A previously published groundwater flow model (https://pubs.usgs.gov/sir/2005/5089/) was revised with refined grid spacing and updated hydrogeolgic framework and hydrologic properties (http://doi.org/10.3133/sir20155061) and used in this study to predict the effects of Upper Floridan aquifer (UFA) groundwater pumpage on horizontal hydraulic-head gradients in the upper-water-bearing zone of the UFA in the downtown Brunswick area, Glynn County, Georgia. The model used MOFLOW-2000 and was calibrated using groundwater-use information for October 2015, which was the basis for the 2015 Base Case simulation. A comparison of the 2015 Base Case simulation with seven groundwater-management scenarios evaluated potential changes to the upper-water-bearing zone of the UFA near downtown Brunswick. Particle-tracking analysis, using MODPATH, provided pathlines and time-of-travel for the 2015 Base Case simulation and scenario C. 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/sir20195035).

An existing three-dimensional model (MODFLOW-2000) by Fine, Petkewich, and Campbell (2017) (https://doi.org/10.3133/sir20175128) was used to evaluate 7 water-management scenarios and predict the effects on the groundwater flow and groundwater-level conditions in the Mount Pleasant, South Carolina area. This model was originally developed in 2007, by Petkewich and Campbell (https://pubs.er.usgs.gov/publication/sir20075126), then updated and recalibrated to conditions from 1900 to 2015. Results of six previous scenario simulations (scenarios 1-6) for the Mount Pleasant Water Works are published in a U.S. Geological Survey (USGS) Scientific Investigations Report (https://doi.org/10.3133/sir20175128). The archived model input and output files are available in a USGS data release (https://doi.org/10.5066/F7S181FC). Seven additional MODFLOW-2000 scenarios (numbered 7-13), using this updated and recalibrated model, were developed to evaluate different withdrawal strategies which are included in this data release: (7) Mount Pleasant Waterworks bringing online a new well (located at the old well 5 location) at 3.51 million gallons per day (Mgal/d) in 2025; (8) Maximizing withdrawals from Mount Pleasant Waterworks wells 2 and 5 (3.51 Mgal/d each) in 2020 and 2025, respectively; (9) Same as Scenario 7, but removing well 3 from production in 2025; (10) Same as Scenario 9, but removing well 4 from production in 2025 (11) Same as Scenario 7, but converting well 3 to an injection well in 2025 (12) Same as Scenario 11, but converting well 4 to an injection well in 2030; and (13) Same as scenario 8, but with two injection wells added (one in 2025 and one in 2035) to Mount Pleasant Waterworks well field. Nine alternate simulations for scenarios 11-13 (three MODFLOW and six MODPATH) were done to evaluate the effects of different porosity on the groundwater flow system, water levels, and the time-of-travel of particles from injection wells to the main water source. This USGS data release contains all the input and output files for the simulations described above and in the readme.txt file of this data release (https://doi.org/10.5066/P9GZEE4E).

An existing three-dimensional model (MODFLOW-2000) by Fine, Petkewich, and Campbell (2017) (https://doi.org/10.3133/sir20175128) was used to evaluate 7 water-management scenarios and predict the effects on the groundwater flow and groundwater-level conditions in the Mount Pleasant, South Carolina area. This model was originally developed in 2007, by Petkewich and Campbell (https://pubs.er.usgs.gov/publication/sir20075126), then updated and recalibrated to conditions from 1900 to 2015. Results of six previous scenario simulations (scenarios 1-6) for the Mount Pleasant Water Works are published in a U.S. Geological Survey (USGS) Scientific Investigations Report (https://doi.org/10.3133/sir20175128). The archived model input and output files are available in a USGS data release (https://doi.org/10.5066/F7S181FC). Seven additional MODFLOW-2000 scenarios (numbered 7-13), using this updated and recalibrated model, were developed to evaluate different withdrawal strategies which are included in this data release: (7) Mount Pleasant Waterworks bringing online a new well (located at the old well 5 location) at 3.51 million gallons per day (Mgal/d) in 2025; (8) Maximizing withdrawals from Mount Pleasant Waterworks wells 2 and 5 (3.51 Mgal/d each) in 2020 and 2025, respectively; (9) Same as Scenario 7, but removing well 3 from production in 2025; (10) Same as Scenario 9, but removing well 4 from production in 2025 (11) Same as Scenario 7, but converting well 3 to an injection well in 2025 (12) Same as Scenario 11, but converting well 4 to an injection well in 2030; and (13) Same as scenario 8, but with two injection wells added (one in 2025 and one in 2035) to Mount Pleasant Waterworks well field. Nine alternate simulations for scenarios 11-13 (three MODFLOW and six MODPATH) were done to evaluate the effects of different porosity on the groundwater flow system, water levels, and the time-of-travel of particles from injection wells to the main water source. This USGS data release contains all the input and output files for the simulations described above and in the readme.txt file of this data release (https://doi.org/10.5066/P9GZEE4E).

