The Weeks Bay National Estuarine Research Reserve is a field laboratory and research facilty along Weeks Bay estuary, about 6,000 acres (2,400 ha) in size. It receives freshwater from the Magnolia and Fish Rivers, and drains a 198 square miles (510 km²) watershed into the portion of Mobile Bay via a narrow opening. This sub-estuary of Mobile Bay averages just 4.8 ft (1.5 meters) deep and is fringed with marsh (Spartina, Juncus) and swamp (pine, oak, magnolia, maple, cypress, bayberry, tupelo and others). The reserve lands also include upland and bottomland hardwood forests, freshwater marsh (Typha, Cladium), submerged aquatic vegetation (Ruppia, Valisneria) and unique bog habitats (Sarracenia, Drosera).