Water Availability and Use Science Program

Sustainability of Groundwater Supplies in the Northern 

Atlantic Coastal Plain Aquifer System

Groundwater is the Nation’s principal reserve of freshwater. 

It provides about half our drinking water, is essential to food 

production, and facilitates business and industry in developing 

economic well-being. Groundwater is also an important source 

of water for sustaining the ecosystem health of rivers, wetlands, 

and estuaries throughout the country. The decreases in groundwater levels and other effects of pumping that result from largescale development of groundwater resources have led to concerns about the future availability of groundwater to meet all our 

Nation’s needs. Assessments of groundwater availability provide 

the science and information needed by the public and decision 

makers to manage water resources and use them responsibly 

(Alley and others, 2013).

The U.S. Geological Survey (USGS) is conducting largescale multidisciplinary regional studies of groundwater availability as part of its ongoing assessments of the principal aquifers of 

the Nation (Reilly and others, 2008). These regional studies are 

intended to provide citizens, communities, and natural resource 

managers with knowledge of the status of the Nation’s groundwater resources and how changes in land use, water use, and 

climate have affected and are likely to affect those resources now 

and in the future (Dennehy and others, 2015).

Northern Atlantic Coastal Plain Aquifer System

The Northern Atlantic Coastal Plain (NACP) aquifer system 

extends from Long Island in New York to northeastern North 

Carolina and includes aquifers primarily within New York, 

New Jersey, Delaware, Maryland, Virginia, and North Carolina 

(fig. 1). This aquifer system is made up of 10 regional aquifers 

and 9 interlayered confining units that form a seaward-dipping 

wedge of unconsolidated to partially consolidated sediments that 

are typically thousands of feet thick along the coastline, with a 

maximum thickness of about 10,000 feet near the edge of the 

Continental Shelf.

The NACP aquifer system is one of the smallest of the 66 

principal aquifer systems in the Nation, and yet it ranks 7th in 

population served and 13th overall in total groundwater withdrawals (Reilly and others, 2008). Increases in population and 

changes in land use during the past 100 years have resulted in 

diverse increased demands for freshwater, with groundwater 

serving as a vital source of drinking water for the nearly 20 million people who live in the region. Groundwater withdrawals in 

2013 were estimated to be about 1,300 million gallons per day 

(Mgal/d) and account for about 40 percent of the drinking water 

supply for the area of the NACP aquifer system. Densely populated areas tend to have high rates of withdrawals and, therefore, 

are most susceptible to the effects of these withdrawals over 

time. Water level decreases in some aquifers are more than 

100 feet from levels before 1900 (Masterson and others, 2016a). 

Regional hydrological effects also extend across State lines and 

under large embayments, making the State-level management of 

competing local domestic, industrial, agricultural, and environmental demands for water increasingly more problematic.

Hydrologic Budget

A hydrologic budget quantitatively accounts for inflows, 

outflows, and changes in storage of a hydrologic system. 

Analyses of hydrologic budgets are necessary to understanding 

the sources of water for a groundwater system such the NACP 

aquifer system and how groundwater withdrawals affect the 

components of the hydrologic budget. In the end, the amount 

of water entering a groundwater system plus the amount being 

removed from storage must balance the amount of water leaving 

the system (Reilly and others, 2008).

Study area

LONG ISLAND

NEW JERSEY

DELAWARE MARYLAND

VIRGINIA

NORTH CAROLINA

Bedrock

ATLANTIC OCEAN

Piedmont

Groundwater flow

Fall Line

Figure 1. Block diagram showing the Northern Atlantic Coastal 

Plain aquifer system, which includes the areas east of the Fall Line 

from Long Island to northern North Carolina. This multilayer system 

consists of confined aquifers and confining units capped by an 

unconfined, surficial aquifer. Groundwater flows predominantly from 

west to east from the Fall Line to the Atlantic Ocean, except where 

high-capacity pumping wells alter this regional flow pattern.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2016–3046

August 2016
Hydrologic budgets were calculated with a groundwater 

model developed for the NACP aquifer system (Masterson and 

others, 2016a,b) to quantify how much water enters and leaves 

this aquifer system (fig. 2). From 2005 to 2008, water entered the 

aquifer system at a rate of 18,070 Mgal/d as recharge and flows 

through the shallow, unconfined aquifer and discharged either to 

streams or directly to coastal waters without reaching the deep, 

confined aquifers. An additional source of recharge to the aquifer 

system was the return of about 230 Mgal/d of wastewater from 

domestic septic systems.

