Nutrient concentrations in nine surface-water sites within the study area were relatively low compared to nationwide nutrient concentrations. The major dissolved nitrogen species in most of the surface-water sites was organic nitrogen. Among the data collected at these nine sites, the higher values could be attributed to agricultural and urban land use practices, degrading plant and animal material from forest and wetland areas, point-source discharges, or runoff from poultry and dairy farms.
Nitrate concentrations in two of the nine rivers were highest when flows were lowest, indicating contributions from ground-water discharge to the rivers and influence from point-source discharges. At four sites nutrient concentrations increased during increases in discharge and decreased during decreases in discharge, suggesting a flush of nonpoint source contributions followed by dilution.