This data release contains input data for hydrologic simulations of the Alaska Domain application of the U.S. Geological Survey (USGS) Precipitation Runoff Modelling System (PRMS) as implemented in the National Hydrologic Model (NHM) infrastructure (Regan and others, 2018). The NHM Alaska Domain parameter database consists of 114 parameter files in ASCII format (CSV), two files needed to run the Alaska Domain PRMS (control.fy19deliverable and fy19_deliv.param), two xml files (dimensions.xml and parameters.xml) containing descriptive information about the parameters, and a table that defines each parameter (AK_paramDB_datadictionary.csv). The Entity and Attribute element of this metadata record describe the data dictionary (AK_paramDB_datadictionary.csv). Please refer to the Supplemental Information element of this metadata record for references cited.

This metadata record documents a geospatial dataset for the U.S. Geological Survey Precipitation Runoff Modeling System (PRMS) used to drive the National Hydrologic Model (NHM). The Alaska Geospatial Fabric v1 is the spatial representation of the hydrologic response units (HRUs) used for the PRMS NHM Alaska domain. These HRUs were generated using the twelve-digit Hydrologic Unit Code (HUC12) watershed from the U.S. Geological Survey's Watershed Boundary Dataset (USGS, 2019), the Natural Resources Canada National Hydrographic Network (NHN) Work Units (NHN, 2019), similar to USGS eight-digit HUC watersheds, and stream gage locations from the U.S. Geological Survey (USGS, 2019) and Natural Resources Canada (NHN, 2019). Watershed-to-watershed routing was added to all Canadian Work Units and updated in twelve-digit HUCs from topographic map examination to ensure connectivity from the headwaters of the domain to the ocean. Watersheds containing one or more stream gages were bisected using standard watershed delineation techniques to ensure accurate contributing area for each gage. Gages near watershed boundaries were not used to bisect the watershed. Following these processing steps, these watersheds became the HRUs used for the initial version of the National Hydrologic Model Alaska Domain. Overlapping watershed vector lines were not unified. The stream gages used for this exercise became the points of interest (POIs) for use in the Alaska Domain. Stream segments used to route water from HRUs to stream outlets were generated using the routing information in the HRUs and the centroids of the HRUs. Please refer to the lineage elements of this metadata record for the above citations.

This metadata record documents a geospatial dataset for the U.S. Geological Survey Precipitation Runoff Modeling System (PRMS) used to drive the National Hydrologic Model (NHM). The Alaska Geospatial Fabric v1 is the spatial representation of the hydrologic response units (HRUs) used for the PRMS NHM Alaska domain. These HRUs were generated using the twelve-digit Hydrologic Unit Code (HUC12) watershed from the U.S. Geological Survey's Watershed Boundary Dataset (USGS, 2019), the Natural Resources Canada National Hydrographic Network (NHN) Work Units (NHN, 2019), similar to USGS eight-digit HUC watersheds, and stream gage locations from the U.S. Geological Survey (USGS, 2019) and Natural Resources Canada (NHN, 2019). Watershed-to-watershed routing was added to all Canadian Work Units and updated in twelve-digit HUCs from topographic map examination to ensure connectivity from the headwaters of the domain to the ocean. Watersheds containing one or more stream gages were bisected using standard watershed delineation techniques to ensure accurate contributing area for each gage. Gages near watershed boundaries were not used to bisect the watershed. Following these processing steps, these watersheds became the HRUs used for the initial version of the National Hydrologic Model Alaska Domain. Overlapping watershed vector lines were not unified. The stream gages used for this exercise became the points of interest (POIs) for use in the Alaska Domain. Stream segments used to route water from HRUs to stream outlets were generated using the routing information in the HRUs and the centroids of the HRUs. Please refer to the lineage elements of this metadata record for the above citations.

