The St. Johns River is an ancient intracoastal lagoon system. As sea levels dropped, barrier islands became an obstacle that prevented water from flowing east to the ocean. The water collected in the flat valley and slowly meandered northward, forming the St. Johns River.*The St. Johns River is the longest river in Florida — 310 miles. It is one of the few rivers in the United States that flows north.
*The square mileage of the St. Johns River’s drainage basin in 8,840.
*The river gets its tea color from tannins, a natural color caused by decaying plant material.
*The land area that drains into a water body is called a drainage basin, “watershed.” The *St. Johns River is divided into three drainage basins.
*Because the river flows north, the upper basin is the area to the south that forms its marshy headwaters in Indian River and Brevard counties. The middle basin is the area in central Florida where the river widens, forming lakes Harney, Jesup, Monroe and George. The lower basin is the area in northeast Florida from Putnam County to the river’s mouth in Duval County, where the river empties into the Atlantic Ocean.
*The width of the river varies. It is a flat marsh at its headwaters and averages about two miles in width between Palatka and Jacksonville. It widens to form large lakes in central Florida.
The total drop of the river from its source in marshes south of Melbourne to its mouth in the Atlantic near Jacksonville is less than 30 feet, or about one inch per mile, making it one of the “laziest” rivers in the world.
*Because the river flows slowly, it is difficult for the river current to flush pollutants.
Major pollution sources include discharges from wastewater treatment plants and stormwater runoff from urban and agricultural areas. This runoff carries pesticides, fertilizers and other pollutants into canals, ditches and streams that lead to the river. River pollution is concentrated around urban areas.
*Salt water enters the river at its mouth in Jacksonville. In periods of low water, tides may cause a reverse flow as far south as Lake Monroe — 161 miles upstream from the river’s mouth.
Major tributaries, or smaller streams and rivers that flow into the St. Johns River, include the Wekiva River, the Econlockhatchee River and the Ocklawaha River.
*The square mileage of the St. Johns River’s drainage basin in 8,840.
*The river gets its tea color from tannins, a natural color caused by decaying plant material.
*The land area that drains into a water body is called a drainage basin, “watershed.” The *St. Johns River is divided into three drainage basins.
*Because the river flows north, the upper basin is the area to the south that forms its marshy headwaters in Indian River and Brevard counties. The middle basin is the area in central Florida where the river widens, forming lakes Harney, Jesup, Monroe and George. The lower basin is the area in northeast Florida from Putnam County to the river’s mouth in Duval County, where the river empties into the Atlantic Ocean.
*The width of the river varies. It is a flat marsh at its headwaters and averages about two miles in width between Palatka and Jacksonville. It widens to form large lakes in central Florida.
The total drop of the river from its source in marshes south of Melbourne to its mouth in the Atlantic near Jacksonville is less than 30 feet, or about one inch per mile, making it one of the “laziest” rivers in the world.
*Because the river flows slowly, it is difficult for the river current to flush pollutants.
Major pollution sources include discharges from wastewater treatment plants and stormwater runoff from urban and agricultural areas. This runoff carries pesticides, fertilizers and other pollutants into canals, ditches and streams that lead to the river. River pollution is concentrated around urban areas.
*Salt water enters the river at its mouth in Jacksonville. In periods of low water, tides may cause a reverse flow as far south as Lake Monroe — 161 miles upstream from the river’s mouth.
Major tributaries, or smaller streams and rivers that flow into the St. Johns River, include the Wekiva River, the Econlockhatchee River and the Ocklawaha River.
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