WCD-13. Wildfire in the West: Characterizing Drivers of Post-Disturbance Hydrologic and Water Quality Response through Laboratory Analysis

Abstract
Wildfires are a complex and widespread problem across the western U.S, dramatically increasing watershed sedimentation rates and concentrations of chemical constituents, including nutrients, trace heavy metals, and dissolved organic matter. Though the dramatic effects of wildfires on water quality and quantity are known to exist and can have severe implications for water treatment plants and freshwater systems, there are limited tools that provide water managers with an a priori assessment of potential water supply impacts. To address this gap in research, we developed laboratory-scale rainfall and wildfire simulation experiments to measure sedimentation and water quality responses from soils subjected to burning. 140 soil samples were collected from mountain catchments with a history of wildfire and exposed to different combinations of burn severities, rainfall intensities, and representative terrain slopes. Aliquots of runoff and infiltration generated by the rainfall simulator were collected for each soil sample and analyzed for sediment, total organic carbon, and total dissolved nitrogen concentrations, as well as turbidity. These experiments provide insight into the postfire water quality and quantity response from multiple drivers: wildfire severity, rainfall intensity and terrain slope. Preliminary results from the laboratory experiments will be compared to both observational data collected from historical wildfire events in the sampling regions, as well as synthetic sediment data generated from the Revised Universal Soil Loss Equation (RUSLE), and hydrologic response simulated by HYDRUS 1D.