Lake McConnell to have drained first into Lake Agassiz", an even larger lake to the southeast, "then into the Arctic Ocean via the Mackenzie River, then back into Lake Agassiz, and then back to the Arctic Ocean" at various times in its history. Either 8,300 or between 9,000 and 8,000 years ago, it divided to form Great Slave Lake and Lake Athabasca. These two and Great Bear Lake are considered its 'daughter' lakes. Lake McConnell Lake McConnell was a very large proglacial lake that existed in what is now Canada from 11,800 to 8,300 years ago. Other sources give starting and ending
Mackenzie River watershed drains about 20 percent of Canada. It is the largest river flowing into the Arctic from North America, and including its tributaries has a total length of , making it the thirteenth longest river system in the world. Through its many tributaries, the Mackenzie River basin covers portions of five Canadian provinces and territories – British Columbia (BC), Alberta, Saskatchewan, Yukon, and Northwest Territories. Thutade Lake, in the Northern Interior of BC, is the ultimate source of the Mackenzie River via the Finlay–Peace River system, which stretches through BC and Alberta. The Athabasca River originates further south, in Jasper