The Coverage Area

Coverage Area

Coverage Area Map of MBNEP

The Mobile Bay National Estuary Program coverage area includes waters within Baldwin and Mobile Counties and Mobile Bay from the west at the Mississippi state line to the east at the Florida state line, terminating at the Perdido River. This estuary is greatly affected by upstream waters that flow into it from the expansive Mobile Bay Watershed. Other coastal estuaries in and near Alabama include Mississippi Sound westward to the Alabama-Mississippi State Line, Perdido Bay, and their tributaries. The Mobile Bay National Estuary Program service area includes all of Mobile and Baldwin Counties, as well as Alabama state marine waters in the north central Gulf of Mexico, extending three miles south of Dauphin Island and the Fort Morgan Peninsula. The Mobile Bay National Estuary Program study area is shown on the map.

Mobile Bay's average depth is only about 10 feet, which is among the shallowest for a bay of its size. It is approximately 32 miles long from the Mobile-Tensaw Delta to its mouth, 23 miles across at its widest point, and about 10 miles across at the City of Mobile. A combination of wind and tide delivers salty Gulf waters from the south into the Bay that mix with varying amounts of freshwater from the Mobile-Tensaw River Delta. Due to the shallow nature of the Bay, dynamic climatic conditions, and man-made hydrologic modifications, salinity conditions in the Bay are remarkably variable.

Several factors contribute to the ever-changing salinity conditions which characterize Mobile Bay. Summer thunderstorms and winter cold fronts produce heavy downpours contributing to an average of 66 inches of rainfall annually, the highest average nationally for a city the size of Mobile, along with a relatively high frequency of tropical cyclone landfalls. Consequently, river flows are naturally highly variable. The Bay is influenced by a single daily or "diurnal" tidal cycle with tide changes averaging a little less than a foot and a half feet. The resulting hydrology is dynamic, complex, and necessary to support the diversity of plant and animals found in and around the Bay.