The Floridan Aquifer

An aquifer is an underground layer of permeable rock, sand, or gravel that holds water. The water contained in an aquifer is called groundwater.

The Floridan Aquifer System is approximately 100,000 square miles and covers all of Florida and portions of Alabama, Georgia and South Carolina

Aquifer Layers

The aquifer systems in Florida are complex, with many layers of shell, sand, gravel, and rock all functioning a little bit differently. These images show a simplified model of Florida’s aquifer system, focusing on two major groundwater systems: The Surficial Aquifer System and The Floridan Aquifer System

The Floridan Aquifer may be confined or unconfined, depending on the presence or absence of a covering, low-permeability, confining layer.

on the maps below to enlarge them!

Surficial Aquifer

Confining Layers

Floridan Aquifer

The Surficial Aquifer supplies freshwater to areas of Florida where water from a deeper aquifer is not easily accessible, or is salty. The Surficial Aquifer consists mostly of unconsolidated sand and shell, and ranges from approximately 50 to 400 feet thick. Regional sections of the Surficial Aquifer supply freshwater to large municipalities (such as the Sand and Gravel Aquifer in the panhandle and the Biscayne Aquifer in south Florida). Water enters the Surficial Aquifer as rainfall and either evaporates, discharges into streams, or percolates down into the Floridan Aquifer as recharge.

A confining layer is a layer of sediment or rock that has low or no permeability and does not allow water from the surface to easily percolate downward. An unconfined aquifer is an aquifer where there is no confining layer present, allowing water from the surface to move freely into the aquifer. In this model, the Upper Confining Unit has been separated into areas where the confining layer is thick (more than 100 feet), where the layer is thin (less than 100 feet), and where the layer is completely absent. In areas where the confining unit is absent, the aquifer will readily recharge with rainwater. 

The Floridan Aquifer is comprised mostly of a deep series of carbonate rock formations, named (youngest to oldest) Suwannee Limestone, Ocala Limestone, Avon Park Formation, and Oldsmar Formation. The Floridan Aquifer is the primary source of fresh groundwater for Florida’s 1,000+ artesian springs and is used by more than 11 million Floridians. The Floridan Aquifer ranges from 250 feet thick in Georgia, to around 3,000 feet thick in South Florida. The Floridan Aquifer may be confined or unconfined, and at times may be in direct contact with the Surficial Aquifer.

Karst Features

The geology in Florida consists of limerock formations known as karst terrain. Rainwater is naturally slightly acidic, dissolving Florida’s soluble limerock as it percolates through the surface. Cracks, holes, and dents eventually become underground caverns and rivers, storing Florida’s groundwater and accounting for one of the most productive aquifers in the world.  Below are images of typical features of karst terrain. 

Artesian Springs

Artesian springs are areas where pressure in the aquifer causes groundwater to discharge from a karst opening in the land surface. Artesian springs make up the majority of Florida’s 1,000+ freshwater springs. Little River Spring. Photo by John Moran.

Photo 2 Chattahoochee Formation exposed at Falling Waters SP


Sinkholes are areas of karst that have been dissolved by water over time causing the ground surface to collapse. The sinkhole shown here is in Falling Waters State Park. During times of high rainfall, a stream empties into the sinkhole and the caves below. Photo by Florida State Parks.

Dragons Belly Cave


Caves are formed when water dissolves karst. Most of Florida’s cave systems are underwater. Florida Caverns State Park, seen above, is an example of a dry cave. You can experience the caverns on a guided cave tour. Photo by Florida State Parks.

Olson sink crop2 John Moran 2019

Karst Windows

A karst window is an area where a cave has collapsed and exposed a segment of groundwater that is flowing through the aquifer. As karst windows are direct access to the aquifer, contaminants introduced here will enter the aquifer directly. Photo by John Moran

River Rises + Sinks

A sink, also known as a swallet, is an area where surface water goes underground. The area where it emerges again is a feature known as a rise. This photo shows the Alapaha River sink. The river runs underground for several miles before it returns to the surface. Photo by Tessa Skiles.


A polje is a large, flat basin formed by the coalescence of many sinkholes. An example, shown here, is Paynes Prairie in Gainesville. This polje is connected to the Alachua sink. At times of heavy rainfall and high aquifer levels, the prairie looks more like a lake  Photo by  Florida State Parks.

