Assessment Comments
Assessment is based on results of IDNR/UHL biological (biocriteria) monitoring in 1995: Fish IBI= 56(good), BM-IBI= 46(fair).
Basis for Assessment
[Note: For the 2002 report, the previous waterbody segment IA 02-IOW-0090-0, which extended 26 miles from its mouth to its confluence with South Fork Long Creek near Ainsworth, was split into three subsegments: (1) from its mouth (S1, T74N, R4W, Louisa Co.) to confluence with unnamed tributary in N1/2, S21, T74N, R4W, Louisa Co. (IA 02-IOW-0090-1), (2) from confluence with unnamed tributary in N1/2, S21, T74N, R4W, Louisa Co. to N line, S3, T74N, R5W, Louisa Co. (IA 02-IOW-0090-2), and (3) from N line, S3, T74N, R5W, Louisa Co. to confluence with S. Fork. Long Cr. in S26, T75N, R6W, Washington Co. (IA 02-IOW-0090-3). See assessment information for segment IA 02-IOW-0090-2 for earlier Section 305(b) assessments for the original 26-mile stream reach.]
SUMMARY: The Class B(LR) aquatic life uses remain assessed as "partially supported" based on results of IDNR/UHL biocriteria monitoring in September 1995. The assessment category, however, is changed from "monitored" to "evaluated." This assessment is the same as that used for the downstream segment (IA 02-IOW-0090-1). Because this stream segment was assessed as "monitored" and impaird for previous reporting cycles, this stream segment is a candidate for Section 303(d) listing.
EXPLANATION: Continue to use the assessment developed for the 1998 report (see above) that was based on results of the 1995 IDNR biocriteria assessment. That assessment was based on data collected in 1995 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 F-IBI score was 56 (good) and the BM-IBI score was 46 (fair). The aquatic life use support was assessed as partially supported (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2000 Section 305(b) report. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-1998. Bbecause these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is changed from "monitored" (indicating an assessment with relatively high confidence) to "evaluated" (indicating an assessment with relatively low confidence).
