The United States is divided and sub-divided into successively smaller hydrologic units which are classified into four levels: regions, subregions, accounting units, and cataloging units. The hydrologic units are arranged or nested within each other, from the largest geographic area (regions) to the smallest geographic area (cataloging units). Each hydrologic unit is identified by a unique hydrologic unit code (HUC) consisting of two to eight digits based on the four levels of classification in the hydrologic unit system. The intent of defining Hydrologic Units (HU) within the Watershed Boundary Dataset is to establish a base-line drainage boundary framework, accounting for all land and surface areas. Hydrologic units are intended to be used as a tool for water-resource management and planning activities particularly for site-specific and localized studies requiring a level of detail provided by large-scale map information. The WBD complements the National Hydrography Dataset (NHD) and supports numerous programmatic missions and activities including: watershed management, rehabilitation and enhancement, aquatic species conservation strategies, flood plain management and flood prevention, water-quality initiatives and programs, dam safety programs, fire assessment and management, resource inventory and assessment, water data analysis and water census. The Watershed Boundary Dataset (WBD) is a comprehensive aggregated collection of hydrologic unit data consistent with the national criteria for delineation and resolution. It defines the areal extent of surface water drainage to a point except in coastal or lake front areas where there could be multiple outlets as stated by the "Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD)" "Standard" (http://pubs.usgs.gov/tm/11/a3/). Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. This dataset represents the hydrologic unit boundaries to the 12-digit (6th level) for the entire United States. Some areas may also include additional subdivisions representing the 14- and 16-digit hydrologic unit (HU). At a minimum, the HUs are delineated at 1:24,000-scale in the conterminous United States, 1:25,000-scale in Hawaii, Pacific basin and the Caribbean, and 1:63,360-scale in Alaska, meeting the National Map Accuracy Standards (NMAS). Higher resolution boundaries are being developed where partners and data exist and will be incorporated back into the WBD. WBD data are delivered as a dataset of polygons and corresponding lines that define the boundary of the polygon. WBD polygon attributes include hydrologic unit codes (HUC), size (in the form of acres and square kilometers), name, downstream hydrologic unit code, type of watershed, non-contributing areas, and flow modifications. The HUC describes where the unit is in the country and the level of the unit. WBD line attributes contain the highest level of hydrologic unit for each boundary, line source information and flow modifications.View Dataset on the Gateway

This child item provides a snapshot of the watershed boundary dataset which consists of a shapefile with 87,020 12-digit hydrologic unit codes (HUC12) for the conterminous United States retrieved 10/26/2020. The National Watershed Boundary Dataset (WBD) is a comprehensive set of digital spatial data that represents the surface drainages areas of the United States. Although versions of the WBD are published as part of U.S. Geological Survey National Hydrography Products, the version used to produce the water-use reanalysis was not archived and is provided here. This dataset is part of a larger data release using machine learning to predict public supply water use for 12-digit hydrologic units from 2000-2020. Public-supply water use estimates for the HUC12s included in this shapefile are provided on the data release main landing page and on the public supply water use machine learning model child item. This page includes the following file: WBD_HUC12_CONUS_pulled10262020.zip - a zi ...

The Watersheds Hydrologic Unit 12 (HUC12) dataset used in the CA Nature Biodiversity Explorer was taken from the National Watershed Boundary (WBD) Dataset published as part of the National Hydrography Dataset (NHD), developed and maintained by the US Geological Survey. The watersheds are clipped to the California boundary.This version of the WBD for California was downloaded from the NHD prior to 2018 by the California Department of Fish and Wildlife for use in the Areas of Conservation Emphasis (ACE) project, which is a basis of much of the data in the Biodiversity Explorer. Therefore, this HUC12 dataset may not be up to date with the most recent official release from the NHD/WBD.For additional information on the WBD, go to https://www.usgs.gov/core-science-systems/ngp/national-hydrography/watershed-boundary-dataset.

