Simulation of the Effects of Wildfires on Water Yield and Water Quality
in Rangelands of Northern Utah

The wildfire season of 2007 left thousands of acres burned all over the state of Utah. Th e fire events affected several ecosystems but were mostly concentrated over rangelands, which constitute a fragile ecosystem subject to disturbances that worsen its actual condition. Wildfires have a negative influence on the water balance since the processes of interception; runoff and infiltration are altered with land cover perturbations. We used the Soil and Water Assessment Tool (SWAT) to simulate and assess the effects of wildfires on Northern Utah. The land cover conditions before the fire were taken from the SWRGAP land cover project. We used MODIS products to extract the fire scar and derive the land cover conditions after the fire. We were able to simulate the water balance before the fire, and using available water yield measurements we were able to refine our model. Once the model was refined for the particular conditions of the region, we simulated the water yield and water quality patterns with the land cover conditions after the fire. The results suggest that with the lost of interception and infiltration opportunities, temporal increases in runoff will be observed in the watershed analyzed. Furthermore, the sediment load in the water is higher compared to the conditions before the fires. Such a scenario will invariably affect water availability for general uses. We show the convenience of using SWAT for a quick assessment of rangelands’ water balance condition. These results could be integrated into a decision making process regarding natural resources management.