Wapsipinicon River IA 01-WPS-347

Assessment Comments

Assessment is based on results of (1) USGS monitoring of fish tissue and water quality near Tripoli in 2001 and (2) statewide survey of freshwater mussels in 1998-99. See attached document for details.

Basis for Assessment

No info.  available; not assessed for the 1994 or 1996 reports.  

For 1998 report, used results of fish tissue monitoring conducted for the USGS National Water Quality Assessment (NAWQA) program in the eastern Iowa river basins study area in September 1995.  The whole fish composite sample of white sucker was analyzed for several oranochlorine compounds, including chlordane, dieldrin, DDT and PCBs.   Levels of these contaminants in the composite sample were relatively low compared to the other 15 sites in the study.   Thus, assess support of fish consumption uses as FS.  See USGS Fact Sheet FS-027-97 (March 1997) for more information.  Information from the March/April Iowa Conservationst suggests that the Class B(WW) aquatic life uses are fully supported; i.e., this reach is identified as providing good angling opportunities for northern pike.   Additional information, however, is needed on the status of the aquatic communities of this river reach in order to develop an accurate assessment of support of the Class B(WW) uses.  

For the 2000 report:  SUMMARY:  The Class B(WW) aquatic life uses were assessed as "fully supported;" the fish consumption uses remain assessed as "fully supported."  EXPLANATION:  Results of monitoring conducted on the Wapsipinicon River near Tripoli from March 1996 to September 1998 by USGS as part of the National Water Quality Assessment Program (NAWQA) (eastern Iowa river basins study unit, station 05420680) showed (1) no violations of Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the 36 samples collected and (2) no violations of Class B(WW) criteria for toxic organic compounds or pesticides in the 22 samples analyzed.   This lack of violations suggests "full support" of the Class B(WW) aquatic life uses.   Fish consumption uses remain assessed as "fully supported" based on results of the USGS/NAWQA fish tissue monitoring in September 1995 that showed levels of organochlorine contaminants in the composite sample of whole fish white sucker was less than ½ of the respective FDA action levels and DNR levels of concern (see assessment for the 1998 report above).    

[Note:  For the 2002 report, the previous waterbody segment IA 01-WPS-0020-2, which extends 18 miles from Snyder Access to the Little Wapsipinicon River in Chickasaw County, was renamed IA 01-WPS-0020-8.]

For the 2002 report:  SUMMARY:  The Class B(WW) aquatic life uses are assessed (evaluated) as "fully supported / threatened"; the fish consumption uses are "not assessed."  The sources of information for this assessment include (1) the results of monitoring conducted on Wapsipinicon River near Tripoli from (a) March 1996 through September 1998 and (b) from January through September 2001 by USGS as part of the National Water Quality Assessment Program (NAWQA) (eastern Iowa river basins study unit, station 05420608) and (2) results of a statewide survey of freshwater mussels conducted by Iowa State University in 1998-99.   EXPLANATION:  Similar to results of USGS monitoring from 1996 through 1998, the results of USGS NAWQA monitoring in 2001 suggest "full support" of the Class B(WW) aquatic life uses.   This monitoring showed (1) no violations of Class B(WW) water quality criteria for pH, dissolved oxygen, or ammonia-nitrogen in the 9 samples collected from January through September 2001 and (2) no violations of the Class B(WW) chronic water quality criterion for pesticides in the 9 samples analyzed during this period.   Results from the 1998-99 statewide assessment of freshwater mussels in Iowa streams, however, suggest a potential threat to full support of the aquatic life uses of this stream segment.   As part of this study, sampling results from 1998 and 1999 (Arbuckle et al.  2000) were compared to results from stream sites surveyed in 1984 and 1985 by Frest (1987).   In general, this comparison showed sharp declines in the numbers of mussel species ("species richness") from the mid-1980s to the late 1990s.   For purposes of Section 305(b) reporting, 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.   This assessment included the following factors:  (1) the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey and (2) the number of mussel species found in the 1998-99 survey.   Greater than a 50% decline in species richness from the 1984-84 to the 1998-99 period suggests an impairment of the aquatic life uses.   In addition, low species richness in the 1998-99 survey suggests potential impairment.   For purposes of Section 305(b) assessment only, staff of the IDNR Water Quality Bureau used results from Arbuckle et al.  (2000) to define categories of species richness for Iowa's mussel communities:  less than three species indicates low species richness and "nonsupport" or "partial support" of aquatic life use; from four to seven species indicates moderate species richness and potential minor impacts (="fully supported / threatened"); more than seven species indicates high species richness and "full support" of aquatic life uses.   Species richness of freshwater mussels at the three sample sites in this stream segment were 8, 6, and 4 in the 1984-85 period and were 6, 6, and 4, respectively, in the 1998-99 period for an average percent change of only -8%.   The comparison of species richness between the 1984-85 and 1998-99 periods thus suggest relatively little change in the mussel community of this stream segment.   Based on these results, and based on the assessment framework described above, the "full support" of aquatic life uses suggested by results of USGS ambient monitoring is downgraded slightly to "fully supported / threatened."  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.   Fish consumption uses are "not assessed" due the lack of recent fish contaminant monitoring in this river segment.   The previous assessment of fish consumption uses for this river segment ("fully supported") was based on results of the USGS/NAWQA fish tissue monitoring in September 1995 (see assessment for the 1998 report above).   These data are now considered too old (greater than five years) for characterizing current water quality conditions.