A third revision of the New Jersey Coastal Plain (NJCP) groundwater flow model, using MODFLOW-2005 (version 1.12.00), was completed to maintain the model’s usefulness for water-resource managment and development. The regional groundwater-flow model was initially developed for the U.S. Geological Survey (USGS) Regional Aquifer System Analysis (RASA) program. Periodic revision of the model is required as the result of changing hydrologic stresses, different and more complex water management needs, and increased knowledge of hydrologic conditions. The RASA model was initially constructed in the 1980’s as a quasi-3D model with 10 aquifers. The 9 intervening confining units were simulated using vertical leakage parameters at the aquifer contacts. The model was revised in the late 1990’s by (1) rediscretizing the model parameters with smaller grid spacing, (2) rediscretizing the stream cells for a better representation of streams, (3) using a spatially variable recharge rate based on studies conducted by the New Jersey Water Science Center since the model was initially developed, and (4) updating groundwater withdrawal data to 1998. For this study, the USGS, in cooperation with the New Jersey Department of Environmental Protection, again revised the model, updating the hydrogeologic framework, hydraulic parameters, and groundwater withdrawals. The revised 21-layer, fully three-dimensional, NJCP groundwater-flow model extends into Delaware and parts of Maryland and simulates 11 aquifers and 10 intervening confining units. The revisions include spatially and temporally variable recharge estimated using a Soil-Water-Balance (version 1.0.1) model; updated hydrologic parameters using UCODE_2014 (version 1.004) including the confining units in New Jersey and the hydrogeologic units in Maryland and Delaware; updated boundary flows from the North Atlantic Coastal Plain groundwater-flow model; groundwater withdrawals from 1980-2013 for the New Jersey Coastal Plain and from 1980-2010 for the modeled areas in Delaware and Maryland; and additional model layers to refine the simulated flow in Atlantic and Cape May Counties, New Jersey. The revisions to the model allows for (1) refined boundary flows for local models, (2) improved simulated interaction between water levels in southern New Jersey and withdrawals in Delaware, (3) simulation of the unconfined Kirkwood-Cohansey aquifer system and confined Rio Grande water-bearing zone, and (4) the ability to do particle tracking to determine regional sources of flow and times of travel. The groundwater flow model provides water managers with a tool to better understand the groundwater system of the New Jersey Coastal Plain, evaluate groundwater budget components, and make informed water-resource management decisions. This USGS data release contains all the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20235066).

Three withdrawal scenarios spanning from 2014 through 2040 were simulated using a previously published three-dimensional groundwater flow model of the New Jersey Coastal Plain (NJCP) (Gordon and Carleton, 2023). This model, run in MODFLOW-2005 (version 1.12.00), was recently updated by the U.S. Geological Survey (USGS) ensuring the models continued relevance for water-resource management and development. The three withdrawal scenarios were simulated in support of an update to the New Jersey Statewide Water Supply Plan by the New Jersey Department of Environmental Protection (NJDEP). The scenarios simulate nominal-water loss, optimal-water loss, and full-allocation conditions. The nominal water-loss scenario assumes that all public community water supply (PCWS) systems will achieve the current (as of 2018) median values from the systems reporting data on water loss in their distribution systems. The optimal water-loss scenario assumes that all systems will achieve water loss rates roughly equivalent to the systems with the least amount of water loss. Withdrawal rates for both scenarios were based on analysis done at Rutgers University (Van Abs, 2018). In the full-allocation scenario the withdrawal amounts were site specific from an NJDEP Bureau of Water Allocation allocation tool calculation based on data from May 20, 2021 and represents withdrawal amounts at the full-allocation level of each well. This USGS data release contains all the input and output files for the simulated scenarios described above in the associated model documentation report (https://doi.org/10.3133/sir20245028). References: -Gordon, A.D., and Carleton, G.B., 2023, Updates to the regional groundwater-flow model of the New Jersey Coastal Plain, 1980-2013: U.S. Geological Survey Scientific Investigations Report 2023-5066, 116 p., accesses on March 14, 2024, at https://doi.org/10.3133/sir20235066. -Van Abs, D.J., Jiayi, D., and Pierson, E., 2018, Water needs through 2040 for New Jersey public community water supply systems: New Jersey Department of Environmental Protection, Division of Water Supply and Geoscience, prepared by Rutgers University, New Brunswick, New Jersey, accesses May 9, 2024, at https://dep.nj.gov/wp-content/uploads/water-supply-plan/van-abs-et-al-2018.01.19-water-needs-through-2040-for-nj-pcws_final-.pdf.

