Ground water is water that is stored in the cracks and spaces between soil and rock particles below the ground. It is one of Florida's most vital natural resources--the source of drinking water for more than 90 percent of the state's population. Floridians use about 4.6 billion gallons of ground water per day.
Ground water is a part of what can be called the oldest recycling program--the hydrologic cycle. See Fig. 1. The hydrologic cycle involves the continuous movement of water between the earth and the atmosphere. As water falls to the earth in the form of rain and snow, much of it either runs into surface water bodies, evaporates, or is used by plants. The rest of the water soaks into the ground until it reaches the water table. The water table is the top of the saturated zone, or the area in which all interconnected spaces in rocks and soil are filled with water. The water in the saturated zone is called ground water. Where the water table occurs at the ground's surface, ground water discharges into marshes, lakes, springs or streams.
Ground water is stored under many types of geologic conditions. An aquifer is an area where ground water exists in sufficient quantities to supply wells or springs. See fig. 2. Aquifers are either confined or unconfined. If the aquifer is sandwiched between layers of relatively impermeable materials it is called a confined aquifer.
Confined aquifers are generally found at greater depths than unconfined aquifers, and the water within them can either be pumped to the
surface or it may rise to the surface by a natural pressure called artesian pressure. In contrast, unconfined aquifers are not sandwiched between layers of impermeable materials and their upper boundaries are generally closer to the surface.
PROTECTING OUR GROUND WATER
Ground-water protection is crucial to Florida. High rainfall and the state's unique geology--a thin, permeable soil cover, high water table, porous limestone formations, and the high potential for salt-water intrusion--makes our ground water extremely vulnerable to contamination.
The threats to ground water can come from many sources, both natural and man-made. Nature can change the quality of our ground water through severe weather, droughts and contamination that enters through sinkholes. Unfortunately, human activity is the main contributor to ground-water contamination. Several threats to our ground water are explained below.
Stormwater Runoff
The water that runs off impervious surfaces such as streets and parking lots contains many pollutants. These include oils, greases, heavy metals and coliform bacteria. Stormwater enters ground water directly through sinkholes and drainage wells, and indirectly in areas with very sandy soils or where porous limestone is at or near the surface.
Pesticides and Fertilizers
Because of its climate and diverse agricultural and urban pest problems, Florida is one of the nation's largest users of pesticides.
Where ground water is very vulnerable to pollution, contamination can occur from even normal use of some pesticides.
Homeowners contribute to this type of ground water pollution with the chemicals they apply to lawns and gardens. Fertilizers can add nitrates to the ground water. Nitrates can cause a condition called blue baby syndrome, which is dangerous to pregnant women and infants.
Septic Tanks
Approximately one-forth of all homes in Florida rely on septic systems to dispose of wastes. If these systems are built improperly or poorly maintained, they can contaminate ground water with bacteria, nitrates, viruses, synthetic detergents and household chemicals.
Underground Storage Tanks
Between fifty and sixty thousand underground storage tanks store a variety of materials in Florida, including gasoline, fuel oil and chemicals. Over time, exposure to the elements can cause the tanks to corrode and leak, thus contaminating ground water.
Hazardous Waste
Hazardous wastes are a major threat to Florida's ground water. Many industries in Florida create hazardous wastes such as used oils and greases, reactive wastes, heavy metals, and solvents as a part of their manufacturing process. Hazardous wastes are also produced in your home, at school, by government agencies, and by farmers and small business.
Landfills
The major environmental threat from landfills is ground water contamination. Water enters landfills, seeps (leaches) through the layers of garbage, becomes polluted and then goes on to contaminate ground water. Today, landfills are constructed with clay or synthetic liners and leachate collection systems to help keep polluted water from entering ground water.
Surface Impoundments
Impoundments or reservoirs often are used to store untreated wastewater from factories. Toxic chemicals in the wastewater can leach through the bottom of unlined impoundments and end up in drinking water wells.
Abandoned Wells
Before there were community water supply systems, most people relied on wells to provide their drinking water. In many rural areas this is still the case. If a well is improperly built or is abandoned without being properly sealed, it can act as a direct channel for contaminants to reach ground water.
Accidents and Illegal Dumping
Many toxic materials are transported throughout the country by truck, train and airplane. Every day, accidental chemical or petroleum spills occur that, if not handled properly, can result in contamination. There are also many instances of contamination from illegal dumping of hazardous or harmful wastes.
STATE GROUND WATER PROTECTION
The Department of Environmental Protection is charged with protecting, conserving and restoring Florida's valuable ground water resource. The Department achieves its ground water mission by direct administration of programs, supervision of the five water management districts and delegation of its powers to its district offices and to local governments.
Florida's comprehensive ground water rule puts Florida in the forefront of efforts to protect ground water. The rule establishes minimum water quality criteria that are designed to prevent the introduction of toxic and cancer-causing materials into water supplies.
WHAT YOU CAN DO TO HELP PROTECT GROUND WATER
The way you and your family dispose of products you use at home can contribute to the contamination of your community's ground water. Products like motor oil, pesticides, left-over paints or paint cans, mothballs, flea collars, weedkillers, household cleaners, batteries and medicines can be harmful to the environment. Here's what you can do:
For further information on Florida's ground water management programs, write: Office of Environmental Education, Florida Department of Environmental Protection, 3900 Commonwealth Blvd. MS-30, Tallahassee, Florida 32399-3000. Or call the DEP's Ecosystem Management and Environmental Education BBS at (800) 217-2934, using basic communications settings of 8-N-1 and ANSI terminal emulation.
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