Assessment Comments
Assessment based on 2002 REMAP data: FIBI = 13 (Poor). FIBI BIC = 33.
Basis for Assessment
[Note: Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current (2008) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY/EXPLANATION: The presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment.
The assessment of the Class B(WW2) aquatic life uses was based on data collected in 2002 as part of the DNR/UHL stream REMAP biological monitoring project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 FIBI score was 13 (poor). The aquatic life use support was assessed as Not Supporting (=NS), based on a comparison of the FIBI score with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The FIBI BIC for this ecoregion is 33.
As part of the 2002 REMAP project, stream physical habitat assessment found significant channel alterations that could contribute to the biological impairment. These include, bank instability, channel widening, shallow water depth, and excessive sediment bar development. Elevated summer water temperature (33.4C) and low D.O. levels at night (4.7 mg/L) were observed. Channel alterations, which have increased the stream width:depth ratio (38.4), probably have also contributed to adverse water quality conditions.