The U.S. Geological Survey in cooperation with Mount Pleasant Water Works updated an existing three-dimensional model (MODFLOW-2000) by Fine, Petkewich, and Campbell (2017) (https://doi.org/10.3133/sir20175128) to evaluate two water-management scenarios and predict the effects of increased pumpage on the groundwater flow and groundwater-level conditions in the Mount Pleasant, South Carolina area. This model was originally developed in 2007, by Petkewich and Campbell (https://pubs.er.usgs.gov/publication/sir20075126), then updated and recalibrated to conditions from 1900 to 2015. The updated model was used to simulate six scenario simulations (scenarios 1-6) for the Mount Pleasant Water Works which are published in a U.S. Geological Survey (USGS) Scientific Investigations Report (https://doi.org/10.3133/sir20175128). The associated model input and output files are available in a USGS data release (https://doi.org/10.5066/F7S181FC). In 2018, using the updated and recalibrated model from 2017, seven additional MODFLOW-2000 scenarios (numbered 7-13), were developed to evaluate additional withdrawal strategies. The archived model input and output files for those scenarios are available in a USGS data release (https://doi.org/10.5066/P9GZEE4E). For these scenarios future groundwater withdrawals for Mount Pleasant Water Works were modified while maintaining 2015 pumping rates for all other pumping wells. The model simulates from 1900-2015 with the addition of 2016-2500 for the predictive scenarios. This data release present the model data sets for 2 additional scenarios. The 2017 model, by Fine and others, was slightly updated to simulate two predictive water-management scenarios that evaluate potential changes in groundwater flow and groundwater-level conditions from the increased withdrawals in the Mount Pleasant, South Carolina area. The model was updated to include 2016-2019 groundwater use data for the Charleston aquifer wells in the Charleston, SC area, along with several periodic tape-down measurements at two recording wells (CHN-14 and BRK-431). The model was not recalibrated for this study. Two scenario simulations were completed, and the results are included in this data release. In scenario 1, Mount Pleasant Waterworks demonstrated reasonable need of 2,409 million gallons per year. This scenario simulates 5 of the 6 Mount Pleasant wells each pumping 1.32 million gallons per day from 2020 to 2050, for a total of 6.6 million gallons per day. No withdrawals from the sixth Mount Pleasant well are simulated during the 2020-2050 time period. In scenario 2, the South Carolina Department of Health and Environmental Control recommended withdrawal of 1,679 million gallons per year is simulated. This scenario simulates 5 of the 6 Mount Pleasant wells each pumping 0.92 million gallons per day from 2020 to 2050, for a total of 4.6 million gallons per day. No withdrawals from the sixth Mount Pleasant well are simulated during the 2020-2050 time period. This USGS data release contains all the input and output files for the simulations described above and in the readme.txt file of this data release (https://doi.org/10.5066/P9FA07XD).

