Assessment Comments

Assessment based on 2001 biocriteria data: Fish IBI=68 (good), BM-IBI=52(fair).

Basis for Assessment

[Note:  For the 2002 report, the previous waterbody segment IA 01-WPS-0110-0 from the mouth of Buffalo Creek to Coggon Dam was split into three subsegments:  (1) mouth to Jones/Linn county line (IA 01-WPS-0110-1), (2) Jones/Linn county line to Boulder Creek (IA 01-WPS-0110-2), and (3) Boulder Creek to Coggon Dam (IA 01-WPS-0110-3).   The assessment information above applies to the original waterbody segment (IA 01-WPS-0110-0).]

SUMMARY:  The Class B(WW) aquatic life uses were assessed as fully supporting / threatened (=FST).   Fish consumption uses were "not assessed."  The source of data for this assessment is the results of  IDNR/UHL monthly monitoring conducted from March to November, 2001, near the mouth of Buffalo Creek at Anamosa (Site 11) in support of TMDL development for this stream reach.   EXPLANATION:  The Class B(WW) aquatic life uses were assessed as "fully supported" due to the lack of violations of state water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in the nine samples collected from the TMDL monitoring station during 2001.   These samples were not analyzed for toxic metals or toxic organic compounds.   The available data do, however suggest good water quality, including relatively low levels of ammonia-nitrogen.   No fish kills were reported for this segment of Buffalo Creek in 2000 or 2001.   The fish consumption uses remain "not assessed" due to the lack of recent fish tissue monitoring in this river reach.  

Biological assessment data were collected in 2001 as part of the DNR/UHL stream biocriteria project.   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 (F-IBI) and a benthic macroinvertebrate index (BM-IBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2001 Fish IBI score was 68 (good) and the BM-IBI score was 52 (fair).  The aquatic life use support was assessed as fully supporting / threatened (=FST) based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report.  The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.