Hydrologic Units layer

The Hydrologic Units layer shows the levels 1 through 4 of hydrologic units.

Hydrologic units of Montana Detail of eastern Montana

Details

Name

The name of the level 4 unit (cataloging unit)

Region

The name of the enclosing level 1 unit (region)

Subregion

The name of the enclosing level 2 unit (subregion)

Area

The area of the cataloging unit

Code

The HUC code for the cataloging unit, composed of 4 2-digit parts, one per level.

Options

Transparency

Determines how much the underlying layer(s) will show through this layer.

Color by

  • Region: color each region with a different random color
  • Subregion: color each subregion with a different random color
  • Acc. unit: color each accounting unit with a different random color
  • Cat. unit: color each cataloging unit with a different random color

Line color

Defines the color used to draw the region outlines

Show names

Whether to show the names of the cataloging units when the zoom level is appropriate

Origin

Steeves, Peter and Douglas Nebert, U.S. Geological Survey
Hydrologic Units 250K

This data is available directly from the USGS.

Description of data source

Abstract

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.