Wildfires in the western United States are happening more often and burning larger areas, partly because of past fire suppression and hotter, drier conditions. These fires can affect how much water is available in the region.

To better understand why, we studied two fires in California’s Upper Russian River watershed. We looked at how vegetation, water loss from plants and soil (evapotranspiration, or ET), and streamflow changed after the fires. We used satellite data (Landsat-8 and MODIS) and on-the-ground measurements from the U.S. Geological Survey and the Center for Western Weather and Water Extremes (CW3E), including precipitation, soil moisture, and streamflow.

We examined changes in ET and streamflow over different time periods: immediately after the fires (less than a year), in the short term (1–5 years), and in the long term (more than 5 years). Early results show that areas severely burned by the 2017 Redwood Complex Fire lost more ET at first but also recovered faster than similar areas burned by the 2018 Mendocino Complex Fire. We also saw increases in the number and flow of natural springs in one severely burned area.

This work could help guide decisions about managing water resources after fires.