Assessing Future Hydroclimatic Impacts of Climate Change on the Potohar Region using CMIP6 Climate Projections and the SWAT Model

Abstract

Climate change poses one of the greatest challenges of the 21st century, necessitating a comprehensive investigation into its regional hydroclimatic impacts. This thesis examines future climatic trends over the Potohar region and assesses hydrological responses across its primary Basins (Haro, Soan, and Kanshi) utilizing high-resolution datasets and the Soil and Water Assessment Tool (SWAT) model. We evaluate these changes under three Shared Socioeconomic Pathways (SSPs: 245, 370, and 585) spanning the 21st century. After meticulously evaluating precipitation and temperature data from 54 General Circulation Models (GCMs), we identify the top two models best suited for this study: CNRM-ESM2-1 r1i1p1f2 and EC-EARTH3-VEG r3i1p1f1. These models undergo bias correction via Linear Scaling to provide accurate projections of future climate. Our results reveal a wetter and warmer climate over Potohar. Temperature shows a consistent increase across all scenarios, with projections ranging from 0.60°C to 3.38°C for SSP245, 0.47°C to 3.84°C for SSP370, and 0.57°C to 6.26°C for SSP585, intensifying as the century progresses. Precipitation projections, unlike temperature, exhibit significant temporal and spatial variability. However, most SSPs indicate increased precipitation during the monsoon (JJAS) and reduction in winter (DJF). The Potohar region may experience an annual precipitation increase of 3-17% for SSP245, 1-28% for SSP370, and a range of -5% to 23% for SSP585, till century end. Streamflow projections across the HARO (-4% to 98%) and SOAN (-10% to 44%) basins generally indicate an annual increase over future periods, while KANSHI (-24% to 31%) exhibits a mixed trend across the GCMs. Seasonal analysis further reveals distinct flow patterns across the three basins. Also, the EC-EARTH predicts a one-month earlier attainment of peak flow across all basins in most SSPs. Interannual projections of hydroclimatic variables suggest more frequent extreme events. The changes quantified in this study underscore the urgent need for adaptive water management and region-specific climate action plans to mitigate climate change impacts on water resources, agriculture, urban planning, and disaster risk reduction in the Potohar region.