Many river basins border on the Kootenay—some are part of the Columbia Basin, while others drain to distant shores of the North American continent. On the south and southeast, the divide formed by the Cabinet and Whitefish ranges separate the Kootenay and Flathead River watersheds. The Flathead is a tributary of the Clark Fork River-Pend Oreille River system which borders the Kootenay watershed on the southwest. The upper Columbia River basin forms the boundary on the north, and the Kicking Horse River watershed also borders the north side of the Kootenay basin. To the southwest is the Priest River, a Pend Oreille tributary. On the east side, over the Continental Divide, the Bow River and Oldman River take rise. Both are tributaries of the South Saskatchewan River, which is part of the Hudson Bay drainage basin.