Alaska National Hydrologic Model (NHM) application,1980 - 2021 (ver. 2.0, September 2025)

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.

Tags: alaska, british-columbia-province, canada, hydrologic-processes, hydrology, inlandwaters, mathematical-modeling, streamflow, usgs-64a84670d34e70357a27dd86, water-resources, yukon, yukon-territory
Organization: Department of the Interior