The Watershed Boundary Dataset (WBD) is a seamless, national hydrologic unit dataset. Simply put, hydrologic units represent the area of the landscape that drains to a portion of the stream network. More specifically, a hydrologic unit defines the areal extent of surface water drainage to an outlet point on a dendritic stream network or to multiple outlet points where the stream network is not dendritic. A hydrologic unit may represent all or only part of the total drainage area to an outlet point so that multiple hydrologic units may be required to define the entire drainage area at a given outlet. Hydrologic unit boundaries in the WBD are determined based on topographic, hydrologic, and other relevant landscape characteristics without regard for administrative, political, or jurisdictional boundaries. The WBD seamlessly represents hydrologic units at six required and two optional hierarchical levels.The hydrologic units (HU) in the WBD form a standardized system for organizing, collecting, managing, and reporting hydrologic information for the nation. The HU in the WBD are arranged in a nested, hierarchical system with each HU in the system identified using a unique code. Hydrologic unit codes (HUC) are developed using a progressive two-digit system where each successively smaller areal unit is identified by adding two digits to the identifying code the smaller unit is nested within. WBD contains eight levels of progressive hydrologic units identified by unique 2- to 16-digit codes. The dataset is complete for the United States to the 12-digit hydrologic unit. The 14- and 16-digit hydrologic units are optional and are not complete for the nation. Efforts are ongoing to complete 10- and 12-digit unit delineations within 8-digit hydrologic units extending across the U.S. – Canada border. Additional information about this effort and access to data is linked on the “resources” section on this page. A similar effort is complete for the 10- and 12-digit units extending across the U.S. – Mexico border.More information can be found here: https://www.usgs.gov/core-science-systems/ngp/national-hydrography/watershed-boundary-dataset?qt-science_support_page_related_con=4#qt-science_support_page_related_con

The Watershed Boundary Dataset (WBD) is a comprehensive aggregated collection of hydrologic unit data consistent with the national criteria for delineation and resolution. It defines the areal extent of surface water drainage to a point except in coastal or lake front areas where there could be multiple outlets as stated by the "Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD)" “Standard” (http://pubs.usgs.gov/tm/11/a3/). Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. This dataset represents the hydrologic unit boundaries to the 12-digit (6th level) for the entire United States. Some areas may also include additional subdivisions representing the 14- and 16-digit hydrologic unit (HU). At a minimum, the HUs are delineated at 1:24,000-scale in the conterminous United States, 1:25,000-scale in Hawaii, Pacific basin and the Caribbean, and 1:63,360-scale in Alaska, meeting the National Map Accuracy Standards (NMAS). Higher resolution boundaries are being developed where partners and data exist and will be incorporated back into the WBD. WBD data are delivered as a dataset of polygons and corresponding lines that define the boundary of the polygon. WBD polygon attributes include hydrologic unit codes (HUC), size (in the form of acres and square kilometers), name, downstream hydrologic unit code, type of watershed, non-contributing areas, and flow modifications. The HUC describes where the unit is in the country and the level of the unit. WBD line attributes contain the highest level of hydrologic unit for each boundary, line source information and flow modifications.

The latest 12-Digit HUC boundaries, along with the calculated US Census population within each subwatershed area. HUC boundaries are from the USGS National Hydrography Watershed Boundary Dataset. US Census 2020, 2010, and 2000 Block Data was acquired through NC OneMap.Subwatershed population estimates were derived from the 2020, 2010, and 2000 Block population data from the US Census. The ArcGIS Tool "Summarize Within" was used to calculate the total population within each subwatershed for each census period. As census blocks and subwatershed boundaries do not always coincide, the calculated population is only an estimate and is not to be used as an exact figure.

The Watershed Boundary Dataset (WBD) is a comprehensive aggregated collection of hydrologic unit data consistent with the national criteria for delineation and resolution. It defines the areal extent of surface water drainage to a point except in coastal or lake front areas where there could be multiple outlets as stated by the "Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD)" “Standard” (http://pubs.usgs.gov/tm/11/a3/). Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. This dataset represents the hydrologic unit boundaries to the 12-digit (6th level) for the entire United States. Some areas may also include additional subdivisions representing the 14- and 16-digit hydrologic unit (HU). At a minimum, the HUs are delineated at 1:24,000-scale in the conterminous United States, 1:25,000-scale in Hawaii, Pacific basin and the Caribbean, and 1:63,360-scale in Alaska, meeting the National Map Accuracy Standards (NMAS). Higher resolution boundaries are being developed where partners and data exist and will be incorporated back into the WBD. WBD data are delivered as a dataset of polygons and corresponding lines that define the boundary of the polygon. WBD polygon attributes include hydrologic unit codes (HUC), size (in the form of acres and square kilometers), name, downstream hydrologic unit code, type of watershed, non-contributing areas, and flow modifications. The HUC describes where the unit is in the country and the level of the unit. WBD line attributes contain the highest level of hydrologic unit for each boundary, line source information and flow modifications.