Groundwater Withdrawals

The Floridan Aquifer provides drinking water for over 11 million Floridians and the millions of tourists that visit Florida each year. 

The aquifer also provides groundwater for agricultural, commercial, and industrial operations throughout the state. 

Withdrawals from the Floridan Aquifer in 2015

In 2015, an estimated were withdrawn from the Floridan Aquifer.

Water Use 2015 Infographic_UPDATE

Data Source: USGS 2015

How much groundwater did your county withdraw from the Floridan Aquifer?

Use this web map to learn how groundwater withdrawals throughout Florida differ by county.

florida's springs

through the photography of john moran

florida's springs

through the photography of john moran


Florida’s 1,000 + freshwater springs are categorized by the average amount of water that they discharge. These categories are also known as magnitudes.


Greater than 65 million gallons per day

That’s more than 100 cubic feet/second!

Silver Spring, Troy Spring, Manatee Spring, Rainbow Spring

6.5-65 million gallons per day

That’s between 10 – 100 cubic feet/second!

Gilchrist Blue Spring, Wekiva Spring, Ichetucknee Head Spring, Salt Spring

.65-6.5 million gallons per day

That’s between 1 – 10 cubic feet/second!

Peacock Springs, Convict Springs, Ruth Spring, Johnson Spring

4th-8th MAGNITUDE=
Less than .65 million gallons per day

That’s less than 1 cubic feet/second! 

Many springs that are 4th magnitude or higher have been given generic names (such as Gil928972) that indicate their county (Gilchrist County). 


Healthy spring systems are teaming with life. From trees that have developed special adaptations to living bank-side, to submerged aquatic vegetation that thrives due to crystal clear spring water, the flora of a spring system is as unique as the springs themselves. Below are examples of vegetation that you are likely to come across while visiting the springs.

on the name of the species to learn more!


Sagittaria subulata (dwarf sagittaria) along the Gilchrist Blue Spring run. The thin, 0.5 cm wide leaves have the ability to grow to more than 90 cm under the right conditions, which includes dense planting. Less dense plantings keep the leaves in the 5-10cm range. A fast grower, dwarf sagittaria propagates by runners. Occasionally, Sagitarria subulata will send long stems to the surface, which will bloom small white flowers. Photo by John Moran. 


Vallisneria americana (eelgrass) at IchetuckneeEel-grass is a large, submersed, perennial plant that is native to Florida. Eel-grass grows from underground runners, and often forms tall underwater meadows.  Eelgrass is often mistaken for Sagittaria kurtziana or strap-leaf sagittaria, which looks similar. To distinguish between eel-grass and sagittaria, eel-grass has rounded leaf tips and strap-leaf sagittaria has pointed tips. Photo by John Moran.

Water Hyacinth

Eichhornia crassipes (water hyacinth). Water hyacinth is native to Brazil and considered a Category 1 invasive plant by the Florida Exotic Pest Plant Council (FLEPPC). Water hyacinth is a floating plant that grows in all types of fresh water and reproduces both vegetatively and sexually. Water hyacinth populations may double very quickly, forming mats that clog waterways, and making a nuisance for boaters. Yet water hyacinths are certainly a permanent naturalized part of Florida’s aquatic landscape and provide numerous water quality and wildlife benefits.  Photo by Dominick Martino.

Red ludwigia

Ludwigia repens (red ludwigia) on the Rainbow River. There are about 30 ludwigia species found throughout the state, most commonly found growing in marshes as emergent aquatic vegetation. Although all ludwigia species can display red leaf coloration, Ludwigia repens can be identified by its opposite (not alternate) leaf arrangement, and is considered submerged aquatic vegetation (SAV). Ludwigia repens blooms from spring until fall. Photo by David Schrichte.

Spider lily

Hymenocallis latifolia (spider lily) at Naked Spring.  Spider lily is a Florida native. emergent wetland plant, with attractive blooms and foliage growing directly from an underground bulb that can reach a height of two to three feet. This plant is tolerant of drought, floods, and even salt spray, but cannot tolerate cold temperatures. Photo by John Moran.


