In 2015, the second of several Regional Stream Quality Assessments (RSQA) was done in the southeastern United States. The Southeast Stream Quality Assessment (SESQA) was a study by the U.S. Geological Survey (USGS) National Water Quality Assessment (NAWQA) project. One of the objectives of the RSQA, and thus the SESQA, is to characterize the relationships between water-quality stressors and stream ecology and subsequently determine the relative effects of these stressors on aquatic biota within the streams (Van Metre and Journey, 2014). 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 115 water-chemistry sites sampled for the SESQA, and is one of the four fundamental geospatial data layers that were developed for the Southeast study.
Users please note:
(1) 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 sampling site.
(2) 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 U.S. Environmental Protection Agency (EPA) National Rivers and Streams Assessment (NRSA) program (U.S. Environmental Protection Agency, 2013, 2016); whereas, the length of the digitized riparian reach was defined 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).
(3) 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 sampling sites are rarely located within the sampled ecological reaches. For this reason, the most downstream point of a SESQA riparian-zone boundary does not align with the respective SESQA watershed boundary, which corresponds to the water-chemistry sampling location.
