Rio Grande water resource region
The Rio Grande 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. The Rio Grande region, which is listed with a 2-digit hydrologic unit code (HUC) of 13, has an approximate size of , and consists of 9 subregions, which are listed with the  4-digit HUCs 1301 through 1309. This region includes the drainage within the United States of: (a) the Rio Grande Basin, and (b) the San Luis Valley, North Plains, Plains of San Agustin, Mimbres River, Estancia, Jornada Del Muerto, Tularosa Valley, Salt Basin, and other closed basins. Includes parts of Colorado, New Mexico, and Texas.