By Kathy Hart 



face is the aeration zone. Water and air bubble 

 through this zone. 



Underneath is a zone where all of the rock 

 openings are full of water. This zone is the 

 saturated zone, and the water taken from it is 

 groundwater. 



The water table marks the top of the saturation 

 zone. The depth of the water table varies with the 

 topography of the land, the climate and the 

 amount of rainfall. 



The water table rises above the ground's surface 

 in lakes, streams and swamps. But it may fall hun- 

 dreds of feet below a desert. 



Along the barrier islands and nearshore coastal 

 areas, the groundwater system acts differently. 

 Salt water infiltrates the aquifers. 



When this occurs, the water that collects from 

 rainfall forms a freshwater lens which floats on 

 the underlying, denser salt water. 



From Ocracoke north along the Outer Banks, 

 this freshwater lens is the only source of 

 drinkable water with the exception of a small lake 

 near Nags Head. 



The lens, which begins only a few feet below 

 the land's surface, may be 25 to 100 feet deep and 

 is solely dependent on rainfall for replenishment. 



"On the Outer Banks you have a very finite 

 amount of resource because there's not a lot of 

 land for infiltration of rain," says Allan Dietemann 

 of the N.C Division of Water Resources. 



And Dietemann says this limited resource is 

 quenching the thirst of an expanding population 

 that swells by sixfold during the hottest, driest 

 season of the year. 



Therein lies the problem. 



As more houses and businesses suck water 

 from the lens, it diminishes. And when water sup- 

 plies decrease, problems are created that are 

 characteristic to barrier islands everywhere. 



Wells can go dry. Or they can draw salt water 

 from the aquifer below or partially treated sewage 

 from the septic tanks nearby. 



These problems haven't reared their heads along 

 North Carolina's barrier islands. Outer Banks city 



Adapted from "Basic Elements of Cround-Water Hydrology" 



Saltwater Encroachment 



Freshwater lens floating on salt water 

 Freshwater Land surface Water table 



Sea — ^1^^^ Sea 











Salt water 



and county planners are making sure they don't 

 by planning for the future (see story, page 4). 



On the barrier islands south of Ocracoke, water 

 supplies are more abundant. A deep freshwater 

 aquifer exists beneath these islands. 



"There's plenty of groundwater available to the 

 south," Dietemann says. 



"There, it's just a matter of how to pump it, who 

 pays for it and how to handle the fluctuating 

 needs caused by tourists." 



But quantity isn't the only concern among 

 residents in coastal North Carolina. Quality is 

 also a worry. 



People are realizing that the wastes that are 

 pumped and dumped into our soils are potential 

 contaminants for our water supply. 



"At meetings and hearings, people express 

 strong opinions about the quality and quantity of 

 their water supplies," says Perry Nelson of the 

 N.C. Division of Environmental Management. 



"That's why it's important now to make a careful 

 evaluation of those supplies and a careful evalua- 

 tion of what affects those supplies. Water 

 definitely affects our quality of life." 



