ARS | Publication request: Potential hydrologic response to a prescribed fire on a small mountainous watershed

Submitted to: First Interagency Conference on Research in the Watersheds
Publication Type: Proceedings
Publication Acceptance Date: June 15, 2003
Publication Date: October 27, 2003
Citation: Flerchinger, G.N., Clark, P.E., First Interagency Conference on Research in the Watersheds, 2003. p. 631-636

Interpretive Summary: Prescribed fire is a potential way to reduce fuel loads and control invasive-woody weeds on millions of acres of mountain-sagebrush rangelands in the western United States. Very little research has been conducted, however, to assess the hydrologic impact of prescribed fire on runoff, infiltration and erosion at a watershed scale. The USDA Northwest Watershed Research Center is developing and testing hydrologic models that can be used to assess prescribed-fire impacts on these processes. Model simulations for the Reynolds Creek Experimental Watershed indicate that increased streamflow might not occur in the year immediately following fire in systems that are dominated by subsurface-water flow. These systems might show flow increases of as much as 25%, however, in the second year following fire. Modeling tools to predict post-fire hydrologic response will help managers assess alternative management options and to develop mitigating strategies for short-term soil disturbance after prescribed fire.

Technical Abstract: Prescribed fire is often used to control invasive weeds, improve habitat, and deter wildfire. The Northwest Watershed Research Center plans to burn a heavily studied 26-ha watershed. This paper investigates the potential hydrological response to that prescribed fire. Changes in water repellency and infiltration capacity were assumed not to limit the low intensity snowmelt input to the basin. Percolation, subsurface flow and runoff during the first runoff season are influenced by the soil moisture deficit created by pre-burn vegetation conditions and will likely not be influenced greatly by the fire. A year of reduced evapotranspiration following the fire is necessary to reduce the soil moisture deficit and increase percolation beyond the root zone and subsurface flow to the stream. Results indicate significant changes in streamflow in this subsurface-flow-dominated watershed may not be observed until the second snowmelt season following the fire and could increase by 25%. These results are unlike watersheds dominated by overland flow and surface runoff where increased flows are more likely to occur during the first year following a fire.