A water resource region is the first level of classification used by the United States Geological Survey to divide and sub-divide the United States into successively smaller hydrologic units as part of the U.S. hydrologic unit system.
This first level of classification divides the United States into 21 major geographic areas, or regions. These geographic areas contain either the drainage area of a major river, or the combined drainage areas of a series of rivers.[1][2]
- ^ "Science in Your Watershed - Locate Your Watershed". USGS. Retrieved 2015-11-28.
This article incorporates text from this source, which is in the public domain.
- ^ "Hydrologic Unit Maps". USGS. Retrieved 2015-11-28. This article incorporates text from this source, which is in the public domain.