Groundwater pumping in the confined part of the aquifer 

system (below the fine-grained confining units) can cause a 

reduction in water pressure, which can result in water lost or 

released from storage. This release of water from storage is 

considered an additional inflow into the aquifer system because 

Surficial aquifer

Natural recharge 

18,070 (<99%) Pumping 240 (<1%) Pumping 1,090 (6%)

Wastewater 

230 (1%)

Streamflow 

6,370 (35%) 

Subsea

coastal

inflow

30 (<1%)

Shallow

coastal

discharge

6,520 (35%)

Confined aquifers

Confining unit

Net downward flow

1,000

(5% of total recharge)

Storage release 60 (<1%)

Tidal waters

4,170 (23%)

Figure 2. Flow diagram showing the hydrologic budget for the 

Northern Atlantic Coastal Plain aquifer system. From 2005 to 2008, 

about 18,300 million gallons per day of water entered and left 

this multilayered aquifer system. Modified from Masterson and 

others (2016a). Values are in million gallons per day; percentages (%) 

are of total recharge. <, less than.

it contributes to the hydrologic budget as an inflow component 

to balance groundwater withdrawals. From 2005 to 2008, water 

was released from storage at a rate of about 60 Mgal/d (fig. 2).

Discharge to streams and the coast and groundwater 

withdrawals make up the outflows that balance the inflows in 

the NACP aquifer system. From 2005 to 2008, 93 percent of the 

total outflow from the aquifer system was to surface waters, with 

58 percent of total outflow discharging directly to coastal areas 

and 35 percent discharging to streams. The remaining 7 percent 

of the total outflow from the aquifer system was accounted for 

by withdrawals of groundwater from pumping wells.

In addition to understanding how inflows and outflows 

currently are balanced for the entire aquifer system, it is also 

important to understand how only the confined part of the aquifer system is responding to groundwater withdrawals because 

that is where most of the pumping occurs in the NACP area. 

About 92 percent of groundwater withdrawals from the confined aquifers are replaced by the increase in downward flow of 

water from the surficial aquifer. The remaining 8 percent of the 

groundwater removed by pumping is balanced by water released 

from storage (5 percent) and the inflow of saline groundwater 

(3 percent) from subsea coastal areas into the freshwater part of 

the aquifer system (fig. 2).

The response of the aquifer system to groundwater withdrawals can happen slowly and change over time; therefore, a 

hydrologic budget was developed to quantify how the NACP 

aquifer system has responded to groundwater withdrawals since 

large-scale pumping began in 1900 (fig. 3). The hydrologic 

budget presented in figure 3 illustrates how the NACP aquifer 

system has responded to 27.8 trillion gallons (Tgal) of groundwater being removed by pumping from 1900 to 2013. This 

response to pumping includes changes in four hydrologic budget 

components—reduction in the amount of groundwater discharge 

to streams, reduction in the amount of groundwater discharge to 

the coast, increased release (or depletion) of groundwater from 

storage, and increased wastewater return flow. About 72 percent 

of the water pumped from the aquifer system from 1900 to 

2013 was groundwater that otherwise would have discharged to 

streams and the coast. Over that period, this reduction in groundwater discharge to the coast was about 57 percent of the total 

water pumped from the NACP aquifer system. About 20 percent 

of the water pumped from the aquifer system was returned into 

the system as recharge from wastewater through septic systems (the wastewater return flow component). The remaining 

8 percent of the water removed by pumping was water released 

from storage (groundwater storage depletion).

20

57

15

8

Net release from storage

Net wastewater return flow

Net reduction in streamflow

Net reduction in coastal discharge

EXPLANATION

Figure 3. Pie chart showing cumulative change in hydrologic 

budget components (as percentages) in response to groundwater 

pumping for the entire Northern Atlantic Coastal Plain aquifer 

system from 1900 to 2013. Most of the 27.8 trillion gallons of water 

removed from the aquifer system by pumping was as a reduction in 

the amount of groundwater that otherwise would have discharged to 

the coast (57 percent) and streams (15 percent).

