New Jersey Water Science Center
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The unconfined Kirkwood-Cohansey aquifer system in the upper part of the Maurice River Basin, N.J., provides fresh ground water for a variety of uses. The study area encompasses eastern Gloucester and Salem Counties, northern Cumberland County, and western Atlantic County. Three-dimensional steady-state and transient models of the Kirkwood-Cohansey aquifer system were developed to simulate ground-water flow in the study area for predevelopment conditions, post-development conditions, and future conditions based on ground-water withdrawal alternatives.
A comparison of predevelopment conditions with post-development (1995-97) conditions using a transient simulation reveals considerable base-flow reduction in the headwaters area of Scotland Run as a result of withdrawals from nearby public-supply wells, especially during months of low recharge. Results of simulations indicate base-flow reduction was nearly 62 percent at Scotland Run near Williamstown, N.J. (01411460), in August 1995. Agricultural withdrawals in the Muddy Run Basin affected base flow at Muddy Run at Centerton, N.J. (01411700), reducing base flow by 38 percent during August 1995. Base-flow reduction near the southern boundary of the flow model, corresponding to the location of the streamflow-gaging station Maurice River at Norma, N.J. (01411500), was due to the combined effect of public-supply, commercial, industrial, agricultural, and low-volume institutional ground-water withdrawals in the Maurice River Basin. Base flow in the Maurice River at Norma, N.J. (01411500), decreased by nearly 26 percent during August 1995, between predevelopment and post-development conditions. Base flow was reduced by a comparable quantity at the same streamflow-gaging stations during September 1996, even though higher recharge rates lead to higher base-flow values at this time of year.
The future conditions scenario used projections of ground-water demand by municipality for 1995-2040 to simulate the effects of potential ground-water withdrawals in 2010-11 and 2040-41. Hydrologic conditions for 2010 and 2040 were simulated with below-average recharge and for years 2011 and 2041 with above-average recharge. Results indicate that base flow would cease at Scotland Run near Williamstown (01411460) and would decline to 4.32 cubic feet per second (ft3/s) at Muddy Run at Centerton, N.J. (01411700), and 28.48 ft3/s at Maurice River at Norma, N.J. (01411500), during August 2010. Similar base-flow values were projected for 2040. Simulated base flow ceased at Scotland Run near Williamstown, N.J. (01411460); was 4.09 ft3/s at Muddy Run at Centerton, N.J. (01411700); and 25.14 ft3/s at Maurice River at Norma, N.J. (01411500), during August 2011. Simulated base flow during 2011 and 2041 rebounded from lows in 2010 and 2040, respectively, because conditions were simulated with higher recharge rates than those used in the preceding year.
A scenario representing maximum allocation ground-water withdrawal conditions was simulated using all wells in the study area that had been issued a water allocation permit by 1997. Ground-water withdrawal rates from each well were set to the maximum monthly and annual rates specified by the permit. Results of this simulation indicated considerable reductions in base flow in the Maurice River, particularly during periods of low recharge. When climatic conditions that occurred during 1994-97 were used, results indicated that during a dry year like 1995, simulated base flow would stop at Scotland Run near Williamstown, N.J. (01411460) from June through September. Simulated base flow at Scotland Run at Franklinville, N.J. (01411462), and at Muddy Run at Centerton, N.J. (01411700), would stop during August 1995. A comparison of maximum allocation conditions with predevelopment conditions indicated a reduction of simulated base flow by 93 percent during August 1995 and by 41 percent during September 1996 at Maurice River at Norma, N.J. (01411500).
Results of a simulation using additional withdrawals from three hypothetical public-supply wells demonstrated that locating the wells in the upper part of the Maurice River Basin affected the magnitude of base-flow reduction. When the wells were located adjacent to Scotland Run there was nearly a one-to-one correspondence between the amount of ground water withdrawn and the amount of base-flow reduction in Scotland Run. When the wells were positioned on a surface-water basin divide between Scotland Run and Little Ease Run, ground-water withdrawals were offset by a reduction in base flow that was distributed between the two streams.
Abstract
Introduction
Purpose and scope
Previous investigations
Well-numbering system
Hydrogeologic Framework and Ground-Water Flow
Geologic setting
Kirkwood-Cohansey aquifer system
Aquifer properties
Recharge
Water use
Ground-water levels
Ground-Water Flow Model Development
Aquifer geometry and model grid
Boundary conditions
Calibrated hydraulic properties
Steady-state calibration
Water levels and base flow
Sensitivity analysis
Transient calibration
Recharge
Water levels and base flow
Sensitivity analysis
Model Limitations
Simulations of Pre- and Post-Development Conditions
Predevelopment conditions
Post-development conditions
Simulations of Additional Ground-Water Withdrawals
Projected water demands
Maximum allocation withdrawals
Hydrologic boundaries and public-supply well location
Summary and Conclusions
Acknowledgments
Literature Cited
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