Whitewater Creek IA 01-NMQ-103

The Class A1 (primary contact recreation) uses remain assessed (monitored) as “not supported” based on results of IDNR bacteria monitoring in 2012 and 2013.  The geometric means of indicator bacteria (E. coli ) in the 14 samples collected during the recreational seasons of 2012 and 2013 at station 15310001 were as follows:  the 2012 geometric mean was 717 orgs/100 ml, and the 2013 geometric mean was 4,404 orgs/100 ml.  Both geometric means exceed the Class A1 criterion of 126 orgs/100 ml.  Thirteen of the 14 samples (93%) exceeded the Class A1 single-sample maximum criterion sample maximum criterion of 235 orgs/100 ml.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.” 

For purposes of Section 303(d) listing, the assessment of the Class B(WW1) aquatic life uses remains based on the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey.  For stream segments having four or more species reported for the 1984-95 survey, results of this comparison were used by staff of the Iowa DNR Water Quality Bureau to assess the degree to which the aquatic life uses of the sampled stream segments are supported.  Greater than a 50% decline in species richness from the 1984-85 to the 1998-99 period suggests an impairment of the aquatic life uses.  Species richness of freshwater mussels at the two sample sites in this segment of Whitewater Creek was 8 and 3, respectively, in the 1984-85 period (average of 5 species) and was zero at both sites  in the 1998-99 period for an average percent change of minus 100%.  Based on these results, the aquatic life uses are assessed (monitored) as “not supported.”  As presented by Arbuckle et al.  (2000), the potential causes of declines in species richness of Iowa's freshwater mussels include siltation, destabilization of stream substrate, stream flow instability, and high instream levels of nutrients (phosphorus and nitrogen).  Their study also suggested the importance of stream shading provided by riparian vegetation to mussel species richness. 

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).  Despite this change in assessment type, this waterbody remains in IR Category 5b. 

Previous assessments of the aquatic life uses of this stream segment were based on occurrence of a fish kill in June 2011.  The kill was attributed to runoff of animal waste.  Iowa DNR follow-up monitoring in October 2013 showed that the fish community in this stream segment was similar to other non-fish kill-affected streams in this ecoregion.  Thus, the fish kill-related impairment of the designated aquatic life uses was moved from IR Category 4d (impaired but TMDL not required) to IR Category 3a (not assessed) for the 2014 Integrated Reporting cycle.  

 Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment