Cedar Creek IA 04-RAC-1156

The aquatic life uses remain assessed (evaluated) as “fully supporting” based on biological data collected in 1998 and 2002 as part of the DNR/SHL REMAP and DNR Fisheries sampling projects. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological 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 (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 1998 Fisheries FIBI score was 41 (fair). The 2002 FIBI score was 43 (fair) and the BMIBI score was 64 (good). The aquatic life use support was assessed 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 1994-2008. The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. This segment passed the FIBI BIC 2/2 times in the last 19 years and passed the BMIBI BIC 1/1 times in 2002.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years over a recent five-year period to be considered “monitored”. This segment had multiple FIBI samples collected in the previous 19 years (1998-2016); however, the multiple samples were not collected during a recent five-year period. 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.

Threats to the continued support of the Class B(WW2) uses include over-pasturing of the riparian corridor and channelization in headwater reaches.