Turkey River IA 01-TRK-149

Assessment Comments

Assessment remains based on 2000 IDNR Fisheries data: FIBI = 51 (good). FIBI BIC = 52.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses remain "not assessed" due to lack of information upon which to base an assessment.    The Class B(WW1) aquatic life uses remain assessed (evaluated) as "fully supported" based on DNR Fisheries stream sampling in 2000.  

EXPLANATION:  The assessment of the Class B(WW1) aquatic life uses remains based on data collected in 2000 as part of an IDNR Fisheries stream sampling project: Manchester research station.    A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data.    The biological metrics are based on the numbers and types of 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).    The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).    The 2000 evaluated FIBI was 51 (good).    The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI  score with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.    The FIBI BIC for this ecoregion is 52.    This site meets the FIBI BIC with the use of the uncertainty adjustment value (UAV) of seven points applied to single sample assessments.    This assessment is considered evaluated because the drainage area (1000 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 the FIBI BIC, 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.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology.   IDNR now requires a segment have two or more biological samples collected from the segment in multiple years between 2004 and 2008 to be considered “monitored”.   This segment had a single sample collected in 2000.   Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).    Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.