This dataset is the digital hydrologic unit boundary layer for the 8-digit subwatershed boundaries for the conterminous United States. This dataset is intended to be used with the following two tabular dBase files: https://water.usgs.gov/lookup/getspatial?ds573_tillage_lu92e and https://water.usgs.gov/lookup/getspatial?ds573_tillage_lu01. The two tabular datasets contain the Tillage Practices in the Conterminous United States, 1989-2004---Datasets Aggregated by Watershed. This dataset and the two tabular datasets can be linked using the common attribute HUC8_N. Information about how the tabular data and geospatial data can be related are given in the data series report: https://pubs.usgs.gov/ds/ds573/ .The original dataset is the 12-digit Subwatershed boundaries (WBD_archive_17nov2009_9.2_file). The 12-digit boundaries were dissolved to 8-digit boundaries to be used with the two tabular .dbase data files containing the tillage practice data for the United States.

     ORIGINAL METADATA: This data set is a complete digital hydrologic unit boundary layer to the Subwatershed (12-digit) 6th level for the entire United States. This data set consists of geo-referenced digital data and associated attributes created in accordance with the "Federal Guidelines, Requirements, and Procedures for the National Watershed Boundary Dataset; Chapter 3 of Section A, Federal Standards, Book 11, Collection and Delineation of Spatial Data; Techniques and Methods 11-A3" (04/01/2009). http://www.ncgc.nrcs.usda.gov/products/datasets/watershed/index.html . Polygons are attributed with hydrologic unit codes for 4th level sub-basins, 5th level watersheds, 6th level subwatersheds, name, size, downstream hydrologic unit, type of watershed, non-contributing areas and flow modification.

The Watershed Boundary Dataset (WBD) is a comprehensive aggregated collection of hydrologic unit data consistent with the national criteria for delineation and resolution. It defines the areal extent of surface water drainage to a point except in coastal or lake front areas where there could be multiple outlets as stated by the "Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD)" "Standard" (https://pubs.usgs.gov/tm/11/a3/). Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. This dataset represents the hydrologic unit boundaries to the 12-digit for the entire United States. Some areas may also include additional subdivisions representing the 14- and 16-digit hydrologic unit (HU). At a minimum, the HUs are delineated at 1:24,000-scale in the conterminous United States, 1:25,000-scale in Hawaii, Pacific basin and the Caribbean, and 1:63,360-scale in Alaska, meeting the National Map Accuracy Standards (NMAS). Higher resolution boundaries are being developed where partners and data exist and will be incorporated back into the WBD. WBD data are delivered as a dataset of polygons and corresponding lines that define the boundary of the polygon. WBD polygon attributes include hydrologic unit codes (HUC), size (in the form of acres and square kilometers), name, downstream hydrologic unit code, type of watershed, non-contributing areas, and flow modifications. The HUC describes where the unit is in the country and the level of the unit. WBD line attributes contain the highest level of hydrologic unit for each boundary, line source information and flow modifications. For additional information on NHD, go to https://www.usgs.gov/national-hydrography.

This dataset summarizes impairment status for HUC12 watersheds at the CONUS scale using the EPA publicly available Assessment, Total Maximum Daily Load (TMDL) Tracking and Implementation System (ATTAINS) geospatial package and the USGS Watershed Boundary Dataset (WBD). ATTAINS is an online system maintained by the EPA containing information about the condition of the Nation’s surface waters, as reported by individual states. These data were downloaded in October 2023 and primarily reflect 2022 stream conditions. Because of the varying data types that exist in the database, an independent methodology was developed for summarizing impairment status for HUC12 watersheds using the USGS WBD as detailed in this metadata record. These process steps ensured consistency, standardization, and transparency of various spatial attributes. HUC12 watersheds flagged as “Impaired” indicate there are impaired waters within the HUC12 watershed, but does not imply all waters within the HUC12 are listed as impaired. A supplemental table indicating the cause of impairment at the HUC12 scale, where known, is also provided.

