Lac de Gras

Lac de Gras is a lake approximately 300 km 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 but stable population of some eight species of cold-water fishes, including round whitefish, cisco, and lake trout. Lake trout dominate the lake, both numerically and in terms of biomass. Other native fish species include common whitefish, Arctic grayling, burbot, longnose sucker, and slimy sculpin.

Diavik Diamond Mines is conducting open-pit mining of kimberlite pipes using explosives near the lake.

Lac de Gras' surface area is 56910.8 ha; the historical surface area was 57107.2 ha, about 196.4 ha larger than today. The subbasin area is 413570 ha with the number of lakes smaller than 1 ha 3,487; 1-10 ha 2,080; 10-100 ha 663; and larger 100 ha 106, together with a total surface area of 135035 ha.

Lac du Sauvage is a small lake that drains into Lac de Gras through a 45 m wide and 210 m long stream called the Narrows. The median flood peak discharge in the Narrows is 17.5 m3/s making it an important corridor for fish movements.