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September 16, 2002 The Geological Survey of Alabama (GSA) has received three groundwater monitoring sensors from the Mobile Bay National Estuary Program (Mobile Bay NEP). In an effort to better understand the delicate balance of fresh and saltwater in the Gulf Shores area, the Mobile Bay NEP purchased the sensors which will monitor salt content in the freshwater aquifers on the Island. GSA runs on a tight budget and was unable to afford the $1800 cost. "We (the GSA) conducted a salt water encroachment study in 1984-85 and found salt water in shallow aquifers at a few places in Gulf Shores. Since that time we have been interested in continuously monitoring for salt water encroachment, particularly as all of Baldwin County relies solely on ground water for public water supplies and because ground water development has increased greatly since then," reported Danny Moore who is the Director of the Hydrogeology Division at GSA. Saltwater encroachment has been a problem for many resort communities in many areas along the Gulf Coast. Rapid population growth accompanied by increased demand for this limited resource has resulted in declining water levels and saltwater encroachment. Fresh water becomes a high commodity with increasing costs. Often towns find themselves purchasing water from other places as their own groundwater is diminished in quality from over pumping and high demand. Tampa Bay, Florida is currently completing construction on their first desalination plant. Residential water fees are expected to increase significantly. When it rains water percolates into the ground as well as running over the surface. The excess water penetrates downward until it reaches the water table. If water is withdrawn from a well, the water table is lowered in the immediate vicinity of the well. As the pumping continues, the groundwater levels within the aquifer can be lowered. If pumping stops, the levels will rise. These water levels also respond to seasonal conditions of rainfall and drought. Many urban communities pump more water than the aquifer can recharge. Saltwater encroachment can occur within an aquifer through several mechanisms. Some aquifers are zoned with freshwater on top and saltwater on the bottom. As the freshwater is drawn down, the saltwater is encountered. On islands and in coastal communities, a delicate balance exists between the freshwater and the marine fringes of the Gulf. This boundary is like an invisible wall. As the freshwater is withdrawn, the saltwater wall moves closer and closer eventually moving into areas which were once fresh. The new GSA monitors will be installed on September 17 and 18. The first set of data is expected to be retrieved during the first or second week of October. The data will be available to the public. Area agencies are in the process of educating the public on how to care take this valuable commodity. The Weeks Bay National Estuarine Research Reserve is hosting a one day workshop on October 16. Presentations will include information on hydrology, groundwater contamination as well as groundwater recharge and municipal programs. Contact Mike Shelton at 928-9792. Additional workshops are planned for 2003 through the Mobile Bay National Estuary Program. These will focus on hydrology, water conservation, alternative uses for grey water, and landscaping alternatives that use less water. To be involved call Dr. Diana Sturm at 431-6409
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