Narragansett Bay, Little Narragansett Bay, and the Southwest Coastal Ponds are the three estuarine study areas under the purview of the Narragansett Bay Estuary Program. This dataset represents the 12-digit hydrologic units (HUC12) that drain, directly and indirectly, to the three estuaries. HUC12 drainage areas were sourced from the U.S. Geological Survey (USGS) Watershed Boundary Dataset (WBD) which contains a nested, hierarchical system of hydrologic units. Hydrologic units define the boundaries of surface water drainage to a given set of outlet points or a dendritic stream network. The boundaries are determined by topographic, hydrologic, and other relevant landscape characteristics. Within the Little Narragansett Bay watershed, NBEP delineated the drainage area for the western portion of Little Narragansett Bay. This area, “Part of Southeast Coastal-Pawcatuck River to Eastern Point,” drains to a smaller outlet than any hydrologic unit available in the WBD. All coastal watershed boundaries were updated with NBEP’s estuarine coastline delineation (for details about NBEP’s coastline delineation, see metadata for BAYS_NBEP2019). This dataset is intended for use in general planning, GIS analysis, and mapping at watershed and subwatershed scales. For more information, please reference the 2017 State of Narragansett Bay & Its Watershed Technical Report (nbep.org).

This layer shows a multi-component analysis for California stream gage priorities at the Hydrologic Unit Code 12 (HUC12) watershed resolution. The Stream Gage Prioritization Analysis is part of the Senate Bill 19 Stream Gaging Plan, which seeks to prioritize areas for additional stream gaging efforts. The dataset includes the gaged proportion of each HUC12 based on a Gage Gap Analysis and information on prioritization results based on five management criteria. The management criteria include scores for ecosystem, water quality, water supply, flood, and reference gages. The priorities are the top scoring 200 watersheds for each management criteria area, for a total of 921 watersheds with overlap between the priorities. The 921 priorities are assigned a primary (highest scoring) benefit. Included is the presence of gages that could be reactivated or upgraded in the watershed. The presence of underrepresented communities, as defined in the Department of Water Resources DAC Mapping Tool, is also noted for each watershed.Data Dictionary: Field Name Range Description

huc12 4469 Hydrologic unit code (HUC) size 12, subbasin, 10-40 thousand acres

huc12_name

Name of the HUC12

huc10 1039 Hydrologic unit code (HUC) size 12, watershed, 40-250 thousand acres

huc10_name

Name of the HUC10

tier 3-Jan Prioritization category number, with 1 being the highest

category

Prioritization category description

best_in_huc10 0 or 1 1 indicates that HUC12 watershed is the top score within its HUC10, which comprises several HUC12s; 0 indicates that it is not the top scoring HUC12.

primary benefit

Primary benefit based on top score for management criteria. If "multi-benefit", it scores in top 100 in multiple categories; if "high combined score", it scores in the top 200 in no categories but the sum of the scores is in the top 200. If the category has a "+" this indicates a multibenefit that has a clear primary benefit in top 100.

total_individual_priority_score 0 - 5 Summary of XX priority scores, with a maximum possible value of 5.

ecosystem priority 1, 0.5, 0 Score = 1 is rank 1-100; Score = 0.5 is rank 101-200 for ecosystem

waterquality priority 1, 0.5, 0 Score = 1 is rank 1-100; Score = 0.5 is rank 101-200 for waterquality

watersupply priority 1, 0.5, 0 Score = 1 is rank 1-100; Score = 0.5 is rank 101-200 for watersupply

flood priority 1, 0.5, 0 Score = 1 is rank 1-100; Score = 0.5 is rank 101-200 for flood

reference priority 1, 0.5, 0 Score = 1 is rank 1-100; Score = 0.5 is rank 101-200 for reference

score_summary priority 1, 0.5, 0 Score = 1 is rank 1-100; Score = 0.5 is rank 101-200 for raw score summary

huc12_proportion_need_gage 0 - 1 Proportion of huc12 watershed that is ungaged, by stream segment length

community_present_in_huc12

Presence and type of underrepresented community in HUC12 watershed

huc12_gg_combined 0 - 4 Sum ecosystem_gg, watersupply_gg, waterquality_gg, and flood_gg

huc12_gg_combined_plus_reference 0 - 5 Same as huc12_gg_combined plus reference_score

huc12_raw_combined

Sum Ecosystem Raw, Water Supply Raw, Water Quality Raw, and Flood Raw

ecosystem_gg 0 – 1 Final ecosystem score = ecosystem_raw x huc12_proportion_need_gage

ecosystem_rank Jan-96 Final ecosystem ranking based on ecosystem_gg, with 1 the highest. Equal scores receive equal highest rank.

