Program to Maintain and Update Groundwater Models

Since 1975, 41 groundwater-flow models that simulate confined and unconfined conditions in various aquifer types present in New Jersey-- including fractured rock, Coastal Plain, and glacial aquifers-- have been developed and are documented by USGS publications. Of these, 29 models are currently archived shown in figures 1A and 1B.  Twelve non-archived models are listed on the Web pages. These models typically are older models with little to no computer files or models with a limited extent. For these models, a link to the published report on the USGS publication warehouse website is available.

The existing models in the N.J. Water Science Center have been archived to a central location and are available to the public. Care has been taken to standardize each model and to update and revise models when needed.  As of 2016, model archives must conform with the USGS Open data Policy and must be formally distributed online to the public as a USGS data release concurrent with the information product that describes the model.

The NJ Coastal Plain RASA (Regional Aquifer System Analysis) model simulates groundwater flow in the confined aquifers of the New Jersey Coastal Plain and is one of the most widely used models by hydrologists in the NJWSC (Martin, 1998). The model was updated in the late 1990’s to include water use from 1981 through 1998, rediscritized to a finer cell size, and modified to include spatially variable recharge rates based on recent studies (Voronin, 2004). Simulations using this published RASA model (Voronin, 2004) have provided a detailed understanding of groundwater flow and sources of water to wells in the Wenonah-Mount Laurel aquifer in and around the Deptford Township, Gloucester County (Watt and Voronin, 2006). The RASA model also was used to provide information to the NJDEP for the Water Supply Master Plan. Scenarios were run that evaluated the effects of increased withdrawals on water levels and water budgets within planning areas based on future population estimates (Gordon, 2007).  An optimization module, GWM (Ahlfield and others, 2005), which is part of the MODFLOW program, was used to evaluate how and where increased withdrawals would affect water levels within Critical Area 1 (Spitz and others, 2007). The graph in figure 2 shows that as more drawdown is allowed in the system, the amount of available withdrawal increases. The curves on the graph are for two different well configurations—the current well locations and regularly spaced well locations. 

The model was updated again in 2023 (Carleton and others, 2023) to incorporate a Soil Water Balance (Westenbroek and others, 2010) recharge package, update withdrawals to 2013 values, and extend the model boundary into Delaware to better understand the effects of withdrawals in Delaware on the flow system. This model (Carleton and others, 2023) also was used to provide information to the NJDEP and scenarios were run that evaluated the effects of increased withdrawals on water levels and water budgets within planning areas based on future population estimates to 2040 (Kauffman, 2024).  

The groundwater-flow models can be used to address many water-resources issues. One groundwater-flow model developed by the USGS in the Pennsauken Township area in Camden County was used to delineate contributing areas to the Puchack well field. The contributing areas to this major well field, shown in figure 3, was determined by using particle-tracking analysis that calculates the travel times of water to wells (Pope and Watt, 2005). Other models have been used to address saltwater intrusion or base-flow depletion. The Camden model was used to evaluate the vulnerability of production wells in the Potomac-Raritan-Magothy aquifer to saltwater intrusion from the Delaware River in Camden, Salem, and Gloucester Counties under different drought conditions (Navoy and others, 2005).  Particle tracking was used to delineate the contributing area for production wells and determine time-of-travel for saltwater intrusion. Several archived models describe and characterize the unconfined aquifer system, as well as the confined aquifer systems, and its interaction with the surface-water system in response to increased withdrawals. For example, the Great Egg Harbor and Mullica River Basins model (Pope and others, 2012) evaluated the effects of groundwater withdrawals on water levels and on base-flow depletion.

Conclusions

Since the Model Maintenance program was started, the existing models in the NJWSC have been archived to a central location and have been made available to the public. Care has been taken to standardize each model and to update and revise models when needed. Many of the models have been used to address issues regarding a variety of public supply issues throughout the State. Periodically, the models are evaluated to see what updates or revisions might more fully benefit water managers. This way the models that were developed for a single project may be used multiple times providing manager with efficient use of the models at reduced cost. As more models are completed in the NJWSC, the standardized method of archiving and releasing these models to the public makes them a valuable resource. The continuing use of the models provides important data in guiding future water-supply issues. 

List of Archived Models (available under Related Science)

Link to Information on Non-Archived Models 

Information on Archived Models --

Below is a list of archived models that can be obtained one of two ways. Older models are requested through the New Jersey Water Science Center.   A link will then be sent to you for download.  Newer models, listed in the second column below with Scientific Investigation reports and data releases, can be downloaded directly from a USGS digital repository.

Southern New Jersey Models (Coastal Plain)

Northern New Jersey Models (Fractured Rock and Valley Fill)

NOTE: Model ID 1, 15, and G are not on Figure 1A.