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Lake Tahoe

Lake Tahoe is a designated Outstanding National Resource Water (ONRW) that is renowned for its extraordinary clarity and purity, and deep blue color. Since the late 1960s, Lake Tahoe has become impaired by declining deep water transparency (clarity) and increasing phytoplankton (algae) productivity due to increased fine sediment particles (FSP) and nutrient loading attributable to human activities.

Steep slopes, erodible soils, and a short growing season make the Lake Tahoe Basin acutely sensitive to human activities. Development practices and ongoing soil disturbing land uses that may have little impact elsewhere can cause severe erosion in the Tahoe Basin, increasing FSP, nitrogen and phosphorus loads delivered to the lake. FSP directly reduces water transparency because these fine particles are held in suspension in the waters of Lake Tahoe and scatter light; the nutrients nitrogen and phosphorus support algae growth which in turn also contributes to loss of water transparency and changes to water color.

Human development disturbs vegetation and soils and creates impervious surface coverage that interferes with natural FSP and nutrient removal mechanisms. Runoff from roadways, urbanized landscapes, and from human soil disturbing activities are the primary sources of FSP reaching the lake. Nutrients from fertilizers, sewer leaks, onshore development, and leachate from abandoned septic systems are linked with increased algae growth in Lake Tahoe. Other sources of nutrients that also contribute to algae growth come from atmospheric deposition and groundwater inflows.

Lake Tahoe Total Maximum Daily Load (TMDL)

In 2011, the Lahontan Water Board together with the Nevada Dept. of Environmental Protection (NDEP) adopted the Lake Tahoe Total Maximum Daily Load (TMDL) to address FSP and nutrient impairments and restore deep water transparency. To achieve the goals of the TMDL and restore lake water quality, FSP and nutrient loads to the lake must be reduced by addressing a variety of point and nonpoint sources, including solid and liquid waste disposal, road maintenance, construction, stormwater management, and other human development.

More information about the Lake Tahoe TMDL program is available at this webpage. Other resources regarding the Lake Tahoe TMDL are provided in the resources section below.

Lake Tahoe's Nearshore

The nearshore of Lake Tahoe is the portion of the lake in close proximity to the shoreline. This area is defined by the Lake Tahoe TMDL as extending from the shoreline to 20 meters (66ft.) of water depth. The nearshore receives the most interaction from people, including (but not limited to) viewing the lake from the shore, wading, swimming, enjoying paddle sports, and boating.

Over the last several decades, the public and natural resource agencies have observed changes to nearshore water quality and nearshore lake bottom environment. Changes include increased growth of attached and floating algae, the presence of invasive animals and plants, and a reduction in nearshore water clarity.

The Lahontan Water Board, together with NDEP, the Tahoe Regional Planning Agency (TRPA), and other partners, is actively working to address nearshore water quality issues via administration of monitoring programs, supporting scientific research, and regulating shorezone activities that might contribute to water quality issues.

More information about the Lahontan Water Board’s efforts to protect Lake Tahoe’s nearshore is available in the Nearshore Water Quality Protection Plan. More resources regarding Lake Tahoe’s nearshore water quality are provided in the resources section below.

Lake Tahoe Basin

As well as Lake Tahoe, there are 170 other lakes, 63 tributary streams, and numerous wetlands in the Lake Tahoe Basin; most of the lakes and about half of the streams are in California. There are also two named ground water basins in the California portion of the watershed. Most of these waters are naturally of high quality, and although many are within wilderness areas, they are threatened by heavy recreational use and atmospheric deposition. Other tributary waters have been adversely affected by erosion, stormwater, diversion, channelization, or filling. In particular, wetlands have been drastically disturbed by human activities.

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Lake Tahoe Resources