Estimating the effects of wildfires on water supply in the northern Rocky Mountains

Wildfires during the summer of 1988 burned a significant portion of several Northern Rocky Mountain wastersheds. A procedure was needed to adjust pre-burn calibrated water supply forecasting procedures to reflect post-burn conditions. The described procedure operates with a set of physically based, empirical relationships derived from data collected in Western Montana and Northwestern Wyoming. The premise of the procedure is that a reduction in timber canopy will lead to reduced interception of snowfall and spring precipitation. It is proposed that reduce summer evapotranspiration will have a minor effect on the concurrent seasonal volume. Instead, reduced summer evapotranspiration will have its greatest effect on the following season's volume by providing a higher level of antecedent soil moisture.