Burning Forests Can Impact Water Supplies

A prescribed fire burns in a southern forest.The number of wildland fires and burned areas in the United States is on the rise as a result of a warming climate, drought, and increasing human ignitions. Wildland fires alter the watershed hydrological cycle by modifying soil and forest cover properties, but the effects vary widely across the continental United States due to differences in fire severity and burned area, background climate, and watershed conditions. Climate variability such as drought may mask the effects of wildland fire on water supplies. Though forests and rangelands provide more than half of U.S. water supplies, the long-term impacts of fires, including wildfire and prescribed fire, on water supplies have not previously been measured nor factored into water management strategies. Eastern Threat Center researchers developed a practical framework to evaluate fire impacts on water resources by synthesizing 30-year records of wildland fire, climate, and river flow for 162 locations across the United States. They discovered that wildland fires enhanced annual river flow in western regions with a warm temperate or humid continental climate (the semi-arid Lower Colorado River in particular). In contrast, repeated prescribed burns did not significantly alter river flow in the subtropical Southeast. These outcomes offer new insights into the potential role of wildfire and prescribed fire in water supply augmentation, flood control, and landslide hazard mitigation under a changing climate. Results can help land managers consider local watershed conditions and design effective forest management practices, including prescribed burning, that reduce fire risk and strengthen forest resilience to drought and diseases.

Pictured: A prescribed fire burns in a southern forest. Photo by Dennis Hallema, U.S. Forest Service.

Related publications:

Forest Service Partners/Collaborators:
Southern Research Station

External Partners/Collaborators: Joint Fire Science Program

Contact: Ge Sun, research hydrologist, ge.sun@usda.gov

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