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Aquifers
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The
vast majority of the public water systems in Florida
use ground water as their source. There are approximately
12,000 wells associated with ground water systems
used for public water supply in Florida. These wells
produce water from five major aquifers or aquifer
systems.
The
major source of ground water supply in Florida is
the Floridan Aquifer System,
which underlies the entire state. In the far western
panhandle and in southern Florida, the Floridan aquifer
system is deep, and produces salty and mineralized
water. In these areas, the shallower Sand-and-Gravel
Aquifer (in the west) and the Biscayne
Aquifer (in the south) are used
for water supply. The Surficial
Aquifer System and the Intermediate
Aquifer System generally produce
less water, and, with some exceptions, are used primarily
for domestic and smaller public supply wells. Where
there are clay layers in the intermediate system,
it can serve as a confining unit, slowing the movement
of water and, potentially, contaminants from the surface.
Click
for Higher Resolution
This map shows where the
major aquifers in Florida are found at the land surface.
This is where these sources of drinking water are at their
most vulnerable.
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Floridan Aquifer System
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The Floridan aquifer is one of the highest producing aquifers in the world.
It is found throughout Florida and extends into the southern portions of Alabama,
Georgia, and South Carolina. This aquifer system is comprised of a sequence
of limestone and dolomite, which thickens from about 250 feet in Georgia to
about 3000 feet in south Florida. The Floridan aquifer system has been divided
into an upper and lower aquifer separated by a unit of lower permeability.
The upper Floridan aquifer is the principal source of water supply in most
of north and central Florida. In the southern portion of the state, where
it is deeper and contains brackish water, the aquifer has been used for the
injection of sewage and industrial waste. Groundwater flow is generally from
highs near the center of the state towards the coast. The Floridan aquifer
is the source of many springs in Florida.
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Sand and Gravel Aquifer
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The sand and gravel aquifer is the primary source of water for Santa Rosa
and Escambia Counties in the western panhandle of Florida. The aquifer consists
of sand and gravel with interbedded layers of silt and clay. The clay layers
form local confined conditions within the aquifer. Groundwater flow is generally
towards the coast. In Florida, the aquifer contains two high- permeability
zones separated by less permeable sands and clays. The lower zone, which is
under confined conditions, is referred to as the "main producing zone"
because most of the groundwater use is withdrawn from this zone.
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Biscayne Aquifer System
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The Biscayne Aquifer is the primary source of water for all of Dade and Broward
Counties and the southern portion of Palm Beach County. Water from the Biscayne
is also transported by pipeline to the Florida Keys. The aquifer consists
of highly permeable limestone and less permeable sand and sandstone. The northern
part of the aquifer has more sand and grades northward and westward into the
sandy deposits that are part of the surficial aquifer system. In most places,
the highly permeable rocks of the Biscayne aquifer are covered by a thin veneer
of porous soil and aquifer water levels rise rapidly in response to rainfall.
Water in the Biscayne aquifer is unconfined and generally flows toward streams,
the ocean and the extensive system of canals in south Florida.
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Surficial Aquifer System
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The surficial aquifer system in Florida includes any otherwise undefined aquifers
that are present at land surface. Unlike the sand and gravel aquifer and the
Biscayne aquifer, which supply water to large municipalities, the surficial
aquifer is mainly used for domestic, commercial, or small municipal supplies.
The surficial aquifer system is generally under unconfined, or water-table,
conditions and is made up of mostly unconsolidated sand, shelly sand, and
shell. The aquifer thickness is typically less than 50 feet but can range
up to 400 feet in Indian River and St. Lucie Counties. Groundwater in the
surficial aquifer generally flows from areas of higher elevation towards the
coast or streams where it can discharge as baseflow. Water enters the aquifer
from rainfall and exits as baseflow to streams, discharge to the coast, evapotranspiration,
and downward recharge to deeper aquifers.
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Intermediate Aquifer System
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In southwestern Florida, aquifers that lie between the surficial aquifer system
and the Floridan aquifer system are collectively referred to as the intermediate
aquifer system. This aquifer system starts in Hillsborough and Polk counties
and extends south through Collier County. The intermediate aquifer system
is under confined conditions and is mainly comprised of permeable layers of
sand, shell and limestone separated by clay confining units. It is the main
source of water supply for Sarasota, Charlotte and Lee counties where the
underlying Floridan aquifer contains brackish water. Much of the water pumped
from this aquifer system is used for agriculture. In most places, water percolates
down from the surficial aquifer system above to the intermediate aquifer system.
Lateral flow is generally from a high area in Polk County towards major surface
water features and the Gulf of Mexico.
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Last updated:
September 22, 2015
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3900 Commonwealth Boulevard M.S. 49
Tallahassee, Florida 32399
850-245-2118 (phone) / 850-245-2128 (fax) |
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