RIVER GEOLOGY
Most of Florida's 1700 rivers and streams begin in the northern portion of the state and travel south toward a larger body of water. (Except for the St. Johns, Withlacoochee and Wekiva Rivers, which begin in the south and flow north!) Florida's relatively flat topography results in rivers that generally are sluggish: the St. Johns River "falls" only about 20 feet between its Melbourne headwaters and its Jacksonville exit into the ocean, more than 300 miles north.

Florida's geology allows each river to display unique collections of environmental characteristics in water quality, flow, clarity, temperature, and floral and faunal populations.

Geologists classify Florida's rivers into four categories:

Sand-bottom streams are the most common type in Florida. They are characterized by moderate to swift currents and slightly acidic water.

Calcareous streams usually orginate from springs. They have relatively colder temperatures, and generally clear alkaline water that is easily penetrated by sunlight and is rich in calcium and nutrients such as phosphorus. As a result, calcareous streams have dense vegetation and diverse animal populations.

Larger rivers are characterized by their above-average size. As a result, large amounts of suspended silt and clay create turbid (cloudy) water. Because these rivers flow into the Gulf or the Atlantic, they are occupied by a mixture of freshwater and marine organisms. The largest rivers in Florida are the St. Johns River, the Choctawhatchee River, the Escambia River, and the Apalachicola River.

Swamp and bog streams originate from the swamps, bogs and marshes commonly located in the coastal lowlands. Swamp and bog streams have slow currents. They have dark acidic water with a large amount of suspended organic matter and tannins. The brown or tea color results in the common name "blackwater river". The dark water limits light penetration and therefore reduces plant growth; reduced plant populations results in less diverse animal populations.

DISAPPEARING RIVERS
Some of Florida's rivers disappear underground and drain into a subterreanean limestone labyrinth of aquatic caves. The notable Santa Fe River suddenly disappears underground at O'Leno State Park and reemerges at River Rise municipal park, 2 or 3 miles away. Visitors at Falmouth Springs can watch groundwater emerge from a spring to create a short river that syphons underground a mere 500 feet away.

a subdued Suwannee	strolling by the Withlacoochie	a one-car ferry, on the St. Johns	the heady Hillsborough	spectacular: Chassahowitzka

mild ride, Juniper Creek	quiet beauty, Rainbow River	a bit of fall, the Santa Fe	encompassing Caloosahatchee	wild & free Myakka River

NATIVE FLORIDA RIVER FAUNA
Florida's river systems support a wide variety of native animals. Each year, hundreds of thousands of wildlife observers canoe the waterways or hike along waterside trails for the guaranteed opportunity to catch a glimpse of some of Florida's native river denizens. Alligators, wading birds, manatees, frogs, fish, otters, beavers, and turtles are a small sample of the diverse assemblage of wildlife that occupy and depend on our river environments.

One reason for such animal diversity is the state's slow moving rivers and their ability to host a wide variety of plankton. Plankton are considered the beginning of the food chain and are a source of food for many aquatic animals. A diverse plankon population creates a diverse food chain.

The wide variety of aquatic animals plays an essential role in river ecology. Bottom feeders such as nematodes break down plant matter. Shellbuilders such as snails process calcium in the water. Alligator holes provide all animals with water during drought. River ecology revolves around a web of interactions based on production and consumption.

fish	manatees	other mammals	reptiles

amphibians	birds	insects