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Map Layer Info

1:2,000,000-Scale Hydrologic Unit Boundaries

What this map layer shows:

The boundaries of natural and manmade stream-drainage areas. Included are the boundaries of 2,264 watersheds.
opens the U.S. Geological Survey home page
Background Information
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Hydrologic units are used for collecting and organizing hydrologic data. These units are land areas that catch rain or snow and drain to marshes, streams, rivers, lakes, or ground water. The hydrologic unit system divides and subdivides the United States into four nested levels of units. The largest units are called regions and represent either the drainage area of a major river, such as the Missouri region, or the combined drainage areas of a series of rivers, such as the Texas-Gulf region, which includes numerous rivers draining into the Gulf of Mexico. The successively smaller units within regions are subregions, accounting units, and cataloging units. Cataloging units are also known as watersheds. This map layer was compiled by the U.S. Geological Survey.

The 1:2,000,000-Scale Hydrologic Unit Boundaries map layer shows the boundaries of 2,264 cataloging units within the United States, Puerto Rico, and the U.S. Virgin Islands. The hydrologic units outlined in this map layer represent natural and manmade stream-drainage areas. Descriptive information includes names and codes for the cataloging units, accounting units, subregions, and regions. Further information on hydrologic units is available from the USGS Water Resources Hydrologic Unit Maps page.


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Hydrologic Units (Watersheds)
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Hydrologic Units
Hydrologic Units