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Documentation of revisions to the regional aquifer system analysis model of the New Jersey coastal plain

By Lois M. Voronin


Water-Resources Investigations Report 03-4268

Prepared in cooperation with the New Jersey Department of Environmental Protection


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Abstract

The model, which simulates flow in the New Jersey Coastal Plain sediments, developed for the U.S. Geological Survey Regional Aquifer System Analysis (RASA) program was revised. The RASA model was revised with (1) a rediscretization of the model parameters with a finer cell size, (2) a spatially variable recharge rate that is based on rates determined by recent studies and, (3) ground-water withdrawal data from 1981 to 1998.

The RASA model framework, which subdivided the Coastal Plain sediments into 10 aquifers and 9 confining units, was preserved in the revised model. A transient model that simulates flow conditions from January 1, 1968 to December 31, 1998, was constructed using 21 stress periods.

The model was calibrated by attempting to match the simulated results with (1) estimated base flow for five river basins, (2) measured water levels in long-term hydrographs for 28 selected observation wells, and (3) potentiometric surfaces in the model area for 1978, 1983, 1998, 1993, and 1998 conditions. The estimated and simulated base flow in the five river basins compare well. In general, the simulated water levels matched the interpreted potentiometric surfaces and the measured water levels of the hydrographs within 25 feet.


Contents

Abstract
Introduction
  Purpose and scope
  Location and extent of study area
  Previous investigations
  Conceptual hydrogeologic model
    Hydrogeologic framework
    Ground-water-flow system
Original and revised model designs
  Model approach
  Grid design
  Ground-water withdrawals
  Lateral and lower boundary conditions
  Upper boundary conditions
    Streams
    Recharge
Model calibration
  Revisions to model input data
    Recharge
    Vertical leakance
    Storage coefficient
    Boundary fluxes
  Simulated potentiometric surfaces
    1978 ground-water-flow conditions
    1998 ground-water-flow conditions
  Simulated and measured water-level hydrographs
  Base flow
  Model limitations
Summary
References cited
U.S. Department of the Interior, U.S. Geological Survey
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