Bi-state report: Less sediment, pollution in Lake Tahoe

Submitted to the Tribune

SOUTH LAKE TAHOE, Calif. — The Nevada Division of Environmental Protection and the Lahontan Regional Water Quality Control Board, part of the California Environmental Protection Agency, on Friday announced that efforts to reduce pollution and restore Lake Tahoe’s water clarity remain on track despite some impacts from climate change.

The latest clarity data from the bi-state Lake Tahoe Maximum Daily Load Program’s 2021 performance report found that pollution from fine sediment particles in urban stormwater was reduced by over 523,000 pounds per year in 2020.

The data indicates that a partnership between local governments and California and Nevada transportation agencies is successfully achieving annual goals established to reduce urban stormwater pollution and improve lake clarity.

“The reduction in fine sediment particles going into the lake last year is significant and speaks well of the effort and on-going commitment among our partners to restore Lake Tahoe’s crystal-clear water,” said Mike Plaziak, Executive Officer of the Lahontan Regional Water Quality Control Board. “Put in perspective, 523,000 pounds of fine sediment particles is equivalent in weight to over 180 small-sized vehicles.”

Findings also show that increasing impacts of climate change, including changes to rainfall and snowmelt patterns, increasing lake temperature and reduced mixing that improves water clarity by bringing cold clear water to the surface, are having an impact on water clarity. Looking ahead, partner agencies will continue to engage with the Tahoe Science Advisory Council to fully understand the influence of other factors on seasonal and long- term clarity conditions and to determine solutions to help speed up improvement of the lake’s clarity.

“The challenges in Lake Tahoe continue to grow every day,” said NDEP Administrator Greg Lovato. “The Nevada Division of Environmental Protection, together with our partners,

remains steadfast in our commitment to restore and enhance Lake Tahoe’s iconic water clarity for generations to come.”

“We look forward to building on the great progress that’s been made to address current and emerging challenges head-on by putting forward science-driven solutions to reduce pollution and protect the ecological health and natural beauty of the lake,” said Lovato. “I thank our partners on both sides of the lake for their continued collaboration and support to ensure a vibrant, sustainable, climate-resilient future for Lake Tahoe.”

The Lake Tahoe TMDL Program, a bi-state effort between Nevada and California launched in 2011, is a science-based plan to restore clarity to Lake Tahoe by requiring local governments and highway departments at Lake Tahoe to implement pollutant controls to reduce the amount of clarity-harming pollutants that wash into the lake.

Report Key Findings:

The TMDL Program’s 2021 Performance Report found that pollution from fine sediment particles in urban stormwater was reduced by over 523,000 pounds per year in 2020, and that pollution from nitrogen and phosphorous, which contributes to algae growth, was also reduced by thousands of pounds per year, thanks to efforts of federal, state, and local agencies, as well as private landowners in the basin.

Those efforts include:

Improved road sanding and sweeping to limit dust

Constructing stormwater treatment facilities to treat and infiltrate polluted stormwater runoff

Installing best management practices on developed land and forest roads to minimize pollutants in runoff

Reducing erosion from streams

These measures aim to help Lake Tahoe meet the Clarity Challenge goal of water clarity down to at least 78 feet by the end of 2031. In time, the goal is for people to once again be able to see to depths of 100 feet. Currently, annual clarity stands at about 63 feet, and measurements show the lake’s clarity has plateaued over the past 20 years.

NDEP and the Lahontan Regional Water Quality Control Board, along with the Tahoe Regional Planning Agency, partnered with the Tahoe Science Advisory Council to assess historic clarity data to better understand why clarity improvement does not appear to be tracking with pollutant load reduction progress. The investigation confirmed that fine sediment particles and algae continue to be the primary variables affecting Lake Tahoe’s clarity and concluded that addressing these factors should remain a top priority. To learn more about how these efforts have improved Lake Tahoe’s water quality, view the Lake Clarity Tracker.

The Lake Tahoe Maximum Daily Load Program began in 2011 and is implemented by the California Lahontan Regional Water Quality Control Board and the Nevada Division of Environmental Protection. TMDL Management Agencies help administer the program.

Source: Nevada Department of Conservation and Natural Resources

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