Three withdrawal scenarios spanning from 2014 through 2040 were simulated using a previously published three-dimensional groundwater flow model of the New Jersey Coastal Plain (NJCP) (Gordon and Carleton, 2023). This model, run in MODFLOW-2005 (version 1.12.00), was recently updated by the U.S. Geological Survey (USGS) ensuring the models continued relevance for water-resource management and development. The three withdrawal scenarios were simulated in support of an update to the New Jersey Statewide Water Supply Plan by the New Jersey Department of Environmental Protection (NJDEP). The scenarios simulate nominal-water loss, optimal-water loss, and full-allocation conditions. The nominal water-loss scenario assumes that all public community water supply (PCWS) systems will achieve the current (as of 2018) median values from the systems reporting data on water loss in their distribution systems. The optimal water-loss scenario assumes that all systems will achieve water loss rates roughly equivalent to the systems with the least amount of water loss. Withdrawal rates for both scenarios were based on analysis done at Rutgers University (Van Abs, 2018). In the full-allocation scenario the withdrawal amounts were site specific from an NJDEP Bureau of Water Allocation allocation tool calculation based on data from May 20, 2021 and represents withdrawal amounts at the full-allocation level of each well. This USGS data release contains all the input and output files for the simulated scenarios described above in the associated model documentation report (https://doi.org/10.3133/sir20245028). References: -Gordon, A.D., and Carleton, G.B., 2023, Updates to the regional groundwater-flow model of the New Jersey Coastal Plain, 1980-2013: U.S. Geological Survey Scientific Investigations Report 2023-5066, 116 p., accesses on March 14, 2024, at https://doi.org/10.3133/sir20235066. -Van Abs, D.J., Jiayi, D., and Pierson, E., 2018, Water needs through 2040 for New Jersey public community water supply systems: New Jersey Department of Environmental Protection, Division of Water Supply and Geoscience, prepared by Rutgers University, New Brunswick, New Jersey, accesses May 9, 2024, at https://dep.nj.gov/wp-content/uploads/water-supply-plan/van-abs-et-al-2018.01.19-water-needs-through-2040-for-nj-pcws_final-.pdf.

A three-dimensional groundwater flow model was developed to simulate the effects of withdrawals on the groundwater-flow systems of five aquifers in and around Ocean County, New Jersey—the unconfined Kirkwood-Cohansey aquifer system and Vincentown aquifer, and three confined aquifers--the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, and the Piney Point aquifer. A transient model was used to simulate conditions that represent no groundwater withdrawals, 2000–2003 groundwater withdrawals, and maximum-allocation groundwater withdrawals. Particle-tracking analysis, using results from two steady-state simulations, determine flow paths and travel times to near-shore wells screened in the unconfined Kirkwood-Cohansey aquifer system, the Rio Grande water-bearing zone, and the Atlantic City 800-foot sand. Sources of water to wells in both unconfined and confined aquifers and travel times based on particle-tracking analysis are used to assess the susceptibility of selected wells to saltwater intrusion from bay or ocean water. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20165035).

A three-dimensional groundwater flow model was developed to simulate the effects of withdrawals on the groundwater-flow systems of five aquifers in and around Ocean County, New Jersey—the unconfined Kirkwood-Cohansey aquifer system and Vincentown aquifer, and three confined aquifers--the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, and the Piney Point aquifer. A transient model was used to simulate conditions that represent no groundwater withdrawals, 2000–2003 groundwater withdrawals, and maximum-allocation groundwater withdrawals. Particle-tracking analysis, using results from two steady-state simulations, determine flow paths and travel times to near-shore wells screened in the unconfined Kirkwood-Cohansey aquifer system, the Rio Grande water-bearing zone, and the Atlantic City 800-foot sand. Sources of water to wells in both unconfined and confined aquifers and travel times based on particle-tracking analysis are used to assess the susceptibility of selected wells to saltwater intrusion from bay or ocean water. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20165035).

