Floridan Aquifer

Cara Haas

GO571 Hydrogeology
Emporia State University, Spring 2007



Table of Contents


Introduction

Hello, my name is Cara Haas and I am a Earth Science major at Emporia State University in Emporia, Kansas. This webpage was designed for an Hydrogeology class assignment.

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Floridan Aquifer Overview

The Floridan Aquifer is one of the most productive aquifers in the entire world. This system is a major source of groundwater in the United States. This prominent aquifer consists of about 100,000 square miles of area that provide water for four states. Those four states include: southern Alabama, southeastern Georgia, southern South Caroline and all of Florida. The Floridan Aquifer is a provider for several large cities including Savannah and Brunswick, cities in Georgia. The aquifer also provides for Jacksonville, Tallahasse, St. Petersburg and Orlando, cities in Florida. In addition to providing water for these major cities, the Floridan Aquifer also provides for millions of citizens in smaller communities.

The Floridian Aquifer is pumped mainly for industrial and irrigation purposes. The aquifer is a multi-use system that contains both freshwater and saltwater. Because there are several places within the aquifer that contains saltwater, drainage wells are placed within the system for desalinizations purposes. This concept is important in the areas of the Florida Keys where there is not any source of freshwater. Each day more than three billion gallons of water are prodcued from the Floridan Aquifer. This number is a representation of less than thirty perecent of the actual flow that moves through the aquifer daily.

Figure 1: Image of the Floridan Aquifer
Image taken from: http://content.answers.com/main/content/wp/en-commons/thumb/f/f9/300px-Floridan_Aquifer_USGS.gif
Modifications by Cara Haas

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Floridan Aquifer Composition

The Floridan Aquifer is composed of a thick layer of carbonate rocks that are from the Teritary age. The most productive areas within the aquifer are the Avon Park and Ocala Limestone formations. These formations are the thickest areas of the aquifer. The Suwanne Limestone is also a large, productive area of the Floridan, but is considerably thinner that the Avon Park or Ocala Limestone. The base of the aquifer system lies in much of Florida in the Cedar Keys formation and is known to be highly permeable. Northern Flordia consists of sandy rocks that tend to be less permeable than the carbonate rocks of the Floridan.

Figure 2: Image of the Floridan Aquifer composition
Image taken from: http://capp.water.usgs.gov/gwa/ch_g/jpeg/G049.jpeg
Modifications by Cara Haas

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Upper and Lower Floridan

The Floridan Aquifer system has been defined as a basis of permeability. The system can be divided into the Upper and Lower Floridan, seperated by a less-permeable areas. The area that divides the two Floridan's is known as the middle confining unit. This areas allows water to leak through more easily and is composed of mostly clay or very fine-grained limestone. The Upper Floridan consists of the Suwanne and Ocala Limestones and also the upper portion of the Avon Park formation. This areas is highly permeable and for the most part provides sufficient water volumes, therefore there is not a need to drill in the Lower Floridan. The Lower Floridan is not as well-known or researched because of its low depths, but we do know that this area includes the lower part of the Avon Park formation as well as the Oldsmar Limestone and the upper part of th Cedar Keys formation. This area consists of large volumes of freshwater that moves upward through the confining unit and eventually reaching the upper Floridan.

Figure 3: Image of the Upper and Lower Floridan
Image taken from: http://capp.water.usgs.gov/gwa/ch_a/gif/A031.gif
Modifications by Cara Haas

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Groundwater Flow

The exsistence of groundwater flow was first realized during the 1930's and 40's. Water moved coastward from the outcropped areas in all directions. Recharge in the Floridan Aquifer is estimated between 10-20 inches per year. Before development of the aquifer, nearly all of the discharge was to springs and streams. Discharhe to offshore springs was common in the gulf and coastal areas. Groundwater construction of the Floridan Aquifer began in the 1880's. People first constructed wells for municipal reasons in Savannah, Georgia and Jacksonville, Florida. By the 1930's, large plants were developing quickly which caused large volumes of water to be extracted from the aquifer. By the 50's, the water that was being drawn totaled around 630 million gallons per day. By the 1980's, around three million gallons were being extracted and that number still stands to present day.

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Groundwater Quality

The Floridan Aquifer is very well-known for its production of large amounts of minerals within its water. The concentration, which is the sum of all cations and anions in a solution, are related to two items: 1) the groundwater flow system and 2)the proximity to saltwater. Large volumes of water move through the aquifer at a very quick pace. In result, dissolved-soild concentrations are miniml. The most cations in water that are produced in the Uppper Floridan are calcium, magnesium and sodium. The anions that are common in the Upper Floridan are bicarbonate, chloride and sulfate. The Upper and Lower Floridan are similar in chemical composition except that the Lower Floridan have longer flowpaths and also have more time to dissolve aquifer minerals therefore having overall more dissolved solids.

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Groundwater Contamination

Recently, problems have arose within the aquifer due to saltwater intrusion through coastal areas and inadeqaute supplies of fresh groundwater.Saltwater intrusions is a potential threat to the quality of groundwater in Floridan Aquifer. Initially, saltwater was isolated from all areas including pumping wells for the aquifer, but around the 1970's evidence concluded that slatwater was migrating toward numerous pumping centers. It is believed that teh source of saltwater orignated from the lower Floridan moving its was through the confining unit and continuing its way into the Upper Floridan. There are several possible explanations for the pathways of saltwater inttusion within the Floridan aquifer system: (1) the movement fromunflushed pockets containing seawater (2) movement on land of the freshwater-saltwater mixing; (3) upconing of saltwater below pumped wells; and (4) leakage of saltwater from deeper, saline from joints, fractures, collapse features, or other structural anomalies.

Figure 4: Image explaining the contamination in Brunswick
Image taken from: http://ga2.er.usgs.gov/publications/graphics/gwrc2001payne3.gif
Modifications by Cara Haas

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Floridan Aquifer Today

Although the Floridan Aquifer issues three billion gallons of water a day, there is presently no real danger of this water source coming to extinction. Although the use of water from the aquifer has had a major increase in the overall the aquifer has not had a major decline in water volume. Depsite the increas in consumption, the aquifer is just as successful and prodcutive as it always has been. Though increase in consumption and manmade alterations within the aquifer have occurred, overall the Floridian Aquifer is in a good, stable condition and it is predicted to be utilized for centuries to come.

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References and Links

  • USGS.Groundwater Atlas of the United States Alabama, Florida, Georgia, South Carolina HA 730-G: World Wide Web, URL: http://capp.water.usgs.gov/gwa/ch_g/G-text6.html
  • Boldenbaugh Press, 2007.National Water Rights Diegest Refernce Florida : World Wide Web, URL: http://www.ridenbaugh.com/nwrd/nwref/fl.htm
  • USGS.(2005).Hydrogeology, Water Quality, and Water Supply Potential of the Lower Floridan Aquifer, Coastal Georgia, 1999-2002. World Wide Web, URL: http://pubs.usgs.gov/sir/2005/5124/
  • Meyer, Fredrick W. USGS. (2005). Hydrogeology, Groundwater Movement, and Subsurface Storage in the Floridan Aquifer System in Southern Florida. World Wide Web, URL: http://sofia.usgs.gov/publications/papers/pp1403g/
    Webpage created 11/2006. Questions? Email
    Cara Haas.

    Copyright 2006 Cara Haas.