Assessment Comments
Assessment is based on results of fish / benthic macroinvertebrate monitoring in 1998 and 1999.
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses were assessed as "fully supporting / threatened." EXPLANATION: The support of the Class B(LR) aquatic life uses was upgraded from "partially supported" to "fully supported / threatened" based on results of biological monitoring (fish and benthic macroinvertebrates) conducted from 1997 through 1998 by the University of Iowa Hygienic Laboratory (see UHL 1999). Based on the Hilsenhoff Biotic Index, these studies showed that water quality in the upper (general use) reaches of this Class B(LR) stream reach (sites TR2 and TR3) was rated as "good" in 1997 and 1998, with only a slight (and probably not significant) decrease in water quality noted in 1999. Based on the characterization of water quality as "good," and based on the suggestion of a least some level of organic pollution, the Class B(LR) aquatic life uses were assessed as "fully supported / threatened." In addition, improved water quality is suggested by the cessation of grazing along portions of east branch of Trout Creek (site TR3) and the resultant increase in streambank stability and decrease in the percentage of silt substrates. Although these studies have been conducted to document changes in water quality in response to improved watershed management practices, this connection has not been demonstrated in the project thus far, with annual changes in fish populations and benthic macroinvertebrate populations more likely a response to variations in precipitation, runoff, stream flow, temperature, and other climate-related factors (see UHL 1999).
