High Country News
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High Country News

The toxic, soupy biomass choking water systems in California

Algae blooms in Clear Lake are a public health risk and increase water treatment costs.

Cyanobacteria blooms on Clear Lake in June 2020 resembled whorls of green and white paint.
Courtesy of Micah Swann

On a good day, usually in late winter and early spring, the magnificent waters of Clear Lake seem to live up to their name. Under the shadow of the volcano Mount Konocti, the oldest lake in North America and second largest in California sparkles in an array of blues while fishing boats ply the shallow nearshore, their anglers hoping to hook a trophy bass.

From his office two miles inland, Frank Costner knows that the lake’s waters also shelter a treacherous occupant — potentially toxic blooms of cyanobacteria. As general manager of Konocti County Water District, Costner is responsible for supplying drinking water from Clear Lake to 4,500 people who live in this region a two-hour drive north of San Francisco.

This piece is part of a collaboration that includes the Institute for Nonprofit News, California Health Report, Center for Collaborative Investigative Journalism, Circle of Blue, Columbia Insight, Ensia, High Country News, New Mexico In Depth and SJV Water. It was made possible by a grant from The Water Desk, with support from Ensia and INN’s Amplify News Project.

Costner has worked at the district for 32 years and he knows when lake conditions deteriorate. Mats of cyanobacteria ring Clear Lake during warm months, covering its crystal waters along the shoreline with paint-like swirls of green and white. When the wind comes from the west, foul odors waft toward his office.

“Kind of like dog poop,” Costner told Circle of Blue. “It’s pretty rough.” He searched for the right adjectives. “Poopy? I don’t know. Not like feces, per se — like human feces — but definitely like a dog poop smell. Decaying matter? It does smell bad.”

Not only an aesthetic affront, the harmful algal blooms are a threat to public health, recreation, and the local economy. For the 18 public water systems that draw from the lake the noxious blooms are something else: an operating hazard that is complicating their treatment processes and increasing the cost of providing clean water in one of the state’s poorest counties. For more than three decades, Costner has had a front-row seat.

“I’ve just seen the continual decrease in water quality, getting worse and worse as the years go by,” Costner said, reflecting on his career. “Water treatment is becoming harder and harder.”

Read more: https://www.hcn.org/articles/south-water-the-toxic-soupy-biomass-choking-water-systems-in-california



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