South Fork Iowa River IA 02-IOW-749

Assessment Comments

Assessment is based on occurrence of fish kills.

Basis for Assessment

The Class B(LR) aquatic life uses remain assessed as "partially supported."  EXPLANATION:  The previous assessment of support of the Class B(LR) uses ("partially supported"; see assessment for the 1998 report) was based primarily on the occurrence of two fish kills on this stream reach within a two-year period (July 1995 to August 1997).   The 1998 assessment was also based on the results of DNR stream use assessments in May and June of 1992.   Fish kill information from the 1997 kill was used for the current assessment; the results of the 1992 stream assessments, however, are greater than five years old and are thus considered too old to be useful for assessing current water quality conditions.   The most recent fish kill in this stream reach occurred in August 1997; this kill was caused by the illegal discharge of hog manure.   According to DNR's assessment methodology for Section 305(b) reporting, the occurrence of a single pollution-caused fish kill within the most recent three-year period (1997-1999) indicates that the aquatic life uses of a waterbody are only "partially supported."  Thus, the Class B(LR) aquatic life uses remain assessed as "partially supported" due to fish kills.   As stated in the assessment for the 1998 report, follow-up monitoring is needed to better define the status of the aquatic communities  in the stream reach and to determine the degree to which the Class B(LR) uses may be impaired, especially by residual effects of illegal/accidental discharges of animal waste.