Download 2.4.2 North Carolina Aquifers

North Carolina’s Water Resources
Name _____________________________
Period _______ Date _________________
Background
North Carolina is rich in water, both surface water and ground water. Rivers course across the entire
state, tand the Coastal Plain is underlain by water-filled layers of sedimentary rock. While lakes occur all over
North Carolina, those in the Mountains and Piedmont are actually reservoirs, made by damming rivers. The
Coastal Plain is the only province with naturally occurring lakes, including Lake Mattamuskeet, Lake Phelps, and
Lake Waccamaw.
Most municipalities in the Mountains and Piedmont use surface water to provide drinking water. This
water is often collected in reservoirs made by damming a river. Wells in the Mountains and Piedmont typically
have low yields that are suited for private use, but not for an entire town. That’s because the rocks that
underlie the Mountains and Piedmont are metamorphic and igneous, which are impermeable – that is, water
cannot move in between the mineral grains in the rock. Water can move along fractures in these rocks,
however, and it is these water-filled fractures that can supply a family with a well.
In the Coastal Plains, however, most municipalities use ground water. The Coastal Plain is underlain by
thick layers of sedimentary rocks that hold water in the spaces between individual grains of sediment. Wells
drilled into these layers can produce thousands of gallons of water a minute. Rock layers that hold water in
large quantities are called aquifers.
Rain water enters an aquifer where the aquifer intersects the land surface. North Carolina’s aquifers
all tilt so that they are closer to the surface in the west, and deeper to the east. Thus, they receive an inflow
of fresh water from the west (see Figure 3). Near the ocean, the aquifers contain salty water. The boundary
between the fresh water and salty water can change depending on various conditions. Adding extra freshwater
to the system, in the form of heavier-than-usual rainfall, can push the salty water to the east. Pumping too
much fresh water out of an aquifer can cause the salty water to be sucked westward. This is called salt water
encroachment. Sometimes the salty water can contaminate fresh water wells. In 2002, new North Carolina
regulations went into effect to reduce the amount of water that big users (towns, big farms, industries)
withdraw from the aquifers.
The low relief of the Coastal Plain has led to the formation of many wetlands – areas such as bogs,
marshes, and swamps where the soil is often saturated. Wetlands are not only important as wildlife habitats,
but also as natural filtration systems. As water moves slowly through a wetland, soil and organisms remove
contaminants. Wetlands also help control flooding by soaking up a lot of water during periods of high rainfall.
Part 1 – Aquifers
1. Wells drilled in the Coastal Plain produce much, much more water than wells in the Piedmont or
Mountains. Given what you learned in “Get the Ground Water Picture” and the background information,
explain why. _________________________________________________________________
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2. North Carolina’s Coastal Plain has many aquifers – rock units that are capable of storing large amounts
of water. Maps of some of these aquifers are shown below. Notice that the aquifers vary in thickness
and in depth.
a. If you drilled a well in central Pender County, what are some of the aquifers you would expect
to run into (list them in top to bottom order)? ___________________________________
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b. If you drilled a well in Gates County, would you expect to hit the Castle Hayne aquifer before or
after the Upper Cape Fear Aquifer? __________________________________________
Why? _________________________________________________________________
Part 2 – Wetlands
1.
Wetlands are areas where the soil is often saturated and there may be standing water. Bogs, swamps,
and marshes are wetlands. Look at the Wetlands Map below. Given the topography of the Mountains,
piedmont, and Coastal Plain, why do you think most of North Carolina’s wetlands are located in the
Coastal Plain? ________________________________________________________________
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2. Wetlands store huge amounts of water. When it rains, water soaks in and accumulates in a wetland
before moving slowly to the nearest stream. As the water travels through the wetland soils,
contaminants are filtered out. By contrast, when rain falls on an area that is not a wetland, the water
moves more quickly to a nearby stream, picking up and carrying with it whatever it meets on its way –
sediment, fertilizer, animal wastes, or motor oil. Why do you think wetlands might be important for
water quality? _______________________________________________________________
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