The data set contains stream water concentrations of herbicides and nutrients for 153 sites in the northern Missouri/southern Iowa region from 1994 to 1995. The data are available in Microsoft Excel 2010 format. Sheet 1 (Metadata) of the file contains supporting information regarding the length of record, site locations, parameters measured, concentrations units, method detection limits, describes the meaning of zero and blank cells, defines the major land resource areas (MLRAs) of the region, and provides a link to the U. S. Geological Survey discharge data. Sheet 2 (Site names and locations) has a list of the site names by MLRA, river system, and site name. It also contains site locations, provided as Universal Transverse Mercator coordinates, drainage areas, and indicates which sites were co-located at U. S. Geological Survey gauge sites. Sheet 3 (Concentration Data) contains data for 15 herbicide and nutrient analytes along with the corresponding site name, river system, and MLRA. Atrazine concentrations in Goodwater Creek Experimental Watershed (GCEW) were shown to be among the very highest of any watershed in the United States based on comparisons using the national Watershed Regressions for Pesticides (WARP) model and by direct comparison with the 112 watersheds used in the development of WARP. The herbicide data collected in GCEW are documented at plot, field, and watershed scales. This 20-yr-long (1991-2010) effort was augmented with a spatially broad effort within the Central Mississippi River Basin encompassing 12 related claypan watersheds in the Salt River Basin, two cave streams on the fringe of the Central Claypan Areas in the Bonne Femme watershed, and 95 streams in northern Missouri and southern Iowa. The research effort on herbicide transport has highlighted the importance of restrictive soil layers with smectitic mineralogy to the risk of transport vulnerability. Near-surface soil features, such as claypans and argillic horizons, result in greater herbicide transport than soils with high saturated hydraulic conductivities and low smectitic clay content.
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