Digital-simulation and projection of head changes in the Potomac-Raritan-Magothy aquifer system, coastal plain, New Jersey

A digital model was used to stimulate the response of the Potomac-Raritan-Magothy aquifer system to pumping stresses during the 18-year period, 1956-73. The model was used to compute projected potentiometric heads and trends to the year 2000. Three sets of conditions were simulated: (1) no increase in extractions; (2) continued growth in ground-water extractions at the rate of 3 percent; and (3) continued growth in ground-water extractions at the rate of 3 percent annually, in conjunction with the activation of a freshwater head barrier in the fresh-salty water transition zone. Under the first set of conditions, further head reduction would cease over very within two years. Under the second set of conditions, the broad cone of depression would broaden and deepen. Heads would range from 60 to 160 feet below National Geodetic Vertical Datum (NGVD) of 1929 with declines after 1973 approaching 90 feet in some areas. The resultant steeper hydraulic gradients would accelerate the movement of salty ground water toward the pumping centers. If a freshwater head barrier were constructed across a 35-mile stretch in Gloucester, Camden, and Burlington Counties, the total rates of injection needed would range from about 56 cubic feet per second in year 1984 to about 95 cubic per second in year 2000. Barrier recharge rates would be equivalent to about 20 percent of the ground water pumped.The USGS publication code is: USGS/WRI/NTIS/80-11