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.[1][2]
The Texas–Gulf region, which is listed with a 2-digit hydrologic unit code (HUC) of 12, has an approximate size of 181,886 square miles (471,080 square kilometers), and consists of 11 subregions, which are listed with the 4-digit HUCs 1201 through 1211.
The coastal drainage and associated waters from and including Sabine Pass to the Brazos River Basin boundary, but excluding the Neches and Sabine River Basins above Sabine Lake and the Trinity River Basin above Trinity Bay.
The Brazos River Basin below the confluence of the Double Mountain Fork Brazos River and the Salt Fork Brazos River Basins to and including the Castleman Creek Basin.
The Colorado River Basin below the Oak Creek Basin; and the Coastal drainage and associated waters from the Brazos River Basin boundary to the Colorado River Basin boundary.
The coastal drainage and associated waters from Aransas Pass, including the Corpus Christi Bay and Nueces River drainages, to the Rio Grande Basin boundary.
