Climate Change and Water Security in Semi-Arid Regions: Integrating Surface and Groundwater Responses

Abstract

Climate change poses significant threats to water resource sustainability and security, necessitating robust evaluation models to quantify the risks. Robust frameworks for assessing climate change impacts on coupled surface and groundwater systems remain limited, particularly in data-scarce, semi-arid regions. This study introduces an integrated climate–hydrological assessment framework that combines process-based modelling with multi-dimensional drought diagnostics. The framework integrates the Soil and Water Assessment Tool (SWAT) with CMIP6 climate projections (SSP3-7.0 and SSP5-8.5) and a suite of novel and traditional drought indices, including the newly developed Standardized Groundwater Recharge Index (SGRI), the Reconnaissance Drought Index (RDI), the Standardized Precipitation Index (SPI), and the Standardized Runoff Index (SRI). The utility of the framework is demonstrated through a case study in the Damghanroud watershed, central Iran, for the period 2031–2059. Results reveal a projected 59–68% decline in wet-season precipitation, 33–46% reduction in surface runoff, and 36–45% increase in evapotranspiration. Groundwater recharge is projected to decrease by 8.8–9.5%, indicating significant aquifer stress. The RDI captures a marked increase in drought intensity and frequency, especially toward the end of the simulation period. By integrating hydrological modelling with advanced drought diagnostics, this framework offers a transferable approach for diagnosing climate-induced water stress across diverse hydroclimatic settings. The combined use of SGRI and RDI enhances early warning capabilities and supports more informed, adaptive water management strategies. This methodological advancement contributes to global efforts in building climate resilience in vulnerable water systems.