Wapsipinicon River IA 01-WPS-350

Results from the IDNR/SHL biological sampling in 2004, 2010 and 2014 suggest that the Class B(WW1) uses should be assessed (evaluated) as "fully supported."  This assessment is based on data collected in 2004, 2010 and 2014 as part of the IDNR/SHL stream REMAP and biocriteria projects.  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 of fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).  The 2004 REMAP BMIBI scores were 86, 79 (excellent), and 70 (good).  The 2010 FIBI score was 57 (good) and the BMIBI score was 60 (good).  The 2014 FIBI score was 63 (good) and the BMIBI score was 50 (fair). The aquatic life use support assessment was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports.  The biological impairment criteria were determined 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 44, the natural substrate BMIBI BIC for this ecoregion is 70 and the artificial substrate BMIBI BIC is 52.  This segment passed the FIBI BIC 2/2 times in the last five years (2010-2014) and passed the BMIBI BICs 4/5 times (2x natural and 2x artificial) in the last 11 years.  For the 2006 assessment, this segment was assumed to contain stable riffle habitat based on best professional judgment and anecdotal data.  However, quantitative habitat data from the 2004 REMAP sampling was discovered and analyzed.  After comparing the results of the quantitative habitat data analysis to the riffle habitat requirements, it was determined that the sample site should be classified as "non-riffle" instead of "riffle". 

This aquatic life assessment is now considered "monitored" 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 a recent five-year period to be considered “monitored”.  This segment had multiple samples collected in the previous five years (2010-2014).

Results of IDNR surveys of freshwater mussels at two sites in this assessment segment in August 2012 suggest that the previously-identified biological impairment of the Class B(WW1) aquatic life uses based on the apparent decline of freshwater mussels no longer exists.  The following is a summary of these surveys:

--Number of freshwater mussel species from surveys conducted in 1984 (Frest (1987), in 1998 (Arbuckle et al. 2000), and IDNR Watershed Improvement Section staff (J. Kurth) in August 2012:

               1984      1998        2012
Site 12:      10          2             9
Site 13:       9           6            12

The original impairment was based on a comparison of sampling results from 1998 and 1999 (Arbuckle et al. 2000) to results from stream sites surveyed in 1984 and 1985 by Frest (1987).  Impairment was based on the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey.  Greater than a 50% decline in species richness from the 1984-85 to the 1998-99 period suggested an impairment of the aquatic life uses.  Based on IDNR’s assessment approach, the degree of decline (>50%) in the number of freshwater mussel species in this segment suggested “partial support” (impairment) of the Class B(WW) aquatic life uses for purposes of both Section 303(d) listing and 303(d) reporting.  Results of the IDNR's surveys in 2012, however, show recovery in the number of freshwater mussel species at the sites used to identify the original impairment (Sites 12 and 13), with 90% as many species found at Site 12 in 2012 than were found in 1984, and three more species were found at Site 13.  Due to the lack of a protocol for identifying biological thresholds that indicate "full support" of a freshwater mussel community, this impairment was moved from Category 5b of Iowa's Integrated Report to IR Category 3a (insufficient information to develop an assessment of support of uses). 

The assessment of support of fish consumption uses is changed from “fully supported” to “not assessed” due to age of data.  Previous assessments of fish consumption uses (“fully supported”) were based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Twin Ponds Park in 2003.  These data are now considered too old (greater than 10 years) for assessing current water quality conditions.  As water quality data age, they become less able to represent current water quality conditions.  Thus, according to IDNR’s assessment/listing methodology, non-impairment assessments based on data older than ten years will be considered “not assessed”.