Catchment response to climate change under CMIP6 scenarios: a case study of the Krishna River Basin

Abstract

This study assessed the impacts of climate change on the water balance of the Krishna River Basin (KRB) in India. A frequency-based metric, known as symmetric uncertainty, was used to select the top 50% of global climate models (GCMs) from a pool of 18 Coupled Model Intercomparison Project Phase 6 (CMIP6) GCMs for hydrological modelling. The impact of climate change was projected for three future time frames, namely, near future (NF: 2026–2050), mid-future (MF: 2051–2075) and far future (FF: 2076–2100), using four scenarios from shared socio-economic pathways (SSPs): SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. The Soil and Water Assessment Tool model was used to simulate climate change impact during historical and future periods in the basin. The results showed a significant increase in the annual average precipitation, surface runoff, water yield and streamflow in the future under all SSP scenarios. The increase in the projected annual average precipitation ranges from 12 to 54% for four SSP scenarios compared to the historical ensemble average. Future periods showed a shift in the monthly peak flows compared to the baseline period. More availability of water in the future in the KRB can be effectively used for various water management works. HIGHLIGHTS The impact of climate change on the water balance of the Krishna River Basin was assessed using CMIP6-based climate models.; The symmetric uncertainty concept was used to screen the 50% suitable GCMs from a pool of CMIP6 climate models.; High values of NSE and R2 at different gauging locations across the KRB suggested that the SWAT model is spatially performing well.; The uncertainty bounds of simulated water balance components were estimated to understand the behaviour of selected GCMs.;

Keywords

• climate change
• cmip6 scenarios
• swat
• symmetric uncertainty
• water resources