ADBNet

Routine water quality monitoring is not conducted in this river segment; thus, data upon which to base assessments of the Class A1 uses are not available.

The Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supported” based on results of IDNR/SHL biological (REMAP) sampling in 2002 and 2005. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 FIBI score was 33 (fair) and the 2005 FIBI scores were 36 (fair) and 45 (fair). The 2002 BMIBI score was 42 (fair) and the 2005 BMIBI scores were 19 (poor) and 16 (poor). The aquatic life uses were assessed (evaluated) as partially supported (=PS), based on a comparison of the FIBI score with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC is 62. This segment passed the FIBI BIC 3/3 times and passed the BMIBI BIC 0/3 times in the last 13 years. This assessment is considered evaluated because the drainage area (2210-2236 mi2) above the sampling sites 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 and failed to meet the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the sites used for the assessment don’t fall in the calibrated watershed size. Several game fish species and species considered sensitive to stream degradation were present in the fish survey.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over the recent five-year period to be considered “monitored”. This segment had multiple samples collected in the previous 13 years (2002-2014); however, the multiple samples were not collected in multiple years during 2010-2014. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).

Fish consumption uses are now considered “not assessed” due to the lack of recent fish contaminant monitoring in this assessment segment. Previous assessments of support of the fish consumption uses (“fully supporting”) were based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Adel in 2000. The composite samples of fillets from channel catfish had low levels of contaminants. Because the data upon which these assessment were based are now more than ten years old, the Class HH/fish consumption uses are now considered “not assessed.” As water quality data age, they are less able to represent current water quality conditions. As data age beyond ten years, their ability to represent current water quality conditions is increasing suspect.