Climate change poses significant challenges to water resource availability and watershed management worldwide, altering hydrological regimes and exacerbating imbalances between water supply and growing societal demands. This study presents a comprehensive analysis of water resource supply and demand dynamics in a representative watershed system under changing climatic conditions, integrating hydrological modeling with scenario-based projections to assess current and future water balances. A coupled modeling framework combining the Soil and Water Assessment Tool and Water Evaluation and Planning approach was developed to simulate hydrological processes, project water availability under multiple climate scenarios, and evaluate sectoral water demands including agricultural, domestic, industrial, and environmental requirements. Climate projections from five general circulation models under Representative Concentration Pathways RCP4.5 and RCP8.5 were downscaled and bias-corrected for the baseline period, mid-century, and end-century time horizons. Results indicate that annual average streamflow is projected to decline by 12.4 to 28.7 percent across scenarios, with more pronounced seasonal shifts including increased winter flows and substantially reduced summer low flows. Groundwater recharge shows decreasing trends of 8.3 percent under RCP4.5 and 19.6 percent under RCP8.5 by end-century. Agricultural water demand increases by 15.8 percent due to elevated evapotranspiration and extended growing seasons, while total water demand exceeds supply during summer months in all future scenarios. Water stress indices indicate that the watershed transitions from moderate stress to severe stress conditions under RCP8.5, with supply-demand deficits reaching 34.7 million cubic meters annually by 2080 to 2100. Spatial analysis reveals distinct patterns of water surplus in headwater regions and acute deficits in downstream agricultural areas. These findings underscore the urgency of implementing adaptive watershed management strategies including demand-side management, infrastructure investments, and nature-based solutions to enhance water system resilience under climate change.

Yunbo Pu. Analysis of Watershed Water Resource Supply and Demand Balance under Climate Change. Academic Journal of Environment & Earth Science (2026), Vol. 8, Issue 1: 51-56. https://doi.org/10.25236/AJEE.2026.080108.

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