Groundwater flow model for the island of Oahu. Data is from the following sources: Rotzoll, K., A.I. El-Kadi. 2007. Numerical Ground-Water Flow Simulation for Red Hill Fuel Storage Facilities, NAVFAC Pacific, Oahu, Hawaii - Prepared TEC, Inc. Water Resources Research Center, University of Hawaii, Honolulu.; Whittier, R.B., K. Rotzoll, S. Dhal, A.I. El-Kadi, C. Ray, G. Chen, and D. Chang. 2004. Hawaii Source Water Assessment Program Report - Volume VII - Island of Oahu Source Water Assessment Program Report. Prepared for the Hawaii Department of Health, Safe Drinking Water Branch. University of Hawaii, Water Resources Research Center. Updated 2008.; and Whittier, R. and A.I. El-Kadi. 2009. Human and Environmental Risk Ranking of Onsite Sewage Disposal Systems - Final. Prepared by the University of Hawaii, Dept. of Geology and Geophysics for the State of Hawaii Dept. of Health, Safe Drinking Water Branch. December 2009.

Groundwater flow model for Hawaii Island. Data is from the following sources: Whittier, R.B., K. Rotzoll, S. Dhal, A.I. El-Kadi, C. Ray, G. Chen, and D. Chang. 2004. Hawaii Source Water Assessment Program Report - Volume II - Island of Hawaii Source Water Assessment Program Report. Prepared for the Hawaii Department of Health, Safe Drinking Water Branch. University of Hawaii, Water Resources Research Center. Updated 2008; and Whittier, R. and A.I. El-Kadi. 2014. Human and Environmental Risk Ranking of Onsite Sewage Disposal Systems For the Hawaiian Islands of Kauai, Molokai, Maui, and Hawaii - Final. Prepared by the University of Hawaii, Dept. of Geology and Geophysics for the State of Hawaii Dept. of Health, Safe Drinking Water Branch. September 2014.

This shapefile represents the spatial distribution of mean annual groundwater recharge, in inches, for Oʻahu, Hawaiʻi for a set of drought and land-cover conditions represented in six water-budget scenarios. The six scenarios include: (1) historical drought rainfall and 2020 land cover, (2) future drought rainfall and 2020 land cover, (3) historical drought rainfall and Conversion 1 land cover, (4) future drought rainfall and Conversion 1 land cover, (5) historical drought rainfall and Conversion 2 land cover, and (6) future drought rainfall and Conversion 2 land cover. Historical drought rainfall is monthly rainfall during 1998–2002 from Frazier and others (2016), whereas future drought rainfall is monthly rainfall during 1998–2002 from Frazier and others (2016) adjusted for a Representative Concentration Pathway 8.5 2071–99 (RCP8.5 2071–99) projection from Elison Timm and others (2015). Monthly rainfall for historical and future drought conditions was disaggregated into daily values using daily rainfall during 1998–2002 from Longman and others (2019). A 2020 land-cover map developed by Kāne and others (2024a, 2024b) was used to define the land-cover conditions and the model subareas. Conversion 1 land cover is a hypothetical land-cover condition in which roughly 50 percent of forest and shrubland areas within the cloud zone are converted to grassland. Conversion 2 land cover is a hypothetical land-cover condition in which 100 percent of forest and shrubland areas within the cloud zone are converted to grassland. Groundwater recharge for each model subarea was computed for each scenario using a water-budget model developed by Oki (2022). The shapefile attribute information associated with each subarea present an estimate of mean annual groundwater recharge, and select geographic and land-cover attributes. Brief descriptions of the groundwater recharge estimates and attributes are included in this metadata file. Refer to Mair and others (2024) for further details of the methods and sources used to determine groundwater recharge and the attributes.

