Scientists Study Wildfires’ Effect on California Utility’s Drinking Water Source

The Sonoma County Water Agency’s natural riverbank filtration system has been a successful method for getting high-quality water to customers, but how was it impacted by October’s wildfires?

Scientists Study Wildfires’ Effect on California Utility’s Drinking Water Source

Aquifers 20 meters beneath the Russian River are the main drinking water source for 600,000 Sonoma County Water Agency customers. (Photo by Berkeley Lab)

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Scientists at the Lawrence Berkeley National Laboratory have spent a decade studying the factors behind the success of Sonoma, California’s riverbank filtration system. It’s key for the health of the Russian River and surrounding groundwater system, what the Sonoma County Water Agency uses as the main source of drinking water for 600,000 Sonoma and Marin county residents.

Now, because of the catastrophic wildfires that burned more than 110,000 acres in Northern California last month — including 8 percent of the Russian River watershed — the scientists have an important area to apply their research. And it’s a real-world situation rather than a hypothetical.

“We were already studying the potential impact of fires on the nutrient, solute, and metal delivery to the river,” one of the Berkeley Lab researchers, Michelle Newcomer, said in a news release. “With this unfortunate turn of events, our developed approaches are ready to address real questions about water availability and water quality.”

The Sonoma County Water Agency is helping support Berkeley Lab, as well as the U.S. Geological Survey, in assessing the recent fires’ impact on water quality.

“The timing of the fires has presented a big challenge. Coming so close to the rainy season, folks who get their water from the Russian River are worried about potential impacts of runoff from the thousands of homes destroyed and thousands of acres scarred,” says Jay Jasperse, chief engineer and groundwater program manager for the Sonoma County Water Agency. “The partnership with Berkeley Lab and USGS will provide vital information.”

The agency pumps groundwater from about 20 meters below the river that has been naturally filtered by sediments and microbes in the ecosystem. The system greatly reduces the need for chemical pretreatment to get rid of pathogens and contaminants.

“We believe that successful riverbank infiltration requires two things: The aquifer below and adjacent to the river must have sediments that are the right type and size, made up of the right minerals; and the ecosystem of the river must provide a lot of the sustaining food for the microbes in those sediments,” Newcomer says. “It’s the combination of these two things that are helping this filtration system maintain its productivity, and these two factors change with seasonal and operational practices.”

Through its research over the years, Berkeley Lab has developed models aimed at maintaining the production of high-quality water while optimizing aquifer water infiltration and pumping. The researchers are currently applying those models to determine appropriate action for the Sonoma County Water Agency in the wake of last month’s fires. They are collecting data from throughout the watershed to understand how ash-based carbon generated by the fires and mobilized by storms will impact infiltration rates and microbial growth. Carbon is an energy source for riverbed microorganisms, so it influences how much water can get into the aquifers and how fast contaminants can degrade. The concern is that following a fire, a lot of potentially toxic chemicals found in common household items could find their way into a groundwater system.

“Mostly we’re worried about chemicals from personal household items, such as fire retardant in furniture, paint, pesticides, and items that burned in people’s homes,” Newcomer says. “We’re also worried about metals getting mobilized, such as mercury, which is commonly found in batteries and light bulbs.”

“We are encapsulating our understanding about the connections between hydrology, fire-derived carbon, geochemistry, and biology in a predictive model that can enable the Sonoma County Water Agency to best make decisions about how to optimize its riverbank filtration system and deliver water to its customers,” adds Susan Hubbard, associate laboratory director of Berkeley Lab’s Earth and Environmental Sciences division.

Source: Berkeley Lab


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