Assessment of surface water demand and potential with climate change impacts on subcatchments with tank-based irrigation using WEAP

ABSTRACT This study investigates the microlevel resilience of surface water resources in microlevel subcatchments within the lower Palar basin (LPB), Tamil Nadu, India, as it experiences shrinking water resources, rising demand with the changing climate. This study employs the Water Evaluation and Planning (WEAP) model to assess LPB's surface water potential and demand, along with projections for future scenarios. Archival data of comprehensive hydrological, climatic, and socioeconomic data for 32 years (1991–2022) are simulated using the WEAP model for understanding the surface water potential and its demand. The future climate scenarios were explored using Shared Socioeconomic Pathways (SSP) 126, 245, 370, and 585 (CMIP6_MPI-ESM1-2-HR), representing low to very high greenhouse gas (GHG) emissions. With a current surface water potential (581 MCM) and demand (310 MCM) for the LPB, the present study provides, for the first time, future water accounting for the region. A hydroclimate simulation study shows high surface water runoff in SSP 585 and lowest in SSP 126 and experiences increasing reduction in surface water resilience, dominated by evapotranspiration (27.5%) during the severe climate scenario. The present study provides insights for policymakers by recommending the capacity augmentation of surface water bodies, ensuring LPB's future water security by increasing water potential and addressing future water demand.