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.
Users please note:
1. Although there were 100 sampled sites in the MSQA study, there are 99 riparian-zone boundaries in this dataset because one site was not sampled for ecology: LeSueur River near Rapidan, MN (05320500). This site was not sampled because of safety considerations due to high-flow conditions.
2. Water-chemistry and ecology sampling along Massac Creek in Illinois were conducted at separate locations, approximately 750 stream meters apart. Accordingly, the site identification numbers and station names differ at these two locations: the water-chemistry samples were collected at site 03611100, Massac Creek near Metropolis, IL, and the ecology samples were collected at site 03611200, Massac Creek at Metropolis, IL. The riparian-zone boundary in this dataset is associated with the ecology-sampled site, 03611200. Just as for riparian-zone boundaries at other sites, the length of the digitized riparian reach used to create the riparian-zone polygons was calculated from the base-10 logarithm of the watershed area for the water-chemistry site; for the Massac Creek reach, this is site 03611100, Massac Creek at Metropolis, IL site.
3. The digitized riparian reaches used to create the riparian-zone boundaries are not the same as the sampled ecological reaches, although they overlap. The main difference lies in the length of the reaches. The length of the sampled ecological reach was determined as 40-times the mean wetted width of the stream, following protocols defined by the USEPA National Rivers and Streams Assessment (NRSA) program (U.S. Environmental Protection Agency, 2013, 2016); whereas, the length of the digitized riparian reach was determined as the base-10 logarithm of the geospatially-derived watershed area for the water-chemistry site, in units of kilometers and kilometers squared, respectively (Johnson and Zelt, 2005).
4. Because water-chemistry sampling sites are typically located at road crossings over streams, and thus are located in disturbed aquatic environments that are avoided for ecological surveys, water-chemistry sites are rarely located within the sampled ecological reaches. For this reason, the most downstream point of a MSQA riparian-zone boundary does not align with the respective MSQA watershed boundary, which corresponds to the water-chemistry sampling location.
The geographic information system (GIS) software and specific tools mentioned in this metadata document are from the ArcToolbox, version 10.1, a component of the ArcGIS for Desktop (Esri, 2014).
References cited:
Esri, 2014, ArcGIS 10.1 for Desktop: Redlands, Calif., Esri, accessed at http://www.esri.com/software/arcgis/arcgis-for-desktop.
Johnson, M.R., and Zelt, R.B., 2005, Protocols for mapping and characterizing land use/land cover in riparian zones: U.S. Geological Survey Open-File Report 2005-1302, 16 p., available at http://pubs.usgs.gov/of/2005/1302/.
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. Environmental Protection Agency, 2013, National Rivers and Streams Assessment 2013-2014: Field Operations Manual – Wadeable. EPA-841-B-12-009b. U.S. Environmental Protection Agency, Office of Water, Washington, DC.
U.S. Environmental Protection Agency, 2016, National Rivers and Streams Assessment, accessed July 2016 at https://www.epa.gov/national-aquatic-resource-surveys/nrsa.
U.S. Geological Survey, 2012, The Midwest stream quality assessment: U.S. Geological Survey Fact Sheet 2012-3124, 2 p.
