Petitot is a river in northern Alberta and British Columbia, Canada. It is a tributary of the Liard River. Petitot River in western Canada Petitot River originates from Bistcho Lake in northwestern Alberta, and flows westwards along the northern borders of Alberta and British Columbia. It then passes in the Northwest Territories, where it discharges in the Liard River at the village of Fort Liard. From there, its waters are carried to the Arctic Ocean through the Mackenzie River. It has a total length of 404 kilometres (251 mi) and a drainage area of 23,200 square kilometres (9,000 sq mi).