Central Florida Has Underground Rivers?

The state of Florida has many forms of "naturally" clean, refreshing, and exciting fun for all who seek. Some of the best destinations in Florida are freshwater venues such as cool, clear rivers and springs. Springs are especially interesting, and many of Florida's visitors flock to these outstanding natural wonders (1). Over $500 million is injected into Florida's economy yearly from just state-owned freshwater aquatic venues.

Central Florida springs appear in many shapes, sizes, and magnitudes. Some springs are artesian in nature, flowing millions of gallons per minute, some springs bubble up slowly between your toes in the sand, while others are entirely underground and never seen. Many of these springs are hidden from sight, all over central Florida, while others are out for all to see.

Virtually all of these springs are pure, clear, clean, and breathtaking, with a constant temperature of about 72 degrees. (1) Many of the springs I speak of are undiscovered treasures, hidden by dense forest, mostly undisturbed or state-owned areas left in natural settings. Florida purchases large parcels for their strategic location, such as natural watersheds, springs, lakes, rivers, and other highly critical ecosystems responsible for Florida's freshwater sources. Many of Florida's springs are owned by private citizens and industry as well.

Central Florida's springs, rivers, lakes, ponds, and the like, are delivered by aquifer water stored in the central Florida earth as underground water tables or "aquifer systems". Many call the aquifer systems, underground rivers because the water within the aquifer systems can move at a considerable flow rate, such as a river.

Aquifers can be thought of as vast caverns of permeable rock, "containing" water and creating hydrogeological movement through holes within the rock due to naturally developed "head" pressures. (3) Aquifers can form from different types of earthen materials, such as sands, clays, shell, limestone, and karst.

Interestingly, water can be trapped in these aquifer systems for years before rising to the surface, flowing out of a spring. Natural springs give us a glimpse of the aquifer systems and how they may appear underground as well.

Some of Florida's rivers disappear entirely only to surface again downstream. This can happen when a sinkhole develops in a river bed. The river can be swallowed completely, with no sign it ever existed. (2) Then, as suddenly as it disappeared, it reappears and continues flowing at the surface. The Santa Fe River in north Florida is a great example of a disappearing river. This particular river flows into a large sinkhole in O'Leno State Park and reappears close by in River Rise Preserve State Park.

Florida Sinkholes

The type of landscape we are discussing is excellent for natural springs and aquifer systems to form. However, sinkholes are also a common natural occurrence due to the central Florida landscape as well. The surface of the central Florida earth can suddenly open as a sinkhole and swallow everything above it. Sinkholes naturally occur in central Florida, but recently, their frequency has increased.

Unfortunately, when sinkholes develop suddenly, loss of property and life can occur. A sinkhole opened in a residential area of Seffner, Florida where a man sleeping in his house was swallowed by the sinkhole and never found. Sinkholes can form when the earth collapses due to weather patterns causing too much rain or too little rain as well. Over pumping of Florida's groundwater resources can also cause sinkholes to form.

Florida's Karst Landscape

Florida's "karst" rock sub-surface is relatively brittle and does not sustain compression loads well. Uncompressible water contained in the sub-surface aquifer systems acts as a solid to support the surface soils. When the hydrogeological pressure is released for whatever reason, sinkholes can and do occur suddenly. Karst rock landscapes are known for sinkhole formation, and Florida's karst landscape is no exception. (2)

These subterranean cavities and conduits are major elements in one of the most productive sources of freshwater in the world; the Floridan Aquifer, which underlies the entire state and extends below parts of Mississippi, Alabama, Georgia, and South Carolina. Meaning, pollutants enter the aquifer system and can travel long distances rapidly. The Department of Environmental Protection (DEP) confirmed this fact by injecting dye into Florida's subterranean waterways and waiting for it to reappear downstream. In most cases, the DEP found the dye far from its source where it appeared in the waterways in question.

The unique karst landscape, as you can see, "hides" much of Florida's rainwater by absorbing it into the earth and contains it in naturally functional caverns, aquifers, and springs. If one can imagine, the karst surface of central Florida "floats" on a bubble of freshwater called the Floridan aquifer system.

Reference
1. Cool escapes: Florida's refreshing springs | Florida Rambler.
2. Santa Fe River (Florida). (2015). Retrieved on December 21, 2015, from https://en.wikipedia.org/wiki/Santa_Fe_River_(Florida).
3. University of Florida, UF Research: Underground Rivers, Springs