous studies have emphasized that both climate change and human pressures drive the decline in Iran’s water resources. In this context, the use of General Circulation Models (GCMs) under various Shared Socioeconomic Pathways (SSPs), particularly SSP5-8.5, provides a more accurate projection of future water resource conditions. This study investigates the long-term impacts of climate change on groundwater resources in the Damghanroud watershed using climate projections from CMIP6 models and the Soil and Water Assessment Tool (SWAT) hydrological model. The research offers valuable insights into the annual interactions between surface runoff, drought, and aquifer recharge, contributing to improved water resource management in semi-arid environments.
Methods: The SWAT model was applied in a semi-arid watershed in central Iran to assess the future impacts of climate change on surface runoff and groundwater recharge. Model setup involved the preparation of spatial and climatic input data, including topography, land use, soil characteristics, and daily meteorological records. Following data preparation, the model was calibrated and validated to ensure reliable simulation performance. Daily climate projections for the 2030–2060 period were obtained from selected CMIP6 climate models. Bias correction techniques, including quantile mapping for precipitation and normalization for temperature data, were applied to improve the accuracy of these projections. All input data were processed using ArcSWAT, and the model was executed to simulate monthly surface runoff and groundwater recharge, which were subsequently aggregated to an annual time scale. To identify trends in the hydrological and meteorological time series, the non-parametric Mann-Kendall test was employed to assess statistical significance, while Sen’s slope estimator was used to measure the rate of change. Furthermore, two drought indices—the Standardized Precipitation Index (SPI) and the Standardized Runoff Index (SRI)—were calculated to analyze the frequency, intensity, and duration of meteorological and hydrological droughts under future climate scenarios. All spatial modeling and analyses were conducted using ArcGIS, while statistical analyses were performed using R and Excel software.
Results: The simulation results under the SSP5-8.5 scenario revealed a significant upward trend in the mean annual temperature for the period 2030–2060. Specifically, temperature increases were estimated at approximately 0.4 °C per decade during dry years and 0.2 °C per decade during wet years. Annual precipitation showed a noticeable decline, with reductions of up to 36% and 28% projected for dry and wet years, respectively. Surface runoff also followed a declining trend, with an estimated average annual reduction of 0.15 mm, and particularly in dry years, the reduction exceeded 40%. Groundwater recharge is expected to experience a substantial decrease, especially during drought periods, with annual reductions reaching up to 90% above the long-term average. On average, the annual decline in recharge was projected to be around 0.9 mm. Analysis of drought indices (SPI and SRI) indicates that, although drought intensity may slightly decrease compared to the baseline period, the frequency of drought events is projected to increase. These changes suggest growing instability in groundwater resources due to sharp fluctuations between wet and dry periods in the future.
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.
Background: In recent decades, climate change has emerged as one of the most serious threats to the sustainability of freshwater resources worldwide. This challenge is particularly severe in semi-arid regions, where rapid population growth, economic development, and unsustainable resource exploitation have increasingly disrupted the balance between water supply and demand. Changes in precipitation patterns, rising temperatures, and increased evapotranspiration have significantly affected hydrological processes, especially groundwater recharge. In addition, land use changes and poor water management practices have further exacerbated these impacts. Numerous studies have emphasized that both climate change and human pressures drive the decline in Iran’s water resources. In this context, the use of General Circulation Models (GCMs) under various Shared Socioeconomic Pathways (SSPs), particularly SSP5-8.5, provides a more accurate projection of future water resource conditions. This study investigates the long-term impacts of climate change on groundwater resources in the Damghanroud watershed using climate projections from CMIP6 models and the Soil and Water Assessment Tool (SWAT) hydrological model. The research offers valuable insights into the annual interactions between surface runoff, drought, and aquifer recharge, contributing to improved water resource management in semi-arid environments.
Methods: The SWAT model was applied in a semi-arid watershed in central Iran to assess the future impacts of climate change on surface runoff and groundwater recharge. Model setup involved the preparation of spatial and climatic input data, including topography, land use, soil characteristics, and daily meteorological records. Following data preparation, the model was calibrated and validated to ensure reliable simulation performance. Daily climate projections for the 2030–2060 period were obtained from selected CMIP6 climate models. Bias correction techniques, including quantile mapping for precipitation and normalization for temperature data, were applied to improve the accuracy of these projections. All input data were processed using ArcSWAT, and the model was executed to simulate monthly surface runoff and groundwater recharge, which were subsequently aggregated to an annual time scale. To identify trends in the hydrological and meteorological time series, the non-parametric Mann-Kendall test was employed to assess statistical significance, while Sen’s slope estimator was used to measure the rate of change. Furthermore, two drought indices—the Standardized Precipitation Index (SPI) and the Standardized Runoff Index (SRI)—were calculated to analyze the frequency, intensity, and duration of meteorological and hydrological droughts under future climate scenarios. All spatial modeling and analyses were conducted using ArcGIS, while statistical analyses were performed using R and Excel software.
Results: The simulation results under the SSP5-8.5 scenario revealed a significant upward trend in the mean annual temperature for the period 2030–2060. Specifically, temperature increases were estimated at approximately 0.4 °C per decade during dry years and 0.2 °C per decade during wet years. Annual precipitation showed a noticeable decline, with reductions of up to 36% and 28% projected for dry and wet years, respectively. Surface runoff also followed a declining trend, with an estimated average annual reduction of 0.15 mm, and particularly in dry years, the reduction exceeded 40%. Groundwater recharge is expected to experience a substantial decrease, especially during drought periods, with annual reductions reaching up to 90% above the long-term average. On average, the annual decline in recharge was projected to be around 0.9 mm. Analysis of drought indices (SPI and SRI) indicates that, although drought intensity may slightly decrease compared to the baseline period, the frequency of drought events is projected to increase. These changes suggest growing instability in groundwater resources due to sharp fluctuations between wet and dry periods in the future.
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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