Development of a National Watershed Boundaries Data Set

Author: Alan Rea
Organization: U.S. Geological Survey

230 Collins Road
Boise, ID 83702-4520
USA

Phone: (208)387-1323
Fax: (208)387-1372
ahrea@usgs.gov

Federal agencies coordinating spatial water data have identified the development of the National Watershed Boundaries Data Set as a top priority for inclusion in the National Spatial Data Infrastructure (NSDI).

The proposed NSDI Watershed Boundaries Data Set will have the following key characteristics:

o Nationally consistent digital data set
o Nested subdivisions of established cataloging units
o Five to 15 watersheds per cataloging unit
o Boundaries based on 1:24,000-scale topographic maps
o Hydrologically based watersheds, not political divisions
o 10-digit Hydrologic Unit Codes
o Formally established watershed names
o Attribute information to identify all upstream and downstream units

Where watershed boundaries have not already been mapped using appropriate criteria, new watershed boundaries will be developed using a semiautomated procedure based on elevation data from the National Elevation Dataset. The boundaries will be checked and edited using 1:24,000-scale digital raster graphics.

The National Watershed Boundaries Data Set, National Elevation Dataset, and National Hydrography Dataset inherently are related. Early maintenance efforts will seek to identify inconsistencies between these three data sets and use those inconsistencies to help improve the quality of each national data set.