Jonathan P. Traylor Skylar J. Kaminski Benjamin J. Dietsch Alec R. Weisser 2026 Version 1.0 groundwater model Reston, VA, USA U.S. Geological Survey https://doi.org/10.5066/P9HZWI8S Jonathan P. Traylor Moussa Guira Leslie L. Duncan Benjamin J. Dietsch Skylar J. Kaminski Michele Reba Joseph Massey 2026 Publication Scientific Investigation Report ### Reston, VA, USA U.S. Geological Survey The Mississippi Alluvial Plain (MAP) is one of the most important agricultural regions in the United States and underlies about 32,000 square miles of Missouri, Kentucky, Tennessee, Mississippi, Louisiana, and Arkansas. The MAP region supports a multibillion-dollar agricultural industry. The MAP is part of the Mississippi Embayment with several water-bearing units that make up the Mississippi Embayment Regional Aquifer System (MERAS). These water bearing units include the Mississippi River Valley Alluvial aquifer, Claiborne aquifers and Wilcox aquifers. In northeastern Arkansas, the Grand Prairie area has been designated as a critical groundwater area (CGWA) because of decades of groundwater declines that resulted from past and current water use. The objective of the report associated with this data release is to document and describe the construction, simulation, and results of scenario forecasts run for the Grand Prairie scenario model with a focus on results within the designated Grand Prairie CGWA. The calibrated Grand Prairie model from Traylor and others (2024) were used as the base model for each forecast scenario model. Scenarios for the Grand Prairie model included seven climate scenarios, five global groundwater pumping reduction scenarios, and four groundwater pumping reduction scenarios by crop and location. Each scenario was outlined by the researchers and managers at U.S. Department of Agriculture (USDA) Agricultural Research Service, Natural Resource Conservation Service, Bayou Meto Water Management District, and White River Irrigation District to target and simulate the expected reductions in groundwater pumping that could result from the adoption of various on-farm conservation practices. The scenario models do not simulate the conservation practices, but only the expected reductions in groundwater pumping from the implementation of the conservation practices. The climate scenarios were chosen from an ensemble of 32 Coupled Model Intercomparison Project Phase 5 (CMIP5) Localized Constructed Analogs downscaled Global Climate Models (GCMs) for the Representative Concentration Pathway 8.5 (RCP8.5; van Vuuren, 2011). A MERAS extent Soil Water Balance (SWB) model simulated recharge and irrigation water use using the 32 CMIP5 downscaled RCP8.5 GCM precipitation and temperature data as direct inputs (Nielson and Westenbroek, 2023; Villers and Ladd, 2023). Those seven GCMs were ccsm4_rcp85, cesm1_bgc_rcp85, cesm1_cam5_rcp85, cmcc_cm_rcp85, cmcc_cms_rcp85, cnrm_cm5_rcp85, mpi_esm_lr_rcp85. The management scenarios included a suite of round 1 and round 2 simulations where round 1 scenarios were developed and run before the round 2 scenarios. Round 1 management scenarios included a global reduction in agricultural groundwater pumping (all crop types: aquaculture, corn, cotton, other crops, rice, and soybean) across the entire Grand Prairie model domain by 10, 20, 30, 40, and 50 percent, respectively. Round 2 scenarios consisted of eight management scenarios that explored the impacts of reductions in groundwater pumping tied to (a) irrigation savings assumed for each of the specific crops grown in 2020 and (b) irrigation savings applied inside and outside of the CGWAs. An additional scenario (scenario 11) specific to the Grand Prairie CGWA investigated how the availability of surface water delivered by the Bayou Meto Water Management Project and Grand Prairie Area Demonstration Project will impact future groundwater levels. For Round 2 scenarios 1-4, 7, 9, and 11, specific crop types, harvest areas, and locations were based on the 2020 USDA NASS cropland data layer (USDA NASS, 2020). The purpose of this data release is to publish the groundwater flow model scenarios for the Grand Prairie region. The calibrated Grand Prairie model from Traylor and others (2024) was used as the base model for each forecast scenario model. Each forecast scenario model was added onto the calibration model for a total simulation period from January 1, 1900 through December 31, 2055 where the forecast scenario period is from January 1, 2019 through December 31, 2055. The forecast scenario period used monthly stress periods. The Grand Prairie region model scenarios in this data release include model inputs and outputs for seven alternate climate scenarios, five separate global groundwater pumping reduction scenarios, and eight specific groundwater pumping reduction scenarios. Scenario construction and results for the Grand Prairie model domain is described in the associated Scientific Investigations Report (Traylor and others, 2026). 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 (Traylor and others, 2024) to understand the purpose, construction, and limitations of this model. The models, along with pre- and post-processing tools, 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 file which can be downloaded as part of this data release. 19000101 20551231 publication date Complete Not planned -92.2045 -91.0127 35.0888 33.9520 ISO 19115 Topic Category geoscientificInformation inlandWaters environment USGS Thesaurus groundwater hydrogeology groundwater flow streamflow groundwater and surface-water interaction water budget None MODFLOW MODFLOW-6 PEST++ usgsgroundwatermodel groundwater model groundwater-flow modeling integrated hydrologic-flow modeling USGS Metadata Identifier USGS:68af0dc2d4be0253bb2c7c68 Common geographic areas Mississippi River Valley alluvial aquifer Mississippi Alluvial Plain Arkansas None. Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from this data release. These groundwater model input and output files are provided to support the analyses documented in the associated report (Traylor and others, 2026). Although the information contained in the model files may be useful for other purposes, it is incumbent on the user to understand the purpose, construction, and limitations of this model. Data have been checked to ensure consistency with the accompanying report. If any errors are detected, please notify the originating office. Central Plains Water Science Center U.S. Geological Survey mailing and physical