This data release contains 15 variables from the National Hydrologic Model Infrastructure with the Precipitation-Runoff Modeling System (NHM-PRMS) modeling application forced with Daymet version 4 (Koczot and others, 2025) from January 1980 through December 2021 that are summarized to a monthly time step and a twelve-digit hydrologic unit code for the spatial extent of Alaska. The following fluxes and storages are included: total monthly precipitation, evapotranspiration, lateral flow, surface runoff, interflow, recharge, groundwater flow, and the average monthly snow water equivalent, interflow storage, groundwater storage, total storage, and soil moisture. These data can be found in the “AK_huc12_monthly_nhmprms_daymet_1980_2021.nc” file. Additionally, two supplementary files are also included in this data release. The first file (“AK_weights_hru_to_huc12_nhmprms_daymet.csv”) contains the spatial weights or fraction that is used to “weight” the modeling output in the area-weighting process. The second file (“AK_summed_weights_per_huc12_nhmprms_daymet.csv”) contains the total fractional area within each twelve-digit hydrologic unit code that is covered by the modeling output and is important for filtering results in the data file (where a fractional coverage may be less than one).

This data release contains 15 variables from the National Hydrologic Model Infrastructure with the Precipitation-Runoff Modeling System (NHM-PRMS) version 1.1 modeling application forced with CONUS404-BA (Markstrom and others, 2024) from January 1980 through September 2021 that are summarized to a monthly time step and a twelve-digit hydrologic unit code for the spatial extent of the conterminous United States. The following fluxes and storages are included: total monthly precipitation, evapotranspiration, lateral flow, surface runoff, interflow, recharge, groundwater flow, and the average monthly snow water equivalent, interflow storage, groundwater storage, total storage, and soil moisture. These data can be found in the “huc12_monthly_nhmprms_conus404ba_1980_2021.nc” file. Additionally, two supplementary files are also included in this data release. The first file (“weights_hru_to_huc12_nhmprms_conus404ba.csv”) contains the spatial weights or fraction that is used to “weight” the modeling output in the area-weighting process. The second file (“summed_weights_per_huc12_nhmprms_conus404ba.csv”) contains the total fractional area within each twelve-digit hydrologic unit code that is covered by the modeling output and is important for filtering results in the data file (where a fractional coverage may be less than one).

This work contributes to an understanding of the hydrologic cycle of the State of Alaska, USA, and the part of the Canadian Yukon Territory and British Columbia Province draining into Alaska. For purposes of this study, the domain is simply referred to as “Alaska (AK)". This data release contains inputs for and outputs from hydrologic simulations for the Alaska (AK) 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. Specific file types include: 1) monthly calibration target baselines derived from Global Circulation Model (GCM) simulations (Koczot and others, 2025), 2) map of permanent snow during January 1980 - October 2022 and resulting parameter values of initial snowpack depths, 3) 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, 2022) and input parameter and control files for each release (Bock and others, 2024; Markstrom and others, 2015), 4) output files of simulated water budget components for each hydrologic response unit and stream segment and 5) performance statistics at selected streamgage locations. Figure 1 (Rosa and others, 2025) shows the calibration methodology that was used for the model application (see Hay and others, 2023 for additional information). Figure 2 shows all the HRUs in the geospatial fabric for the AK domain (Bock and others, 2024). Table 1 (Table_1_AK_gages.csv) lists the 279 stream gages that are included in the model application’s streamflow data file (sf_data). A subset of 249 sites were used as calibration targets in the final calibration step, byPOIobs (added after this data release’s first publication, January 10, 2025). The first three 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 files to run the model configurations has also been included. CONTENTS OF THIS PARENT PAGE: 1. Figure 1.png = Schematic of calibration procedure. 2. Figure 2.png = Map of Hydrologic Response Units (HRUs). 3. Table_1_AK_gages.csv = List of Alaska and Canadian streamflow gages and streamflow data provided as part of this modeling application (279 total). 4. control_data_dictionary.csv = Control File parameter and variable definitions. 5. AK_output_variables_data_dictionary.csv = Output variables definitions. 6. parameters_data_dictionary.csv = Parameter definitions. 7. AK_simulated_streamflow_data_dictionary.csv = Streamflow-specific variable definitions. 8 AK_DR_V2_revision_history.txt = Readme to record changes since version 1.0 was published at this same URL (10/1/2025). See Child Items.

