There are four water divisions whose boundaries are formed by the natural divides between drainages and the borders of the state of Montana and which are described as follows:
(1) The Yellowstone River basin water division consists of those areas drained by the Yellowstone and Little Missouri Rivers and any remaining areas in Carter County.
(2) The lower Missouri River basin water division consists of those areas drained by the Missouri River from below the mouth of the Marias River and any remaining areas in Glacier and Sheridan Counties.
(3) The upper Missouri River basin water division consists of those areas drained by the Missouri River to below the mouth of the Marias River.
(4) The Clark Fork River basin water division consists of the areas drained by the Clark Fork River, the Kootenai River, and any remaining areas in Lincoln County.