Oct. 9, 2019 — As the Camp Fire tore through the foothills and canyons of California’s Sierra Nevada mountains last year, it was fueled not only by high winds but also years of drought that left the landscape desperately dry and scattered with dead trees. Interspersed with a heavy grass cover due to a wet spring, the landscape was primed for burning. The fast-moving inferno scorched more than 150,000 acres and caused the death of 86 people, making it the deadliest and most destructive wildfire in California history.
The destruction from the Camp Fire and the multitude of other wildfires that have blazed through California with alarming frequency over the past few years have taken an enormous toll on the people and environment of California. Scientists at Berkeley Lab recently took a closer look at one aspect of how wildfires affect the environment: California’s watersheds. As the vegetation that holds soil in place and retains water is burned away, wildfires are changing the state’s water cycle. The absence of vegetation in the watershed can create conditions conducive to erosion and even flooding, while the acres of scorched land can make snowpack formation easier and increase water runoff downstream.
With projections of California climate showing increased wildfire frequency and magnitude, Fadji Maina and Erica Woodburn, both scientists in Berkeley Lab’s Earth and Environmental Sciences Area, used the Lab’s National Energy Research Scientific Computing Center (NERSC) to simulate how these factors would affect watersheds. Using a model based on one of California’s largest undammed watersheds, scientists ran high-performance computer (HPC) simulations to project how future wildfire events would affect hydrological processes such as stream flow, groundwater levels, and snowpack and snowmelt. Using HPC to simulate watershed dynamics over a period of one year, and assuming a 20 percent burn area based on historical occurrences, the study allowed them to identify the regions in the watershed that were most sensitive to wildfire conditions, as well as the hydrologic processes that are most affected.