The St. Mary's River forms the boundary between Georgia and Florida. It is a 'black water' river with very high dissolved organic carbon concentrations, and it drains part of the Okefenokee Swamp. Average flow in the St. Mary's is 20 cubic meters per second, and its drainage area (at 3,600 square kilometers) is the smallest of the five GARLMER rivers.
Land use and land cover in the St. Mary's river watershed
