North Carolina Aquifers

The aquifers in North Carolina are highly varied in their character and water producing capabilities. Several of these aquifers can be traced over large geographic areas and hence form principal aquifers; significant sources of groundwater for potable water supplies and other agricultural or industrial interests in large portions of North Carolina. Other aquifers in the State provide less significant amounts of water and cover smaller areas of the State. The following material describes briefly some attributes of the principal aquifers, which include the Lower Cape Fear, Upper Cape Fear, Black Creek, Peedee, Castle Hayne, Yorktown, Surficial, and Bedrock aquifers. Minor aquifers in the State include the Lower Cretaceous, Beaufort, and Pungo River.

Aquifers, or more accurately, aquifer systems, are hydraulically connected materials (sands, limestone, and fractured rock) that provide water through a properly constructed well open to those materials. In the coastal plain, an aquifer is typically composed of one to several layers of eastward thickening, permeable sands or limestone split by discontinuous, clay-rich materials. Confining units, consisting of clay-rich sediments, exist above and below an aquifer. These confining units are more continuous clay layers and separate the aquifers. The surficial or unconfined aquifer overlies all the confined aquifers in the coastal plain.

In the Piedmont and Blue Ridge Provinces of North Carolina, two major aquifer systems exist, and usually interact with one another. The surficial materials or regolith of these provinces forms the unconfined aquifer and the fractured rock beneath, is the unconfined to semi-confined bedrock aquifer. Usually the surficial aquifer feeds the fractures in the bedrock aquifer.

Several of the principal aquifers deserve further classification. The Upper and Lower Cape Fear, Black Creek, Peedee, and Castle Hayne aquifers form regional aquifers. In large portions of these aquifers, sands and limestone materials are so well connected that withdrawals cause pressure reductions many miles from the pumping center. This is good news in that wells are very high yielding. The negative outcome is that pumping at one well affects water levels in wells for miles around. This can be seen in water level data from the central coastal plain in the Upper Cape Fear, Black Creek, and Peedee aquifers; Robeson, Bladen and Columbus counties in the Upper Cape Fear aquifer; northeastern North Carolina in the Lower Cape Fear aquifer; and Beaufort and surrounding counties in the Castle Hayne aquifer.

Carbon 14 age dating of the groundwater in the Black Creek and Upper Cape Fear aquifers reinforces our understanding of the groundwater flow patterns in these aquifers. The ages of the water increased with depth and with distance from the fall line eastward and ranged from 400 years to over 26,000 years [1]. The major source of recharge to these aquifers comes from where they are in communication with the surficial aquifer near their westward limit. The water flows down gradient for tens of thousands of years before being withdrawn by water users in the coastal plain.

The following correlation chart illustrates the relation between North Carolina coastal plain aquifers, geologic time, geologic formations, and similar information from South Carolina and Virginia.

NC-VA-SC Correlation Chart

Principal Aquifers (links to the latest potentiometric surface maps available)

Additional historical maps are available on the Interactive Map Interface. Using the MAKE POTMAP tool, this interface also allows the end user to create potentiometric surface maps for the regional aquifer and time period of interest.

Lower Cape Fear aquifer (pdf): This aquifer is present in the northwestern portion of the coastal plain at elevations of -71 to -3267 feet, averaging -767 feet (referenced to mean sea level). The Lower Cape Fear aquifer ranges from 23 to 2730 feet thick and averages 400 feet thick. The aquifer is composed of fine to coarse sands. Wells typically yield 200-400 gallons per minute.
Upper Cape Fear aquifer (pdf): This aquifer is present in the western portions of the coastal plain at elevations of 295 to -2401 feet, averaging -318 feet. The Upper Cape Fear aquifer ranges from 8 to 728 feet thick and averages 164 feet thick. The aquifer is composed of very fine to coarse sands and occasional gravels. Wells typically yield 200-400 gallons per minute.
Black Creek aquifer (pdf): This aquifer is present in the central and southwestern portions of the coastal plain at elevations of 318 to -1483 feet, averaging -136 feet. The Black Creek aquifer ranges from 17 to 448 feet thick and averages 148 feet thick. The aquifer is composed of very fine to fine "salt and pepper" sands. Wells typically yield 200-400 gallons per minute.
Peedee aquifer (pdf): This aquifer is present in the central to southeastern portion of the coastal plain at elevations of 114 to -1849 feet, averaging -158 feet. The Peedee aquifer ranges from 8 to 750 feet thick and averages 133 feet thick. The aquifer is composed of fine to medium sand. Wells typically yield up to 200 gallons per minute.
Castle Hayne aquifer (pdf): This aquifer is widely used in the eastern portions of the coastal plain at elevations of 65 to -1103 feet, averaging -131 feet. The Castle Hayne aquifer ranges from 12 to 755 feet thick and averages 153 feet thick. The aquifer is composed of limestone, sandy limestone, and sand. It is the most productive aquifer in North Carolina. Wells typically yield 200-500 gallons per minute, but can exceed 2000 gallons per minute.
Yorktown aquifer: This aquifer is present throughout most of the northern coastal plain at elevations ranging from 97 to -227 feet, averaging -12 feet. The Yorktown aquifer ranges from 4 to 992 feet thick and averages 99 feet thick. Several localities tap this aquifer and produce high yielding wells including Roanoke Island, Kill Devil Hills, and Elizabeth City. Yorktown aquifer is composed of fine sand, silty and clayey sand, shell beds, and coarser sand beds. Wells typically yield 15-90 gallons per minute.
Surficial aquifer: This aquifer is widely used throughout the State for individual home wells. The surficial aquifer is the shallowest and most susceptible to contamination from septic tank systems and other pollution sources. Commonly, large diameter wells (up to 3 feet in diameter) are drilled up to 60 feet deep to store large quantities of water in the well casing. The surficial aquifer is also very sensitive to variations in rainfall amounts -- they are the first to dry-up in a drought. On the Outer Banks shallow wells are subject to rainfall amounts, saltwater intrusion, poor quality groundwater, and ocean overwash. Wells typically yield 25-200 gallons per minute.
Fractured Bedrock aquifer: This aquifer is widely used for home water supply in the western coastal plain, Piedmont, and Blue Ridge Provinces. Usually six inch wells are drilled to intercept water bearing fractures which are more common in valleys or draws. Thick sequences of regolith (surficial aquifer) above fractured bedrock can improve yields to 200 gallons per minute or more. Industries and county or municipal well fields look for these higher yielding bedrock wells. Wells typically yield 5-35 gallons per minute.

