Iowa River IA 02-IOW-647

Assessment Comments

Assessment based on 2005 REMAP data: FIBI = 63 (good), 71 (excellent); BMIBI = 68 (good), 71 (good).

Basis for Assessment

SUMMARY/EXPLANATION:  The Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment.

The evaluated biological assessment of the Class B(WW1) aquatic life uses was based on data collected in 2005 as part of the DNR/UHL stream REMAP project.   A series of biological metrics that 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 collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2005 FIBI scores were 63 (good), 71 (excellent) and the BMIBI scores were 68 (good), 71 (good).   The FIBI average was 67 and the BMIBI average was 69.5.   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   This site segment passed all of the FIBI and BMIBI BICs from both the 47b and 47f ecoregions.   This assessment is considered evaluated because the drainage area (748 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site passed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.