Indian Creek IA 02-CED-1875

Assessment Comments

Assessment based on 2000 biocriteria data: Fish IBI= 44 (fair), BM-IBI= 79 (excellent).

Basis for Assessment

[Note:  For the 2002 report, the previous waterbody segment for the Indian Creek (IA 02-CED-0210-0), which extended 16 miles from its mouth to an unnamed tributary in Linn County, was split into two subsegments:  (1) mouth to Dry Creek (IA 02-CED-0210-1) and (2) Dry Creek to unnamed tributary in S20, T84N, R6W, Linn Co, approximately 2 miles NNE of Marion (IA 02-CED-0210-2).   See the assessment information for segment IA 02-CED-0210_1 for previous Section 305(b) assessments for the original 16-mile river reach.]

[For the 2002 report, data that was collected in waterbody segment IA 02-CED-0211-0 was erroneously used to assess waterbody segment IA 02-CED-0210-2.   That assessment has now been deleted and can be found here.]

The assessment was based on data collected in 2000 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 2000 Fish IBI score was 44 (fair) and the BM-IBI score was 79 (excellent).  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.