Bushfire‐Induced Water Balance Changes Detected by a Modified Paired Catchment Method

Abstract

AbstractWhile bushfires are often regarded as a vital trigger that alters the partitioning of hydrological fluxes, their role in water balance changes remains poorly quantified, especially in regions where the impacts of frequent bushfires and climate variability overlap. Here, we estimated the fire‐induced water balance changes based on a modified paired catchment method that considers the partial effect of annual precipitation differences. In the application for eight forested catchments impacted by the 2009 Victorian Bushfires with multiple burned areas (12%–89%), we found that evapotranspiration declined by 33 ± 20 mm yr−1 (mean ± standard deviation) and streamflow increased by 68 ± 32 mm yr−1 during the post‐fire decade. For the interannual changes within this decade, the decline in evapotranspiration due to fires gradually recovered after the first year since bushfires, while the increase in streamflow mostly peaked in the second or third year and diminished in subsequent years. We surmised that such asynchronous responses of the two fluxes to bushfires occurred with the initial increase and the later decrease in terrestrial water storage. Averaged for the post‐fire decade, there seems to be an overall decline in terrestrial water storage for burned catchments relative to unburned catchments.