Lake Tahoe (; Washo: Dáʔaw) is a freshwater lake in the Sierra Nevada of the Western United States, straddling the border between California and Nevada. Lying at above sea level, Lake Tahoe is the largest alpine lake in North America, and at it trails only the five Great Lakes as the largest by volume in the United States. Its depth is , making it the second deepest in the United States after Crater Lake in Oregon ().
The lake was formed about two million years ago as part of the Lake Tahoe Basin, and its modern extent was shaped during the ice ages. It is known for the clarity of its water and the panorama of surrounding mountains on all sides. The area surrounding the lake is also referred to as Lake Tahoe, or simply Tahoe; its English name is derived from its Washo name, . More than 75% of the lake's watershed is national forest land, covered by the Lake Tahoe Basin Management Unit of the United States Forest Service.
Lake Tahoe is a major tourist attraction in both Nevada and California. It is home to winter sports, summer outdoor recreation, and scenery enjoyed throughout the year. Snow and ski resorts are a significant part of the area's economy and reputation. The Nevada side also offers several lakeside casino resorts, with highways providing year-round access to the entire area.
Toponym
The name for Lake Tahoe derives from the Washo word for the lake, , meaning 'the lake.' Even though is used in the names of other lakes with modifiers (for example, for Pyramid Lake, meaning 'trout lake'), it often is used without a modifier to refer to Lake Tahoe. This may be because of Tahoe's importance to Washo culture.
Geography
Lake Tahoe is the second deepest lake in the U.S., with a maximum depth of , trailing Oregon's Crater Lake at . Tahoe is the 17th deepest lake in the world, and the sixth deepest in average depth. It is about long and wide and has of shoreline and a surface area of . The lake is so large that its surface is noticeably convex due to the curvature of the Earth. At lake level the opposing shorelines are below the horizon at its widest parts; by nearly at its maximum width, and by some along its length. Visibility may vary somewhat with atmospheric refraction; when the air temperature is much greater than the lake temperature, looming may occur where the lake surface or opposing shoreline is lifted above the horizon. Fata Morgana may be responsible for Tahoe Tessie sightings.
Approximately two-thirds of the shoreline is in California. The south shore is dominated by the lake's largest city, South Lake Tahoe, California, which adjoins the town of Stateline, Nevada, while Tahoe City, California, is located on the lake's northwest shore. Kings Beach, California, and Incline Village, Nevada anchor the lake's north shore. Although highways run within sight of the lake shore for much of Tahoe's perimeter, many important parts of the shoreline lie within state parks or are protected by the United States Forest Service. The Lake Tahoe Watershed (USGS Huc 18100200) of is the land area that drains to the lake and the Lake Tahoe drainage divide traverses the same general area as the Tahoe Rim Trail.
Lake Tahoe is fed by 63 tributaries. These drain an area about the same size as the lake and produce half its water, the other half by direct precipitation.
The Truckee River is the lake's only outlet, flowing northeast through Reno, Nevada, into Pyramid Lake which has no outlet. It accounts for one third of the water that leaves the lake, the rest evaporating from the lake's surface. Evaporation is thought to account for 40 to 60 percent of the water usage. The flow of the Truckee River and the height of the lake are controlled by the Lake Tahoe Dam at the outlet. The natural rim is at above sea level. The maximum legal limit to which the lake can be allowed to rise in order to store water is at ; a spillway at the dam controls overflow. Around New Year 1996/1997 a Pineapple Express atmospheric river melted snow and caused the lake and river to overflow, inundating Reno and surrounding areas.
Natural history
Geology
The Lake Tahoe Basin was formed by vertical motion (normal) faulting. Uplifted blocks created the Carson Range on the east and the main Sierra Nevada crest on the west. Down-dropping and block tilting (half-grabens) created the Lake Tahoe Basin in between. This kind of faulting is characteristic of the geology of the adjoining Great Basin to the east.
Lake Tahoe is the youngest of several extensional basins of the Walker Lane deformation zone that accommodates nearly per year of dextral shear between the Sierra Nevada-Great Valley Block and North America.