This region begins at International Amistad Reservoir in ValVerde County, which separates the Upper and Lower Rio Grande regions, and extends to the Rio Grande Valley region near the Gulf of Mexico. It contains six major lakes/reservoirs, including two that border the U.S. and Mexico, 14 counties (some partial) and 10 major cities.

Population Estimate (2019): 936,558
Approximate Area: 43,204 square miles
Approximate Stream Miles: 5,300
Approximate NFIP Claims (1975-2019): $173,104,689