The Souris–Red–Rainy region is one of 21 major geographic areas, or regions, in the first level of classification used by the United States Geological Survey to divide and sub-divide the United States into successively smaller hydrologic units. These geographic areas contain either the drainage area of a major river, or the combined drainage areas of a series of rivers. The Souris–Red–Rainy Region, which is listed with a 2-digit hydrologic unit code (HUC) of 09, has an approximate size of , and consists of 3 subregions, which are listed with the 4-digit HUC codes of 0901 through 0903. This region includes the drainage within the United States of the Lake of the Woods and the Rainy, Red, and Souris River Basins that ultimately discharges into Lake Winnipeg and Hudson Bay. Includes parts of Minnesota, North Dakota, and South Dakota. List of water resource subregions See also List of rivers in the United States Water resource region References Regions of the United States Drainage basins Watersheds of the United States Water resource regions