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, 2012a). 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. This dataset represents the boundaries for the 100 watersheds studied in the MSQA, and is one of the four fundamental geospatial data layers that were developed for the Midwest study.
The MSQA watershed boundaries were delineated using the following four data sources listed in order of precedence: 1) the Watershed Boundary Dataset (U.S. Department of Agriculture, 2012, 2013); 2) StreamStats (U.S. Geological Survey, 2012b); 3) the National Hydrography Dataset Plus Version 2.1, or "NHDPlusV2" (U.S. Environmental Protection Agency and U.S. Geological Survey, 2012); and 4) 1:24,000-scale U.S. Geological Survey (USGS) topographic maps (U.S. Geological Survey and National Geographic Society, 2013). Initially, draft watershed boundaries were developed from the NHDPlusV2 dataset and StreamStats, in states where StreamStats was fully implemented (IL, IA, IN, OH, MN, KY, and SD). The WBD line segments that closely followed the draft watershed boundaries were duplicated in the MSQA watershed boundaries. To close the remaining gaps between the (water-chemistry) sampling site and the closest WBD line segment(s) uphill laterally from the stream, selected line segments were copied from the draft watershed delineation developed using StreamStats (U.S. Geological Survey, 2012b) if it was available; otherwise, line segments were copied from the draft watershed boundary delineated from NHDPlusV2 (U.S. Environmental Protection Agency and U.S. Geological Survey, 2012). In some cases, the watershed boundary was further refined near the sampling site on the basis of on contour data USGS topographic maps (U.S. Geological Survey and National Geographic Society, 2013).
The geographic information system (GIS) software and specific tools mentioned in this metadata document are from the ArcToolbox, version 9.3.1, a component of the ArcGIS for Desktop (Esri, 2013).
References cited in this document:
Esri, 2013, ArcGIS 9.3.1 for Desktop: Redlands, Calif., Esri, accessed at http://www.esri.com/software/arcgis/arcgis-for-desktop.
Nakagaki, N., Qi, S.L., and Baker, N.T., 2016, Selected environmental characteristics of sampled sites, watersheds, and riparian zones for the U.S. Geological Survey Midwest Stream Quality Assessment: U.S. Geological Survey data release, http://dx.doi.org/10.5066/F77W699S
U.S. Department of Agriculture, 2012, Watershed Boundary Dataset - 12-digit hydrologic units: Fort Worth, Tex., Natural Resources Conservation Service, National Cartography and Geospatial Center, accessed May 2012 at ftp://ftp.ftw.nrcs.usda.gov/wbd/ [Current version of the database moved by time of publication; available August 25, 2016, at http://nhd.usgs.gov/wbd.html].
U.S. Department of Agriculture, 2013, Watershed Boundary Dataset - 12-digit hydrologic units: Fort Worth, Tex., Natural Resources Conservation Service, National Cartography and Geospatial Center, accessed July 2013 at ftp://ftp.ftw.nrcs.usda.gov/wbd/ [Current version of the database moved by time of publication; available August 25, 2016, at http://nhd.usgs.gov/wbd.html].
U.S. Environmental Protection Agency and U.S. Geological Survey, 2012, National Hydrography Dataset Plus - NHDPlus Version 2.1: Herndon, Va., Horizon Systems, accessed in April 2013, at http://www.horizon-systems.com/nhdplus/.
U.S. Geological Survey and National Geographic Society, 2013, USA Topo Maps: Redlands, Calif., Esri, an ArcGIS online map service, accessed November 2013 at http://goto.arcgisonline.com/maps/USA_Topo_Maps.
U.S. Geological Survey, 2012a, The Midwest stream quality assessment: U.S. Geological Survey Fact Sheet 2012-3124, 2 p.
U.S. Geological Survey, 2012b, The StreamStats program: U.S. Geological Survey Office of Surface Water Web page, accessed November 2013 at http://streamstats.usgs.gov.