The U.S. Geological Survey in cooperation with Mount Pleasant Water Works updated an existing three-dimensional model (MODFLOW-2000) by Fine, Petkewich, and Campbell (2017) (https://doi.org/10.3133/sir20175128) to evaluate two water-management scenarios and predict the effects of increased pumpage on the groundwater flow and groundwater-level conditions in the Mount Pleasant, South Carolina area. This model was originally developed in 2007, by Petkewich and Campbell (https://pubs.er.usgs.gov/publication/sir20075126), then updated and recalibrated to conditions from 1900 to 2015. The updated model was used to simulate six scenario simulations (scenarios 1-6) for the Mount Pleasant Water Works which are published in a U.S. Geological Survey (USGS) Scientific Investigations Report (https://doi.org/10.3133/sir20175128). The associated model input and output files are available in a USGS data release (https://doi.org/10.5066/F7S181FC). In 2018, using the updated and recalibrated model from 2017, seven additional MODFLOW-2000 scenarios (numbered 7-13), were developed to evaluate additional withdrawal strategies. The archived model input and output files for those scenarios are available in a USGS data release (https://doi.org/10.5066/P9GZEE4E). For these scenarios future groundwater withdrawals for Mount Pleasant Water Works were modified while maintaining 2015 pumping rates for all other pumping wells. The model simulates from 1900-2015 with the addition of 2016-2500 for the predictive scenarios. This data release present the model data sets for 2 additional scenarios. The 2017 model, by Fine and others, was slightly updated to simulate two predictive water-management scenarios that evaluate potential changes in groundwater flow and groundwater-level conditions from the increased withdrawals in the Mount Pleasant, South Carolina area. The model was updated to include 2016-2019 groundwater use data for the Charleston aquifer wells in the Charleston, SC area, along with several periodic tape-down measurements at two recording wells (CHN-14 and BRK-431). The model was not recalibrated for this study. Two scenario simulations were completed, and the results are included in this data release. In scenario 1, Mount Pleasant Waterworks demonstrated reasonable need of 2,409 million gallons per year. This scenario simulates 5 of the 6 Mount Pleasant wells each pumping 1.32 million gallons per day from 2020 to 2050, for a total of 6.6 million gallons per day. No withdrawals from the sixth Mount Pleasant well are simulated during the 2020-2050 time period. In scenario 2, the South Carolina Department of Health and Environmental Control recommended withdrawal of 1,679 million gallons per year is simulated. This scenario simulates 5 of the 6 Mount Pleasant wells each pumping 0.92 million gallons per day from 2020 to 2050, for a total of 4.6 million gallons per day. No withdrawals from the sixth Mount Pleasant well are simulated during the 2020-2050 time period. This USGS data release contains all the input and output files for the simulations described above and in the readme.txt file of this data release (https://doi.org/10.5066/P9FA07XD).

A regional groundwater-flow model and particle-tracking program were used to delineate areas contributing groundwater to coastal and freshwater bodies and to estimate travel times from the water table to saline water bodies under average conditions from 1968 to 1983 on Long Island, New York. The coastal waters of Long Island are important economic and recreational resources for the region. The coastal water bodies receive freshwater from inflow of both surface water and groundwater, in addition to tidal exchanges of saltwater. Excessive nitrogen inputs associated with development and urbanization in the freshwater recharge areas to coastal water bodies can adversely affect marine and estuarine ecosystems. The results from this study will be beneficial for developing informed strategies to address nutrient loading to these systems, to provide a basis for additional scientific studies, and to engage the public. This is the first phase in the development of an updated groundwater-flow model for Long Island as part of the National Water Quality assessment Program (NAWQA). The study modified and used the model documented in the publication 'Simulation of the effects of development of the ground-water flow system of Long Island, New York by Herbert T. Buxton and Douglas A. Smolensky (https://pubs.er.usgs.gov/publication/wri984069). This data release contains all of the model input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20165138).

