About Lake Tahoe
About 3 to 5 million years ago, the valley that would become the Tahoe Basin sank between parallel fractures in the Earth’s crust as the mountains on either side continued to rise. A shallow lake began to form in the resulting valley.
Roughly 2 to 3 million years ago, erupting volcanoes blocked the outlet, forcing the lake to rise hundreds of feet above its current elevation, and eventually eroded down to near its current outlet.
The Tahoe Basin is mostly granite, with little topsoil, and therefore few nutrients have washed into the lake to promote the growth of algae and other organisms that make water murky.
As well, 40 percent of the precipitation falling into the Tahoe Basin, lands directly on the lake. The remaining precipitation drains through the decomposed granite soil found in marshes and meadows, creating a good filtering system for water.
Urbanization of the Tahoe Basin has eliminated 75 percent of its marshes, 50 percent of its meadows and 35 percent of its stream zone habitats. About 85 percent of all wildlife in the Tahoe Basin use these habitats.
The Truckee River is Tahoe’s only outlet and flows from the dam in Tahoe City east through Reno and eventually drains into Pyramid Lake in the Nevada desert. From there it evaporates into the atmosphere.
However, water releases are not permitted when the lake surface level falls below the natural rim at 6,223′. The lowest lake level on record (measured since 1900) was 6, 220.26′ on Nov. 30, 1992.
The Lake of the Sky appears blue in color as other colors in the light spectrum are absorbed and blue light is scattered back ranging from a deep cobalt blue to a dazzling turquoise.
The University of California, Davis, operates the Tahoe Environmental Research Center, which monitors, amoung other things, the clarity of Lake Tahoe.
Clarity has been measured since 1968 using a Secchi measurement, which is the point below the lake surface at which a 10″ white disk disappears from view. Clarity was measured at 102.4′ in 1968.
The waters of Lake Tahoe were clear to an average depth of 68.9′ in 2011. The lowest average depth on record was 64.1′ in 1997. Lake Tahoe is losing clarity because of microscopic sediments entering the lake and algae growth fueled by nitrogen and phosphorus.
Lake Tahoe’s natural rim is 6,223′ – 6229.1′. The last 6.1′ is controlled by the dam located in Tahoe City. Lake Tahoe is 22 miles long and 12 miles wide, giving it a total of 72 miles of shoreline and a volume of 39 trillion gallons. Its average depth is 1,000′ and its deepest location is 1,645′ making it the second deepest lake the in the US and the eleventh in the world. You can view the current lake level measurements on the USGS website.
Lake Boating Information
Starting in 2010, the TRPA implemented the “Blue Boating Program” in order to address the impacts associated with boating on Lake Tahoe. It was redesigned in 2011 and renamed “Aquatic Invasive Species Inspection”or AIS. This program requires all vessels entering Lake Tahoe to be inspected for invasive species, as well as bilge and grey-water pollution. Once the vessel passes inspection, the vessel is issued a sticker to certify it has passed and can be used on Lake Tahoe. Once a vessel is pulled out of Lake Tahoe, a blue seal is attached to the trailer and the boat. This is to determine if a vessel has been in any other waters after leaving Tahoe. Vessels that are only used in Tahoe waters (including Fallen Leaf Lake and Echo Lake) do not need to re-do an inspection each year, so long as the wire seal was not removed. For more information about the program and inspection you may visit the Tahoe Boating Inspection site or call 888-824-6267.