Johnny Andrews, Chairman; 3923 County Road 7; Repton, Alabama 36475; Tel: 251 248 2378, E-MAIL
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aquifers
Alabama's Groundwater and Aquifers
A Look at the Layers The majority of groundwater is found in the tiny openings called pores that occur between the grains of rocks, soil, and sediment. Many rock formations are fractured, and large amounts of water can be contained in those fractures. Below the water table these openings are filled with water. Rock, sediment, and soil units that contain significant amounts of producible groundwater are called aquifers. Aquifers have two important properties. The first is porosity, which is the amount of open pore space in the aquifer. A high yielding aquifer may contain 10 to 30 percent open space. Permeability is a measure of the interconnectedness of a pore or fracture system and determines the ability of a rock unit to transmit fluids. Another concept critical to the understanding of groundwater availability and protection is that of unconfined and confined aquifers. Unconfined aquifers consist of an upper saturated portion above the water table and a lower saturated zone below the water table. Some aquifers are overlain and underlain by layers of significantly less permeable materials that restrict the flow of water across the boundaries. These aquifers are called confined aquifers. There are generally three kinds of aquifer in Alabama; porous flow, fracture, and conduit. Porous flow is typical of aquifers composed of sand, gravel or sandstone. Water is stored and moves through the open spaces or pores. Sand and gravel layers can range in size from a few square feet to thousands of square miles. Water moves slowly but steadily through sand and sandstone, making many sand and sandstone aquifers reliable sources of large amounts of groundwater. Sand and sandstone aquifers are the most important aquifers in many parts of Alabama. Groundwater in porous aquifers moves at an average rate of an inch per day. In conduit flow aquifers, water actually flows through underground channels in the rock. Conduit flow is commonly associated with carbonate rocks, such as limestone and dolomite. Conduits are formed by a slow chemical reaction between the limestone and fresh water, which flows along fractures in the rock. Large volumes of rock can be dissolved. Because these openings are irregular in shape and distribution, groundwater flow can be unpredictable and extremely fast, sometimes up to several thousand feet per day through larger channels. These aquifers are very susceptible to contamination from surface sources. In nonporous and insoluble rocks, fractures may provide the only way in which fluids can be transmitted. Examples include sandstone, shales, and most crystalline rocks such as igneous and metamorphic rocks. These rocks are very dense and contain few open spaces except for fractures. Fracture dependent aquifers rarely contain enough water to make them reliable sources of water.
The Water Cycle The waters on the surface of the earth and beneath the earth are not separate. Water is constantly moving from one zone to the other, this is called the hydrologic cycle. Alabama receives approximately 56 inches of rain a year. Thirty-three inches of this water is evaporated from the surface of the earth and is transpired by plants that take up water through their roots. Approximately 16 inches will run-off to feed lakes and streams and 7 inches will seep into the ground to become groundwater. Groundwater may discharge as springs or seeps into surface water, completing the cycle. The way that groundwater and surface water move through and on the soils is dependent on the rock types.
WE NEED YOUR HELP!CCSA (Citizens for a Clean Southwest Alabama) was organized in January 2007, when Conecuh Woods first proposed dumping the largest landfill in the United States on Conecuh County. Time, energy and money have been donated for this ongoing fight, but it is far from over. Donations:Send checks to United Bank, P.O. Box 787, Monroeville, Alabama 36465, Attention Phyllis Bell. Make checks payable to CCSA (Citizens for a Clean Southwest Alabama). Our non-profit tax number is 51-0618216. It is retroactive, so you can claim any donations you have made (thank you!), or any donations you are going to make (please!). A copy of our expenditures is available on request. These include: printed information for distribution to the public; advertising space in newspapers; research; signs; renting space for presentations and meetings; materials for fund-raising projects; legal consultations; postal fees. Volunteers:If you want to help with time, energy, ideas or questions contact: JOIN US IN THIS FIGHT!!
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