Hope for restoring Lake Tahoe clarity: Reducing pollution by 35 percent could bring back historical levels | TahoeDailyTribune.com

Hope for restoring Lake Tahoe clarity: Reducing pollution by 35 percent could bring back historical levels

Amanda Fehd

Scientists will reveal a comprehensive pollutant model Tuesday that shows restoring clarity at Lake Tahoe could be within reach.

The UC Davis study indicates if pollutants like sediment and nutrients are reduced by 35 percent from all sources – the ground, air and streams – lake clarity could reach historical levels of almost 100 feet.

“The model results are showing it’s doable, it’s just whether there is political will and resources to do it,” said Geoff Schladow, the creator of the model and a limnologist with UC Davis.

“These are preliminary numbers,” he said. “There’s at least a year’s worth of work left to reduce the uncertainty of those numbers.”

Schladow will present his findings at the Lahontan board meeting tonight at 7 p.m. at Lake Tahoe Airport.

Lake Tahoe gained fame in the late 1800s for its crystal clear waters. Naturalist John LeConte first measured Tahoe’s clarity in 1893 with a white plate attached to a rope, which disappeared from sight at over 100 feet.

When development expanded rapidly in the 1960s, scientists began noticing the lake’s waters were clouding. In 1997, the average clarity depth reached a low of 64 feet, with soil erosion from a record-setting winter flood the likely culprit.

Over $900 million in federal money is slated for restoration projects aimed at restoring Tahoe’s historic clarity.

The model also comes just in time for Tahoe’s next regional plan, expected to be completed in 2008. Policy makers are expected to pinpoint a clarity goal, which is currently 98.7 feet.

Along with erosion, nutrients from fertilizers and air pollution are also thought to play a major role. It could be a challenge to achieve 35 percent reduction in all those pollution sources, said Dave Roberts, environmental scientist at Lahontan Water Board, which helped fund the project.

For instance, it may be impossible to control nutrients from groundwater entering the lake, so more emphasis may have to lie on air and surface water sources.

Pollutant models are required under the 34-year-old Clean Water Act, but the rule was not enforced until the last decade, when environmentalists brought lawsuits forcing states to comply.

Called Total Maximum Daily Load, the model calculates the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards.

Schladow measures clarity at Tahoe year-round by lowering a white plate called a Secchi disk into the water until it disappears from sight.

Tahoe’s model is comparable in scale to the model created to restore Chesapeake Bay, which is part of a much larger watershed than Tahoe. That study commenced after several groups sued the state of Maryland for lack of compliance with the Clean Water Act.

If you go:

What: TMDL model unveiled at Lahontan Water Board meeting

When: Tonight, 7 p.m.

Where: Lake Tahoe Airport

Also on the agenda: stream erosion tour beginning at 1 p.m.

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