Sny Magill Creek IA 01-YEL-430

Assessment Comments

Assessment remains based on (1) results of at Sny Magill project sites monitored for water quality at varying frequencies in 2000-01 and (2) a 2006 DNR summary of trout reproduction.

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 remain assessed (monitored)  as "fully supported."  Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this coldwater stream.   Sources of data for this assessment include (1) an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006 and (2) results of water quality monitoring conducted from January 2000 through September 2001 at three sites on Sny Magill Creek:  Site 1 (IDNR station 15220004), Site 2 (IDNR station 15220005), Site 3 (IDNR station 15220002).

EXPLANATION:  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 remain assessed as "fully supported".   According to the updated summary, Sny Magill Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout.   In previous IDNR summaries of trout reproduction, this stream was placed in the category of Iowa trout streams that have fairly consistent natural reproduction and that are capable of maintaining a viable population for the target trout species without any stocking.   Based on results of surveys by the IDNR Fisheries Bureau, however, this stream is now 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.   Although still considered “fully supporting”, this assessment based on the updated (2006) summary of trout reproduction reflects a decline in the ability of this stream to support natural reproduction of trout.  

This assessment is also supported by results of chemical water quality monitoring conducted from 1996 through 1999 (see assessment for the 2000 report).   Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.   Monitoring of chemical water quality, habitat quality, fish populations, and aquatic macroinvertebrate populations has been conducted at Sny Magill Creek since 1992 as part of the Sny Magill Creek Nonpoint Source Pollution Monitoring Project.   Results of this monitoring show good chemical water quality and aquatic life.  

The Class B(CW1) aquatic life uses were also assessed as "fully supported" based on results of water quality monitoring from January 2000 through September 2001 at three monitoring sites on Sny Magill Creek.   Of the approximately 200 samples analyzed at these stations, no samples violated the respective Class B(CW) water quality criteria for dissolved oxygen and temperature.  

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