ecosystem_raw 0 - 1 Raw management priority score, without gage gap

waterquality_gg 0 – 1 Final waterquality score = waterquality_raw x huc12_proportion_need_gage

waterquality_rank 1 - 1299 Final waterquality ranking based on waterquality_gg, with 1 the highest. Equal scores receive equal highest rank.

waterquality_raw 0 - 1 Raw management priority score, without gage gap

watersupply_gg 0 – 1 Final watersupply score = watersupply_raw x huc12_proportion_need_gage

watersupply_rank Jan-66 Final watersupply ranking based on watersupply_gg, with 1 the highest. Equal scores receive equal highest rank.

watersupply_raw 0 - 1 Raw management priority score, without gage gap

flood_gg 0 – 1 Final flood score = flood_raw x huc12_proportion_need_gage

flood_rank Jan-25 Final flood ranking based on flood_gg , with 1 the highest. Equal scores receive equal highest rank.

flood_raw 0 - 1 Raw management priority score, without gage gap

reference_score 0 – 1 Final reference gage score = (1 – reference_gagepair_score) * reference_impairment_score

reference_rank 1 – 2231 (4469) Final reference ranking based on reference_score, with 1 the highest. Equal scores receive equal highest rank.

reference_gagepair_score 0- 1 Final gage pairing score, which indicates how well each watershed matches to the best fit reference gage. 1 indicates a perfect match.

reference impairment score 0 or 1 Assesses whether or not the watershed is impaired (0) or potentially not impaired (1). Impairment is evaluated based on upstream water storage only.

site_id_upgrade

Recommended Reactivation Gage ID

site_name_upgrade

Recommended Reactivation Gage Name

site_id_reactivate

Recommended Upgrade Gage ID

site_name_reactivate

Recommended Upgrade Gage Name

This data set is a complete digital hydrologic unit boundary layer to the subwatershed (12-digit) 12th level for the State of New Mexico. This data set consists of geo-referenced digital data and associated attributes created in accordance with the "FGDC Proposal, Version 1.0 - Federal Standards For Delineation of Hydrologic Unit Boundaries 3/01/02"(http://www.ftw.nrcs.usda.gov/huc_data.html). Polygons are attributed with hydrologic unit codes for 4th level sub-basins, 5th level watersheds, 6th level subwatersheds, name, size, downstream hydrologic unit, type of watershed, non-contributing areas and flow modification. Arcs are attributed with the highest hydrologic unit code for each watershed, linesource and a metadata reference file.

Subwatersheds (12-digit hydrologic unit codes (HUCs)) in Stark County, Ohio. The features in this layer include the full extent of every subwatershed intersecting the county. The data was download in December, 2022 from the NRCS GeoSpatialDataGateway. This layer is part of the Watershed Boundary Dataset (WBD). The WBD is a 1:24,000 scale expanded version of the hydrologic units created in the mid-1970's by the U.S. Geological Survey (USGS) under the sponsorship of the Water Resources Council. The WBD is a complete set of hydrologic units from new watershed and subwatersheds less than 10,000 acres to entire river systems draining large hydrologic unit regions, all attributed by standard nomenclature. Development of the WBD started in the early 1990's and progressed to the format and attribution in this layer. The delineation and attribution was done on a state basis using a variety of methods and source data.This layer depicts subwatersheds, which have 12-digit hydrologic unit codes (HUCs). They are sometimes referred to as 6th-level HUCs or 6th-level subwatersheds. The complete metadata for this item can be found here: WBD_State_Metadata_Archive.

This data is the latest (Version 6) national hydrologic unit (HU) boundaries at levels 1-6 for Virginia developed and maintained by the Virginia Department of Conservation and Recreation. They have been created in compliance with the most recent published federal standards for delineation of hydrologic units and contain national WBD HU model changes made since that time up to the publication date. The Virginia NWBD schemas include variations from the national WBD schemas. This dataset covers the whole state and is seamless with the WBD products of surrounding states at the time of publication and was developed as part of a seamless hydrologic unit product for the nation at the sixth level to be used for more detailed watershed planning work in the state. This becomes the official statewide sixth level hydrologic unit delineation for Virginia.

