Riparian-Zone Boundaries for the U.S. Geological Survey Midwest Stream Quality Assessment

In 2013, the first of several Regional Stream Quality Assessments (RSQA) was done in the Midwest United States. The Midwest Stream Quality Assessment (MSQA) was a collaborative study by the U.S. Geological Survey (USGS) National Water Quality Assessment (NAWQA), the USGS Columbia Environmental Research Center, and the U.S. Environmental Protection Agency (USEPA) National Rivers and Streams Assessment (NRSA). One of the objectives of the RSQA, and thus the MSQA, is to characterize the relationships between water-quality stressors and stream ecology and to determine the relative effects of these stressors on aquatic biota within the streams (U.S. Geological Survey, 2012). To meet this objective, a framework of fundamental geospatial data was required to develop physical and anthropogenic characteristics of the study region, sampled sites and corresponding watersheds, and riparian zones. The riparian-zone boundaries were created from stream centerlines digitized from imagery (hereinafter the "digitized riparian reach") that were buffered by 50 meters on each side of the stream centerline. The length of the digitized riparian reach was calculated as the distance in kilometers equal to the base-10 logarithm of the geospatially-derived watershed area, in kilometers squared (Johnson and Zelt, 2005). This dataset represents the riparian zones in the MSQA, and is one of the four fundamental geospatial data layers that were developed for the Midwest study.