This shapefile represents the spatial distribution of mean annual groundwater recharge, in inches, for Oʻahu, Hawaiʻi for a set of drought and land-cover conditions represented in six water-budget scenarios. The six scenarios include: (1) historical drought rainfall and 2020 land cover, (2) future drought rainfall and 2020 land cover, (3) historical drought rainfall and Conversion 1 land cover, (4) future drought rainfall and Conversion 1 land cover, (5) historical drought rainfall and Conversion 2 land cover, and (6) future drought rainfall and Conversion 2 land cover. Historical drought rainfall is monthly rainfall during 1998–2002 from Frazier and others (2016), whereas future drought rainfall is monthly rainfall during 1998–2002 from Frazier and others (2016) adjusted for a Representative Concentration Pathway 8.5 2071–99 (RCP8.5 2071–99) projection from Elison Timm and others (2015). Monthly rainfall for historical and future drought conditions was disaggregated into daily values using daily rainfall during 1998–2002 from Longman and others (2019). A 2020 land-cover map developed by Kāne and others (2024a, 2024b) was used to define the land-cover conditions and the model subareas. Conversion 1 land cover is a hypothetical land-cover condition in which roughly 50 percent of forest and shrubland areas within the cloud zone are converted to grassland. Conversion 2 land cover is a hypothetical land-cover condition in which 100 percent of forest and shrubland areas within the cloud zone are converted to grassland. Groundwater recharge for each model subarea was computed for each scenario using a water-budget model developed by Oki (2022). The shapefile attribute information associated with each subarea present an estimate of mean annual groundwater recharge, and select geographic and land-cover attributes. Brief descriptions of the groundwater recharge estimates and attributes are included in this metadata file. Refer to Mair and others (2024) for further details of the methods and sources used to determine groundwater recharge and the attributes.

This data release contains inputs for and outputs from hydrologic simulations for the Hawai‘i (HI) domain using the Precipitation Runoff Modeling System (PRMS) version 5.2.1.1 for the precalibration, by Hydrologic Response Unit (byHRU) release, and by Point Of Interest Observation (byPOIobs) release using the USGS National Hydrologic Model infrastructure (NHM; Regan and others, 2018). These simulations were developed to provide estimates of the water budget for the calendar-year period 1980 to 2021, where the first two years are used for model initialization. Specific file types include: 1) input atmospheric forcings of minimum air temperature, maximum air temperature, and daily precipitation accumulation derived from Daymet Version 4 gridded estimates of daily weather parameters (Thornton and others, 2020) and input parameter and control files for each release (Markstrom and others, 2015), 2) monthly calibration target baselines derived from Global Circulation Model (GCM) simulations (Koczot and others, 2025) that were used in addition to USGS measured streamflow, 3) output files of simulated water budget components for each hydrologic response unit and stream segment and 4) performance statistics at selected streamgage locations. Figure 1 shows the calibration methodology that was used for the model application (see Hay and others, 2023 for additional information). Figure 2 shows all the HRUSs in the geospatial fabric for the HI domain (Bock and others, 2024). Table 1 lists the streamgages that are included in the model application. The first two years of the simulations are considered 'model initialization' and should not be included in any subsequent analysis. The executable used for these simulations may be downloaded from https://www.usgs.gov/software/precipitation-runoff-modeling-system-prms (version 5.2.1.1). A batch file to run the model has also been included.

This data release contains inputs for and outputs from hydrologic simulations for the Hawai‘i (HI) domain using the Precipitation Runoff Modeling System (PRMS) version 5.2.1.1 for the precalibration, by Hydrologic Response Unit (byHRU) release, and by Point Of Interest Observation (byPOIobs) release using the USGS National Hydrologic Model infrastructure (NHM; Regan and others, 2018). These simulations were developed to provide estimates of the water budget for the calendar-year period 1980 to 2021, where the first two years are used for model initialization. Specific file types include: 1) input atmospheric forcings of minimum air temperature, maximum air temperature, and daily precipitation accumulation derived from Daymet Version 4 gridded estimates of daily weather parameters (Thornton and others, 2020) and input parameter and control files for each release (Markstrom and others, 2015), 2) monthly calibration target baselines derived from Global Circulation Model (GCM) simulations (Koczot and others, 2025) that were used in addition to USGS measured streamflow, 3) output files of simulated water budget components for each hydrologic response unit and stream segment and 4) performance statistics at selected streamgage locations. Figure 1 shows the calibration methodology that was used for the model application (see Hay and others, 2023 for additional information). Figure 2 shows all the HRUSs in the geospatial fabric for the HI domain (Bock and others, 2024). Table 1 lists the streamgages that are included in the model application. The first two years of the simulations are considered 'model initialization' and should not be included in any subsequent analysis. The executable used for these simulations may be downloaded from https://www.usgs.gov/software/precipitation-runoff-modeling-system-prms (version 5.2.1.1). A batch file to run the model has also been included.

Groundwater geochemistry data collected for the phase 2 of the Hawaii Play Fairway Analyses. These data are included in a Lautze et al. paper to Geothermics (in review).

