Water Use in the United States
The United States is divided and subdivided into successively smaller water-resource regions (areas), as shown in the above diagram. The regions are arranged within each other, starting from the smallest (water-resources cataloging units) to the largest (water-resources regions). All areas have unique numbers to identify them. Two digits specify each individual area, and the numbers are progressively appended to specify the more detailed areas, as shown in the examples below:
| Water-Resources Region: | 04 |
| Water-Resources Subregion: | 0403 |
| Water-Resources Accounting Unit: | 040302 |
| Water-Resources Cataloging Unit: | 04030201 |
Thus, region 04 includes a number of subregions, one of which is 0403. Subregion 0403 includes a number of accounting units, one of which is 040302. Accounting unit 040302 includes a number of cataloging units, one of which is 04030201.
In some of the water-use files and documentation you may see some alternate terminology. Here's how the terms relate:
| Region: | 2-digit hydrologic unit |
| Subregion: | 4-digit hydrologic unit |
| Accounting Unit: | 6-digit hydrologic unit |
| Cataloging Unit: | 8-digit hydrologic unit |
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://water.usgs.gov/watuse/wuwrregions.html
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Page Last Modified: Friday, 11-Jan-2013 12:44:46 EST
