Donald A. Walter Timothy D. McCobb Michael N. Fienen Martha K. Watt 2019 groundwater model Reston, VA, USA U.S. Geological Survey https://doi.org/10.5066/F77P8XCT Donald A. Walter Timothy D. McCobb Michael N. Fienen 2019 Publication Scientific Investigations Report 2018-5139 Reston, VA, USA U.S. Geological Survey https://doi.org/10.3133/sir20185139 The U.S. Geological Survey, in cooperation with the Air Force Civil Engineer Center, developed a numerical, steady-state regional model, using MODFLOW-2005, to evaluate current (2010) conditions and the potential effects of future (2030) groundwater withdrawals on water levels, streamflows, hydraulic gradients, and advective transport near the Joint Base Cape Cod (JBCC). Two numerical models were used in this analysis. An existing two-dimensional (one layer) model (termed the “coast model”), developed as part of a previous investigation of the potential effects of sea-level rise on the Cape Cod aquifer system (https://doi.org/10.3133/sir20165058), simulates the position of the freshwater/saltwater interface by using MODFLOW-2005 with the SWI2 module. The regional model is a steady-state, three-dimensional (32 layers) model, which incorporates that interface position, and is capable of representing hydrologic conditions on the Sagamore flow lens and advective transport in and near the JBCC. Particle-tracking analysis using the MODPATH program (https://pubs.er.usgs.gov/publication/ofr94464), was done to represent the advective transport of conservative solutes in the aquifer. A number of underlying assumptions inherent in the model, including observations and weights used in the calibration, representation of local-scale heterogeneity, and simulation of the freshwater/saltwater interface, could affect model calibration and predictions; these assumptions were evaluated with alternate models and alternate inverse calibrations. Alternate calibrations were performed in which different, but reasonable, observations and weights were used. In addition, a set of alternate models, in which silts were represented with different correlation distances and hydraulic conductivities, were done to evaluate if explicitly representing silt lenses could affect model calibration. Finally, two alternate models representing silty and sandy sea bottoms and their associated interface positions were developed to test the importance of the assumed coastal-boundary condition. 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/sir20185139). The purpose of the model is to improve the understanding of the hydrologic system and the physical transport of contaminants in the aquifer and determine the effects of future pumping and return flow on the aquifer system, including changes in water levels, streamflows, hydraulic gradients, and advective-transport patterns within and near the JBCC. The model also will provide a regional-scale tool to ensure (1) that local-scale models used in the design and evaluation of remedial systems are linked to a regional model that is, in turn, informed by the most recent hydrologic and lithologic data and (2) that, as local communities address their growing need for potable water, an updated regional model is available to evaluate the effects of contaminants emanating from JBCC on the water resources of western Cape Cod. The development of the model input and output files included in this data release is documented in the U.S. Geological Survey Scientific Investigations Report 2018-5139 (https://doi.org/10.3133/sir20185139) Support is provided for correcting errors in the data release and clarification of the modeling conducted by the U.S. Geological Survey. Users are encouraged to review the model documentation report (https://doi.org/10.3133/sir20185139) to understand the purpose, construction, and limitations of this model. The models will run successfully only if the original directory structure is correctly restored. The model archive is broken into several pieces to reduce the likelihood of download timeouts. Instructions for reconstructing the original directory structure and running the models included in this data release and described in the model documentation report can be found in the readme.txt ASCII file, which can be downloaded as part of this data release. 19950101 20001231 publication date Complete None planned -70.7254 -70.134774 41.805526 41.481709 USGS Thesaurus usgsgroundwatermodel MODFLOW2005 Groundwater InlandWaters Groundwater Model MODPATH Saltwater Intrusion ISO 19115 Topic Category geoscientificInformation inlandWaters environment USGS Metadata Identifier USGS:65c23b3c-a9a6-4dee-b009-2a3c3fd7c1e0 Geographic Names Information Systems Massachusetts Cape Cod Joint Base Cape Cod Falmouth Mashpee Sandwich Bourne Sagamore lens None. Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from this data release. none Donald A. Walter U.S. Geological Survey mailing and physical

