North Cedar Creek IA 01-YEL-431
mouth (S8 T94N R3W Clayton Co.) to west line of S24 T94N R4W Clayton Co.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
- Trend
- Unknown
- Created
- 5/8/2019 11:29:15 AM
- Updated
- 8/30/2019 8:57:50 AM
The Class B(CW1) coldwater aquatic life uses are assessed (monitored) as "fully supported" based on the results of DNR/SHL biological sampling conducted in 2011, 2014 and 2015 and on the January 2019 summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau. The Class A1 (primary contact recreation) uses, Class A2 (secondary contact recreation) uses and Class HH (fish consumption) uses remain "not assessed" due to the lack of information upon which to base an assessment.
The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2011, 2014 and 2015 as part of the DNR/SHL coldwater stream sampling project. A series of biological metrics which reflect coldwater 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 that were collected in the stream sampling reach. The biological metrics were combined to make a coldwater benthic index (CBI). The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2011 CBI score was 63, the 2014 score was 51 and the 2015 scores were 69 and 55. The aquatic life use support was assessed (monitored) as fully supporting (=FS), based on a comparison of the CBI score with biological impairment criteria (BIC) established for the 2012 Section 305(b) report. The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011. The CW BIC is 60 and this segment passed the CW BIC 2/4 times in a six year period (2011-2016). DNR normally requires a segment to have a simple majority of passing scores from multiple years in a five-year period to be considered fully supporting (monitored). However, this assessment of North Cedar Creek includes the professional judgment of DNR staff incorporating an in-depth analysis of the metric scores, sampling conditions and the fish sampling that occurred at the time the benthic macroinvertebrates were sampled. Additionally, the fish sampling conducted at this segment combined with the natural reproduction data (see below) indicate a healthy trout population in this segment. In addition, the B(CW1) aquatic life assessment was based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in January 2019, the Class B(CW1) uses are assessed as "fully supported". According to the updated summary, North Cedar Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the DNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams that exhibit consistent natural reproduction and maintain a wild population of brook and brown trout without any stocking (a Category I stream). The Class A1 (primary contact recreation) uses, Class A2 (secondary contact recreation) uses and Class HH (fish consumption) uses remain "not assessed" due to the lack of information upon which to base an assessment.