Nutrient Sources and Transport from the Goodwater Creek Experimental Watershed

摘要

The Goodwater Creek watershed has been monitored for flow since 1971 and for dissolved nutrients since 1991 for 3 nested watersheds (12.1, 31.5 and 73.0 km~2 drainage area). This watershed includes row crop land (76%), grassland (14%), woodland (6%) and a small town at the upper end (4%). The objectives of this paper are to analyze nutrient loadings at the 3 gauging stations from 1991 to 2004. Daily, monthly and annual loadings and flow-weighted concentrations of ammonium-nitrogen, nitrate-nitrogen,dissolved phosphorus and atrazine were calculated and analyzed using the non parametric tests for differences, homogeneity, and trends. Atrazine was included in the analysis as one compound not implicated with point source discharges in the watershed. Dissolved phosphorus and ammonium-nitrogen concentrations and loads at the upstream weir were significantly greater than those at the two downstream weirs, which suggest wastewater was a potential source of these nutrients. Possible explanations for thesedifferences were drawn from our knowledge of the watershed and tested with a SWAT model of the watershed. These findings provide insight to what should be included in a complete analysis of the nutrient sources in the watershed and how stream processes affect nutrient loadings.