MODELING WATER QUALITY AFTER THE 1988 GREATER YELLOWSTONE AREA FIRES

Wildfires increase surface water nutrient loading through overland flow, but a paucity of research exists studying models to quantify the extent of loading. The Soil and Water Assessment Tool (SWAT) is a river basin model effective at modeling pollution at various scales, but with limited applications to wildfires. SWAT is a proven model with wide use for agricultural, non-point source pollution, but can be similarly applied to quantify the impacts of wildfires. Utilizing USGS stream gauge data before and after the 1988 Greater Yellowstone Area fires, nutrient loading was modelled using SWAT in conjunction with Monitoring Trends in Burn Severity (MTBS) maps, the State Soil Geographic database (STATSGO), and land use information. This study presents the results of SWAT modeling application to a watershed with 10 years of pre-fire data and 20 years of post-fire data for NO₃, Total Nitrogen (TN), Organic N, NH₃, NO₃-NO₂ combined, and P. Nitrogen and Phosphorous represent the two most studied nutrients in surface water. Preliminary results indicate slight nutrient response to the Yellowstone wildfires, which is being further quantified using the SWAT model. Our findings demonstrate the applicability of SWAT modeling for wildfire impacts and contribute to the body of knowledge concerning surface water nutrient loading resulting from wildfires in wildland areas. SWAT can also be used to inform decisions concerning water supply and ecological restoration after wildfires in national parks.