A regional groundwater-flow model and particle-tracking program were used to delineate areas contributing groundwater to coastal and freshwater bodies and to estimate travel times from the water table to saline water bodies under average conditions from 1968 to 1983 on Long Island, New York. The coastal waters of Long Island are important economic and recreational resources for the region. The coastal water bodies receive freshwater from inflow of both surface water and groundwater, in addition to tidal exchanges of saltwater. Excessive nitrogen inputs associated with development and urbanization in the freshwater recharge areas to coastal water bodies can adversely affect marine and estuarine ecosystems. The results from this study will be beneficial for developing informed strategies to address nutrient loading to these systems, to provide a basis for additional scientific studies, and to engage the public. This is the first phase in the development of an updated groundwater-flow model for Long Island as part of the National Water Quality assessment Program (NAWQA). The study modified and used the model documented in the publication 'Simulation of the effects of development of the ground-water flow system of Long Island, New York by Herbert T. Buxton and Douglas A. Smolensky (https://pubs.er.usgs.gov/publication/wri984069). This data release contains all of the model input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20165138).

A three-dimensional groundwater flow model (MODFLOW-2005) of the Mississippi embayment, South-Central United States, was developed as part of a national project initiated by the U.S. Geological Survey Groundwater Resources Program to provide updated assessments of groundwater availability in important principal aquifers across the United States. The goals of the national assessment are to document effects of human activities on water levels and groundwater storage, explore climate variability effects on the regional water budget, and evaluate the adequacy of data networks at a regional scale. The Mississippi embayment was chosen because of the substantial dependency on groundwater for agriculture and municipal needs. Since the development of the original Mississippi Embayment Regional Aquifer system (MERAS) model in 2009, the model has been updated and enhanced and is proving an invaluable tool to evaluate and develop water management pumping strategies. The construction and calibration of the original model (MERAS 1.0) is documented in the U.S. Geological Survey (USGS) Scientific Investigations Report 2009-5172 (https://doi.org/10.3133/sir20095172). MERAS 1.0 contains one transient simulation that quantifies the groundwater availability in the aquifer system from January 1870 to April 2007. The USGS Professional Paper 1785 (https://doi.org/10.3133/pp1785) describes the historical background of the hydrologic system, analyses of the transient water budget, effects of climate change on the groundwater system, and evaluation of the groundwater monitoring network. Minor modifications were done to the model to improve the simulation of groundwater flow (MERAS 1.1) and two climate scenarios were completed using this model. USGS Scientific Investigations Report 2013-5161 (https://doi.org/10.3133/sir20135161) investigated ways to improve the match of observed to simulated groundwater levels within the Mississippi River Valley alluvial and middle Claiborne (Sparta) aquifers. The model was updated with improved water-use estimates and refined parameter estimation by using pilot points (MERAS 2.0). Three water-supply scenarios considered by the State of Arkansas were completed with the MERAS 2.0 model. To assess proposed alternative water-supply scenarios and their impact on future water-supply in the Mississippi Delta, the USGS and the Mississippi Department of Environmental Quality collaborated to update and enhance the MERAS 2.0 model. The MERAS 2.0 model has been updated to April 2014 with the most recent water-use data, precipitation and recharge data, and streamflow and water-level observation data to make MERAS version 2.1 (https://doi.org/10.3133/sir20195116). Five different water-supply options (with a total of 22 sub-scenarios) are run using the MERAS 2.1 model and include: irrigation efficiency, on-farm storage and tailwater recovery, weirs for surface-water augmentation, surface-water transfer, and groundwater transfer and injection. All scenarios are compared with a base scenario which provides a standard for the alternate water-management scenarios. This USGS data release contains all of the input and output files for the simulation of these water-supply option using the new MERAS 2.1 model described in the associated model documentation report (https://doi.org/10.3133/sir20195116).