The U.S. Geological Survey (USGS), in cooperation with the Town of Falmouth, used an existing groundwater flow model to simulate responses of the freshwater hydrologic system in Falmouth, Massachusetts to proposed wastewater-return-flow scenarios. The existing model is a steady-state, three-dimensional MODFLOW-2005 model of the Sagamore flow lens of the Cape Cod aquifer documented by Walter and others (2019). The existing model was updated with groundwater withdrawal and wastewater-return-flow data to represent average conditions for calendar years 2019 through 2023. The updated model was then used to simulate two wastewater-return-flow scenarios associated with the potential installation of an ocean outfall pipe in Falmouth, Massachusetts. This USGS data release contains the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20255066). Associated Scientific Investigations Report: -------------------------------------- Goldstein, K.M.F., and McCobb, T.D., 2025, Simulated hydrologic responses to proposed wastewater-return-flow scenarios in Falmouth, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2025-5066, 19 p., https://doi.org/10.3133/sir2025-5066. References: -------------------------------------- Walter, D.A., McCobb, T.D., and Fienen, M.N., 2019, Use of a numerical model to simulate the hydrologic system and transport of contaminants near Joint Base Cape Cod, Western Cape Cod, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2019-5139, 98 p., https://doi.org/10.3133/sir20185139.

Three groundwater flow models, using MODFLOW-2000, SEAWAT, and SHARP model codes, were used to evaluate plans to supply potable and non-potable water to residents and businesses of Cape May County, New Jersey until at least 2050. The ideal plan would meet projected demands and minimize adverse effects on currently used sources of potable, non- potable, and ecological water supplies. The U.S. Geological Survey used two previously developed groundwater flow models, as well as a newly developed groundwater flow model, to evaluate the shallow and deep aquifer systems in Cape May County. The groundwater flow in the shallow and deep aquifer systems of Cape May County were simulated separately. Flow in the shallow aquifers was simulated with a newly developed small-cell- size numerical model extending to the hydrologic boundaries. The saltwater transport modeling code, SEAWAT, was used to model the shallow system because of the accurate treatment of variable-density groundwater (saltwater front) and surface-water boundary (ecological-water supply) conditions. Flow in the deep aquifers was simulated using MODFLOW-2000 with a previously developed medium-cell-size numerical model encompassing Cape May County. This sub-regional groundwater-flow model (CMAC) was originally developed by Voronin (https://doi.org/10.3133/wri954280) to simulate advective flow in the Atlantic City 800-foot sand from the estimated 250-mg/L isochlor toward Stone Harbor. For this study, the CMAC model was revised to include the Rio Grande water-bearing zone and recalibrated with recent (2003) withdrawal data and water-level measurements. Boundary flows to the CMAC model were provided from the New Jersey Coastal Plain regional model (NJCP SHARP) (https://doi.org/10.3133/wri984216). This coarse-cell-size Coastal Plain-wide model uses the SHARP model code and simulates saltwater movement by treating the transition from freshwater to saltwater as a sharp interface, and therefore, only predicts large-scale movements of the 10,000-mg/L isochlor. To predict the effects of future actions on the water supplies, three baseline and six future scenarios were created and simulated with these three models. Depending on the scenario, proposed production wells would be installed in locations far from the saltwater fronts, in deep freshwater aquifers, in deeper saltwater aquifers, or proposed injection wells would be installed to inject reused water to create a freshwater barrier to saltwater intrusion. Particle- tracking was used with the CMAC model to estimate groundwater-flow paths and travel time from the location of the 250-mg/L isochlor to production wells or hypothetical production wells. This USGS data release contains all the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20095187).

