Streamflow response to fire in large catchments of a Mediterranean-climate region using paired-catchment experiments

SummaryUnderstanding post-fire streamflow dynamics in large California catchments is limited by a lack of direct empirical evidence. Scaling results from small experimental catchments to large catchments for practical applications is challenging. We investigated the possibility of using streamflow data from an existing gauge network in central and southern California to examine the effects of fire on streamflow using a paired-catchment approach. Post-fire streamflow change was examined in six paired catchments at annual, seasonal and monthly time-periods. Prediction intervals associated with the pre-fire calibration regression models were used to identify statistically significant changes in post-fire streamflow. The identification of suitable paired test and control catchments presented a major challenge, despite the large number of potential catchments in the network. The best calibration results were associated with catchment pairs that had similar orographic controls over rainfall, with proximity to one another being a secondary control. The effect of fires on streamflow, regardless of time-period examined, was found to be variable, depending mostly on post-fire wetness conditions. No relation was evident between post-fire streamflow change and catchment size or area burnt.