On a regional scale, hydrogeologic conditions and the 

resulting response to groundwater pumping can vary substantially in both time and space. For example, about 11.3 Tgal of 

water was removed from the local aquifer system on Long Island 

from 1900 to 2013, most of which (77 percent) was groundwater 

that otherwise would have discharged to the coast; only about 

5 percent was from groundwater that otherwise would have 

discharged to streams, and 4 percent was from groundwater 

released from storage. About 14 percent of the total groundwater 

withdrawn from the aquifer system was returned as recharge 

of wastewater by septic systems (fig. 4A). In contrast, about 

2.4 Tgal of water was removed from the local aquifer system 

in Virginia during the same 113-year period, but only about 

15 percent was from groundwater that otherwise would have 

discharged to streams (9 percent) and to the coast (6 percent; 

fig. 4C). Most (about 85 percent) of the response to pumping in 
the local aquifer system in Virginia was balanced by the return 

of wastewater as recharge to the surficial aquifer (36 percent), 

groundwater storage depletion (24 percent), and from inflow of 

groundwater from neighboring States (25 percent; fig. 4C).

Hydrogeologic Controls on Groundwater Flow

Unconfined aquifers in the NACP aquifer system are 

in direct hydrologic connection with surface water features 

and receive inflow directly from recharge from precipitation. 

Confined aquifers are physically separated from the unconfined 

(or surficial) aquifer by overlying confining units (figs. 2 and 5) 

and are not in direct hydrologic connection with surface water 

54

28

18

 <1 D

3 4

5

74

14

B

EXPLANATION

Net inflow from other

geographic areas

Net inflow from other

hydrogeologic units

Net wastewater return flow

Net release from storage

Net reduction in streamflow

Net reduction in coastal

discharge

Net outflow to other

hydrogeologic units

C

36

6

9

24

25

14

77

5 4

 <1

A

Figure 4. Pie charts showing cumulative response of the 

hydrologic budget components (as percentages) to groundwater 

withdrawals from 1900 to 2013 in A, the Long Island aquifer system, 

B, unconfined aquifers of the Long Island aquifer system, C, the 

Virginia aquifer system, and D, the confined Potomac aquifer of the 

Virginia aquifer system. The difference between the Virginia aquifer 

system and the confined Potomac aquifer occurs because, whereas 

water withdrawn by pumping from the unconfined aquifers on Long 

Island directly interacts with the surface waters, water withdrawn 

by pumping in the confined Potomac aquifer induces downward 

flow from overlying hydrogeologic units; the water in the overlying 

hydrogeologic units includes groundwater that otherwise would 

have discharged to surface waters and increased inflow from 

wastewater return flow.

features, thus, only receive water from the downward flow of 

water through overlying hydrogeologic units.

Differences in the hydrogeology on Long Island and in 

Virginia are the reason these local aquifer systems respond differently to groundwater pumping. Almost all (98 percent) withdrawals on Long Island in 2013 were from the surficial aquifer 

Saltwater

Water

table

Confined

aquifers

Coastal

estuary

Fall Line

Freshwater/saltwater

interface

Unconfined

aquifer

Public-supply well

Confining

units

ATLANTIC

OCEAN

Domestic well

NOT TO SCALE

Precipitation

Figure 5. Block diagram showing conceptual model of the flow 

system with the Northern Atlantic Coastal Plain aquifer system. 

The diagram illustrates how water enters the flow system as 

streamflow across the Fall Line and as recharge from precipitation; 

this water then leaves the flow system as groundwater is withdrawn 

by pumping wells or discharges to streams and to the coast. Red 

arrows indicate inflow from recharge and wastewater return flow, 

and blue arrows indicate outflow from groundwater discharge to 

streams and to the coast as well as water removed from private and 

public-supply wells. Modified from DeSimone and others (2014). 

(known locally as the upper glacial aquifer) and the underlying 

Magothy aquifer; both aquifers are essentially unconfined and, 

therefore, in direct hydrologic connection with surface water 

features (fig. 6A). Conversely, about 87 percent of withdrawals 

in Virginia in 2013 were from the Potomac-Patapsco aquifer 

(known locally as the Potomac aquifer), which is a confined 

aquifer separated from the surficial aquifer by multiple aquifers 

and confining units (fig. 6B).

