Assessment Comments
Water quality monitoring conducted by LTRMP office, Bellevue, IA. DNR biocriteria sampling in 1999.
Basis for Assessment
SUMMARY: Continue to assess support of the Class B(WW) aquatic life uses as "partially supported." Fish consumption uses remained "not assessed." EXPLANATION: The assessment of the Class B(WW) uses remains based primarily on results of DNR/LTRMP and DNR Fisheries Bureau sampling of Elk River fish populations that suggest impairment to the aquatic communities of this stream. Preliminary results of a DNR biological assessment in 1999 near Teeds Grove showed relatively few species and numbers per species, thus suggesting a continuing impairment to the aquatic life uses of this stream reach. In addition to biological monitoring, the DNR/LTRMP staff at Bellevue supplied water quality data for 52 samples collected from Elk River during the period September 1997 through September 1999. Samples were collected at least twice per month during this period; the parameters analyzed included dissolved oxygen, pH, ammonia-nitrogen, total phosphorus, total nitrogen, total suspended solids, and chlorophyll. A summary of these data show no violations of the Class B(WW) water quality criteria for temperature, pH, or ammonia-nitrogen. One of the 52 samples violated the Class B(WW) water quality criterion for dissolved oxygen (5.0 mg/l); the sample collected on January 11, 1999 contained 4.1 mg/l of dissolved oxygen. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), however, the percentage of violations of the dissolved oxygen criterion at this station (2%) does not suggest a water quality impairment (these guidelines allow up to 10% violations for conventional parameters such as pH, dissolved oxygen, and temperature before impairment of water quality is indicated). Average levels of total phosphorus were moderately high for Iowa streams (mean = 0.19 mg/l; SE = 0.05 mg/; median 0.12; 75th percentile = 0.16) but do not suggest serious water quality problems. Five samples, however, exceeded 0.5 mg/l total phosphorus (maximum of 1.99 mg/l); these high levels were primarily associated with rainfall runoff events. Fish consumption uses remain "not assessed" due to the lack of monitoring in this river reach.
