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Groundwater Frequently Asked Questions

The major aquifers in North Carolina can be divided into two regions related to the physiographic provinces of the State. The Piedmont and Blue Ridge Provinces extend across the western 60 percent of the State and are, for the most part, underlain by fractured, igneous and metamorphic rocks. The Coastal Plain Province covers the eastern 40 percent of North Carolina, where aquifers are within a wedge of sedimentary rock layers that dip and thicken to the southeast.

Piedmont and Mountains Aquifers || Coastal Plain Aquifers

Piedmont and Mountains Aquifers

Aquifers of the Piedmont and Mountains are localized, complex fractured metamorphic, igneous, and sedimentary (Triassic Basin) rocks. The rocks are covered almost everywhere by regolith, which includes soil, saprolite, alluvium, and colluvium. Most of the groundwater is stored in the shallow, porous regolith. While the crystalline bedrock has extremely low porosity, secondary fractures contain groundwater recharged by the overlying regolith.

FS 112-02 - Fractured-Rock Aquifers: Understanding an Increasingly Important Source of Water

  1. Where does groundwater occur?
    Groundwater occurs below the water table in the porous, shallow regolith (weathered soil, alluvium, colluvium, and rock) and in secondary fractures (crack) in the underlying, deeper crystalline bedrock (extremely low porosity).

  2. Are there water-table maps available?
    In general, regional water-table maps of ground water in the aquifers of the Piedmont and Blue Ridge provinces are not useful because of the local nature of aquifer recharge and discontinuous fracture systems. Some local maps of the shallow water table in the regolith may be available from investigative reports.

  3. Where can I find groundwater?
    Groundwater generally occurs everywhere in the Piedmont and Blue Ridge provinces. Groundwater occurs both in the porous, shallow regolith (below the water table) in large diameter bored wells, and in fractures in the deeper crystalline bedrock in drilled wells (6-10 inches in diameter). Some types of rock may have lower comparable yields than other rock types, and finding enough groundwater to sustain supply needs may be difficult. Dry boreholes are possible in rocks that have few fractures.

  4. How deep is the groundwater level?
    In general, the water table in lower topographic settings such as near streams (generally considered groundwater discharge areas) is shallower than in high elevation topographic settings, such as on mountain tops. In some topographic high areas, the shallow regolith may be dry, and groundwater may only be found in the deeper bedrock. Current groundwater levels for the shallow regolith (including alluvium) and the bedrock is available online.
    Recent groundwater levels
    Climate Response Network
    Monthly Conditions Report

Coastal Plain Aquifers

Aquifers in the Coastal Plain are regional in extent, consisting of porous sand and limestone aquifers. The Coastal Plain sediments have been divided by Winner and Coble (1996) into 10 aquifers separated by confining units. The shallow unconfined aquifer present in most areas is called the surficial aquifer. The confined aquifers include the Peedee, Black Creek, Upper Cape Fear, Lower Cape Fear, Castle Hayne, Beaufort, Pungo River, and Yorktown aquifers.

  1. What aquifer does my well tap?
    Aquifers in the Coastal Plain province occur in gently dipping layers of sediments and sedimentary rock. These aquifers outcrop at land surface in some updip areas, and are buried much deeper in downdip areas (generally to the east and southeast). In general, domestic (household wells) tap either the unconfined surficial aquifer, or the first confined aquifer at depth. Municipal and industrial wells generally tap confined and high yielding aquifers.
    Information on wells in your area can be found online from the USGS. Additional aquifer information can be found online from DENR Division of Water Resources Ground Water Branch database for your County to obtain typical depths for wells within specific aquifers.

  2. Are there water-table maps available for the Coastal Plain ?
    Aquifers in the Coastal Plain are regional in nature, and water-level maps (shallow surficial aquifer) or potentiometric maps (confined aquifers) for specific aquifers are available; however, these data represent a certain time period of measurement, and may not be current. Search online USGS bibliography or NCDENR DWR Ground Water Branch bibliography for report contents.

  3. How deep is the groundwater level?
    In general, depth to groundwater in shallow unconfined aquifers follows topography, being shallower near streams and deeper on hilltops. However, in the deeper confined aquifers, such as the Black Creek and Upper Cape Fear aquifers, the water level (potentiometric head) is under pressure, and is affected by both local and regional pumping.
    Recent groundwater levels
    Climate Response Network
    Monthly Conditions Report

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