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Alberta's rivers flow towards three different bodies of water, the Arctic Ocean, the Hudson Bay and the Gulf of Mexico. Alberta is located immediately east of the continental divide, so no rivers from Alberta reach the Pacific Ocean.
The north of the province is drained towards the Arctic Ocean, and the northern rivers have comparatively higher discharge rates than the southern ones, that flow through a drier area. Most of Alberta's southern half has waters flowing toward the Hudson Bay, the only exception being the Milk River and its tributaries, that flow south through the Missouri and Mississippi River to the Gulf of Mexico.
Albertan rivers in the Arctic Ocean watershed are drained through Great Slave Lake and Mackenzie River, except for Petitot River which is drained through Liard River directly into the Mackenzie River, thus bypassing the Great Slave Lake.
The small areas drained by the Milk River in southern Alberta and southwestern Saskatchewan as well as the Poplar River in southern Saskatchewan are the only areas in Canada that drain into the Gulf of Mexico.