This data release contains inputs for and outputs from hydrologic simulations for the Hawai‘i (HI) domain using the Precipitation Runoff Modeling System (PRMS) version 5.2.1.1 and the USGS National Hydrologic Model infrastructure (NHM, Regan and others, 2018). Simulated streamflow stored in this child item (NHM-PRMS_data_release.nc) and statistics at streamgages (gage_stats_gm.csv) are provided for one pre-calibration and two calibration configurations (byHRU, and byPOIobs). The streamgage statistics file provides the Nash-Sutcliffe Efficiency Index between observed and simulated streamflow using daily, log of daily, monthly, and log of monthly values along with the bias, and drainage area for the model and streamgage for each Point-of-Interest (POI) in the simulation. The simulated streamflow file contains simulated and observed streamflow values for each POI in the simulation for 1980-2021. The main landing page provides additional information about the calibrations and a data dictionary (simulated_streamflow_data_dictionary.csv) which describes the simulated streamflow variables. CONTENTS OF THIS CHILD PAGE: 1. HI_stats_precalibration.zip = Folder containing simulated streamflow and statistics at streamgages from the precalibration release run for the HI domain. 2. HI_stats_byHRU.zip = Folder containing simulated streamflow and statistics at streamgages from the byHRU release run for the HI domain. 3. HI_stats_byPOIobs.zip = Folder containing simulated streamflow and statistics at streamgages from the byPOIobs release run for the HI domain.

This data release contains inputs for and outputs from hydrologic simulations for the Hawai‘i (HI) domain using the Precipitation Runoff Modeling System (PRMS) version 5.2.1.1 and the USGS National Hydrologic Model infrastructure (NHM, Regan and others, 2018). Simulated streamflow stored in this child item (NHM-PRMS_data_release.nc) and statistics at streamgages (gage_stats_gm.csv) are provided for one pre-calibration and two calibration configurations (byHRU, and byPOIobs). The streamgage statistics file provides the Nash-Sutcliffe Efficiency Index between observed and simulated streamflow using daily, log of daily, monthly, and log of monthly values along with the bias, and drainage area for the model and streamgage for each Point-of-Interest (POI) in the simulation. The simulated streamflow file contains simulated and observed streamflow values for each POI in the simulation for 1980-2021. The main landing page provides additional information about the calibrations and a data dictionary (simulated_streamflow_data_dictionary.csv) which describes the simulated streamflow variables. CONTENTS OF THIS CHILD PAGE: 1. HI_stats_precalibration.zip = Folder containing simulated streamflow and statistics at streamgages from the precalibration release run for the HI domain. 2. HI_stats_byHRU.zip = Folder containing simulated streamflow and statistics at streamgages from the byHRU release run for the HI domain. 3. HI_stats_byPOIobs.zip = Folder containing simulated streamflow and statistics at streamgages from the byPOIobs release run for the HI domain.

Previously constructed steady-state numerical groundwater-flow models for the islands of Kauai, Oahu, and Maui, Hawaii (https://doi.org/10.3133/sir20205126) using MODFLOW-2005 with the Seawater Intrusion (SWI2) package, were used to examine the consequences of historical and plausible future withdrawals and changes in recharge. The volcanic aquifers of the Hawaiian Islands supply water to 1.46 million residents, diverse industries, and a large component of the U.S. military in the Pacific. Groundwater also supplies freshwater that supports ecosystems in streams and near the coast. Hawaii’s aquifers are remarkable given their small size, but the islands’ capacity to store fresh groundwater is limited because each island is surrounded by seawater, and saltwater underlies much of the fresh groundwater. The amount of fresh groundwater available for human use from Hawaii’s volcanic aquifers is constrained by the consequences of groundwater withdrawal. Restrictions placed on these consequences can translate to limitations on groundwater availability. Changes in recharge resulting from changes in land cover or climate can alter the effect of withdrawals. Therefore, five scenarios representing current conditions and various historical and projected future groundwater-withdrawal and recharge conditions were simulated using the previously published numerical models. The Current scenario represents conditions in 2010 which were used to calibrate the Kauai, Oahu, and Maui models. This scenario is the baseline to which all other scenarios are compared. Two historical scenarios (No Withdrawal and Predevelopment) represent selected aspects of conditions that existed in 1870, before the first modern well was drilled in 1879; these scenarios were simulated using all three models in this study. Two future scenarios (Future Rainfall and Increased Withdrawal) represent projections of future conditions and were simulated using the Oahu model only. Results of the simulations using the groundwater models of the islands of Kauai, Oahu, and Maui have implications for other islands in Hawaii. Results of the simulations enable quantification of the hydrologic effects of withdrawals and changes in climate, such as water-table depression, saltwater rise, and reduction of natural groundwater discharge to streams, springs, and the ocean. The effects can place limits on groundwater availability. 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/pp1876).