Climate change can profoundly alter precipitation patterns within watershed systems, leading to fluctuations in intensity, timing, and spatial distribution of rainfall, thereby posing significant challenges to water resource management. This study investigates the impacts of climate change on precipitation variability in the Babolrood watershed. To this end, large-scale climate data from the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6) and the CanESM5 model were downscaled using the Statistical Downscaling Model (SDSM) under three Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5). Observational data from four rain gauge stations (Diva, Galougah, Miyandasht, and Ghoran-Talar) were compiled over a common baseline period (1994–2024), following statistical quality control, outlier removal, and homogeneity testing. Model performance was evaluated using Root Mean Square Error (RMSE), Nash–Sutcliffe Efficiency (NSE), and the coefficient of determination (R²). Results indicate a significant decline in precipitation across the watershed during 2020–2100. While the seasonal pattern remains intact—with autumn as the wettest season—precipitation intensity has decreased, particularly in autumn and summer. Monthly rainfall is projected to decline by 10–30% across all scenarios, with SSP5-8.5 showing the most severe reductions. Even under the optimistic SSP1-2.6 scenario, notable decreases highlight the region’s vulnerability. These changes may disrupt hydrological cycles, reduce surface runoff, increase evaporation, and threaten water reserves.