Wildfires in California leave behind acres of scorched land that make snowpack formation easier and more water runoff downstream from the Sierra Nevada to basins in the Central Valley, increasing the amount of water stored underground.
That’s the finding from researchers at Lawrence Berkeley National Laboratory, who discovered that blazes in some parts of the state could result in more water availability.
Scorching the earth and killing a forest also can lead to changes the makeup of the snowpack, researchers said. Because wildfires usually burn through many tree canopies, there’s more room for snow to build up, said Fadji Maina, the lead author of the study.
“You just have surface soil without any vegetation which means the snow is going to reach the soil and then accumulate,” Maina, an expert in earth and environmental sciences.
“After a wildfire, because you have good snow accumulation that means in the summer when you have the snowmelt your runoff is going to increase,” she said. “And because the runoff is going to increase, your groundwater is also going to increase because the river is going to feed the groundwater.”
About 70 percent of the state’s water comes from the Sierra. The study examined the Cosumnes River watershed which flows southwest from the mountain range to the south of Elk Grove. Researchers said the pattern resembles many watersheds in California since more than half of it runs through forests.
The location of the wildfire could have a significant influence. Historically, wildfires have burned in various spots between the valley and the Sierras. The study concluded a wildfire created in the valley would have less of an impact on water since it’s further downstream and snow usually piles up in the mountains.
“If it happened downstream it will not impact the water availability,” Maina.
Maina said the goal was to determine how changes to the landscape could affect other areas in the same watershed. Previous studies examined runoff and groundwater individually but the study ties them all together.
The result could be useful for water resource managers as wildfires become more common, said Erica Woodburn, a co-author. This case shows how the water systems in the two areas are deeply connected.
“The changes to stream flow and groundwater levels following a wildfire are especially important metrics for water management stakeholders, who largely rely on this natural resource but have little way of understanding how they might be impacted given wildfires in the future,” Woodburn said.
The study relied on a predictive model and does not address questions about quality. However, Berkeley Lab researchers are conducting a separate experiment that examines how the Russian River watershed was affected by the 2017 Sonoma County wildfires.
“Developing a predictive understanding of the influence of wildfire on both water availability and water quality is critically important for California water resiliency,” Susan Hubbard, the associate lab director of earth and environmental sciences at Berkeley Lab, said in a prepared statement.