Surficial Aquifer System of the New Jersey Coastal Plain--
Significance to Resource Management
Index of Subjects
An understanding of the interaction between human activities and the
Nation's surficial (water-table) aquifers is critical to maintaining
the quantity and quality of our water resources and the health of the
ecosystems they support. In recognition of the importance of these
aquifers, the U.S. Geological Survey (USGS) is developing a program to
study the surficial aquifers of the New Jersey Coastal Plain.
Virtually all ground water originates at the water table where
infiltration of precipitation or leakage from surface-water bodies
recharges surficial aquifers. As a result, surficial aquifers have the
largest water budget, continually transmitting the greatest quantity
of water. In fact, only a fraction of the water that flows in the
surficial aquifers reaches regional confined aquifers.
Ground water in surficial aquifers is exchanged with surface water,
maintains stream base flow, and supports sensitive wetland
ecosystems. Because ground water and surface water interact where the
water table is near or intersects the land surface, very small
fluctuations in ground-water levels resulting from climatic variations
and human activities can have a significant effect on that
interaction.
Contaminants from human activities typically enter ground-water
systems in the surficial aquifer; they are transported along complex
ground-water flow paths that result from the many flow subsystems
developed in surficial aquifers. The contaminants may discharge after
a few years at wells or surface-water bodies, affecting people and the
environment, or they may flow to deeper aquifers and remain in the
ground-water system for hundreds or thousands of years.
The New Jersey Coastal Plain covers an area of about 4,200 square
miles (Fig. 1). Its aquifers supply water for more than 3 million
residents and are designated by the U.S. Environmental Protection
Agency as "sole-source" aquifers. The surficial aquifer system is
characterized in the east by an extensive sand and gravel aquifer (the
Kirkwood-Cohansey aquifer), and in the west by the outcrop of the
deeper confined aquifers where they are unconfined (Fig.2).
Figure 1. New Jersey Coastal Plain.
Land uses in the New Jersey Coastal Plain vary from mixed urban,
industrial, and residential (about 25 percent of the land area) to
agricultural (25 percent) and undeveloped land (50 percent). Much of
the undeveloped land lies within the Pinelands National Reserve,
designated by Congress in 1978 to preserve a unique ecological
habitat. Subsequent State legislation defines areas where no
degradation of the natural environment is allowed and areas where
development is permitted but is designed to minimize adverse
environmental effects.
Contaminants have been introduced to and transported within the
ground-water system for more than a century. Nutrients (mostly
nitrogen compounds) are the most common contaminants because
agricultural practices and on-site septic systems were the earliest
sources of contamination. However, petroleum products, industrial
organic compounds and pesticides, have been detected throughout much
of the surficial aquifer and in parts of the confined aquifers.
Before development, about 3.5 billion gallons per day recharged this
aquifer system. Virtually all of the water discharged to streams,
lakes, wetlands, and tidal bays; less than 1.5 percent of recharge
entered the confined aquifers. Today, about 450 Mgal/d (million
gallons per day) is pumped from the aquifers in the New Jersey Coastal
Plain. Withdrawals from the surficial aquifer system total 220 Mgal/d
-- 65 Mgal/d from shallow domestic wells and the remainder from larger
capacity public supply, industrial, and irrigation wells. Withdrawals
from confined aquifers, primarily from public supply wells, total 230
Mgal/d. As a result, flow from the surficial aquifer system downward
to the confined aquifers has increased fivefold, and
ground-water-level declines (drawdown) in the confined aquifers exceed
200 feet in places.
Historically, the vulnerability of shallow ground water to
contamination encouraged pumping from the deeper, confined
aquifers. However, limited yield and susceptibility to saltwater
intrusion resulted in "Critical Area" legislation in the 1980's that
restricted pumping from the confined aquifers. Today, surface and
ground water associated with the surficial aquifer system are
identified as likely sources for increased supply.
The State of New Jersey, through the New Jersey Department of
Environmental Protection (NJDEP), is custodian of the State's water
resources and, as such, is responsible for ensuring that these
resources are allocated equitably and are protected from excessive use
or degradation. NJDEP administers many regulatory and
resource-management programs related to:
- ground- and surface-water supplies,
- contamination of surface- and ground-water systems, and
- effects of ground-water withdrawals on streamflow, stream
quality, and ecosystems that depend on ground water.
Implementation of these programs requires:
- knowledge of the processes that govern the exchange of water
between ground- water and surface-water sources, and the related
ground-water-level fluctuations, and
- ability to identify the source area of ground-water recharge,
trace flowpaths from the water table through the ground-water system,
and identify the ultimate points of discharge (such as wells and
streams).
The following resource-management decisions are being made in New Jersey:
- NJDEP issues permits for all ground- water and surface-water
withdrawals greater than 0.1 Mgal/d. These permits can include
requirements that maintain minimum streamflows and minimize drawdown
in wetland areas.
- NJDEP is reevaluating the sustained yield of surface reservoirs
that were designed based on flow conditions during the
1960's. Ground-water withdrawals and urbanization since then may have
changed streamflow and decreased the sustained yield.
- NJDEP, under mandate of the Federal Clean Water Act and the State
Water Pollution Control Act, sets ground-water-quality standards and
wasteload allocations to control the effects of ground-water
contamination on surface-water quality. Some interpretations of these
statutes require regulation of ground-water withdrawals that would
reduce streamflow and thereby affect a stream's ability to meet
water-quality standards.
- NJDEP, through its Safe Drinking Water Program, currently is
developing criteria to determine which public supply wells may be
threatened by bacteria or parasites from infiltrating surface
water.
- Also as part of the Safe Drinking Water Program, NJDEP is
establishing criteria for requiring routine monitoring of public
supply wells for pesticides that will be based on the well's
vulnerability to contamination. NJDEP may face similar decisions as
new drinking-water standards are adopted.
- Although drinking-water standards apply to domestic wells, most
monitoring programs are voluntary. NJDEP acknowledges that criteria
for well placement and design are needed to minimize the potential for
contamination.
- The Federal Coastal Zone Management Act requires enforceable
State policies to minimize contamination of tidal water
bodies. Virtually all of New Jersey's watersheds discharge to
tidewater, and ground-water seepage can contribute significant amounts
of some contaminants to coastal waters.
- Many Federal and State programs, including the Wellhead
Protection, Aquifer Recharge Area Protection, Nonpoint Source, and
Pesticide Programs, emphasize contamination prevention and management
through identification of existing sources and mechanisms of
contamination.
The USGS program to study the surficial aquifers of the New Jersey
Coastal Plain includes projects funded Federally and projects funded
cooperatively by USGS and NJDEP. The program is designed to:
- provide knowledge required to implement State resource-management
policies and programs,
- include long-term monitoring designed to analyze changes in
hydrologic conditions,
- coordinate with the USGS National Water Quality Assessment
(NAWQA) Program so that findings can be applied to analyze regional
water quality, and
- include a research component to identify and explain relevant
hydrologic processes.
Specific research issues include:
- seasonal interaction of streams and ground-water systems,
- ground-water-level fluctuations in areas where depth to water is shallow,
- patterns and rates of ground-water flow,
- ages of ground water within the surficial aquifer, and
- transport and fate of contaminants on a regional scale.
For additional information contact:
District Chief
U.S. Geological Survey
810 Bear Tavern Road
West Trenton, New Jersey 08628
H. T. Buxton
February, 1995
FS 086-95