Western Environmental
Testing Laboratory
Lake Tahoe’s New Standard for Water Quality – TMDL

At the 15th annual Lake Tahoe Summit in Homewood, CA this summer, hosted by Senator Dianne Feinstein and attended by Senator Harry Reid, Senator Dean Heller, California Governor Jerry Brown and Nevada Governor Brian Sandoval, policy makers came up with an important plan for Lake Tahoe.

The Environmental Protection Agency announced plans to restore the lake’s clarity to 97.4 feet by 2076, a lofty goal aiming for historic levels before runoff and pollution clouded the mountain lake’s clear waters.

Most recent measurements have the lake’s clarity – measured by lowering a white disk (called a Secchi disk) into the water and seeing how far down it can still be spotted – at 64.4 feet.

The plan, developed by the Lahontan Regional Water Quality Control Board and the Nevada Department of Environmental Protection, is called the Total Maximum DailyLoad (TMDL), capping the amount of pollution and runoff working its way into the lake – particularly from urban storm water runoff.
It calls for area jurisdictions – the City of South Lake Tahoe, the bordering county governments in both California and Nevada and their respective road departments, to reduce sediment going into the lake by 32 percent over the next 15 years – and that’s where precise water quality monitoring comes into play.
Not only do sediments and pollutants have to be monitored, but nutrients as well, which can cause algae blooms that dramatically cloud the water. The plan targets fine sediments (which tend to “hang” in the water rather than settling to the bottom of the lake), phosphorus, and nitrogen pollutants.
Top sources of those contaminants being targeted include urban and forest storm water runoff, stream channel erosion and atmospheric deposition.
When government agencies take steps like stabilizing and re-vegetating road shoulders and eroding slopes, street sweeping, better landscaping, runoff treatment and filtration, the creation of wetlands, the re-vegetation of ski slopes, and other projects – close monitoring will be necessary to measure success.
And success is critical, considering the plan could cost as much as $100 million per year for the next 15 years, according to the Lahontan regional Water Quality Control Board, so monitoring will insure that is money well spent.