This work contributes to an understanding of the hydrologic cycle of the State of Alaska and the part of the Canadian Yukon Territory draining into Alaska. For purposes of this study, the domain is simply referred to as “Alaska (AK)". This data release contains inputs for and outputs from hydrologic simulations for the Alaska (AK) domain using the Precipitation Runoff Modeling System (PRMS) version 5.2.1.1 for the precalibration and byHRU (by Hydrologic Response Unit) 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 to2021. Specific file types include: 1) monthly calibration target baselines derived from Global Circulation Model (GCM) simulations (Koczot and others, 2025), 2) map of permanent snow during January 1980 - October 2022 and resulting parameter values of initial snowpack depths, 3) 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 (Bock and others, 2024; Markstrom and others, 2015), 4) output files of simulated water budget components for each hydrologic response unit and stream segment and 5) performance statistics at selected streamgage locations. Figure 1 (Rosa and others, 2024) shows the calibration methodology that was used for the model application (see Hay and others, 2023 for additional information). Figure 2 (Bock and others, 2024) shows all the HRUs in the geospatial fabric for the AK domain. Table 1 (Table_1_AK_gages.csv) lists the streamgages that are included in the model application. Of the total 287 in this set, 250 will be used as calibration targets in the third and final calibration step (not included in the first publication of this data release). The first three 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 files to run the model configurations has also been included. CONTENTS OF THIS PARENT PAGE: 1. Figure 1.png = Schematic of calibration procedure. 2. Figure 2.png = Map of Hydrologic Response Units (HRUs). 3. Table_1_AK_gages.csv = List of Alaska and Yukon streamflow gages used in this study. 4. control_data_dictionary.csv = Control File parameter and variable definitions. 5. AK_output_variables_data_dictionary.csv = Output variables definitions. 6. parameters_data_dictionary.csv = Parameter definitions. 7. AK_simulated_streamflow_data_dictionary.csv = Streamflow-specific variable definitions. See Child Items.

The Geospatial Fabric for National Hydrologic Modeling (Viger and Bock, 2014; Bock and others, 2020) is a dataset of hydrographic features and spatial data designed for use within the National Hydrologic Model that covers the conterminous United States (CONUS), Hawaii, and most major river basins that flow in from Canada. This U.S. Geological Survey (USGS) data release consists of the geospatial fabric features and other related spatial datasets created to expand the National Hydrologic Model to Alaska. This child item consists of topographic data themes that cover the Geospatial Fabric for National Hydrologic Modeling, Alaska Domain. The 30-meter (m) raster datasets included under Topographic Derivatives are: digital elevation (dem.tif), topographic wetness index (TWI, twiX100.tif), slope (rise over run, slope.tif), aspect (asp.tif), flow accumulation (fac.tif), and flow direction (fdr.tif). All file formats are in GeoTIFF (Geographic Tagged Imaged Format), and are sourced from NHDPlus Version 2.0 raster layers (Environmental Protection Agency, 2019)

The Geospatial Fabric for National Hydrologic Modeling (Viger and Bock, 2014; Bock and others, 2020) is a dataset of hydrographic features and spatial data designed for use within the National Hydrologic Model that covers the conterminous United States (CONUS), Hawaii, and most major river basins that flow in from Canada. This U.S. Geological Survey (USGS) data release consists of the geospatial fabric features and other related spatial datasets created to expand the National Hydrologic Model to Alaska. This child item consists of topographic data themes that cover the Geospatial Fabric for National Hydrologic Modeling, Alaska Domain. The 30-meter (m) raster datasets included under Topographic Derivatives are: digital elevation (dem.tif), topographic wetness index (TWI, twiX100.tif), slope (rise over run, slope.tif), aspect (asp.tif), flow accumulation (fac.tif), and flow direction (fdr.tif). All file formats are in GeoTIFF (Geographic Tagged Imaged Format), and are sourced from NHDPlus Version 2.0 raster layers (Environmental Protection Agency, 2019)

The Geospatial Fabric for National Hydrologic Modeling (Viger and Bock, 2014; Bock and others, 2021) is a dataset of hydrographic features and spatial data for use within the National Hydrologic Model that covers the conterminous United States (CONUS), Hawaii, and most major river basins that flow in from Canada. This U.S. Geological Survey (USGS) data release consists of the geospatial fabric features and other related spatial datasets created to expand the National Hydrologic Model to Alaska. The National Hydrologic Model database contains parameters for hydrologic response units (HRUs) and stream segments needed to run the NHM. These parameters are generated using python scripts to process input datasets such as digital elevation models, soil maps, and land cover classifications. Many of the parameters were left at their default model value as they would need to be calibrated as part of the PRMS model development process. Please refer to the Supplemental Information and the Process Description elements of this metadata record for more details on the source datasets and scripts used to generate these parameters.