Each drainage area is considered a Hydrologic Unit (HU) and is given a Hydrologic Unit Code (HUC) which serves as the unique identifier for the area. HUC 2s, 6s, 8s, 10s, & 12s, define the drainage Regions, Subregions, Basins, Subbasins, Watersheds and Subwatersheds, respectively, across the United States. Their boundaries are defined by hydrologic and topographic criteria that delineate an area of land upstream from a specific point on a river and are determined solely upon science based hydrologic principles, not favoring any administrative boundaries, special projects, or a particular program or agency. The Watershed Boundary Dataset is delineated and georeferenced to the USGS 1:24,000 scale topographic basemap.Hydrologic Units are delineated to nest in a multi-level, hierarchical drainage system with corresponding HUCs, so that as you move from small scale to large scale the HUC digits increase in increments of two. For example, the very largest HUCs have 2 digits, and thus are referred to as HUC 2s, and the very smallest HUCs have 12 digits, and thus are referred to as HUC 12s.Dataset SummaryPhenomenon Mapped: Watersheds in the United States, as delineated by the Watershed Boundary Dataset (WBD)Geographic Extent: Contiguous United States, Alaska, Hawaii, Puerto Rico, Guam, US Virgin Islands, Northern Marianas Islands and American SamoaProjection: Web MercatorUpdate Frequency: AnnualVisible Scale: Visible at all scales, however USGS recommends this dataset should not be used for scales of 1:24,000 or larger.Source: United States Geological Survey (WBD)Data Vintage: January 7, 2025What can you do with this layer?This layer is suitable for both visualization and analysis acrossthe ArcGIS system. This layer can be combined with your data and other layers from the ArcGIS Living Atlas of the World in ArcGIS Online and ArcGIS Pro to create powerful web maps that can be used alone or in a story map or other application. Because this layer is part of the ArcGIS Living Atlas of the World it is easy to add to your map:In ArcGIS Online, you can add this layer to a map by selecting Add then Browse Living Atlas Layers. A window will open. Type "Watershed Boundary Dataset" in the search box and browse to the layer. Select the layer then click Add to Map. In ArcGIS Pro, open a map and select Add Data from the Map Tab. Select Data at the top of the drop down menu. The Add Data dialog box will open on the left side of the box, expand Portal if necessary, then select Living Atlas. Type "Watershed Boundary Dataset" in the search box, browse to the layer then click OK.Questions?Please leave a comment below if you have a question about this layer, and we will get back to you as soon as possible.

The Watershed Boundary Dataset (WBD) is a comprehensive aggregated collection of hydrologic unit data consistent with the national criteria for delineation and resolution. It defines the areal extent of surface water drainage to a point except in coastal or lake front areas where there could be multiple outlets as stated by the "Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD)" “Standard” (http://pubs.usgs.gov/tm/11/a3/). Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. This dataset represents the hydrologic unit boundaries to the 12-digit (6th level) for the entire United States. Some areas may also include additional subdivisions representing the 14- and 16-digit hydrologic unit (HU). At a minimum, the HUs are delineated at 1:24,000-scale in the conterminous United States, 1:25,000-scale in Hawaii, Pacific basin and the Caribbean, and 1:63,360-scale in Alaska, meeting the National Map Accuracy Standards (NMAS). Higher resolution boundaries are being developed where partners and data exist and will be incorporated back into the WBD. WBD data are delivered as a dataset of polygons and corresponding lines that define the boundary of the polygon. WBD polygon attributes include hydrologic unit codes (HUC), size (in the form of acres and square kilometers), name, downstream hydrologic unit code, type of watershed, non-contributing areas, and flow modifications. The HUC describes where the unit is in the country and the level of the unit. WBD line attributes contain the highest level of hydrologic unit for each boundary, line source information and flow modifications.

