Assessment Comments
Assessment based on 2006 UHL special project benthic macroinvertebrate sampling data: 1/4 coldwater biological indicators met the criteria = PS and on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006.
Basis for Assessment
Note: Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(CW) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is also now presumptively designated for Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses. This segment remains designated for coldwater aquatic life use (now termed Class B(CW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption) uses. This stream segment also remains identified as an “HQ” (high quality) water.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses and presumptive Class A2 (secondary contact recreation) uses are "not assessed" due to the lack of data for indicator bacteria upon which to base an assessment. The Class B(CW1) coldwater aquatic life uses are assessed (monitored) as "partially supported" based UHL benthic macroinvertebrate sampling data. Fish consumption uses are "not assessed."
EXPLANATION: The assessment of the Class B(CW) aquatic life uses was based on data collected in 2006 as part of a UHL special project. A series of four (4) coldwater biological indicators, which reflect stream water quality and habitat integrity, were calculated from the biocriteria sampling data. The coldwater biological indicators are based on the numbers and types of coldwater benthic macroinvertebrate taxa that were collected in the stream sampling reach. Sites that score 4/4 or 3/4 are Fully Supporting (FS), sites that score 2/4 or 1/4 are Partially Supporting (PS), and sites that score 0/4 are Not Supporting (NS). The 2006 coldwater biological indicator score was 1/4. The aquatic life use support was assessed (monitored) as Partially Supporting (=PS), based on a comparison of the coldwater biological indicator score with biological assessment criteria established for previous Section 305(b) reports. The coldwater biological indicators were determined from a statistical analysis of data collected at coldwater stream ecoregion reference sites from 1994-2004.
In contrast to the benthic macroinvertebrate sampling data, an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006, suggests the Class B(CW1) uses are are "fully supported". According to the updated summary, Little Turkey River is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the IDNR 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 for the resident trout species at this time. This assessment is consistent with previous assessments of the ability of this stream to support natural reproduction of trout.
Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.
