Lower Poplar River Watershed Sediment Source Assessment

MPCA's impaired waters list for excessive turbidity. Monitoring of the Lower Poplar River for flow and turbidity was conducted from 2002 through 2006. Both upstream and downstream monitoring was conducted in an attempt to narrow down the source of the turbidity impairment. The monitoring data showed that the turbidity standards for aquatic life were exceeded at the lower monitoring station near the mouth of the Poplar River as it enters Lake Superior, but the standard was not exceeded at the upper station. This result indicates that the source(s) of the excessive sediment is (are) within the Lower Poplar River watershed. This report summarizes the results of an analysis to quantify the annual sediment load in the Lower Poplar River associated with each of these sources. A combination of methods was used to arrive at these estimates and the background for these methods along with estimated results will be presented in the following sections.