Hydrological Response to Compounding Impacts of Climate Change and Forest Management in the Upper Kings River Basin, CA, USA

ABSTRACT In the western United States, the Sierra Nevada region experienced decades of fire suppression‐driven changes in forest structure and composition, resulting in increased vulnerability to drought, water stress, tree mortality, and exposure to severe wildfires. Sierra Nevada's watersheds and forests are predicted to undergo warmer and drier conditions due to climate change, making them even more vulnerable to disturbances. Restoring forests by reducing forest density and fuel accumulation has the potential to improve forest resilience to droughts and climate change, increase water availability, and provide other ecosystem benefits. In this study, we investigated the individual and compounding effects of forest treatments on evapotranspiration and streamflow in the upper Kings River basin under different warming scenarios using the SWAT+ model. We simulated large‐scale forest treatments throughout the landscape to evaluate the hydrological response to warming across a water‐energy gradient and the extent to which forest treatments can offset the warming‐driven response. Warming increased evapotranspiration in energy‐limited forests, while in water‐limited forests, evapotranspiration declined due to increased water stress. The water made available through biomass reduction due to forest treatments was directed towards increasing potential runoff or sustaining the remaining trees by providing additional water for evapotranspiration, controlled by water/energy availability. We found that large‐scale forest restoration in the upper Kings River basin has the potential to partially mitigate warming impacts on streamflow by a maximum of and under °C and °C warming, respectively, thus reducing the severity of warming impacts on streamflow and vegetation water stress. These benefits are most prominent in the first year following forest treatment and gradually decline over time, persisting up to years.