Groundwater withdrawals from the unconfined aquifers 

on Long Island, from 1900 to 2013, were offset primarily 

by a reduction in the amount of groundwater that otherwise 

would have discharged to the coast (74 percent) and to streams 

(5 percent; fig. 4B). Increase in inflow from wastewater return 

flow was about 14 percent of the total 11.3 Tgal of groundwater 

pumped from these aquifers, and release of groundwater 

from storage (groundwater depletion) accounted for about 

4 percent. The remaining 3 percent of change in groundwater 

flow from pumping on Long Island was the downward flow of 

water through the Raritan confining unit from pumping in the 

underlying Lloyd aquifer (fig. 6A). The response of the unconfined aquifers on Long Island (fig. 4B) is very similar to the 

total response of the Long Island aquifer system (fig. 4A) in that 

most (about 79 percent) of the response to pumping from these 

aquifers was as a reduction in the amount of groundwater that 

otherwise would have discharged to surface waters.
NORTH SOUTH

Lloyd aquifer

Magothy aquifer

Upper glacial aquifer

ATLANTIC

OCEAN

200

0

−200

−400

−600

−800

−1,000

−1,200

−1,400

200

FEET FEET

0

−200

−400

−600

−800

−1,000

−1,200

−1,400

A A'

B B'

Long

Island

Sound

A

BElevation, in feet relative to NGVD 29

VERTICAL SCALE GREATLY EXAGGERATED Modified from Buxton and Shernoff (1999)

Raritan confining unit

VERTICAL SCALE GREATLY EXAGGERATED Modified from McFarland and Bruce (2006)

WEST EAST

Surficial aquifer

Chesapeake

Bay

0 10 20 MILES

0 10 20 KILOMETERS

Fall Zone

Elevation, in meters above or

below NAVD 88 150 150

0

–150

–300

–450

Potomac aquifer

Bedrock

Bedrock

0

–150

–300

–450

0 5

0 5

10 MILES

10 KILOMETERS

EXPLANATION

Freshwater aquifer

Saltwater aquifer

Bedrock Confining unit

Groundwater flow direction

Freshwater/saltwater

interface

Figure 6. Cross sections of hydrogeology for the geographic areas 

of A, Long Island, New York, and B, Virginia. About 98 percent of 

the total groundwater withdrawals (pumping) on Long Island are 

from the Magothy and upper glacial aquifers, which are essentially 

unconfined aquifers. In Virginia, about 87 percent of the total 

groundwater withdrawals are from the Potomac aquifer, which is 

separated from the surficial aquifer by intervening confined aquifers 

and confining units. The lines of the sections are shown in figure 7. 

NGVD 29, National Geodetic Vertical Datum of 1929; NAVD 88, North 

American Vertical Datum of 1988.

Even though 87 percent of all withdrawals in Virginia are 

from the Potomac aquifer (fig. 6B), the response of the Potomac 

aquifer (fig. 4D) differs substantially from the response of the 

entire Virginia aquifer system (fig. 4C). The main differences are 

that about half (51 percent) of the response of the entire Virginia 

aquifer system from pumping is from increased inflow of wastewater (36 percent), from neighboring States (other geographic 

areas; 25 percent), and from reductions in the amount of groundwater that otherwise would have discharged to surface waters 

(15 percent), whereas in the Potomac aquifer, about 54 percent 

of the response to pumping is from the downward flow of water 

from overlying hydrogeologic units. These differences indicate 

that pumping from the Potomac aquifer does not directly affect 

groundwater discharge to streams and coastal waters and is not 

receiving recharge directly from the return of wastewater at land 

surface. Instead, pumping from the Potomac aquifer is inducing 

downward flow from the overlying hydrogeologic units, and it 

is that downward flow that indirectly causes reductions in the 

amount of groundwater discharge to streams and to the coast. 

In addition, the return of wastewater as recharge to the surficial aquifer does not directly contribute water to the confined 

Potomac aquifer, but may offset some of the hydrologic effects 

of pumping in the Potomac aquifer on the surficial aquifer.

The unconfined aquifers of Long Island and the confined aquifer in Virginia also differ in the source of the water 

pumped from wells. On Long Island, water pumped from wells 

comes from captured groundwater that otherwise would have 

discharged to streams or coastal waters (fig. 4B), whereas nearly 

all of the water pumped from wells in the confined Potomac 

aquifer comes from the induced downward flow of water from 

the overlying hydrologic units, from the inflow of water from 

neighboring States, and from the release of water from storage 

(fig. 4D). Ultimately, the induced downward flow of water from 

the overlying hydrologic units will result in a decrease in outflow 

to surface waters in Virginia, but the response time for that is 

much slower than that on Long Island and may not be fully 

resolved for many years to come.

