This file contains hydrologic unit boundaries and codes for the conterminous United States along with Alaska, Hawaii, Puerto Rico and the U.S. Virgin Islands. It was revised for inclusion in the National Atlas of the United States of America, and updated to match the streams file created by the USGS National Mapping Division (NMD) for the National Atlas of the United States of America. For the most current data and information relating to hydrologic unit codes (HUCs) please see http://water.usgs.gov/GIS/huc.html. The Watershed Boundary Dataset (WBD) is the most current data available for watershed delineation. See http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/water/watersheds/dataset

This data set has been superseded by huc2m. This file contains hydrologic unit boundaries and codes for the conterminous United States along with Alaska, Hawaii, Puerto Rico and the U.S. Virgin Islands. It was revised for inclusion in the National Atlas of the United States of America, and updated to match the streams file created by the USGS National Mapping Division (NMD) for the National Atlas of the United States of America. For the most current data and information relating to hydrologic unit codes (HUCs) please see http://water.usgs.gov/GIS/huc.html. The Watershed Boundary Dataset (WBD) is the most current data available for watershed delineation. See http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/water/watersheds/dataset

This data set has been superseded by huc2m. This file contains hydrologic unit boundaries and codes for the conterminous United States along with Alaska, Hawaii, Puerto Rico and the U.S. Virgin Islands. It was revised for inclusion in the National Atlas of the United States of America, and updated to match the streams file created by the USGS National Mapping Division (NMD) for the National Atlas of the United States of America. For the most current data and information relating to hydrologic unit codes (HUCs) please see http://water.usgs.gov/GIS/huc.html. The Watershed Boundary Dataset (WBD) is the most current data available for watershed delineation. See http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/water/watersheds/dataset

The Geographic Information Retrieval and Analysis System (GIRAS) was developed in the mid 70s to put into digital form a number of data layers which were of interest to the USGS. One of these data layers was the Hydrologic Units. The map is based on the Hydrologic Unit Maps published by the U.S. Geological Survey Office of Water Data Coordination, together with the list descriptions and name of region, subregion, accounting units, and cataloging unit. The hydrologic units are encoded with an eight- digit number that indicates the hydrologic region (first two digits), hydrologic subregion (second two digits), accounting unit (third two digits), and cataloging unit (fourth two digits). The data produced by GIRAS was originally collected at a scale of 1:250K. Some areas, notably major cities in the west, were recompiled at a scale of 1:100K. In order to join the data together and use the data in a geographic information system (GIS) the data were processed in the ARC/INFO GUS software package. Within the GIS, the data were edgematched and the neatline boundaries between maps were removed to create a single data set for the conterminous United States. NOTE: A version of this data theme that is more throughly checked (though based on smaller-scale maps) is available here: https://water.usgs.gov/lookup/getspatial?huc2m HUC, GIRAS, Hydrologic Units, 1:250 For the most current data and information relating to hydrologic unit codes (HUCs) please see http://water.usgs.gov/GIS/huc.html. The Watershed Boundary Dataset (WBD) is the most current data available for watershed delineation. See http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/water/watersheds/dataset

