By: South Jersey Land and Water Trust
SOUTH JERSEY — If you live in South Jersey, your drinking water comes all or in part from the ground, through domestic or public supply wells. Depending on your location, it is either entirely groundwater or it is a combination of groundwater and treated Delaware River water that is sent to your community through miles of pipes. Most of us know little about our drinking water sources, but it’s a bit easier to understand in South Jersey than the complex systems of North Jersey, which depend on several rivers and large reservoirs and/or on many smaller aquifers.
All of South Jersey lies on the Coastal Plain of New Jersey. The geological dividing line between North and South Jersey is approximately at Route 1, running diagonally across the state.
The geology of the New Jersey Coastal Plain generally can be visualized as a tilted layer cake, with its “layers” or strata formed of gravels, sands, silts, and clays that were deposited as river deltas, seafloor, and beaches starting from the time of the dinosaurs and continuing to the present day. The saturated gravel and sand layers, with their large pore spaces, are called aquifers. Wells draw water from the aquifers. The silt and clay layers, which impede the movement of water, are called confining beds. Confining beds can isolate aquifers from sources of contamination.
A cross section across southern New Jersey from west to east would show that the layers are not horizontal but tilt downward toward the southeast, getting deeper as they cross the state toward the Atlantic Ocean. Because of this tilting, each layer formation emerges on the land surface in a sequential manner. The deepest formations emerge on the surface near the Delaware River. Where a formation emerges is its “outcrop” area. These aquifer outcrops extend north and south across Camden, Burlington, and Salem Counties.
Water enters each aquifer from rainfall directly on the outcrop, referred to as the recharge area. Local recharge from rainfall and infiltration from streams are the primary sources of water to the Coastal Plain aquifers.
THE AQUIFERS OF SOUTH JERSEY
The Potomac-Raritan-Magothy (PRM) formation, the deepest and most abundant aquifer, is a major water source for Inner Coastal Plain communities. The PRM exists from the Delaware River and underlies the entire region.
Other aquifers on top of the PRM are the Englishtown, the Wenonah-Mount Laurel, and the Kirkwood-Cohansey. The Mt. Laurel-Wenonah underlies about two-thirds of the southwestern NJ counties. The Kirkwood-Cohansey is a formation composed of two thick layers, the Kirkwood (lower) and the Cohansey (upper) that overlie the older formations. It begins east of the inner/outer coastal plain divide and underlies about half of South Jersey.
WATER SUPPLY ISSUES
Potomac-Raritan-Magothy Aquifer System (PRM): The PRM is a major source of drinking water to New Jersey residents from Burlington to Salem counties, and regionally in the Camden metropolitan area. The PRM yields the most water of the aquifers in South Jersey. It has a relatively wide recharge area that includes direct contact with the Delaware River.
Because of high usage, PRM aquifer water levels declined dramatically, beginning in the1930s. The water level drop became so serious that the New Jersey Department of Environmental Protection (NJ DEP) established Water Supply Critical Area #2 in 1986. All water supply companies within Critical Area #2 were given annual limits on water withdrawals in the PRM. Usage from the PRM was cut back by 22% and no increases in pumping were allowed.
To fill the gap, piping of treated Delaware River water via the NJ American Water Company’s treatment plant in Delran and a 40-mile pipeline were developed. Nearly all municipalities within the Critical Area #2 now utilize a combination of aquifer water and treated river water during a year. Only those communities that have good local access to the Cohansey-Kirkwood aquifer are unconnected to the pipeline.
OTHER THREATS TO THE AQUIFERS
Potomac-Raritan-Magothy Aquifer
The Delaware Riverfront of Camden and Gloucester Counties is home to many industries and businesses. This same area also sits on the outcrop of the PRM aquifer. Contamination of the aquifer from the land use, notably volatile organic compounds (VOCs), has occurred, making nearby parts of the aquifer nondrinkable. A further concern in this area is that during drought and low flow periods, the reach of the Delaware River along the riverfront can be salty. If future pumpage were to concentrate near the river, saltwater could invade the aquifer.
