The Texas–Gulf 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. This region includes The drainage that discharges into the Gulf of Mexico from and including Sabine Pass to the Rio Grande Basin boundary. Includes parts of Louisiana, New Mexico, and Texas.