Lac de Gras a wide and long stream called the Narrows. The median flood peak discharge in the Narrows is making it an important corridor for fish movements. Lac de Gras Lac de Gras is a lake approximately north east of Yellowknife, in the Northwest Territories of Canada. Lac de Gras was the centre of the diamond rush of the 1990s. There are two working, and one closed, diamond mines in the area, Diavik Diamond Mine, Ekati Diamond Mine, and the care and maintenance Snap Lake Diamond Mine. It was called Ekati by aboriginal peoples. The lake is ultraoligotrophic but supports a slow-growing
Permafrost down to . Discontinuous permafrost is often further divided into "extensive discontinuous permafrost", where permafrost covers between 50 and 90 percent of the landscape and is usually found in areas with mean annual temperatures between , and "sporadic permafrost", where permafrost cover is less than 50 percent of the landscape and typically occurs at mean annual temperatures between . In soil science, the sporadic permafrost zone is abbreviated SPZ and the extensive discontinuous permafrost zone DPZ. Exceptions occur in "un-glaciated" Siberia and Alaska where the present depth of permafrost is a relic of climatic conditions during glacial ages where winters