Catastrophic wildfires are primarily a public health and safety threat. But they also affect water quality and supply in ways that many people don’t always appreciate. Specifically, a better managed forest with regular, low-level burns can improve water supply and quality through increased and cleaner runoff.

UC Berkeley research is bearing this dynamic out. As referenced in the video above, students and faculty have been studying the Illilouette Creek Basin, a “bowl of pure Yosemite granite,” which since the 1970s has been exempted from California’s backwards policy of fire suppression. As a result, the area has been allowed to burn regularly, leading to healthy and balanced forest conditions of fewer, bigger trees, more evenly spaced.

The effect has been significant for water flows, as the lead researchers have found:

[F]ire can also be a boon to both local ecosystems and water users far downstream — including humans — largely because fire-thinned forests consume less water and offer more space for meadows and wetlands.

“If you take out deep-rooted trees and you replace them with more shallow-rooted plants like shrubs and grasses, those don’t have access to as much water and they don’t use as much,” [professor of environmental engineering Sally] Thompson explains. “So in the absence of those trees, you’re storing more water in the soils and groundwater, and that leaves the whole system more primed to start creating runoff and streamflow.”

And regular fires also means greater biodiversity. All in all, it’s another strong benefit from managing our forests more responsibly by thinning out excess small trees and allowing natural burns to occur. We need it for safety, the environment — and our increasingly imperiled water supply.