ADBNet

Assessment Comments

Assessment based on 2002 and 2007 IDNR/UHL biocriteria sampling data: 6/8, 7/8 coldwater biological indicators met the criteria - Fully Supporting (FS) 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 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.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses and the presumptive Class A2 (secondary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment.   The Class B(CW1) coldwater aquatic life uses are assessed (monitored) as "fully supported."  Fish consumption uses remain "not assessed."  The sources of data for this assessment are (1) results of IDNR/UHL biological (biocriteria) monitoring in 2002 and 2007 and (2) results of an IDNR Fisheries Bureau summary of trout reproduction in Iowa’s coldwater streams.

EXPLANATION:  The assessment of the Class B(CW1) coldwater aquatic life uses remains based on data collected in 2002 and 2007 as part of the IDNR/UHL stream biocriteria project.   A series of eight (8) coldwater biological indicators, which reflect stream water quality and habitat integrity, were calculated from the biocriteria sampling data and supplemental IDNR Fisheries Bureau data.   The coldwater biological indicators are based on the numbers and types of coldwater benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach.   Sites that score 5-8 are Fully Supporting (FS), sites that score 2-4 are Partially Supporting (PS), and sites that score 0-1 are Not Supporting (NS).   The 2002 coldwater biological indicator score was 6/8 and the 2007 score was 7/8.   The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the coldwater biological indicator score with biological assessment criteria established for this Section 305(b) report.   The coldwater biological indicators were determined from a statistical analysis of data collected at coldwater stream ecoregion reference sites from 1994-2008 and with assistance from the IDNR Fisheries Bureau.    

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology.   IDNR now requires a segment have two or more biological samples collected from the segment in multiple years between 2004 and 2008 to be considered “monitored”.   This segment had multiple samples collected in the previous seven years (2002-2008); however, the multiple samples were not collected during 2004-2008.   Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.

In addition, based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006, the Class B(CW1) uses are assessed as "fully supported".   According to the updated summary, Smith Creek (aka Trout 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 fairly consistent natural reproduction and maintain a viable population of the listed species without any stocking.  

Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.