The Mobile Bay Watershed

The Mobile Bay Watershed encompasses 65% of the land area for the state of Alabama, along with portions of Mississippi, Georgia and Tennessee. Mobile Bay is the end-point for the Mobile, Tombigbee, Black Warrior, Alabama, Coosa and Tallapoossa Rivers. The watershed is a vast network of over 250 separate waterways, including rivers, bays, creeks, bayous, lakes, cutoffs, branches, and sloughs. 

The outflow of these rivers winds through the Mobile-Tensaw Delta before reaching the Mobile Bay. The expansive delta is comprised of old growth cypress and lush marshlands and is considered one of the most biologically diverse ecosystems in North America. The delta opens into the northern end of Mobile Bay in an area called Five Rivers, which consists of the Mobile, Spanish, Tensaw, Apalachee and Blakley rivers. The Bay is approximately 32 miles long and 23 miles across at its widest point. The average depth in Mobile Bay is only about 10 feet, which makes it one of the most shallow bays of its size.

Mobile Bay is Alabama’s central estuary serving as a transitional zone where the river’s fresh water can mingle with tidally influenced marine waters. An estuary is a partially enclosed body of water formed where freshwater from rivers and streams flows into the ocean, mixing with the salty water of the Gulf or an ocean. Estuaries are environmentally and economically important because of their exceptional biological diversity and productivity.

  • The Mobile Bay Watershed covers two-thirds of Alabama -- Roughly 45,000 square miles.
  • More than 250 rivers, bays, bayous, creeks, inlets and sloughs flow into the watershed.
  • On average, 33.5 trillion gallons pass through annually making it the fourth largest drainage basin in North America.
  • Major Habitat Types:  Submerged aquatic vegetation (seagrass), reefs (artificial), barrier islands/sand bars, lagoon/shallow open water shell fish growing areas, beach/dune (bare & vegetated), sand/mud/salt flats, salt/brackish marsh, freshwater marsh (tidal & non-tidal), forested wetland, seasonal wetland, freshwater lakes/ponds, grass/open field, non-wetland forest, riparian/riverine (forested, tidal, & flood plain) abandoned, & agricultural.

Alabama is home to an immense diversity of plant and animal life, ranking fourth nationally in overall diversity, Alabama ranks number ONE for freshwater fish, mussels, turtles, snails, and crayfish species.

  • Species Diversity: More than 800 species of non-vertebrates, 337 species of fish (36 at risk*), 126 amphibians & reptiles (30 at risk), 355 Birds (38 at risk), 49 mammals (7 at risk)

Federally Endangered or Threatened Species:

  • Mammals: Alabama Beach Mouse, West Indian Manatee
  • Birds: Bald Eagle, Peregrine Falcon, Piping Plover, Red-Cockaded Woodpecker, Wood Stork
  • Reptiles: Alabama Red-Bellied Turtle, Eastern Indian Snake, Gopher Tortoise, Loggerhead Sea Turtle
  • Fish: Gulf Sturgeon
  • Insects: American Burying Beetle
  • Plants: Alabama Canebrake Pitcher Plant, American Chaffseed, Louisiana Quillwort, Barbara's Buttons

*Note: “at risk” not only includes Federal & State protection levels, but also non-regulatory listings by either researchers studying the species or by The Nature Conservancy’s Natural Heritage Program, which catalogues rare plant & animal species. (See Mobile Bay NEP for more info)