Groundwater Storage Depletion

Groundwater storage depletion can be defined as a reduction in the volume of groundwater that is stored in the subsurface; this depletion can have negative effects on water supply 

and can lead to land subsidence, reductions in surface water 

flows and spring discharges, and loss of wetlands (Konikow, 

2013). Only about 8 percent of the total amount of groundwater 

stored in the entire NACP aquifer system from 1900 to 2013 was 

depleted by pumping (fig. 3); however, depletion varied substantially from Long Island to North Carolina (fig. 7). Pumping on 

Long Island and in New Jersey accounted for about 68 percent 

of all withdrawals in the NACP aquifer system, but accounted 

for only about 35 percent of the total depletion of groundwater 

storage from 1900 to 2013. Conversely, pumping in Virginia 

and northern North Carolina, accounted for 14 percent of water 

withdrawn from the NACP aquifer system, yet almost half 

(46 percent) of the total groundwater storage depletion in the 

entire NACP aquifer system occurred in this area. 

The differences in groundwater storage depletion throughout the NACP aquifer system (fig. 7) can be explained by the 

hydrogeologic conditions of the primary aquifers used for 

water supply. In the northern part of the study area, most of the 

groundwater withdrawals are from the shallow, unconfined part 

of the aquifer system and most of the aquifer system response 

to pumping is from captured groundwater that otherwise would 

have discharged to surface waters, resulting in only small 

amounts of pumped water leading to groundwater storage depletion. In the southern part of the study area, most of the withdrawals are from the deep, confined portion of the aquifer system, 

and reductions in the amount groundwater that otherwise would 

have discharged to surface waters is a small amount of the total 

response to pumping, leading to the release of water from storage (groundwater storage depletion) being an important source 

of water to pumping wells.

Implications for Sustainability

Groundwater sustainability can be defined as the development and use of groundwater in a manner that can be maintained 

for indefinite time without causing unacceptable environmental 

or socioeconomic consequences (Alley and others, 1999). The 

primary concern of groundwater sustainability in the NACP 

aquifer system is balancing the increasing demands for a 

potable water supply with the quantity, timing, and quality of 

groundwater flow and storage required to sustain freshwater 
pem16-4133_fig 07

A

A’

Study area

Chesapeake Bay

Delaware Bay

Long Island

CT Sound NY

NEW

JERSEY

PENNSYLVANIA

MARYLAND WV

DC

VIRGINIA

DELAWARE

NORTH CAROLINA

ATLANTIC OCEAN

Pamlico Sound

Albemarle Sound

Base from U.S. Geological Survey digital data, 1:2,000,000 scale

Albers Equal Area Conic projection

Standard parallels 34°30' N and 41°30' N; central meridian 75°30' W 

North American Datum of 1983

0 50 100 MILES

0 50 100 KILOMETERS

78° 72°

39°

36°

75°

EXPLANATION

Percentage of total withdrawals

 and percentage of total depletion

1446

14

46

18 19

68 35

B

A’

A

B’

Figure 7. Cumulative groundwater withdrawals 

(27.8 trillion gallons [Tgal]) and storage depletion 

(2.2 Tgal) as percentages of the total water withdrawn 

and groundwater depletion from 1900 to 2013. 

Groundwater withdrawals in the Long Island-New 

Jersey area accounted for about 68 percent of the 

total water pumped from the NACP aquifer system, but 

groundwater storage depletion in this area was only 

35 percent of the total groundwater depletion in the 

NACP aquifer system from 1900 to 2013. Conversely, 

groundwater withdrawals in the Virginia-North Carolina 

area only accounted for 14 percent of the total water 

pumped in the NACP aquifer system, and yet, about 

46 percent of the total groundwater depletion in the 

NACP aquifer system occurred in this area. Most of 

the withdrawals in the Long Island-New Jersey area 

were from the shallow unconfined part of the aquifer 

system, whereas in the Virginia-North Carolina area, 

withdrawals were mostly from the deep confined part 

of the aquifer. The source of water to wells pumped 

in unconfined aquifers mostly is from “captured” 

groundwater that otherwise would have discharged 

to surface waters unlike in confined aquifers where 

induced downward flow from overlying hydrogeologic 

units and groundwater released from storage are the 

primary sources.

and estuarine ecosystems, such as the New York-New Jersey 

harbor estuary, Barnegat Bay in New Jersey, the meadowlands 

in Hackensack, N.J., the inland bays and seashore of Delaware, the Delaware River Estuary, and the Chesapeake Bay 

(http://www.chesapeakebay.net/), the largest estuary in the 

United States and the first in the Nation to be selected for restoration as an integrated watershed ecosystem.

