Iowa DNR

Water Quality Assessments

Impaired Waters List

Rock River IA 06-BSR-1534

mouth (S1, T95N, R48W, Sioux Co.) to confluence with Little Rock R. in S35, T98N, R46W, Lyon Co.

Assessment Cycle
Release Status
Result Period
1996 - 1998
Assessment Type
Integrated Report
Category 0
Legacy ADBCode
IA 06-BSR-0030_0
Overall Use Support
Aquatic Life Use Support
Fish Consumption
Not assessed
Assessment Comments

Assessment is based on results of IDNR quarterly ambient water quality monitoring near the mouth of the Rock River in 1996 & 1997.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses were assessed as "fully supported."  Fish consumption uses remain "not assessed."  EXPLANATION:  The assessment of support of the Class B(WW) uses was based on results of water quality monitoring during the 1996-1997 biennial period at the DNR quarterly monitoring station near the mouth of the Rock River (station 975005).   For the 1998 report, the Class B(WW) aquatic life uses were assessed as "fully supported" but "threatened" based entirely on "best professional judgement;" the assessment of "threatened" was not supported by field assessments of either habitat or the biological communities.   Until such assessments are conducted, the assessment of support of the Class B(WW) uses will be based only on results of the available information on chemical water quality monitoring and the comparisons of these results to the Iowa Water Quality Standards.   Thus, the assessment of support of the Class B(WW) uses was changed from "fully supported / threatened" to "fully supporting" for the 2000 report.   This assessment was based on results of quarterly monitoring.   Results from stations monitored monthly or more frequently, however, are preferred for Section 305(b) assessments in order to improve the accuracy and confidence level of the assessment.   As part of DNR's expanded water quality monitoring program, monthly monitoring at the Rock River station began in October 1999.   Fish consumption uses remain "not assessed" due to the lack of fish tissue monitoring in this river reach.

Monitoring and Methods
Assessment Key Dates
230 Fixed station physical/chemical (conventional plus toxic pollutants)
Monitoring Levels
Biological 0
Habitat 0
Physical Chemistry 0
Toxic 0
Pathogen Indicators 0
Other Health Indicators 0
Other Aquatic Life Indicators 0
# of Bio Sites 0
BioIntegrity N/A
Causes and Sources of Impairment
Causes Use Support Cause Magnitude Sources Source Magnitude