Quantifying Sectoral Water Stress under future Projections: Insights from a Coupled SWAT-WEAP Analysis

To formulate resilient water management strategies, policymakers require tools that can simultaneously simulate hydrological variability and dynamic sectoral demands. This research introduces a coupled modeling framework that links the Soil and Water Assessment Tool (SWAT) with the Water Evaluation and Planning (WEAP) model to quantify future water stress. We applied this integrated approach to the Chaliyar River Basin (CRB), driving the models with bias-corrected climate projections from 13 CMIP6 General Circulation Models. Hydrological simulations indicate a marked rise in peak flows driven by intensifying extreme rainfall events, although low flow conditions remain relatively stable. On the demand side, agriculture remains the primary consumer, driving total annual water requirements from a baseline of 1,143.2 MCM (2015) to projected levels of 1,289 MCM under SSP2-4.5 and 1,245 MCM under SSP3-7.0 by the century's end. Notably, the assessment identifies counter-intuitive vulnerability patterns: the intermediate SSP2-4.5 scenario results in higher overall unmet demand compared to the high-emission SSP3-7.0 scenario. Specifically, the agricultural sector faces critical shortages, with unmet demand reaching 26.5% under SSP2-4.5 versus only 5.3% under SSP3-7.0. These results validate the proposed coupled framework as a transferable solution for assessing sectoral water security in climatologically comparable river basins.