Lake Tahoe is one of the deepest and clearest lakes in the world. As such, it is a highly sought out destination for recreation, tourism and home ownership. Clarity and exceptional water quality are the basis of Lake Tahoe water quality goals. These important features give Lake Tahoe important designations. Both the federal government and California government have designated Lake Tahoe an "Outstanding National Resource Water
". Nevada has designated Lake Tahoe a "Water of Extraordinary Ecological or Aesthetic Value
". In addition to aesthetic enjoyment, the exceptional quality of water in the Lake Tahoe Basin supports a number of beneficial uses related to human and environmental health, including drinking water supply, water contact recreation, wildlife habitat, and aquatic life and habitat.
The water quality of Lake Tahoe, and its tributaries, highly contributes to the scenic quality of the Lake Tahoe Basin, yet water quality depends on a fragile balance among soil, vegetation, and human impact. The focus of water quality protection in the Basin is to minimize human disturbance, and to reduce or eliminate the addition of pollutants that result from development.
Lake Tahoe is experiencing a phenomenon known as cultural eutrophication, which is the Lake's response to accelerated inputs of nutrients due to development in the Basin. Impervious land coverage
, land disturbance
, and atmospheric deposition
are typical products of development that impact the Lake’s nutrient and sediment load.
Since Lake Tahoe does not benefit from the flushing action of runoff like other water bodies such as Fallen Leaf Lake, correcting Lake Tahoe's imbalanced nutrient and sediment load is a difficult task. Lake Tahoe has a remarkable residence time of 700 years, making the Lake behave like a sink without a drain. Preventing additional sediment from flowing into Lake Tahoe is a complicated endeavor and controlling the sources of nutrients is paramount to reversing the loss of water clarity.
Since the early 1970s, Congress has passed legislation designed to protect and preserve the Earth´s supply of freshwater. Lake Tahoe´s designation as an Outstanding National Resource Water (ONRW) is a result of these legislations. With this designation, Lake Tahoe is provided the highest level of protection under the antidegradation policy and no further degradation should be permitted. (Water Quality Standards Handbook, Second Edition, 1993)
Source water protection is important in the Tahoe basin because the surface and ground waters are tapped for drinking water supplies. Most municipal drinking water suppliers on the Nevada-side of the Lake Tahoe basin and some of the California-side municipal water purveyors receive the majority of their supply directly from the Lake. Most of these municipal water suppliers have received an exemption to the Federal Surface Water Treatment Rule
because Lake Tahoe’s water is exceptionally pure and meets all the mandated drinking water standards without being filtered, though must still be lightly chlorinated as a disinfectant.
The basin waters, including Lake Tahoe and all its tributaries and other water bodies in the basin, continue to be of exceptionally high quality. Anthropogenic
pollutants, such as pesticides and petroleum hydrocarbons, generally have not been detected in the basin surface waters except in certain instances and locations where they have not been a chronic or persistent problem. Aquatic ecosystems in and around the basin’s waters rely on the high water quality and have flourished. Some locations, such as the Tahoe Keys lagoons and other man-made water body areas, exhibit different water quality characteristics than the natural areas and have slightly different aquatic ecosystems.