Yellow River IA 01-YEL-437

Assessment Comments

Assessment is based on (1) the 2000 IDNR/UHL Biocriteria sampling: FIBI = 51 (good); BMIBI = 60 (good) and (2) results of IDNR/UHL ambient monitoring in 2004. FIBI BIC = 52, BMIBI BIC = 61.

Basis for Assessment

SUMMARY:  The Class B(LR) aquatic life uses of this stream segment are assessed (evaluated) as “fully supported” based on data collected in August 2000 as part of the IDNR/UHL stream biocriteria project.   Results of IDNR/UHL water quality monitoring from May to December 2004 at station 15960002 (at the 107th Avenue crossing) do not show problems with levels of dissolved oxygen.

EXPLANATION:  A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data collected on August 15, 2000.   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 (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 2000 FIBI score was 51 (good) and the BMIBI score was 60 (good).  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 for previous Section 305(b) reports.  The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61.   According to IDNR methodology, if both the FIBI (7) and BMIBI (8) scores need to have the uncertainty adjustment value (UAV) applied to meet the BICs, the assessment is considered evaluated.

The results of IDNR/UHL water quality monitoring in 2004 show only 2 violations of the Class B(LR) criterion for dissolved oxygen (5.0 mg/l) in the 26 samples (8%) collected.   These violations were relatively minor (4.4 and 4.9 mg/l).   According to U.S.  EPA guidelines (U.S.  EPA 1997b, page 3-17), a violation frequency of less than 10 % for conventional parameters such as dissolved oxygen suggest "full support" of aquatic life uses.   Thus, the percentages of violations of the dissolved oxygen criterion at this monitoring stations does not suggest an impairment of aquatic life uses.