ATHABASCA or ELK, a river and lake of the province of Alberta, Canada. The river rises in the Rocky mountains near the Yellowhead pass in 5 2 ° 10' N. and 1 17 ° 10' W., and flows north east as far as Athabasca landing, and thence north into Lake Athabasca. It is 74om. long and has a number of important tribu taries, including the McLeod, Pembina, Lesser Slave, which drains the lake of that name, and Clearwater. Athabasca lake is 195m. long, west to east, from 20 to 3 2m. wide, has an area of 3,085 sq.m., and is 69oft. above the sea. It discharges its waters north ward by Slave river and the Mackenzie system to the Arctic ocean. The Athabasca is navigable, with minor rapids, to Grand Rapids, where navigation is interrupted as far as Fort McMurray; thence to Athabasca lake it flows slowly and is suitable for river steamers.