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Concerns mount that ash will affect lake’s clarity

LAKE TAHOE – Sailing these serene blue waters this past weekend was more like a misty scene out of “Brigadoon” – no shore-to-shore visibility because of smoke-filled skies.

Then there was the ash, which covered the boat’s cockpit. When you tried to wipe it away, it just made a messy gray streak.

The thick smoke settling over the lake for the past two to three weeks – caused by the recent spate of Sierra wildfires – has scientists wondering if it will impact Tahoe’s famous clarity.



“If you add nutrients, you get algae blooms on the lake and it lowers clarity,” said Dave Barnes, assistant project scientist for the John Muir Institute of the Environment, based at UC Davis.

Algae blooms caused by organic compounds and toxic materials from burning forests is nothing new at Lake Tahoe. In the 19th century, in so-called “pre-settlement” times, long-lasting summer fires were common in the basin.




Smoke and ash from the Angora fire last year led to a short-term increase in algae growth on the South Shore, said Geoff Schladow of the UC Davis Tahoe Environmental Research Center.

This time, however, the concern is that the fires are burning hotter and longer than many previous ones.

In the past, many of the fires burned low to the ground. These catastrophic fires are burning way up into the tree tops, sending smoke billowing high into the air.

“We believe it creates a different type of smoke than historical types of fires that burn cooler and lower to the ground,” Barnes said.

“It’s a completely different profile in terms of the size and kind of elements,” he said.

This morning, Barnes will head up to Tahoe from UC Davis and install a state-of-the art air sampler to help measure possible toxins being sent to Tahoe by the wildfires.

Three of the instruments already are measuring air samples, one in Incline Village, one in Tahoe City and another on a buoy on the lake.

The fourth sampler also will be installed in Incline Village, at the Sierra Nevada College campus.

The instruments measure particle mass and size, as well as components such as dust and nutrients, to help the scientists understand the effects of the wildfires on Tahoe’s ecosystem.

The sampling is meant to run for 51Ú2 weeks, Barnes said. He estimated it would take at least a month to get the results.

In May, the UC Davis group reported that the historic rate of decline in Lake Tahoe’s clarity has slowed considerably in recent years. It marked the first measurable improvement since researchers began measuring Lake Tahoe’s clarity 40 years ago.

“In a worst-case scenario, the wildfires are going to impact the clarity of the lake this summer, but it’s not the end of the world,” Schladow said. “This summer will pass, and the fires will go out.”

More fires have been burning at one time this year than during any other period in recorded California history.

“If these large-scale fires become more and more frequent, that’s something different,” he said.

To contact Editor Jeff Pelline, e-mail jpelline@theunion.com or call 477-4235.


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