The U.S. state of Texas has a series of estuaries along its coast on the Gulf of Mexico, most of them bounded by the Texas barrier islands. Estuaries are coastal bodies of water in which freshwater from rivers mixes with saltwater from the sea. Twenty-one drainage basins terminate along the Texas coastline, forming a chain of seven major and five minor estuaries: listed from southwest to northeast, these are the Rio Grande Estuary, Laguna Madre, the Nueces Estuary (Corpus Christi Bay), the Mission–Aransas Estuary (Aransas Bay), the Guadalupe Estuary (San Antonio Bay), the Colorado–Lavaca Estuary (Matagorda Bay), East Matagorda Bay, the San Bernard River and Cedar Lakes Estuary, the Brazos River Estuary, Christmas Bay, the Trinity–San Jacinto Estuary (Galveston Bay), and the Sabine–Neches Estuary (Sabine Lake). Each estuary is named for its one or two chief contributing rivers, excepting Laguna Madre, East Matagorda Bay, and Christmas Bay, which have no major river sources. The estuaries are also sometimes referred to by the names of their respective primary or central water bodies, though each also includes smaller secondary bays, inlets, or other marginal water bodies.
These water bodies include some of the largest and most ecologically productive coastal estuaries in the United States and contribute significantly to the ecological and economic resources of Texas. They are included in a number of national protected areas such as National Wildlife Refuges, a National Seashore, and a National Estuarine Research Reserve, as well as various state parks and other regional protected areas. The two most economically important (the Nueces and Trinity–San Jacinto Estuaries) have been designated by the United States Environmental Protection Agency as estuaries of national significance under the National Estuary Program. The Gulf Intracoastal Waterway runs through each of the major estuaries, linking Texas ports with others along the Gulf Coast of the United States.