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Lincoln NE 68512 USA 402-328-4100 GS-W-CPWSC_DC@usgs.gov Data for the Grand Prairie model came from multiple sources and is described in the model documentation report (Traylor and others, 2026). None Unclassified None Christian D. Langevin Joseph D. Hughes Edward R. Banta Richard G. Niswonger Sorab Panday Alden M. Provost 2017 Publication Techniques and Methods 6-A55 Reston, VA, USA U.S. Geological Survey Detailed description of the model input and output files included in this data release can be found in this model code documentation report. https://doi.org/10.3133/tm6A55 Jonathan P. Traylor Leslie L. Duncan Andrew T. Leaf Alec R. Weisser Benjamin J. Dietsch Moussa Guira 20241108 publication Scientific Investigations Report vol. 2024-5088 https://pubs.usgs.gov US Geological Survey https://doi.org/10.3133/sir20245088 Jonathan P. Traylor Randall J. Hunt Jeremy White Michael N. Fienen 20231207 publication Groundwater vol. 62, issue 1 n/a Wiley ppg. 140-149 https://doi.org/10.1111/gwat.13368 Martha G. Nielsen Stephen, M. Westenbroek 20231222 publication Scientific Investigations Report vol. 2023-5080 https://pubs.usgs.gov US Geological Survey https://doi.org/10.3133/sir20235080 Jessica J Villers David E Ladd 20231222 Dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/p9bc6ub8 Detlef P. van Vuuren Jae Edmonds Mikiko Kainuma Keywan Riahi Allison Thomson Kathy Hibbard George C. Hurtt Tom Kram Volker Krey Jean-Francois Lamarque Toshihiko Masui Malte Meinshausen Nebojsa Nakicenovic Steven J. Smith Steven K. Rose 20110805 publication Climatic Change vol. 109, issue 1-2 n/a Springer Science and Business Media LLC ppg. 5-31 https://doi.org/10.1007/s10584-011-0148-z The Grand Prairie model was calibrated using the PEST++Iterative Ensemble Smoother until an acceptable match between the measured and estimated observations and simulated equivalent value was achieved. The Grand Prairie model was calibrated to 13,787 groundwater and streamflow observations using 30,436 parameters. No formal logical accuracy tests were conducted Data set 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 (Traylor and others, 2026) 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 integrated hydrologic flow model is fully described in the model documentation report (Traylor and others, 2024; Traylor and others, 2026). 2025 Raster Pixel NAD_1983_Contiguous_USA_Albers 29.5 45.5 -96 23.0 0.0 0.0 row and column 500 500 meters North American Vertical Datum of 1988 1 meters Attribute values cache.shp ESRI Polygon shapefile U.S. Geological Survey Area Text string indicating whether or not the polygon area is active or inactive in the model. https://doi.org/10.5066/P9HZWI8S usgsgroundwatermodel Delineation of active and inactive areas in the model. https://doi.org/10.5066/P9HZWI8S This model application data release contains all the model input and output files needed to replicate the simulations described in the associated model documentation report (Traylor and others, 2026) (Traylor and others, 2026) GS ScienceBase U.S. Geological Survey mailing and physical

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Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although the data, software, and related material have been processed successfully on a computer system at the U.S. Geological Survey (USGS), reviewed for accuracy and completeness, and approved for release by 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. 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. 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, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Digital datasets None 23.5 https://doi.org/10.5066/P9HZWI8S None. No fees are applicable for obtaining the dataset. 20260408 Central Plains Water Science Center U.S. Geological Survey Center Director mailing

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Lincoln NE 68512 United States 402-328-4100 GS-W-CPWSC_DC@usgs.gov Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998