Author(s): Rahul Sharma; S Sreekesh
Linked Author(s):
Keywords: CMIP6 projection; Hydrological Efficiency Index; Soil and Water Assessment Tool; Water balance projection; Water resource management
Abstract: This study employed a multi-site calibration and validation framework for streamflow using the SWAT hydrological model to simulate and analyse the unobserved water balance components of the Chaliyar River Basin (CRB) under changing future climatic conditions. The use of multi-gauge calibration enhanced the spatial representation of hydrological processes across upstream and downstream sub-basins, resulting in a more robust and spatially consistent model setup. Model performance, evaluated through multiple statistical metrics, indicated satisfactory to very good agreement between simulated and observed streamflow, thereby ensuring reliable estimation of key hydrological components such as actual evapotranspiration (AET), percolation, surface runoff, groundwater flow, and overall water yield. Future hydrological assessments were carried out using a multi-model mean ensemble derived from bias-corrected CMIP6 climate projections. Results revealed a substantial increase in mean annual rainfall, reaching up to 30% during the far-future (FF) period under the SSP5-8.5 emission scenario. Correspondingly, AET is projected to rise by as much as 25%, while surface runoff may increase by up to 30%, indicating intensification of the hydrological cycle. Groundwater flow and percolation exhibited spatially heterogeneous responses, with the most pronounced increases occurring in densely forested upstream regions. Additionally, the Hydrological Efficiency Index (HEI) indicated declining efficiency in several downstream agricultural sub-basins, primarily due to elevated evaporative losses and enhanced surface runoff. Overall, the findings underscore significant spatial variability in hydrological responses across the CRB and highlight the need for climate-resilient water management, improved irrigation strategies, and adaptive planning to sustain agricultural productivity under future climatic stress.
Year: 2026