<p>Climate change and human activities are rapidly altering the hydrological cycle of watersheds, challenging regional water security, particularly in semi-arid areas. This study attributes and projects changes in runoff in the highly human-influenced Liuhe Basin (LB) by analyzing historical hydro-meteorological patterns. The results suggest significant reduction in runoff in the LB, despite minimal changes in precipitation and potential evapotranspiration. The research period was divided into a pre-change and two post-change periods based on the precipitation–runoff relationship. Hydrological and Budyko elasticity models identify human activities, primarily soil and water conservation measures, as the main factors in reducing runoff. To accurately project future runoff, the hydrological model was recalibrated using runoff restoration data (2000 to 2017) obtained through a partitioned survey restoration method, and three climate models from the NEX-GDDP-CMIP6 were input to drive the hydrological model. Projections indicate a 4.1–17.8% increase in precipitation and a 3.7–16.5% rise in evapotranspiration, leading to a 10.97% increase in future runoff. However, since soil and water conservation measures alter upstream runoff properties, future runoff response will decrease by 54.34%. This study enhances the LB’s resilience to climate change risks and provides significant guidance for water resource planning and rational allocation in the watershed.</p>