Shuswap Lake

Shuswap Lake (pronounced /ˈʃuːʃwɑːp/ SHOOSH-wahp) is a lake located in the southern interior of British Columbia, Canada that drains via the Little River into Little Shuswap Lake. Little Shuswap Lake is the source of the South Thompson River, a branch of the Thompson River, a tributary of the Fraser River. It is at the heart of a region known as the Columbia Shuswap or "the Shuswap", noted for its recreational lakeshore communities including the city of Salmon Arm. The name "Shuswap" is derived from the Shuswap or Secwepemc First Nations people, the most northern of the Interior Salish peoples, whose territory includes the Shuswap. The Shuswap call themselves /ʃǝxwépmǝx/ in their own language, which is called /ʃǝxwepmǝxtʃín/.

Shuswap Lake is located in the southern Interior region of the province at the boundary of the Shuswap Highland and the Monashee Range, a sub-range of the Columbia Mountains.

The lake consists of four arms, forming a shape reminiscent of the letter H. The four arms are called Salmon Arm (southwest), Shuswap Arm or Main Arm (west), Anstey Arm (northeast), and Seymour Arm (north). Shuswap Lake connects to Little Shuswap Lake via the Little River, which flows from the end of Shuswap Lake.

To the north-west it is fed by the Adams River, which drains Adams Lake. The Salmon Arm of Shuswap Lake connects to Mara Lake at the Sicamous Channel. The Shuswap River connects via Mara Lake. In the south-west the Salmon River flows into the lake at Salmon Arm. The Eagle River runs down from the Eagle Pass in the Monashees to enter the lake at Sicamous, in the east. The Seymour River empties into the northern end of the Seymour Arm. In addition to these rivers, numerous creeks feed the lake, including Scotch Creek, which runs south to the north shore of the main arm, near the community of the same name.

The central interior plateau of British Columbia drained by the Fraser and Columbia rivers is part of the Shuswap terrane in British Columbia and northern Washington state. It is dissected by numerous elongated, glacially-overdeepened lake basins which are formed by the same mechanisms as coastal fjords. Shuswap Lake consists of two, geologically separate basins - Shuswap/Seymour, and Anstey/Salmon Arm.

The metamorphic bedrock in the area is classified as the Shuswap Complex, and is the result of tectonic buildup of rock in western North America in the Mesozoic era.

From 14000-10000 BCE, at the end of the last glacial maximum, several large glacial lakes formed in the region as ice melt was trapped by the remnants of the ice sheets that had previously covered the area. Glacial Lake Kamloops extended over the Shuswap Lake area, with depths up to 1,000 metres (3,300 ft) above the current surface elevation.

The lake sits at 347 metres (1,138 ft) above sea level, and has a surface area of 310 square kilometres (120 sq mi). The lakeshore has a perimeter of 342 kilometres (213 mi). The mean depth of the lake is 62 metres (203 ft) and its maximum depth reaches 171 metres (561 ft) in Seymour Arm. The Cinnemosun Narrows, where the two basins of the lake join, is only 5 metres (16 ft) deep. The average volume of the lake is 19 cubic kilometres (4.6 cu mi) and water remains in the lake for an average of 2.1 years.