Buffalo Creek IA 01-WPS-374

Assessment Comments

Assessment based on the results of (1) IDNR/UHL monthly ambient water quality monitoring in 2001 and (2) IDNR/UHL biological (biocriteria) monitoring in 2001 (Fish IBI= 73 (excellent), 67 (good); BM-IBI= 71 (good), 57 (good)).

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported/threatened"  based on results of biological monitoring at two locations on this segment of Buffalo Creek in 2001.   Results of ambient water quality monitoring in 2001 did not show violations of state water quality standards.   Fish consumption uses were "not assessed."  The sources of data for this assessment include (1) the results of  IDNR/UHL monthly water quality monitoring conducted on Buffalo Creek from March to November, 2001, approximately 4 miles east of Central City (TMDL Site 13) in support of TMDL development and (2) the results of IDNR/UHL biological (biocriteria) monitoring in 2001 at two locations:  (1) east of Central City (same site as TMDL Site 13) and (2) at Frozen Hill Road.  

EXPLANATION:  The Class B(WW) aquatic life uses were assessed as "fully supported/threatened" due to the biological assessment, based on data 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 scores were 73 (excellent) and 67 (good), and the BM-IBI scores were 71 (good) and 57 (good).  The aquatic life use support was assessed as fully supported/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.      

The results of IDNR/UHL ambient water quality monitoring do not suggest any impairments to water quality.   There were no 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, however, analyzed for toxic metals or toxic organic compounds.   The available data suggest good water quality, including relatively low levels of ammonia-nitrogen (maximum of 0.3 mg/l).   No fish kills were reported for this segment of Buffalo Creek from 2000 through 2002.  

The fish consumption uses remain "not assessed" due to the lack of recent fish tissue monitoring in this river reach.