South Fork Iowa River IA 02-IOW-750

Assessment Comments

Assessment is based on the lack of recent fish kills in this segment of the South Fork Iowa River. Due to the history of repeated kills in this watershed, however, threats to aquatic life continue.

Basis for Assessment

SUMMARY:  Although assessed (evaluated) as “partially supported” for the 2002 reporting cycle due to a fish kill in 1997, the Class B(LR) aquatic life uses are now considered “not assessed” due to the lack fish kills within the last three years (2000-2002).   The history of fish kills in this watershed, however--especially in the upstream reaches--suggests continued threats to the aquatic life uses of this stream segment.

EXPLANATION:  Previous (2000, 2002) assessments of the aquatic life uses were based on the occurrence of a fish kill in 1997 (see assessment for the 2000 report).   According to IDNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period indicates ongoing impairment of the aquatic life uses.   The absence of a fish kill in the three-year period following a fish kill suggest that impacts from the kill have likely dissipated.   Due, however, to the history of fish kills in this watershed, the threat of future kills remains.