A three-dimensional groundwater flow model (MODFLOW-2005) of the Mississippi embayment, South-Central United States, was developed as part of a national project initiated by the U.S. Geological Survey Groundwater Resources Program to provide updated assessments of groundwater availability in important principal aquifers across the United States. The goals of the national assessment are to document effects of human activities on water levels and groundwater storage, explore climate variability effects on the regional water budget, and evaluate the adequacy of data networks at a regional scale. The Mississippi embayment was chosen because of the substantial dependency on groundwater for agriculture and municipal needs. Since the development of the original Mississippi Embayment Regional Aquifer system (MERAS) model in 2009, the model has been updated and enhanced and is proving an invaluable tool to evaluate and develop water management pumping strategies. The construction and calibration of the original model (MERAS 1.0) is documented in the U.S. Geological Survey (USGS) Scientific Investigations Report 2009-5172 (https://doi.org/10.3133/sir20095172). MERAS 1.0 contains one transient simulation that quantifies the groundwater availability in the aquifer system from January 1870 to April 2007. The USGS Professional Paper 1785 (https://doi.org/10.3133/pp1785) describes the historical background of the hydrologic system, analyses of the transient water budget, effects of climate change on the groundwater system, and evaluation of the groundwater monitoring network. Minor modifications were done to the model to improve the simulation of groundwater flow (MERAS 1.1) and two climate scenarios were completed using this model. USGS Scientific Investigations Report 2013-5161 (https://doi.org/10.3133/sir20135161) investigated ways to improve the match of observed to simulated groundwater levels within the Mississippi River Valley alluvial and middle Claiborne (Sparta) aquifers. The model was updated with improved water-use estimates and refined parameter estimation by using pilot points (MERAS 2.0). Three water-supply scenarios considered by the State of Arkansas were completed with the MERAS 2.0 model. To assess proposed alternative water-supply scenarios and their impact on future water-supply in the Mississippi Delta, the USGS and the Mississippi Department of Environmental Quality collaborated to update and enhance the MERAS 2.0 model. The MERAS 2.0 model has been updated to April 2014 with the most recent water-use data, precipitation and recharge data, and streamflow and water-level observation data to make MERAS version 2.1 (https://doi.org/10.3133/sir20195116). Five different water-supply options (with a total of 22 sub-scenarios) are run using the MERAS 2.1 model and include: irrigation efficiency, on-farm storage and tailwater recovery, weirs for surface-water augmentation, surface-water transfer, and groundwater transfer and injection. All scenarios are compared with a base scenario which provides a standard for the alternate water-management scenarios. This USGS data release contains all of the input and output files for the simulation of these water-supply option using the new MERAS 2.1 model described in the associated model documentation report (https://doi.org/10.3133/sir20195116).

An existing three-dimensional model (MODFLOW-2000) by Petkewich and Campbell (2007) (https://pubs.usgs.gov/sir/2007/5126/) was updated to simulate six predictive water-management scenarios that were created to simulate potential changes in groundwater flow and groundwater-level conditions in the Mount Pleasant, South Carolina area. The model was recalibrated to conditions from 1900 to 2015. Simulations included six scenarios: (1) maximize Mount Pleasant Waterworks reverse-osmosis plant capacity by increasing groundwater withdrawals from 3.9 million gallons per day (Mgal/d) in 2015 to 8.6 Mgal/d from the Middendorf aquifer; (2) same as Scenario 1, but with the addition of a 0.5 Mgal/d supply well in the Middendorf aquifer near Moncks Corner, SC; (3) same as Scenario 1, but with the addition of a 1.5 Mgal/d supply well in the Middendorf aquifer near Moncks Corner, SC; (4) maximize Mount Pleasant Waterworks well capacity by increasing withdrawals from the Middendorf aquifer from 3.9 Mgal/d in 2015 to 10.2 Mgal/d (5) minimizing Mount Pleasant Waterworks surface-water purchase from the Charleston Water System by adding supply wells and increasing withdrawals from the Middendorf aquifer from 3.9 Mgal/d in 2015 to 12.2 Mgal/d; and (6) same as Scenario 1, but with the addition of quarterly model stress periods to simulate seasonal variations in the groundwater withdrawals. 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/sir20175128).