Minor Aquifers

Lower Cretaceous aquifer (pdf): This aquifer is rarely used. It is only fresh in the northern part of the coastal plain below Hertford and Northampton Counties at elevations of -468 to -846 feet, averaging -701 feet. The Lower Cretaceous aquifer ranges from 65 to 322 feet thick and averages 142 feet thick. The aquifer consists of fine to medium sand with occasional coarse sand and limestone beds. No direct yield information is available from pumping records, but because of its composition, yields are expected to range up to 200 gallons per minute.
Beaufort aquifer (pdf): This aquifer is present in the eastern-central portion of the coastal plain at elevations of 27 to -1749 feet, averaging -282 feet. The Beaufort aquifer ranges from 8 to 242 feet thick and averages 78 feet thick. This aquifer is composed of fine to medium glauconitic sand, clayey sand, with occasional shell and limestone beds. Wells typically yield 35-50 gallons per minute.
Pungo River aquifer: This aquifer is present in the north-central coastal plain and consists of fine to medium sand.

Aquifer Maps

Maps of the North Carolina regional aquifers follow. Please consider this information as "work in progress." Maps are based on data collected from USGS and NCDEQ sources and will change as mapping and interpretation in DWR project areas progress. Sources include the following: USGS Open-File 87-690, USGS WRIR 93-4049, 89-4128, & 87-4178; and DWR's Hydrogeologic Assessments of Wilmington Harbor, North Albemarle, CUA #1, Southern Coastal Plain, Central Coastal Plain, East Central Coastal Plain, and the Northwestern Coastal Plain. Arcview shape files include a polygonal dataset of the extent of the fresh, transitional, and salty parts of the aquifer; the distribution of boreholes as point data; and line data representing the contours of the aquifer top.

Aquifer	Abbrev.	Date
Yorktown	Ty	5/2024
Castle Hayne	Tch	5/2024
Beaufort	Tb	5/2024
Peedee	Kpd	5/2024
Black Creek	Kbc	5/2024
Upper Cape Fear	Kucf	5/2024
Lower Cape Fear	Klcf	5/2024
Lower Cretaceous	Klcrt	5/2024
The block diagram to the right illustrates how the linked maps show the distribution of salty and fresh water in an aquifer. The width of the transition zone corresponds to the dip of the fresh-salt water interface. A well in the fresh extent shown on the map will be fresh in that aquifer (<250 ppm chloride concentration). A well in the transition extent shown on the map will encounter salty water in that aquifer at some depth. A well in the salty extent shown on the map will be salty in that aquifer.

Please refer to the typical water budget for the NC coastal plain. As is clear in this budget diagram, a very small percentage of rainfall infiltrates into the confined aquifer system. Most rainfall is lost to evapotranspiration, runoff, or infiltrates into the shallow groundwater system then discharges to local rivers and streams. This discharge to surface drainage is commonly referred to as "baseflow." Recharge to the confined aquifers occurs very slowly across confining units. Recharge occurs more readily where the confined aquifer becomes part of the surficial aquifer or where it is directly below the surficial aquifer and the confining unit is thinner and/or discontinuous.

[1] 14C GROUNDWATER AGE AND THE IMPORTANCE OF CHEMICAL FLUXES ACROSS AQUIFER BOUNDARIES IN CONFINED CRETACEOUS AQUIFERS OF NORTH CAROLINA, USA, Casey Kennedy, David P. Genereux, Department of Marine, Earth & Atmospheric Sciences, NCSU, Raleigh, NC, in Radiocarbon, Vol 49, Nr 3, 2007, p. 1181-1203