Tahoe’s Cloudy Future
August 16, 2007
On the eve of a weekend in the national spotlight, Tahoe researchers delivered two pieces of bad news Wednesday: Global warming has arrived at Lake Tahoe and the lake’s famously clear water grew murkier in 2006.
On Friday, as senators, former president Bill Clinton and other political figures congregate on Tahoe’s shores to talk about the lake’s environmental health, they will stand next to a lake that researchers say is growing different algae, supporting warm-water fish and suffering the impacts of an environment that produces less snow and more rain.
The latest scientific numbers in Tahoe’s environmental health ” released in the first “Tahoe: State of the Lake Report 2007″ ” are sobering, and the ties to global warming are clear, say the UC Davis researchers who compiled the report.
“The ecology of the lake is going to change,” said Geoff Schladow, director of UC Davis’ Tahoe Environmental Research Center in Incline Village.
Although largely dictated by the volume of water runoff during the basin’s spring and summer months, Tahoe’s water clarity slipped in 2006 ” a dip of 4.6 feet to 67.7 feet.
Tahoe’s clarity is measured approximately 25 times during the year, and a measurement is pegged at the depth where a white disk disappears from view.
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When measurements first began, Tahoe’s clarity stood at 102.4 feet deep.
But global warming at Tahoe could have a much larger impact than the often-ballyhooed clarity numbers ” altering the bottom of the food chain and affecting how deep lake’s water mixes during the change of seasons, said John Reuter, associate director of the Tahoe Environmental Research Center.
“If the upper levels of the lake did warm up and stay warm later in the year ” the lake would stay stratified,” said Reuter.
Reuter said the mixing of the lake ” where layers of the lake’s upper third mix with each other ” is essential to the lake’s function and similar to a human’s “blood pressure.”
A rainier Lake Tahoe would also mean an earlier spring runoff, something that researchers said has already advanced by two weeks, giving algae a longer season to grow and feed on nutrients washed into the lake. Researchers say warming research is in its “infancy” at Lake Tahoe.
“Other people have seen similar types of things in large lakes, but this type of research has never been done before for this particular lake,” said Reuter.
New findings could influence what types of erosion-control and water-filtration programs are completed around the lake, since a shift to a rainier, less snowy climate could call for different measures.
“I think what we’ve learned in the last few years is that we don’t have enough of the right kinds of projects,” said Schladow, of water filtration and erosion work that has been completed around Tahoe.
The Tahoe Regional Planning Agency also said that water-quality projects have been successful despite the measured loss in clarity.
“I think without the restoration work of the [environmental improvement projects], we’d be in a much worse situation than we are today,” said Julie Regan, the agency’s communications chief. “We were in a nose dive of decline prior to the [projects’] implementation.”
Regan said the clarity loss should galvanize continued environmental work at the lake.
“Turning around an ecosystem ” it’s a commitment for generations,” said Regan.
The Tahoe Regional Planning Agency is working to keep future projects flexible to adapt to new scientific findings, she said.