Science Center Objects

Documentation of Revisions to the Regional Aquifer System Analysis Model for the New Jersey Coastal Plain

By Lois M. Voronin

 

MODEL VERSION/TYPE: MODFLOW-96, steady state and transient

AREA STUDIED: New Jersey Coastal Plain

AQUIFERS SIMULATED: 10 regional New Jersey Coastal Plain aquifers

MOST RECENT WITHDRAWALS SIMULATED: 1998

MODEL SIZE: 10 layers, 135 rows, 245 columns

MINIMUM GRID SPACING:0.5 miles x 0.5 miles

MODEL ARCHIVE is available by email request at gs-nj-model-request@usgs.gov

 

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) groundwater 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.