10 Bearfoot Road

Northborough MA 01532 USA 508-490-5050 dawalter@usgs.gov https://water.usgs.gov/GIS/browse/SIR2018-5139Thumbnail.jpg Image of the model domain and active area of the model. jpg Air Force Civil Engineer Center None Unclassified None Donald A. Walter Timothy D. McCobb John P. Masterson Michael N. Fienen 2016 Scientific Investigations Report 2016-5058 Reston, VA, USA U.S. Geological Survey https://doi.org/10.3133/sir20165058 The regional model was calibrated by using a series of alternate calibration simulations and inverse-calibration methods to determine the model parameters that best fit a given set of observations. In this analysis, the inverse-modeling software package PEST (https://pubs.usgs.gov/sir/2010/5169/pdf/GWPEST_sir2010-5169.pdf) was used to calibrate the regional model of the Sagamore flow lens. The software package allows for the use of highly parameterized model inputs and has a large degree of flexibility in defining observations as derived quantities. Water-level and streamflow measurements at 5,626 wells and ponds and 78 streamflow sites, age measurements at 162 groundwater-sampling points, and estimates of the center of mass at 31 plume cross sections derived from water-quality samples were used as calibration targets. A total of 547 water-level observations were determined to generally be representative of long-term average conditions and suitable for calibration of the steady-state model. Measurements at an additional 19 partial-record sites were made during times of average conditions or were calculated by using a regression approach to extend the record period. Contaminant plumes on and near the JBCC determined to be suitable as calibration targets on the basis of confidence in the source location and plume definition along downgradient transverse sections. The calibration period generally is consistent with hydrologic data, pumping stresses, and return flow for the period 1995–2000; this period generally predates the initiation of large-scale plume remediation at the JBCC. No formal logical accuracy tests were conducted Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record and the associated model documentation report (https://doi.org/10.3133/sir20185139) for additional details. No formal positional accuracy tests were conducted No formal positional accuracy tests were conducted The process used to develop, calibrate, and apply the model is fully described in the model documentation report (https://doi.org/10.3133/sir20185139). 2018 NAD_1927_StatePlane_Massachusetts_Mainland_FIPS_2001 41.71666666666667 42.68333333333333 -71.5 24.33333333 600000.0 0.0 row and column 400.0 400.0 survey feet National Geodetic Vertical Datum of 1929 1.0 feet Attribute values SIR2018_5139.shp ESRI Polygon shapefile U.S. Geological Survey Area Text string indicating is polygon area is active or inactive in the model. https://doi.org/10.3133/sir20185139 usgsgroundwatermodel Delineation of active and inactive areas in the model. https://doi.org/10.3133/sir20185139 Walter, D.A., McCobb, T.D., Fienen, M.N., and Watt, M.K., 2019, MODFLOW-2005 and MODPATH used to simulate the hydrologic system and transport of contaminants near Joint Base Cape Cod, Western Cape Cod, Massachusetts: U.S. Geological Survey data release https://doi.org/10.5066/F77P8XCT U.S. Geological Survey Michael Ierardi IT Specialist mailing address

455 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov The data have been approved for release by the U.S. Geological Survey (USGS). Although the data have been subjected to rigorous review and are substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, the data are released on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from authorized or unauthorized use. Although the data, software, and related material have been processed successfully on a computer system at the USGS, no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. readme.txt 1.0 ASCII text file This file documents the structure, directories and files, and instructions on how to run the simulations includedin this data release. 0.046 https://water.usgs.gov/GIS/dsdl/gwmodels/SIR2018-5139/readme.txt modelgeoref.txt 1.0 ASCII text file ASCII file with the four corners of the model domain in decimal degrees. 0.001 https://water.usgs.gov/GIS/dsdl/gwmodels/SIR2018-5139/modelgeoref.txt ancillary.zip 1.0 Compressed (zipped) Folder This directory contains model input and output files, programs, and Python scripts used in the alternate calibration simulations of the model. Alternate calibrations were performed in which different, but reasonable, observations and weights were used. A set of alternate models, in which silts were represented with different correlation distances and hydraulic conductivities, were done to evaluate if explicitly representing silt lenses could affect model calibration. Two alternate models representing silty and sandy sea bottoms and their associated interface positions were developed to test the importance of the assumed coastal-boundary condition as described in the report (https://doi.org/10.3133/sir20185139). This directory also contains a GIS shapefile of the model grid and documentation for the SWI2 package used with MODFLOW-2005. 537.583 https://water.usgs.gov/GIS/dsdl/gwmodels/SIR2018-5139/ancillary.zip bin.zip 1.0 Compressed (zipped) Folder This directory contains the 64-bit executables used to do the analysis documented in https://doi.org/10.3133/SIR20185139. MODFLOW-2005 was used for the simulations. MODPATH4_2 was used for the particle-tracking analysis. These executables were compiled for the 64-bit Windows 7 Operating System. 2.712 https://water.usgs.gov/GIS/dsdl/gwmodels/SIR2018-5139/bin.zip georef.zip 1.0 Compressed (zipped) Folder This directory a shapefile defining the active and inactive areas of the model documented in the report https://doi.org/10.3133/SIR20185139. .0024 https://water.usgs.gov/GIS/dsdl/gwmodels/SIR2018-5139/georef.zip model.zip 1.0 Compressed (zipped) Folder This directory contains all of the input files for the calibrated model and the two scenario models, as well as, the 2D (one layer) model that provides the saltwater/freshwater interface as documented in the report. https://doi.org/10.3133/sir20185139. 66.457 https://water.usgs.gov/GIS/dsdl/gwmodels/SIR2018-5139/model.zip output.zip 1.0 Compressed (zipped) Folder This directory contains the MODFLOW and MODPATH output files for the calibrated model and the two scenario models, as well as, the 2D (one layer) model that provides the saltwater/freshwater interface as documented in the report. https://doi.org/10.3133/sir20185139. 310.071 https://water.usgs.gov/GIS/dsdl/gwmodels/SIR2018-5139/output.zip source.zip 1.0 Compressed (zipped) Folder This directory contains the standard code version of MODFLOW-2005 and MODPATH4 used to run model documented in the report https://doi.org/10.3133/sir20185139. 14.519 https://water.usgs.gov/GIS/dsdl/gwmodels/SIR2018-5139/source.zip None 20201117 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing and physical

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998