Hydrologic Unit Code Level 4 Boundaries - Northeast River Basin (2002)

This dataset contains 1:250,000-scale hydrologic unit code level 4 boundaries for those cataloging units comprising the Northeast Wyoming River Basins Planning Area - this dataset is clipped to the planning area. 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 USGS Office of Water Data Coordination, together with the list descriptions and name of region, subregion, accounting units, and cataloging units. 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 1:250,000. Some areas, notably major cities in the west, were recompiled at a scale of 1:100,000. In order to join the data together and use the data in a geographic information system (GIS) that data were processed in the ARC/INFO GIS software package. Within the GIS, the data were edgematched and the neatline boundaries between maps were removed to create a single data sest for the conterminous United States.