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 is a dataset of spatial modeling units for use within the National Hydrologic Model that covers Alaska, 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 datasets created to expand the National Hydrologic Model to Alaska. This U.S. Geological Survey (USGS) child item consists of 17 different spatial layers in GeoTIFF format for Alaska. They are 1) average water capacity (awc.zip), 2) percent sand (sand.zip), 3) percent silt (silt.zip), 4) percent clay (clay.zip), 5) soil texture (TEXT_PRMS.zip), 6) land use/land cover (LULC.zip), 7) snow values (snow.zip), 8) summer rain values (SRain.zip), 9) winter rain values (WRain.zip), 10) leaf presence values (keep.zip), 11) leaf loss values (loss.zip), 12) percent tree canopy (CNPY.zip), 13) percent impervious surface (imperv.zip), 14) snow depletion curve numbers (CV_INT.zip), 15) rooting depth (RootDepth.zip), 16) permeability values (Lithology_exp_Konly_Project.zip), and 17) water bodies (wbg.zip). All data cover the National Hydrologic Model's (NHM) Alaskan domain. The 250-meter (m) raster datasets for soils (in sand.zip, silt.zip, clay.zip, TEXT_PRMS.zip) are derived from the Zonodo data (Hengl, 2018). The 30-meter raster of land use and land cover data are a simplified re-classification version of the North American Land-Change Monitoring System (NALCMS, Latifovic and others, 2012) data following the guidance and crosswalk table (crosswalk.csv) in Viger and Leavesley (2007). This layer was used to derive rasters representing dominant vegetative cover type, snow, summer and winter rain interception values, leaf cover and loss, and rooting depth. The impervious data were compiled from the Global Man-made Impervious Surface (GMIS) Dataset from Landsat, v1 (Brown de Colstoun, 2010). The tree canopy data were compiled from MOD44B MODIS/Terra Vegetation Continuous Fields Yearly L3 Global 250m SIN Grid V006, (Sexton and others, 2013). The snow depletion data was compiled from data by Liston (2009) and further processed using methods provided in a snow depletion table (SDC_table.csv) by Sexstone and others (2020). All file formats are in GeoTIFF (Geograhpic Tagged Imaged Format).

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 dataset contains 474 drainage basin boundaries for U.S. Geological Survey (USGS) streamgages in Alaska, including supplemental drainage basin boundaries for alternate conditions for 3 of the 471 streamgages. The basin boundaries were delineated from the streamgage location to the nearest USGS Watershed Boundary Dataset (WBD) HUC boundary and along HUC boundaries from that intersection to the basin headwaters. The dataset also includes the streamgage locations used for delineation, which consist of points snapped from the streamgage coordinates in the USGS National Water Information System to the USGS National Hydrography Dataset flowline representing the respective streams. Streamgages selected for drainage basin delineation included: (1) streamgages having at least 10 years of peak-streamflow data through water year 2012, used for a statewide flood frequency study (Curran and others, 2016), and (2) streamgages in Cook Inlet Basin, regardless of record length, used for development of Cook Inlet Basin Streamstats in 2016 (https://streamstats.usgs.gov/ss/). For three streamgages, a supplemental drainage basin boundary was delineated for the drainage area associated with regulated (diverted) streamflow conditions contemporaneous with a period of streamflow record other than the present. Selected basins were previously published in the WBD as "NWISDrainageArea" features.

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. These datasets are found as child items to this landing page: 1) Data Layers for the Geospatial Fabric for National Hydrologic Modeling, Alaska Domain, 2) GIS (Geographic Information Systems) Features of the Geospatial Fabric for National Hydrologic Modeling, Alaska Domain, 3) Parameter Database for the National Hydrologic Modeling, Alaska Domain, and 4) Topographic derivative datasets for the Geospatial Fabric for National Hydrologic Modeling, Alaska Domain. See each item for more details.

This data release contains fractional intersectional weights used to crosswalk data from the National Water Use Program to the National Integrated Water Availability Assessment (IWAAs) projects. The Watershed Boundary Dataset (WBD; https://www.usgs.gov/national-hydrography/watershed-boundary-dataset) is a companion dataset to the National Hydrography Dataset and contains polygons that define the spatial boundaries of hydrologic units (i.e., the area of land the landscape that drains into a portion of the stream network). These are periodically updated as these boundary definitions are refined by incorporating better, more localized data. When aggregating data from multiple sources that rely on data from the WBD, a situation can occur where different datasets rely on different versions (or “snapshots”) of the WBD. This was the case for the IWAAs National Report which relied upon data using a version of the WBD found in the Mainstem Rivers data release (https://doi.org/10.5066/P92U7ZUT) as well as data that relied upon a version used by the National Water Use Program (https://doi.org/10.5066/P9FUL880). This dataset is the output of a pipeline of R code published as a software release (https://doi.org/10.5066/P1UANON8) and contains the fraction of spatial overlap (i.e., weights) between the subwatershed (HUC12) boundaries from these two versions of the WBD. These weights can be used as a crosswalk between the two snapshots of the WBD.