South Fork Iowa River IA 02-IOW-748

Assessment Comments

Assessment based on results of (1) IDNR/UHL biocriteria sampling in 1999, (2) IDNR/UHL biocriteria sampling in 1995, (3) IDNR stream use assessments in 1995 SUAs, and (4) the history of fish kills in this watershed.

Basis for Assessment

SUMMARY:  The Class B(WW) uses remain assessed as “fully supported / threatened” based on the history of fish kills in this watershed.   Results of biological monitoring suggest “full support” of the Class B(WW) aquatic life uses.   The sources of data for this assessment include (1) results of IDNR and IDNR/UHL biological monitoring in 1995 and 1999 and (2) the history of fish kills in this watershed.   Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream reach.  

EXPLANATION:  The assessment was based on data collected in 1999 as part of the DNR/UHL stream biocriteria project.   The 1999 Fish IBI score was 73 (excellent) and the BM-IBI score was 81 (excellent).   The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report.  The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.   The September 1995 DNR stream use assessments W of Eldora and E of Buckeye and results of the July 1995 IDNR/UHL biocriteria sampling at Logsdon Park also suggest "full support" of the Class B(LR) aquatic life uses as FST due to presence of a diverse fish community (see assessment for the 1998 report for more information).   Although the results of biological monitoring suggest “full support” of aquatic life uses, the watershed of the South Fork Iowa River has a history of repeated fish kills, often in the upper reaches of the stream.   Despite the lack of fish kills in this lower reach of the South Fork Iowa River during 2000-2002 assessment period, fish kills continue to occur in this watershed (for example, a fish kill attributed to animal waste occurred in the headwaters of this stream on September 6, 2001).   Thus, based on results of USGS monitoring and on the history of fish kills in this watershed, the Class B(WW) aquatic life uses remain assessed as "fully supported / threatened."  

Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream reach.