Abstract

Wildfires, a global phenomenon, significantly impact watershed hydrology by increasing surface runoff, reducing infiltration, and changing groundwater recharge. The intensity of the wildfire and the type of vegetation primarily determine the severity of these effects. In Chile, wildfires have burned approximately 65,000 ha annually over the last 60 years, but in recent years, this number has risen to an average of 155,000 ha per year. This study evaluates the hydrological impacts of wildfires in the south hillside Andes Mountains of Chile between latitudes 38 degrees 37 ' S and 38 degrees 50 ' S. The Soil & Water Assessment Tool (SWAT) assesses key processes such as runoff, infiltration, and evapotranspiration, helping to understand recovery times and offering insights for improving postfire management. The analysis focuses on three catchments within the Quepe River watershed: Bridge Codinhue, Bridge El Tigre, and Bridge Honduras. It incorporates data on historical burned areas, topography, meteorology, land cover, and soil for modelling. Results indicate that evapotranspiration decreased by an average of 32 % during the three years following the fire. Groundwater contribution to streamflow also declined, with an average reduction of 25 %, while percolation decreased by 20 %. In contrast, surface runoff increased substantially-by more than tenfold-highlighting a marked shift in the dominant hydrological processes post-fire. These findings highlight the need for tailored post-fire management strategies to reduce surface runoff and enhance infiltration to restore hydrological balance in mountainous regions like the Andes.