The Watershed Boundary Dataset (WBD) is a seamless, national hydrologic unit dataset. Simply put, hydrologic units represent the area of the landscape that drains to a portion of the stream network. More specifically, a hydrologic unit defines the areal extent of surface water drainage to an outlet point on a dendritic stream network or to multiple outlet points where the stream network is not dendritic. A hydrologic unit may represent all or only part of the total drainage area to an outlet point so that multiple hydrologic units may be required to define the entire drainage area at a given outlet. Hydrologic unit boundaries in the WBD are determined based on topographic, hydrologic, and other relevant landscape characteristics without regard for administrative, political, or jurisdictional boundaries. The WBD seamlessly represents hydrologic units at six required and two optional hierarchical levels.The hydrologic units (HU) in the WBD form a standardized system for organizing, collecting, managing, and reporting hydrologic information for the nation. The HU in the WBD are arranged in a nested, hierarchical system with each HU in the system identified using a unique code. Hydrologic unit codes (HUC) are developed using a progressive two-digit system where each successively smaller areal unit is identified by adding two digits to the identifying code the smaller unit is nested within. WBD contains eight levels of progressive hydrologic units identified by unique 2- to 16-digit codes. The dataset is complete for the United States to the 12-digit hydrologic unit. The 14- and 16-digit hydrologic units are optional and are not complete for the nation. Efforts are ongoing to complete 10- and 12-digit unit delineations within 8-digit hydrologic units extending across the U.S. – Canada border. Additional information about this effort and access to data is linked on the “resources” section on this page. A similar effort is complete for the 10- and 12-digit units extending across the U.S. – Mexico border.More information can be found here: https://www.usgs.gov/core-science-systems/ngp/national-hydrography/watershed-boundary-dataset?qt-science_support_page_related_con=4#qt-science_support_page_related_con

This resource contains a shapefile of HUC-8 (eight digit Hydrologic Unit Codes) for the Continental United States (CONUS).

The Watershed Boundary Dataset (WBD) is a comprehensive aggregated collection of hydrologic unit data consistent with the national criteria for delineation and resolution. It defines the areal extent of surface water drainage to a point except in coastal or lake front areas where there could be multiple outlets as stated by the "Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD)" “Standard” (http://pubs.usgs.gov/tm/11/a3/). Watershed boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. This dataset represents the hydrologic unit boundaries to the 12-digit (6th level) for the entire United States. Some areas may also include additional subdivisions representing the 14- and 16-digit hydrologic unit (HU). At a minimum, the HUs are delineated at 1:24,000-scale in the conterminous United States, 1:25,000-scale in Hawaii, Pacific basin and the Caribbean, and 1:63,360-scale in Alaska, meeting the National Map Accuracy Standards (NMAS). Higher resolution boundaries are being developed where partners and data exist and will be incorporated back into the WBD. WBD data are delivered as a dataset of polygons and corresponding lines that define the boundary of the polygon. WBD polygon attributes include hydrologic unit codes (HUC), size (in the form of acres and square kilometers), name, downstream hydrologic unit code, type of watershed, non-contributing areas, and flow modifications. The HUC describes where the unit is in the country and the level of the unit. WBD line attributes contain the highest level of hydrologic unit for each boundary, line source information and flow modifications.

The USGS has published United States water-use data every five years since 1950. To increase the temporal and spatial availability of water use estimates using nationally consistent methods, the USGS is developing national water-use models for each major water-use category. This data release publishes crop irrigation withdrawals for the conterminous United States (CONUS) that are calculated using modeled irrigation consumptive use (Martin and others, 2023), irrigation efficiencies, and source-water proportions (Dieter and others, 2018). Crop irrigation withdrawals and irrigation consumptive use refer to water removed and consumed, respectively, from a groundwater or surface-water source to produce agricultural crops. Monthly withdrawals provided include groundwater, surface water, and the combined total withdrawal for areas contained in the twelve-digit watershed boundary (HUC12) dataset during the reanalysis period, 2000-2020. HUC12 annual 2000-2020 irrigation efficiencies included in this data release combine efficiencies from irrigation system types (accounting for water lost during application to crops) and conveyances (accounting for water lost during transmission through canals and pipes). Irrigated crops were mapped using the Landsat-based Irrigation Dataset (LANID; Xie and Lark, 2021; Martin and others, 2023) and the Cropland Data Layer (USDA NASS, 2022) that were linked to irrigation system types (USDA NASS, 2014) to estimate irrigation system efficiencies for each HUC12 in the CONUS (Howell, 2003 and FAO, 1989). Conveyance loss volumes (USDA NASS, 2020) were used to estimate and map surface-water conveyance efficiencies. Total efficiencies were calculated for HUC12 units by combining irrigation system and conveyance efficiencies. Irrigation withdrawals and efficiencies were produced using published data sources to provide these estimates in a timely manner. On-going work to develop dynamic maps of irrigation system type and other datasets for the CONUS will be used in the future to refine the estimates provided here. Estimation of irrigation withdrawals using irrigation consumptive use and efficiencies neglects some components of water use for crops, including water used for frost protection, salt leaching, harvesting, and other non-consumptive-use based treatments. For this reason, irrigation withdrawals provided here may under-estimate total withdrawals where non-consumptive treatments are significant.