Iowa DNR

Water Quality Assessments

Impaired Waters List

West Nishnabotna River IA 05-NSH-1441

from confluence with Silver Cr. (S21, T71N, R41W, Mills Co.) to confluence Farm Cr. in S9, T73N, R40W, Mills Co.

Assessment Cycle
Release Status
Result Period
1996 - 1998
Assessment Type
Integrated Report
Category 0
Legacy ADBCode
IA 05-NSH-0080_1
Overall Use Support
Aquatic Life Use Support
Fish Consumption
Not assessed
Assessment Comments

Assessment is based on results of IDNR ambient monthly water quality monitoring near Malvern.

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 is based on results from the DNR quarterly monitoring station on the West Nishnabotna River near Malvern.   The Class B(WW) uses were assessed as "fully supported" due to (1) the lack of violations of Class B(WW) criteria for pH, dissolved oxygen, and ammonia-nitrogen in the eight samples analyzed during the 1998-1999 biennial period and (2) the lack violations of Class B(WW) chronic criteria for toxic metals in the two samples analyzed during this biennial period.   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 Malvern 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
9/4/2001 Fixed Monitoring End Date
10/4/1999 Fixed Monitoring Start Date
230 Fixed station physical/chemical (conventional plus toxic pollutants)
Monitoring Levels
Biological 0
Habitat 0
Physical Chemistry 3
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