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Lake Tahoe could turn murky green within a decade

Posted by: Aqua Blog Maven on March 25, 2008 at 5:36 am

lake-tahoe-by-leto-a.jpgFrom the Los Angeles Times:

Global climate change may be causing a pivotal shift in the depths of Lake Tahoe that could fundamentally alter its ecology by the end of the next decade and turn its famed jewel-blue waters a murky hue, according to a recent study.

The research and computer modeling by scientists at UC Davis predict that warming could limit the lake’s natural mixing cycle, disrupting the food web and potentially robbing it of the clarity that has helped make Tahoe a world-class tourist destination.

Experts from the university’s Tahoe Environmental Research Center suspect the changes could occur within a decade and prove irreversible. Among the likely results are fewer native fish and larger populations of invasive species, such as large-mouth bass, bluegill and carp.

But the most visible shift could be to its waters, which have inspired awe since the Gold Rush days, earning Tahoe the nickname “Jewel of the Sierra.” Those waters have been losing clarity as urban development carpeted the basin, prompting a crash government effort to stem the effect of runoff. The Tahoe region now has some of the toughest development and environmental rules in the world.

The latest threat to the lake, however, stems from the far more intractable problem of worldwide greenhouse gas emissions and a warming globe. Tahoe is another victim,” said John Reuter, the center’s associate director and one of the report’s authors. “The world views the lake as a pristine place, a refuge. When you hear global warming is affecting Tahoe, is anywhere safe? The answer is no.”

For the full text of this story from the Los Angeles Times, click here.

A story in the San Jose Mercury-Times adds this about the mixing of the lake:

The lake is made up of many layers of water, with the surface being rich in oxygen. When the wind is right and temperature is ideal, the top layer sinks, and in the best years goes to the bottom. This is not a constant process, but happens, on average, about every four years, usually in late February. Through the process, oxygen from the surface is distributed throughout the lake, benefiting plants and fish at the bottom that are dependent upon it to survive, especially trout.

Through extensive computer modeling, the scientists determined the deep mixing may not occur as frequently in the future because of global warming. And by 2019, it might not occur at all. The finding, Schladow said, came as a complete surprise.

The wintertime process is an important one as the churning about of water also dilutes all the contaminants that come into the lake the previous spring. Deep mixing also moves nutrients from the lake bottom to the water surface where they promote the growth of algae.

“If greenhouse gas emissions continue at their present levels, there are pretty big changes in store for the lake itself, for its mixing environment and water quality within the next 10 to 20 years,” Schladow said. “This brings home the urgency of the need to reduce emissions.”

Read the full text of this story from the San Jose Mercury-Times by clicking here.

Picture of Lake Tahoe by flickr photographer Leto A.

March 25, 2008 · Filed Under Lake Tahoe & the Sierra's

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