Assessment Comments

Assessment is based on (1) results of monitoring of fish, macroinvertebrates, habitat & water quality as part of the Sny Magill / Bloody Run project and (2) DNR summary of trout reproduction. Highlighted in Iowa Conservationist.

Basis for Assessment

SUMMARY:  The Class B(CW) coldwater aquatic life uses were assessed as "fully supported / threatened" (minor impacts).   Fish consumption uses remain "not assessed."  EXPLANATION:  Based on a summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau, the Class B(CW) uses were assessed as "fully supported / threatened."  According to Moeller (1999), Bloody Run Creek is in the category of Iowa trout streams that have at least some documented natural reproduction but that are generally unable to maintain a viable trout population at this time.   Monitoring of chemical water quality, habitat quality, fish populations, and aquatic macroinvertebrate populations has been conducted at Bloody Run 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.   Results of weekly chemical water quality monitoring from October 1996 through September 1999 at stations on the lower and middle reaches of this stream show (1) no violations of the Class B(CW) water quality criterion for dissolved oxygen (7.0 mg/l) in the 312 samples collected and (2) three estimated violations of the Class B(CW) chronic criterion for ammonia-nitrogen in 311 samples collected (estimated violations occurred at the middle reach station on March 11, 1997 and at both the lower and middle reach stations on March 18, 1997).   Results of monthly monitoring at the upper reach station show no violations of criteria for dissolved oxygen and one estimated violation of ammonia-nitrogen in the 36 samples collected.   The estimated violation of ammonia nitrogen occurred on March 31, 1998.   According to U.S.  EPA guidelines for Section 305(b) reporting (U.S.  EPA 1997b, page 3-18), these violations suggest an impairment of the aquatic life uses.   For the following reasons, however, these violations were not used in the assessment of the aquatic life uses:  (1) violations of the temperature/pH-dependent water quality criteria for ammonia-nitrogen were based on "worst case" estimated values of pH (pH was not measured during sample collection at the Sny Magill / Bloody Run project sites); (2) three of the four estimated violations were relatively close to the corresponding water quality criteria (March 11, 1997:  NH3-N = 0.6 mg/l; WQ criterion = 0.4 mg/l;  March 18, 1997:  NH3-N = 0.7 mg/l; WQ criterion = 0.55 mg/l; March 31, 1998:  0.40 mg/l; WQ criterion = 0.39 mg/l)).   The episodes of low dissolved oxygen that occurred in the Sny Magill and Bloody Run watersheds from 1992-1994 (see assessments for the 1996 and 1998 reports above) were due, at least in part, to problems with field equipment and certain reagents used to measure dissolved oxygen.   Since July 1995, measurements have been made with a YSI portable dissolved oxygen meter.   During the period October 1996 through September 1999, none of the samples collected at monitoring sites in the Sny Magill Nonpoint Source project have violated the Class B(CW) water quality criterion for dissolved oxygen of 7.0 mg/l.   Based on the Hilsenhoff Biotic Index, results of biological monitoring for benthic macroinvertebrates suggest "very good" water quality.   Fish consumption uses remain "not assessed" due to lack of recent fish tissue monitoring in this stream reach.   For more information on the Sny Magill Creek Nonpoint Source Pollution Monitoring Project visit the DNR-Geological Survey Bureau web site at http://www.igsb.uiowa.edu/inforsch/waterag.htm.