20230420 19084800 1.0 TRUE TRUE NCDOT_HUC8 The Geographic Information Retrieval and Analysis System (GIRAS) was developed in the mid 70s to put into digital form a number of data layers which were of interest to the USGS. One of these data layers was the Hydrologic Units. The map is based on the Hydrologic Unit Maps published by the U.S. Geological Survey Office of Water Data Coordination, together with the list descriptions and name of region, subregion, accounting units, and cataloging unit. The hydrologic units are encoded with an eight- digit number that indicates the hydrologic region (first two digits), hydrologic subregion (second two digits), accounting unit (third two digits), and cataloging unit (fourth two digits). The data produced by GIRAS was originally collected at a scale of 1:250K. Some areas, notably major cities in the west, were recompiled at a scale of 1:100K. In order to join the data together and use the data in a geographic information system (GIS) the data were processed in the ARC/INFO GUS software package. Within the GIS, the data were edgematched and the neatline boundaries between maps were removed to create a single data set for the conterminous United States. Latest Publication Date: 03/15/2026 : 17:45 NC North Carolina NCDOT ESM Last Publication Date: 03/15/2026 : 18:06 NCDOT GIS Unit iVBORw0KGgoAAAANSUhEUgAAASwAAADICAYAAABS39xVAAAAAXNSR0IB2cksfwAAAAlwSFlzAAAO xAAADsQBlSsOGwAAAqpJREFUeJzt1DENADAMwLAd5U+5o7BvimQjyJXZ3T0AAfM7AOCVYQEZhgVk GBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFY QIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZ hgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgW kGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECG YQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYF ZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBh WECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEB GYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQY FpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhA hmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmG BWQYFpBhWECGYQEZhgVkGBaQYVhAhmEBGYYFZBgWkGFYQIZhARmGBWQYFpBhWECGYQEZhgVkGBaQ YVhAhmEBGYYFnIoLreIHHblfYqUAAAAASUVORK5CYII=