Assessment Comments
Assessment based on 2002 biocriteria data: Fish IBI = 30 (fair), BM-IBI = 47 (fair) and on 2002 IDNR Fisheries data: Fish IBI = 23 (poor).
Basis for Assessment
NOTE: Keg Creek was divided into two subsegments for the 1998 Section 305(b) report. The previous segment was excessively long (44 miles) for a Class B(LR) stream, and physical differences exist (extensively channelized vs. moderately channelized to meandering) between the downstream and upstream subsegments. The subsegment boundary (confluence with Little Keg Creek 3 miles NW of Treynor, Pottawattamie Co.) was chosen due to these differences. (JRO, Sept. 1998)]
The assessment was based on data collected in 2002 as part of the DNR/UHL REMAP project and on data collected in 2002 as part of a DNR Fisheries stream sampling project: Cold Springs Fish Management. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (F-IBI) and a benthic macroinvertebrate index (BM-IBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 IDNR/UHL Fish IBI score was 30 (fair) and the BM-IBI score was 47 (fair). The 2002 IDNR Fisheries Fish IBI score was 23 (poor). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established for previous Section 305(b) reports. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.
Data from the physical habitat assessment and 3 grab water samples collected for the REMAP project did not identify a specific cause of impairment. Additional sampling data are needed to assess the current status of aquatic life uses and causes/sources of impairment.
