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1:250,000-scale Hydrologic Units of the United States

Metadata Updated: July 8, 2024

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:

HUC, GIRAS, Hydrologic Units, 1:250

For the most current data and information relating to hydrologic unit codes (HUCs) please see The Watershed Boundary Dataset (WBD) is the most current data available for watershed delineation. See

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date June 1, 2023
Metadata Updated Date July 8, 2024

Metadata Source

Harvested from DOI EDI

Additional Metadata

Resource Type Dataset
Metadata Created Date June 1, 2023
Metadata Updated Date July 8, 2024
Publisher U.S. Geological Survey
Identifier USGS:9c6a0008-865b-478f-ba1e-ab574481e7fe
Data Last Modified 20201117
Category geospatial
Public Access Level public
Bureau Code 010:12
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Harvest Object Id f3fb03a5-0fbf-4f1b-9805-47130429e186
Harvest Source Id 52bfcc16-6e15-478f-809a-b1bc76f1aeda
Harvest Source Title DOI EDI
Metadata Type geospatial
Old Spatial -127.90613546,22.8757219,-65.32190735,48.28250713
Publisher Hierarchy White House > U.S. Department of the Interior > U.S. Geological Survey
Source Datajson Identifier True
Source Hash 03efa3909a1d011d5d2e95cd6c3bd1b9b8170b1c7233be1fd32490c186891e1a
Source Schema Version 1.1
Spatial {"type": "Polygon", "coordinates": -127.90613546, 22.8757219, -127.90613546, 48.28250713, -65.32190735, 48.28250713, -65.32190735, 22.8757219, -127.90613546, 22.8757219}

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