South Fork Iowa River IA 02-IOW-746

Assessment Comments

Assessment is based on occurrence of fish kills in the watershed.

Basis for Assessment

Continue to use the assessment of support of the Class B(WW) aquatic life uses developed for the 1996 report (=FST).   Fish kills related to animal feeding operations continue to occur in this watershed (e.g., S.  Fk.  Iowa R near Blairsburg in August 1997, Tipton Cr.  S of Williams in  August 1996 and in July 1998), and aquatic life uses of the lower South Fork Iowa River remain threatened as a result of these kills and the potential negative water quality impacts related to livestock waste (especially ammonia and phosphorus).   Used results of USGS fish tissue monitoring conducted near New Providence in September 1995 for the National Water Quality Assessment (NAWQA) program to develop an assessment of support of fish consumption uses.   The whole-fish composite sample of carp from this site was analyzed for several organochlorine compounds, including chlordane, dieldrin, DDT, and PCBs.   Levels of all contaminants in the sample were less than 1/2 of the respective FDA action levels, thus suggesting full support (FS) of fish consuption uses.   For more information on the USGS fish tissue study, see USGS Fact Sheet FS-027-97 (March 1997).  A review of the field sheet from the September 1990 DNR stream use assessment in Hardin County shows a very diverse fish community of 21 species from 5 families, nearly all the expected fish taxa (9 of 11) for streams in the Des Moines Lobe subecoregion (47b), presence of the expected game fish species (smallmouth bass and channel catfish), presence of several environmentally sensitive species (e.g., banded darter, smallmouth bass, northern hogsucker, and tadpole madtom), and above average habitat quality.   Although fish kills in the headwater reaches of this drainage threaten full support of the Class B(WW) uses, the exceptional diversity during the time of the September 1995 DNR assessment suggest that impacts related to animal waste have not yet affected this lower reach of the South Fork Iowa River.