Wapsipinicon River IA 01-WPS-344

The Class B(WW1) (aquatic life) uses remain assessed (evaluated) as "partially supported" due to a fish kill in April of 2006.  The kill occurred on or before April 19, 2006; no cause of the kill was identified.  Approximately 24 dead fish were observed in a pool on the Wapsipinicon River.  The species of fish could not be identified due to the level of decay.  Levels of ammonia in the water were below the detection limit.  Dissolved oxygen concentrations were greater than 10 mg/L and the temperature was 48 ?F.  No estimate of the value of the fish was developed. 

This is the same assessment as that developed for the previous assessment/listing cycles.  The continuance of the IR Category 3b listing is based on assessment methodology that states the following:  the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”.  If a cause of the kill was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated” and will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.  Thus, this assessment segment will remain in Category 3b of Iowa’s 2016 Integrated Report.

In contrast to the fishkill data, the evaluated biological assessment based on data collected in 2007 as part of the IDNR Fisheries Bureau sampling project, suggests that that the aquatic life uses of this segment should be assessed as "fully supported". A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2007 FIBI score was 53 (good). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI score with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008. The non-riffle FIBI BIC for this ecoregion 44. This assessment is considered evaluated because the drainage area (676 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed the FIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the site used for the assessment doesn’t fall in the calibrated watershed size.