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Simulation of the ground-water flow system in 1992, and simulated effects of projected ground-water withdrawals in 2020 in the New Jersey Coastal Plain

U.S. Geological Survey Water-Resources Investigations Report 03-4000

By Alison D. Gordon


View the report in Portable Document Format (PDF) WRIR03-4000 (3.78 MB)


Abstract

In 1992, ground-water withdrawals from the unconfined and confined aquifers in the New Jersey Coastal Plain totaled about 300 million gallons per day, and about 70 percent (200 million galllons per day) of this water was pumped from confined aquifers. The withdrawals have created large cones of depression in several Coastal Plain aquifers near populated areas, particularly in Camden and Ocean Counties. The continued decline of water levels in confined aquifers could cause saltwater intrusion, reduction of stream discharge near the outcrop areas of these aquifers, and depletion of the ground-water supply. Because of this, withdrawals from wells located within these critical areas have been reduced in the Potomac-Raritan-Magothy aquifer system, the Englishtown aquifer system, and the Wenonah-Mount Laurel aquifer.

A computer-based model that simulates freshwater and saltwater flow was used to simulate transient ground-water flow conditions and the location of the freshwater-saltwater interface during 1989-92 in the New Jersey Coastal Plain. This simulation was used as the baseline for comparison of water levels and flow budgets. Four hypothetical withdrawal scenarios were simulated in which ground-water withdrawals were either increased or decreased. In scenario 1, withdrawals from wells located within critical area 2 in the Potomac-Raritan-Magothy aquifer system were reduced by amounts ranging from 0 to 35 percent of withdrawals prior to 1992. Critical area 2 is mainly located in Camden County, and most of Burlington and Gloucester Counties. With the reductions, water levels recovered about 30 feet in the regional cone of depression centered in Camden County in the Upper Potomac-Raritan-Magothy aquifer and by 20 ft in the Lower and Middle Potomac-Raritan-Magothy aquifers.

In scenarios 2 to 4, withdrawals projected for 2020 were input to the model. In scenario 2, withdrawal restrictions within the critical areas were imposed in the Potomac-Raritan-Magothy aquifer system, the Englishtown aquifer system, and the Wenonah-Mount Laurel aquifer, but withdrawals were increased outside the critical areas to the projected 2020 demand. With withdrawals restrictions in critical areas, water levels recovered about 20 feet at the center of the regional cone of depression in the Upper Potomac-Raritan Magothy aquifer. Water levels recovered by about 20 feet at the center of a regional cone of depression in the Englishtown aquifer system in Ocean County, and by about 20 feet in the Wenonah-Mount Laurel aquifer in the same area. In scenario 3, withdrawals were increased to the projected 2020 demand inside and outside the critical areas. As a result, water levels declined as much as 20 feet at the center of a regional cone of depression in the Englishtown aquifer system in Ocean County, and as much as 10 feet in the Wenonah-Mounty Laurel aquifer near this area. The Englishtown aquifer system and the Wenonah-Mount Laurel aquifer are particularly sensitive to increases and decreases in withdrawals because in certain areas the transmissivities of these aquifers are lower than the transmissivities of other confined aquifers of the New Jersey Coastal Plain, and because these aquifers are hydraulically connected. Simulated water levels declined by as much as 10 ft at the center of the regional cone of depression in Atlantic County. In scenario 4, withdrawal amounts were equal to that in scenario 2, except an additional 13.2 million gallons per day was withdrawn from hypothetical wells located outside the critical areas in the Upper Potomac-Raritan-Magothy aquifer, Englishtown aquifer system, and the Wenonah-Mount Laurel aquifer. The additional withdrawals resulted in increased leakage from overlying aquifers to the Wenonah-Mount Laurel aquifer and subsequently to the Englishtown aquifer system.

Table of Contents

Abstract
Introduction
     Purpose and Scope
     Location and extent of study area
     Previous Studies
Hydrogeologic setting and conceptual model
Simulation of the ground-water flow system
     Model limitations
     Model design and input data
     Ground-water-withdrawal data
     Description of the ground-water-withdrawal simulations
     Simulation results
          Baseline simulation, 1989-92
               Lower Potomac-Raritan-Magothy aquifer
               Middle Potomac-Raritan-Magothy aquifer
               Upper Potomac-Raritan-Magothy aquifer
               Englishtown aquifer system
               Wenonah-Mount Laurel aquifer
               Vincentown aquifer
               Piney Point aquifer
               Confined Kirkwood aquifer
          Simulation of withdrawal scenarios
               Scenario 1--Ground-water system with withdrawal reductions in critical area 2 after 1992
               Scenario 2--Ground-water system with withdrawal restrictions in critical area 1
                and withdrawal reductions in critical area 2, 1993-2020
               Scenario 3--Ground-water system with increased withdrawals inside and outside the critical areas, 1993-2020
               Scenario 4--Ground-water system with withdrawal restrictions in critical area 1, withdrawal reductions in critical area 2,
                and withdrawals from hypothetical wells, 1993-2020
Summary
Acknowledgments
References Cited


Suggested citation:
Gordon, A.D., 2003, Simulation of the ground-water flow system in 1992, and simulated effects of projected ground-water withdrawals in 2020 in the New Jersey Coastal Plain: U.S. Geological Survey Water-Resources Investigations Report 03-4000, 61 p.


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View the report in Portable Document Format (PDF) WRIR03-4000 (3.78 MB)


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