Three groundwater flow models, using MODFLOW-2000, SEAWAT, and SHARP model codes, were used to evaluate plans to supply potable and non-potable water to residents and businesses of Cape May County, New Jersey until at least 2050. The ideal plan would meet projected demands and minimize adverse effects on currently used sources of potable, non- potable, and ecological water supplies. The U.S. Geological Survey used two previously developed groundwater flow models, as well as a newly developed groundwater flow model, to evaluate the shallow and deep aquifer systems in Cape May County. The groundwater flow in the shallow and deep aquifer systems of Cape May County were simulated separately. Flow in the shallow aquifers was simulated with a newly developed small-cell- size numerical model extending to the hydrologic boundaries. The saltwater transport modeling code, SEAWAT, was used to model the shallow system because of the accurate treatment of variable-density groundwater (saltwater front) and surface-water boundary (ecological-water supply) conditions. Flow in the deep aquifers was simulated using MODFLOW-2000 with a previously developed medium-cell-size numerical model encompassing Cape May County. This sub-regional groundwater-flow model (CMAC) was originally developed by Voronin (https://doi.org/10.3133/wri954280) to simulate advective flow in the Atlantic City 800-foot sand from the estimated 250-mg/L isochlor toward Stone Harbor. For this study, the CMAC model was revised to include the Rio Grande water-bearing zone and recalibrated with recent (2003) withdrawal data and water-level measurements. Boundary flows to the CMAC model were provided from the New Jersey Coastal Plain regional model (NJCP SHARP) (https://doi.org/10.3133/wri984216). This coarse-cell-size Coastal Plain-wide model uses the SHARP model code and simulates saltwater movement by treating the transition from freshwater to saltwater as a sharp interface, and therefore, only predicts large-scale movements of the 10,000-mg/L isochlor. To predict the effects of future actions on the water supplies, three baseline and six future scenarios were created and simulated with these three models. Depending on the scenario, proposed production wells would be installed in locations far from the saltwater fronts, in deep freshwater aquifers, in deeper saltwater aquifers, or proposed injection wells would be installed to inject reused water to create a freshwater barrier to saltwater intrusion. Particle- tracking was used with the CMAC model to estimate groundwater-flow paths and travel time from the location of the 250-mg/L isochlor to production wells or hypothetical production wells. This USGS data release contains all the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20095187).

A previously developed groundwater-flow model of the Great Egg Harbor and Mullica River Basins, N.J. (https://doi.org/10.3133/sir20125187) by the U.S. Geological Survey (USGS) was used to analyze the effects on groundwater levels and stream base flow from possible changes in groundwater withdrawals and effluent infiltration in Winslow Township, Camden County, New Jersey. The Camden County Municipal Utilities Authority (CCMUA) infiltrated treated sewage effluent at their infiltration/percolation lagoons in Winslow Township, New Jersey, from 1985 to 2014. Increasing effluent volumes strained the capacity of the sewage-treatment plant and infiltration/percolation facility which closed in 2014. The treatment plant began pumping effluent from Winslow Township to the main CCMUA treatment facility which discharges treated effluent to the Delaware River. Eliminating infiltration of treated effluent in Winslow Township reduced groundwater recharge in the Great Egg Harbor River Basin and ultimately reducing groundwater discharge (base flow) to the Great Egg Harbor River. A study was conducted to determine the effects of eliminating the infiltration of treated effluent and reducing groundwater withdrawals from wells completed in the Kirkwood-Cohansey aquifer system on groundwater levels and base flow in the Great Egg Harbor River. The model simulates a baseline scenario with 2003-2007 withdrawals and five scenarios with different effluent infiltration conditions and 2008-2010 withdrawals using MODFLOW-2000 (version 1.18.01). This USGS data release contains all of the input and output files for the baseline scenario and five scenarios described in the associated report (https://doi.org/10.3133/sir20235002).

A previously developed groundwater-flow model of the Great Egg Harbor and Mullica River Basins, N.J. (https://doi.org/10.3133/sir20125187) by the U.S. Geological Survey (USGS) was used to analyze the effects on groundwater levels and stream base flow from possible changes in groundwater withdrawals and effluent infiltration in Winslow Township, Camden County, New Jersey. The Camden County Municipal Utilities Authority (CCMUA) infiltrated treated sewage effluent at their infiltration/percolation lagoons in Winslow Township, New Jersey, from 1985 to 2014. Increasing effluent volumes strained the capacity of the sewage-treatment plant and infiltration/percolation facility which closed in 2014. The treatment plant began pumping effluent from Winslow Township to the main CCMUA treatment facility which discharges treated effluent to the Delaware River. Eliminating infiltration of treated effluent in Winslow Township reduced groundwater recharge in the Great Egg Harbor River Basin and ultimately reducing groundwater discharge (base flow) to the Great Egg Harbor River. A study was conducted to determine the effects of eliminating the infiltration of treated effluent and reducing groundwater withdrawals from wells completed in the Kirkwood-Cohansey aquifer system on groundwater levels and base flow in the Great Egg Harbor River. The model simulates a baseline scenario with 2003-2007 withdrawals and five scenarios with different effluent infiltration conditions and 2008-2010 withdrawals using MODFLOW-2000 (version 1.18.01). This USGS data release contains all of the input and output files for the baseline scenario and five scenarios described in the associated report (https://doi.org/10.3133/sir20235002).