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Disturbance Effects on Water Yield in Western Coniferous Forests

Photo of Recent broad-scale mortality due to drought, insects, and wildfire has led to increased interest in how forest disturbance interacts with hydrologic processes in forested watersheds.

Recent broad-scale mortality due to drought, insects, and wildfire has led to increased interest in how forest disturbance interacts with hydrologic processes in forested watersheds. Snapshot : Decades of research on interactions between forest dynamics and water supply has suggested that water availability increases as forest cover decreases. This led to the expectation that water yield would increase following recent widespread tree mortality in the West. However, in many cases, water yield actually decreased. This new review examines where and why water yield increases or decreases following disturbance in western forests.

Principal Investigators(s) :
Goeking, Sara A.  
Research Location : Western United States
Research Station : Rocky Mountain Research Station (RMRS)
Year : 2020
Highlight ID : 1709

Summary

Previous research on the link between forest management and water yield led to the expectation that water yield would increase following recent tree mortality in the Western United States. Our paper presents a review of papers published during 2000–2019 on the effects of forest disturbance on streamflow in western coniferous forests. Although some studies observed post-disturbance increases in water yield, as expected, in many cases water yield did not change or even decreased. Decreases were generally observed in areas with the following characteristics: high total radiation and high solar radiation (i.e., at low latitudes and south-facing aspects); rapid growth of post-disturbance vegetation; and non-stand-replacing disturbances, such as drought and insect-caused mortality. Although one objective of forest management may be to increase water yield, another might be to encourage post-disturbance forest recovery and resilience by optimizing growing-season soil moisture, which depends on snow accumulation and retention. The ability to meet such goals, and the treatments to accomplish them, depends on residual vegetation, latitude, and aspect. Our review suggests that recommendations for meeting specific management objectives in forested watersheds of the semiarid West—and the best available scientific information about the link between forest cover and water yield—are changing rapidly.

Forest Service Partners

External Partners

 
  • Dave Tarboton - Utah State University