As wildfires become increasingly intense and frequent in California, particularly near reservoirs, experts say threats to water resources will require more proactive preventative measures.

Massive swaths of land have burned annually across the state, and rebuilding can take years after the ashes have been swept away.

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Toxic chemicals linger in the scorched soils even longer, and can make their way into water sources, said Ann Willis, California regional director with American Rivers, a nonprofit focused on protecting clean water resources.

Those toxins – including heavy metals such as lead, zinc and copper – could be harmful if consumed, said Willis, a scientist who’s led a program seeking to implement stream conservation strategies across California.

“We really want people thinking about not just the immediate impacts of wildfire or when the immediate rebuilding will be complete and out of mind, but that these can be persistent problems that can show up for years and the health impacts are considerable,” Willis said.

Wildfires are a natural part of California’s ecosystem, but the public can’t rely on them staying relatively small like the Tiger Fire, which in August burned 118 acres right off the Mokelumne River, a watershed that feeds into the Bay Area, Willis said.

Major fires like the 2018 Camp Fire in Butte County, the 2020 CZU Lightning Complex in Santa Clara and San Mateo counties and the Eaton and Palisades fires in Los Angeles County earlier this year are becoming more common, according to the United States Geological Survey’s California Water Science Center.

Cal Fire and other agencies are currently responding to at least 16 fires across the state, according to Cal Fire data. They include the Gifford Fire, which has burned about 131,614 acres in San Luis Obispo and Santa Barbara counties, and the TCU September Lightning Complex, in which 13,869 acres have burned near the Don Pedro Reservoir in Toulumne, Calaveras, Stanislaus and San Joaquin counties.

Educating the public about the dangers of fires near water resources isn’t meant to stoke fear, Willis said. Instead, the aim is to galvanize the public around wildfire mitigation measures by helping them understand the long-term, real world consequences natural disasters could have on public health.

A study conducted by American Rivers found that clean water was ranked as a top issue for respondents regardless of political affiliation, Willis said.

“People are already scared enough. What they need is a solution. They need to see a thing that they know matters and will feel good to them, and will make a material difference to everybody,” Willis said.

The many agencies responsible for providing safe drinking water, such as the San Francisco Public Utilities Commission and the East Bay Municipal Utility District, have long invested in infrastructure improvement meant to adapt to climate change and ensure high water quality.

“Our mission is to provide clean, safe water and to protect the lands we are entrusted to manage,” East Bay Municipal Utility District spokesperson Andrea Pook said.

Just last year, the district hired divers to install silt curtains along 1,000 linear feet of the intake tower at the Pardee Reservoir in the Sierra Foothills, Pook noted. For the cost of about $145,000, the curtains are meant to catch sediment that accumulates after wildfires or heavy rain, reducing pollutants before the water reaches treatment plants 90 miles away.

Aerial view of Pardee Lake and Dam, the primary source of water for the East Bay Municipal Utility District on Thursday, June 16, 2022. (Ken James/California Department of Water Resources) 

The agency has also invested $325 million into an addition to the Orinda Water Treatment Plant that will use ultraviolet light to decontaminate water from the Mokelumne watershed. Slated to be activated in 2026, the project is meant to fend off an increase of pathogens, viruses and natural organic matter caused by more frequent flooding, warmer waters and runoff.

Investments into wildfire fuel mitigation are more cost effective than renovating or overhauling hard infrastructure like processing plants, Willis said.

“By far the most effective way of keeping drinking water clean is by managing our waters,” Willis said. Water treatment plants “are the last line of defense, but the first and cheaper line of defense are natural resources.”

Pook agreed that fuel management is vital, noting the Upper Mokelumne River Watershed Authority, a joint powers authority of which East Bay Municipal Utility District is a member, has focused on reducing fuel along the upper Mokelumne River watershed, which provides about 90% of the agency’s water supply.

California voters also seem to agree that fuel management is important, having approved Proposition 4 during the November 2024 election, giving the state permission to borrow $10 billion for climate and environmental projects, including a specific focus on clean water.

Those investments come after the Trump administration attempted to fire thousands of Forest Service employees and as the congressional Republican-approved budget makes substantial cuts to the agency, a particular concern for Willis who said the public needs to now pressure federal representatives to fund the Forest Service and advocate for Proposition 4 dollars to be spent wisely.

“Californians have spoken. They’ve said we want to make this investment,” Willis said. “But now we have to make sure that money goes to the right organizations.”

Visitors sit on the edge of a dock at the Lafayette Reservoir on Tuesday, Sept. 9, 2025, in Lafayette, Calif. (Aric Crabb/Bay Area News Group)