The Missouri water resource 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.[1][2]
The Missouri region, which is listed with a 2-digit hydrologic unit code (HUC) of 10, has an approximate size of 520,960 square miles (1,349,300 square kilometers), and consists of 30 sub-regions, which are listed with the 4-digit HUCs 1001 through 1030.
This region includes the drainage within the United States of: (a) the Missouri River Basin, (b) the Saskatchewan River Basin, and (c) several small closed basins. Includes all of Nebraska and parts of Colorado, Iowa, Kansas, Minnesota, Missouri, Montana, North Dakota, South Dakota, and Wyoming.[3]