Assessing sustainability in the thick, multilayered NACP 

aquifer system can be complicated because the effects of 

groundwater pumping can differ throughout the system, depending on if groundwater is being withdrawn from the shallow, 

unconfined aquifers or the deep, confined aquifers. In the shallow aquifers such as on Long Island, the hydrologic response 

to pumping can be much quicker than in the deep aquifers in 

Virginia where the effects tend to manifest themselves slowly 

over time and the full effects of pumping from these deep confined aquifers may not be evident for many years after pumping 

began. Therefore, in unconfined aquifers (either the surficial 

aquifer or in aquifers in direct hydrologic connection with the 

surficial aquifer), which are the primary water-supply source 

in locations such as the Long Island-New Jersey area (fig. 7), 

groundwater storage depletion is of less concern than in confined aquifers because the unconfined aquifer system is able to 

reach a new hydraulic equilibrium more quickly and with fewer 

unresolved long-term effects.

Although groundwater storage depletion from unconfined 

aquifers may be of lesser concern than from confined aquifers, 

concerns exist that groundwater pumped from these unconfined 

aquifers potentially could be more susceptible to agricultural, 

industrial, or urban land-use activities (fig. 5), which could 

adversely affect water quality in these areas. Furthermore, 

groundwater withdrawals from these unconfined aquifers have 

the potential to reduce groundwater discharge to receiving 

waters on the surface such as rivers and coastal waters that 

depend on groundwater to sustain freshwater and estuarine 

ecosystems and the livelihoods that depend on them.

Conversely, in parts of the NACP aquifer system such 

as in Virginia and North Carolina (fig. 7) where the majority of groundwater pumping is from the confined aquifers, the 

primary source of water to these aquifers is downward flow 

from overlying hydrogeologic units (fig. 4D) rather than directly 

from recharge from precipitation at the water table (fig. 5). 

Groundwater withdrawals from these confined aquifers may be 

less susceptible in the short term to adverse land-use activities 

than those from unconfined aquifers and less likely to cause 

hydrologic effects on groundwater-dependent surface waters; 

however, because these confined aquifers are not replenished 

directly by recharge at the water table, groundwater withdrawals in the long term may outpace replenishment, resulting in 

overuse of this resource.
Additionally, groundwater storage depletion from the confining units that separate the confined aquifers from the surficial 

aquifer is of particular concern because water removed from the 

clayey sediments in confining units, unlike from the sandy sediments that make up the confined aquifers, cannot be replenished 

as these units gradually compress. This nonrecoverable loss of 

water from storage can result in land subsidence. Moreover, 

where these confining units are thick and the amount of water 

released from storage is relatively large, rising sea levels at 

low land surface elevations, such as in the lower part of the 

Chesapeake Bay, could result in increased flooding and surface 

inundation (Eggleston and Pope, 2013).

Another concern in coastal aquifer systems such as the 

NACP aquifer system is saltwater intrusion from overpumping 

of groundwater near the coast. This concern is one that affects 

both unconfined and confined aquifers and results from pumping that captures groundwater that otherwise would discharge to 

the coast. Once the balance between freshwater and saltwater is 

altered, the interface between freshwater and saltwater begins 

to move landward, and pumping wells near this hydrologic 

boundary are at increased risk of saltwater intrusion (figs. 2 

and 5). Masterson and others (2016a) assessed the potential for 

saltwater intrusion in the NACP aquifer system and determined 

that the potential for regional-scale effects are small for conditions in 2013 but may be of local concern in parts of Long 

Island, New Jersey, and Virginia where high-capacity pumping 

wells are in close proximity to the interface between freshwater 

and saltwater.

Informed management of the NACP aquifer system can 

help ensure a regionally sustainable groundwater resource. 

Long-term monitoring and assessment of water quality and 

environmental conditions and of the potential for overexploitation of this groundwater resource can assist decision makers 

in the management of this vital resource. Groundwater models 

such as that detailed in Masterson and others (2016b) serve 

as tools to advance the understanding of the responses of the 

various components of hydrologic budgets for the entire NACP 

aquifer system and for each of the subregional systems within 

the study area. Models also can be used to forecast future 

system response to development at a scale relevant to regional 

water management decisions and to examine the NACP aquifer 

system at different spatial and temporal scales to better understand how changing hydrologic stresses across the aquifer 

system can influence the sustainability of groundwater resources 

in the area.

For more information, contact

Water Availability and Use Science Program

U.S. Geological Survey

150 National Center

12201 Sunrise Valley Drive

Reston, VA 20192

http://water.usgs.gov/wausp/

By John P. Masterson and Jason P. Pope

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ISSN 2327-6916 (print)

ISSN 2327-6932 (online)

http://dx.doi.org/10.3133/fs20163046