Mackenzie River from the Peace-Athabasca system are significantly slowed by the delta area at the western end of Lake Athabasca causing the lake to rise, and the excess water can only flow out after the rivers have receded. The same phenomenon occurs at Great Slave Lake, which naturally regulates the flow from the Slave River into the Mackenzie. There are river gages at several upstream points along the Mackenzie River. The average flow rate at the outlet of Great Slave Lake is . At Fort Simpson, below the Liard River, it is . At Norman Wells it is , and at the
Oil sands sands and merge at Lake Athabasca to form the Slave River, which flows into the MacKenzie River, one of the largest rivers in the world. All of the water from these rivers flow into the Arctic Ocean. The Peace River oil sands probably contain over 30 billion cubic metres (200 billion barrels) of oil-in-place. The thickness of the deposit ranges from and it is buried about deep. Whereas the Athabasca oil sands lie close enough to the surface that the bitumen can be excavated in open-pit mines, the smaller Peace River deposits are too deep, and must be exploited using