 Lemna valdiviana (small duckweed) hiding a gator. Duckweed are floating plants and are considered the smallest flowering plant known to man. Due to its rapid growth habit and ability to take up nutrients, duckweed has shown promise for use in bio-remediation of waterways that have excessive amounts of phosphorus and nitrogen. Photo by John Moran.

Bald cypress

Taxodium distichum (bald cypress) along the Ichetucknee spring run. The massive, buttressed trunks and accompanying cypress “knees” found at the base of older bald cypress trees are thought to have developed in response to growing in soft, saturated wetland soil. In the wild, bald cypress trees can live more than 600 years and are typically found near streams and rivers, as well as in swamps with slow moving water. Bald Cypress are one of the largest deciduous trees in North America. Photo by Tessa Skiles.


Nuphar advena (spatterdock, cow lily) at Cypress Springs. Spatterdock flowers are yellow and “half-opened” at or above the water surface, with large heart-shaped leaves, typically with wavy margins. Spatterdock may be confused with water lily. Photo by John Moran.

Coral bean

 Erythrina herbacea (Cherokee bean, coral bean) at Emerald Spring. Coral bean is native to Florida and flowers late in winter to spring. Growing bank-side or in the woodlands surrounding a spring, this plant can be identified when it is not flowering by its alternately arranged, deltoid shaped leaves or by its bright red seeds. Photo by John Moran.

& Fauna

Spring systems support a wide variety of wildlife which can be viewed year round. Healthy spring systems are home to many animal species both above and below water. Below you can find a list of animals that you might spot while visiting the springs.  

on the name of the species to learn more!


Trichechus manatus (Florida manatee) enjoying Fanning Spring. Florida’s state marine mammal, the Florida manatee is an aquatic relative of the elephant. Historically, manatees in north Florida relied on natural springs to stay warm during cold weather. Photo by David Schrichte.

mother and child

Alligator mississippiensis (American alligator) at Manatee Spring. These reptiles can live up to 50 years, with adult males reaching up to 15 feet in length and 1,000 lbs in weight. The American alligator can swim close to 20 mph, and run up to 11 mph on land. Photo by John Moran.

Apple snail

Pomacea paludosa (the Floridan apple snail) is typically 2-3 inches long and the shell is often flat across the top. The native Florida apple snail can take up to six moths to reach sexual maturity with typically 20-80 eggs per clutch. Limpkins feed almost exclusively on  apple snails. Photo by John Moran. 

Musk turtle

Sternotherus minor (loggerhead musk turtle) in Manatee Spring. Loggerhead musk turtles are rarely found outside of Florida’s springs. These tiny turtles absorb oxygen through their skin and reach a maximum size of only five inches. Photo by John Moran.


Aramus guarauna (limpkin) at Ichetucknee Spring. The limpkin is a mottled brown, medium sized wading bird commonly seen stalking the edges of springs and spring runs. In north Florida, the limpkin feeds almost exclusively on Pomacea paludosa (apple snail) and is dependent on their abundance for its survival. Photo by John Moran. 

Red bellied cooter

Pseudemys nelsoni (Florida red bellied cooter) in the Ichetucknee spring run. These medium to large freshwater turtles are distinguished from river cooters by a serrated pattern on their jaw. Their distinctive red tint fades as they age. These turtles will occasionally lay their eggs in an alligator nest for protection from predators. Photo by John Moran.

Double Crested Coromorant (Phalacrocorax auritus) Also known as the White-crested Cormorant. Photographed swimming and searching for food in the warm waters of the Three Sisters Springs. Crystal River, Florida.

Phalacrocorax auritus (double crested cormorant) in Three Sisters springs. These large birds have long, hooked beaks that are roughly the length of their head. Adult cormorants are brown/black with a patch of yellow/orange on their face. Cormorants sit low in the water and dive for small fish. Photo by David Schrichte.

River otter

Lontra canadensis  (river otter) is found throughout all of Florida, with the exception of the Keys. River otters are social animals and will often be spotted frolicking in the river with other otters. These lovable animals are mostly nocturnal, feeding on fish and crayfish. Photo by John Moran.

Swallow tailed kites

Elanoides forficatus (swallow tailed kite). These large, arboreal raptors migrate annually to Florida from South America, usually arriving late in February or March. They spend summers nesting in north Florida’s Springs Region feeding on snakes, insects, and other birds. Photo by John Moran.


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