Water quality regulators at Lake Tahoe were skeptical Wednesday about a new report's claims of dangerous levels of mercury and pesticides in Lake Tahoe.
More than three-quarters of Sierra Nevada's seemingly pristine watersheds have had a portion of their waterways deemed unsuitable for fishing, swimming or drinking at some point over the last five years, according to the report by the Tahoe-based Sierra Nevada Alliance, a consortium of environmental groups from throughout the mountain range.
The 170-page report, entitled "State of Sierra Waters," paints a grim health picture of 24 Sierra Nevada watersheds, all but one of which have been listed as "impaired" in some way by pollution ranging from pesticides and heavy metals to sediment, according to the alliance.
While the group claims Lake Tahoe has been "impacted" by mercury - a heavy metal that can affect the nervous system - scientists at Lahontan Water Board said they were unaware of any issue with mercury here. The agency regulates water quality at Lake Tahoe.
In addition, the report alleges "The EPA has listed the lake as threatened for drinking, fishing, threatened and endangered species, habitat, fish tissue and freshwater habitat," but Lahontan environmental scientist Dave Roberts said the EPA does not even have a "threatened" list.
Roberts compiles data on pollutants entering Lake Tahoe for a massive project called the Total Maximum Daily Load, required by the Clean Water Act.
The report alleges the lake has been listed by EPA as "impaired for nutrients, pesticides, swimming, recreational use, non-native species, dissolved oxygen, sediment/siltation and flow alterations" but Roberts found that wording unclear.
Lake Tahoe is only "impaired" for having too many nutrients and sediments, he said, according to the EPA list available at http://www.waterboards.ca.gov/tmdl/docs/2002reg6303dlist.pdf. The lake has especially strict standards for these pollutants because they cause declining clarity.
The standards reflect esthetic values rather than health values, Roberts said.
Alliance executive director Joan Clayburgh said the report was intensively fact checked and compiled from several government sources.
The EPA's listing system is a guilty-until-proven-innocent approach. If a pollutant is detected, the river, lake or stream goes on the list until further studies show it is or is not a problem, Roberts said.
"Things get listed as impaired because they don't meet the standards for that water body, and standards for Lake Tahoe are much more strict," said Lahontan division manager Laurie Kemper. "Water quality in Tahoe remains better than most people's drinking water."
Still, alliance members said their findings were cause for concern.
"This snapshot of Sierra waterways is surprising and very disappointing," said spokeswoman Kate Winston.
The alliance is asking that both California and Nevada make public more information on the state of mountain water.
The health of Sierra Nevada waters is important not only to mountain communities, but to the state at large, the report noted.
More than 60 percent of the state's water comes from the 400-mile-long mountain range, according to the alliance.
Water rights tied to the Sierra Nevada are worth more than $1.3 billion per year.
The report comes on the eve of a critical time for water quality and river health in the Sierra Nevada. Bonds approved by California voters in 2000 and 2002 will hand out the last of their funds for water quality projects and river restoration in 2007. The funding handed out next year can still be used until 2011.
The propositions (numbered 13, 40 and 50) funneled a good portion of their combined $8 billion into water quality projects across the state.
"If there are no further bonds it will be really hard to raise the money to do the restoration and protection work needed in the Truckee River," said Lisa Wallace, executive director of the Truckee River Watershed Council.
The state bond money, and matching federal grants, have supplied Wallace's group with approximately 85 percent of their funding since its inception. The funding has gone into restoration work in all corners of the watershed.
• David Bunker of the Sierra Sun and The Associated Press contributed to this report.
Local waters allegedly showing pollution in last five years:
• Lake Tahoe - pollutants include iron, mercury, sediment and pesticides and nutrients. The lake has been at some point in the last five years impaired for swimming and recreational use. It has been threatened for drinking, fishing and habitat.
• East Fork Carson River - zinc, silver, iron and aluminum, as well as for sulfate. Impairments have threatened drinking and fishing.
• West Fork Carson - metals including iron, nutrients and pathogens
The watershed is also threatened for fishing.
• Heavenly Valley Creek - unspecified metals, impaired for swimming, recreational use, wildlife habitat and freshwater habitat.
• Trout Creek - iron, impaired for nutrients and pathogens, and for drinking, habitat, sediment/siltation, and freshwater habitat.
• Middle Truckee River - Pollutants include iron, silver and zinc. The river's impaired uses include swimming, drinking. The river is threatened for fishing.
• Little Truckee River - This river is impaired by sediment and flow alterations. Fishing is threatened.
• Stampede Reservoir - Pollutants include unspecified metals. The reservoir is impaired by pesticides. Fishing, habitat and threatened and endangered species are threatened in the reservoir.
• Martis Creek - Pollutants include unspecified metals. The creek is impaired for swimming, drinking, sediment and habitat.
• Squaw Creek - Pollutants include unspecified metals. The creek is impaired for fishing, swimming drinking and recreational uses. Sediment and silt affect this creek.
• Boca Reservoir - Pollutants include unspecified metals.
• Donner Lake - Pollutants include unspecified metals. The lake is impaired by pesticides sediment and pathogens. Its threatened uses include drinking, swimming and recreation and habitat.
-Source: Sierra Nevada Alliance