Watershed Boundary Dataset for Mississippi - Hydrologic Unit Codes (HUC)

The U.S. Geological Survey, in cooperation with the Mississippi Department of Environmental Quality, U.S. Department of Agriculture-Natural Resources Conservation Service, Mississippi Department of Transportation, U.S. Department of Agriculture-Forest Service, and the Mississippi Automated Resource INformation System developed a 1:24,000-scale Watershed Boundary Dataset for Mississippi including watershed and subwatershed boundaries, codes, names, and areas. The Watershed Boundary Dataset for Mississippi provides a standard geographical framework for water-resources and selected land-resources planning. The original 8-digit subbasins (Hydrologic Unit Codes) were further subdivided into 10-digit watersheds (62.5 to 391 square miles (mi²)) and 12-digit subwatersheds (15.6 to 62.5 mi²) - the exceptions being the Delta part of Mississippi and the Mississippi River inside levees, which were subdivided into 10-digit watersheds only. Also, large water bodies in the Mississippi Sound along the coast were not delineated as small as a typical 12-digit subwatershed. All of the data - including watershed and subwatershed boundaries, subdivision codes and names, and drainage-area data--are stored in spreadsheet format, which are available for download here: OFR 2008-1198 Table 1

This map shows information on drainage and hydrography in the form of U.S. Geological Survey hydrologic unit boundaries for water-resource 2-digit regions, 4-digit subregions, 6-digit basins (formerly called accounting units), 8-digit subbasins (formerly called cataloging units), 10-digit watershed, and 12-digit subwatersheds in Mississippi. A description of the project study area, methods used in the development of watershed and subwatershed boundaries for Mississippi, and results are presented in Wilson and others (2008). The data presented in this map and by Wilson and others (2008) supersede the data presented for Mississippi by Seaber and others (1987) and U.S. Geological Survey (1977).

The northwestern part of Mississippi in the lower part of the Yazoo River Basin (locally referred to as the Mississippi Delta) is an area of intense agricultural production , where previous attempts to delineate watersheds in the Delta to the sub-watershed boundaries were unsuccessful due to the following reasons: topographically-uniform, low relief land elevations (less than 100 feet of rise in land-surface elevation from Vicksburg to Memphis); land management practices employed by land owners and growers who frequently change drainage patterns; multiple man-made canals and straightened channels (Wilson and others, 2008); and the fact that the area did not previously have a sufficient scale of digital elevation data that would allow delineation of subtle topographic features.

It was proposed that the Mississippi Delta would not be delineated to the sub-watershed level until more precise digital elevation tools were available for use. Since the publication of the Mississippi WBD in 2009, the entire Yazoo River Basin has been mapped using Light Detection and Ranging (LiDAR) technology, which has a bare earth vertical land surface accuracy of 8.5 centimeters.

The LiDAR survey was funded by the U.S. Army Corps of Engineers (US ACOE) Vicksburg District. With the availability of LiDAR data, it is now possible to delineate the Delta to the sub-watershed level. The U.S. Geological Survey, in cooperation with the Mississippi Department of Environmental Quality, will delineate the sub-watershed boundaries (12-digit basins) for northwestern Mississippi. Boundaries will be delineated using automated tools within a Geospatial Information System. The complete, updated watershed and sub-watershed boundary dataset will be available on the web at the National Resources Conservation Service Geospatial Data Gateway after certification and inclusion by the National Watershed Boundary Dataset.