Climate warming modifies hydrological responses in the southern Western Ghats and the western coastal plains (India): Insights from CMIP6-VIC simulations

Abstract

Recent changes in global precipitation patterns have led to unparalleled floods, landslides, and droughts, significantly impacting lives, infrastructure, and the environment. Understanding regional-scale climate change impacts on hydrological responses has attracted researchers, primarily using climate projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6). This study focuses on the southern Western Ghats (SWG) and western coastal plains (WCP) of the Indian subcontinent to assess climate change impacts on regional hydrology. By analyzing climate data from nine CMIP6 General Circulation Models (GCMs) and simulating hydrological fluxes with the Variable Infiltration Capacity (VIC) model, we demonstrate that all models robustly project an intensification of the hydrological cycle due to climate warming under two shared socioeconomic pathways (SSPs) - SSP245 and SSP585 - especially during the Indian Summer Monsoon (ISM) season. The region is projected to experience up to a 20 % increase in annual precipitation per 1 °C rise in temperature, with extreme precipitation events (EPEs) potentially increasing by up to 16 % per degree of warming. Future runoff is expected to rise under both SSP scenarios, with watersheds experiencing markedly wetter ISM season and drier pre-monsoon (PRM) season compared to the baseline period, leading to risks associated with concurrent floods/landslides and droughts. These changes underscore the necessity for region-specific adaptation strategies to manage water resources effectively. Adaptation strategies to enhance short-term water storage during the ISM season could partially mitigate water shortages during the PRM season, offering potential benefits in the wake of climate change. Our findings highlight the need for integrated water resources management plans to address the challenges posed by climate change, ensuring sustainable water availability, agricultural productivity, and hydropower generation.