Spring water is aquifer water

Clean, fresh water is our most precious natural resource. In Florida, fresh water comes from subsurface aquifers that are composed of multiple layers of water-bearing limestone. Groundwater released from the aquifers sustains thousands of ecosystems, and is an essential resource for human health, outdoor recreation, industry and agriculture.

Supplying nearly 100% of the state's drinking water, Florida's aquifers discharge over 8 billion gallons of water each day; they are among the most productive in the world.

Groundwater comes to the surface through more than 600 natural springs found throughout the state. Groundwater is also pumped to the surface by artificial wells, bringing millions of gallons of drinking water into residential homes and into bottling plants that ship Florida's groundwater all over the planet.

Source: USGS

FLORIDA HAS MORE THAN ONE AQUIFER
Florida's aquifers vary in depth, composition, and location, and are divided into two general categories: Surficial and Floridan.

Surficial aquifers are shallow beds of shells and sand that lie less than 100 feet underground. They are separated from the Floridan aquifer from a confining bed of soil. Some have been contaminated by saltwater, yet they provide most of the public freshwater supply southwest of Lake Okeechobee and along the Atlantic coast north of Palm Beach.

In surficial aquifers, the groundwater continuously moves along the hydraulic gradient from areas of recharge to places of discharge. Surficial aquifers are recharged locally as the water-table fluctuates in response to drought or rainfall. Therefore, the temperature and flow from water-table springs varies.

Important surficial aquifers include:

The Biscayne aquifer is a surficial aquifer located in southeast Florida. It covers over 3,000 square miles, and is the most intensely used water source in Florida, supplying water to Dade, Broward, Palm Beach, and Monroe counties. The aquifer lies close to the surface and is extremely vulnerable to pollutants that leach through the shallow limestone bedrock. In some areas, it has been contaminated by fuel spills, industrial discharge, landfills, and saltwater.

The sand and gravel aquifer stretches 2,400 square miles across the Panhandle. Although this surficial aquifer is replenished with rainfall, water levels have dropped due to water-well use (pumping), and it has been contaminated by industrial waste and saltwater instrusion.

The Chokoloskee aquifer is another surficial aquifer in the state; it covers 3,000 square miles in southwest Florida. It is recharged by rainfall. It is believed that artificial drainage canals have lowered water levels and increased saltwater intrusion.

Read "December South Asian Earthquake Impacts Floridan Aquifer - Thousands of Miles Away" (PDF 788 KB), by the South Florida Aquatic Plant Management Society

The Floridan aquifer, in contrast to surficial aquifers, is the portion of the principal artesian aquifer that extends into Florida. The principal artesian aquifer is the largest, oldest, and deepest aquifer in the southeastern U.S. Ranging over 100,000 square miles, it underlies all of Florida and parts of southern Alabama, southeastern Georgia, and southern South Carolina. The Floridan portion developed millions of years ago during the late Paleocene to early Miocene periods, when Florida was underwater.

Source: USGS

Unlike water in surficial aquifers, groundwater in the Floridan aquifer is contained under pressure by a confining bed of impermeable sediments. When the water pressure is great enough, the groundwater breaks to the surface and a spring flows. Water temperature and flow from a Floridan spring is relatively constant.

The Floridan aquifer supplies fresh water to many cities such as Daytona, Gainesville, Jacksonville, Ocala, St. Petersburg, Tallahasse, and numerous rural communities. In areas where the Floridan contains saltwater, due to saltwater intrusion along the southwest Florida coast, it is injected with sewage and industrial waste.

In addition to the surficial and Floridan aquifers, several intermediate aquifers comprised of limestone beds lie between the surficial and Floridan aquifers, and a variety of undifferentiated aquifers store approximately ten percent of Florida's groundwater.

WELLS
In order to extract water, a well must penetrate the water-table. The amount of water released from a well depends on the permeability of the bedrock. Wells drilled into confined aquifers must pierce the confining bed. When the well penetrates the aquifer, the hydrostatic pressure pushes the water above the confining bed where it can be pumped to the surface.

The demand for well-pumping increases as Florida's population continues to rise. Over-pumping can lower the water-table, and as a result, accelerate sinkhole formation and decrease springflow. For more information about wells under the direct influence of surface water, permitting and construction regulations, and protection areas, visit the Wellhead Protection website of the Florida DEP.

Source:USGS

AQUIFERS and the HYDROLOGIC CYCLE
Groundwater in the aquifer is replenished by surfacewater that leaches into the water-bearing limestone bedrock. Rainfall accumulates on the surface and seeps into the soil. Water that is not absorbed by plants percolates deep underground into the porous limestone bedrock until it reaches the water-table, the level where the limestone is saturated with water.

The quantity of water stored in the bedrock depends on the porosity of the limestone. Very porous limestone will hold more water. When the aquifer is full and unable to accept additional water, surface water drains into nearby lakes, rivers, and oceans where it evaporates back into the atmosphere and eventually precipitates to the surface again.

GROUNDWATER MOVEMENT
Beneath the surface, groundwater moves from areas of recharge and replenishment, such as sinkholes, to areas of discharge, such as springs.

Groundwater travels along a hydraulic gradient, the downward horizontal slope of the subsurface bedding plane. As water accumulates underground, water pressure, or the hydrostatic head, increases. Groundwater movement is directed by a combination of the hydraulic gradient, the hydrostatic head, and confining beds of impermeable materials such as clay.

Moving groundwater chemically erodes joints and fractures in the limestone bedding plane creating subsurface cavities, caves, drainage basins, sinkholes and other geologic features that characterize Florida's karst topography. For more information about groundwater flow patterns, read this article found on the Woodville Karst Plains Project website.

DRINKING WATER
Underground aquifers are the reservoirs for Florida's natural water filtration systems. Aquifers provide nearly 100% of the state's drinking water and more than 60% of the state's freshwater usage in agriculture and industry. Beneath the surface, organic matter and impurties are removed from groundwater as it filters through the porous limestone bedrock. Water that has not spent enough time filtering through the aquifer can emerge turbid or smelly when it is extracted. Clean groundwater can become polluted by certain contaminants in the surfacewater that replenishes the aquifer, or by subsurface septic tanks and fuel receptacles.

(For much more about drinking water in Florida, see the freshwater consumption page of this web site.)

Florida's Department of Environmental Protection requires drinking water suppliers to provide customers with consumer confidence reports that show where the water comes from, and if any contaminants are present. Home-owners can also purchase water-testing kits to investigate the purity of their well water. For more information about DEP's role in protecting drinking water, read this Open Letter to a Concerned Citizen found on the Florida DEP Drinking Water website.

HUMAN IMPACTS
Groundwater, our drinking water, stored in Florida's aquifers, is increasingly threatened by human activities. Drinking water in Florida is particularly susceptible to contamination because the water-table is close to the surface and the limestone bedrock is permeable. Human and animal bacteria, agriculture, pesticides and fertilizers, fuel spills, salt and methane gas are human impacts that are discussed on this page of our web site.

The long term health effects of many pollutants are still unknown. For more information, visit the Health Effects Caused by Drinking Water Contamination web page of the Florida D.E.P.

PROTECTING OUR AQUIFERS
Proper management of chemicals and waste can help protect Florida's groundwater and help prevent the spread of pollutants throughout the aquifer, and into residential homes. Safeguarding primary recharge areas and responsible waste disposal can help preserve our most precious natural resource - fresh water.