Dutton Creek IA 01-TRK-6285

The assessment of the presumptive Class B(WW1) aquatic life uses was based on data collected in 2011 and 2014 as part of the DNR/SHL cold water stream sampling projects. 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 (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 2011 BMIBI score was 84 (excellent) and the 2014 BMIBI score was 79 (excellent). The 2014 FIBI score was 19 (poor) because only one species, Brook Trout, was collected in this segment. The aquatic life use support was assessed (monitored) as fully supporting (=FS), based on a comparison of the BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The BMIBI BIC for this ecoregion is 61 and the FIBI score was not used in the assessment. Even though this site passed the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small headwater stream and doesn’t fall in the calibrated watershed size.

The 2011 and 2014 sampling data suggest that this stream is a coldwater stream. However, until a Use Attainability Assessment can be completed, the presumptive designated uses for this stream are the presumptive Class A1 (primary contact recreation) and Class B(WW1) aquatic life. Below is the cold water assessment for this segment.

The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2011 and 2014 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 65 and the 2014 CBI score was 66. The aquatic life use support was assessed (monitored) as fully supporting (=FS), based on a comparison of the CBI scores 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 2/2 times in the last six years.

The CW assessment was also based on the updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in January 2019. This summary also suggests the Class B(CW1) uses are "fully supported". According to the updated summary, Dutton (Cave) 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 recent, but inconsistent reproductive success and that are generally not capable of maintaining a viable population of Brook Trout at this time (a Category II stream).