SHORT AND LONG-TERM RECOVERY IN BURNED WATERSHEDS AND THE IMPACT ON STREAMFLOW DYNAMICS (Invited Presentation)

Wildfires, which have consumed 5.8 million acres on average over the last decade in the U.S., have a direct and immediate impact on both physical and chemical processes, including acute loss of vegetation and soil organic matter, variations in snowpack accumulation and ablation, and changes in forest canopy cover, interception, and evapotranspiration. These changes greatly impact both the magnitude and timing of post-fire streamflow, increasing the potential for flooding as well as altering dry season flows. These effects are especially evident in the western U.S., where prolonged drought has increased insect outbreaks, fire risk, and tensions related to seasonal water supply. This presentation will overview current work on the hydrologic response of post-fire watersheds, focusing on both short and long-term recovery and altered streamflow regimes. We highlight case studies where remote sensing products as well geomorphologic parameters and climatology are used to understand and model temporal and spatial recovery and related streamflow dynamics in western U.S. watersheds. Semi-arid systems are especially sensitive after fire, and in many cases, streamflow patterns do not return to pre-fire levels for five to ten years after fire, with dry season flows significantly impacted in many cases. Elevated flows can continue to deliver larger suspended sediment and bed loads until watershed vegetation recovers. Conversely, increased water yield can contribute to regional water supply. This presentation will highlight these contradicting issues with the goal towards improving short and long-term water resource management after wildfires.