Mt. Laurel Wenonah Aquifer: The Mt. Laurel-Wenonah is tapped by public water supplies and individual domestic wells in the center of western South Jersey. The Mt. Laurel-Wenonah aquifer has a narrower recharge area with more limited sources of rainwater recharge than the PRM. Its permeability by rainwater is also lower. Therefore, its yield of drinkable water is much lower than the PRM. With the implementation of Critical Area #2 for the PRM, pumpage from the Mt. Laurel has increased as it is being used as an alternative supply. Consequently, water levels in the aquifer have been declining. The iron content of water from the aquifer can also be high in some places, making treatment necessary prior to use.
Kirkwood-Cohansey Aquifer System: The Kirkwood-Cohansey is the primary source of water to individual domestic wells, public water supplies, and irrigation wells from the central part of Southern new Jersey to its southern border. This aquifer system is the uppermost, or surface aquifer layer so it exists at land surface throughout the southern half of South Jersey. This exposes the aquifer to a considerable amount of recharge from rainfall, but it also exposes it to possible contamination from various land uses.
Because of its surface position, the Kirkwood-Cohansey aquifer is connected to the streams of the area. The baseflow of the streams (water not flowing directly from storm runoff) is groundwater that enters (discharges to) the streams. This baseflow is the major part of the water of Coastal Plain streams and sustains their flow during dry periods and drought.
Any pumping from the aquifer will reduce the stream baseflow. If the well is too close to the stream, its pumpage can dry up the stream. This situation results primarily from pumpage by public water supply wells and tends to occur in late summer.
There is also a net loss of water from the aquifer because of the subsequent exportation of the resulting area sewage which is sent to treatment plants along the Delaware River and then discharged into the river. Conversely, private home well pumpage uses less water and relies on waste disposal through septic tanks. This keeps the aquifer water nearer to its source and has less of a depletion effect.
The surface nature of the Kirkwood-Cohansey makes it vulnerable to contamination from various land uses. Industrial chemicals (VOCs), agricultural chemicals used for crop production, and residential landscaping, pesticides, and products of septic tank effluent have all been found in water from the aquifer. Recently radium and mercury have been found in the water from the aquifer. Where possible, care must be taken to site wells to avoid proximity to harmful land use and contamination. Also, a high priority must be given to maintaining a routine water-quality monitoring program for all wells, including private domestic wells, to ensure that contamination would be detected before any harmful consequences are realized.
South Jersey Land & Water Trust works to preserve land that is important for groundwater recharge and also monitors surface water conditions – the flow and quality of streams and rivers. We all must advocate for good land use practices and maintaining high water quality standards to protect our drinking water and preserve surface water habitats.
Sources:
–This article is derived principally from the Anthony S. Navoy article.
-Canace, Robert J. and Jeffrey L. Hoffman. Potential Rate of Stream-Base-Flow Depletion from Groundwater Use in New Jersey. NJ Geological Survey, Technical memorandum 09-1. Trenton, NJ, New Jersey Department of Environmental Protection, 2009.
-Forsman, Charles R. Compilation of records from Tri-County files and his personal experience on the Tri-County Board.
-McCarthy, Suzanne B. Compilation of the history of the Tri-County Water Management Area from Tri-County files held by the Delaware Valley Regional Planning Commission, personal communication.
-Navoy, Anthony S. “Gloucester County Ground-Water Resources and Issues.” Watershed News Early Spring 2001. The Newsletter of the Federation of Gloucester County Watersheds and the South Jersey Land Trust, Gloucester Co., April 2001.
-Zapecza, Otto S. Hydrogeologic Framework of the New Jersey Coastal Plain. US Geological Survey Professional Paper 1404-B. Washington D.C.: United States Government Printing Office, 1989.
The South Jersey Land and Water Trust is a non-profit 501(c)(3) conservation organization that works to protect and preserve the land and water resources of southern New Jersey.
- WATCH: What’s Good in South Jersey? American Training Center Graduation Celebration
- WATCH: What’s Good in South Jersey? Cinco De Mayo Celebration
- WATCH: What’s Good in South Jersey? Salem Donates House For Full Renovation
Follow South Jersey provides local journalism which highlights our diverse communities; fosters transparency through robust, localized, and vital reporting that holds leaders and institutions accountable; addresses critical information needs; supports people in navigating civic life; and equips people with the information necessary to partake in effective community engagement. If there is a story or event you think we should cover, please send your tips to news@followsouthjersey.com with “NEWS” in the subject line.
