Iowa DNR

Water Quality Assessments

Impaired Waters List

Walnut Creek IA 03-SSK-953

mouth (S5 T82N R23W Story Co.) to confluence with unnamed tributary in SE 1/4 S34 T83N R24W Story Co.

Assessment Cycle
Result Period
2000 - 2002
Assessment Methodology
Assessment Type
Integrated Report
Category 5b
Legacy ADBCode
IA 03-SSK-0058_0
Overall Use Support
Aquatic Life Use Support
Assessment Comments

Assessment is based on results of IDNR/UHL biological (biocriteria) monitoring in 1999: Fish IBI= 42(fair), BM-IBI= 59(good).

Basis for Assessment

SUMMARY:  The Class B(LR) aquatic life uses are assessed (monitored) as "partially supported"  based on results of IDNR/UHL biological (biocriteria) sampling in 1999.   This is the same assessment as that developed for the 2002 reporting cycle.

EXPLANATION:  The assessment was based on data collected in 1999 as part of the DNR/UHL stream biocriteria project.   A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (F-IBI) and a benthic macroinvertebrate index (BM-IBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 1999 Fish IBI score was 42 (fair) and the BM-IBI score was 59 (good).  The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report.  The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.

Monitoring and Methods
Assessment Key Dates
7/15/1999 Biological Monitoring
7/15/1999 One-time Chemical Monitoring
320 Benthic macroinvertebrate surveys
330 Fish surveys
380 Quan. measurements of instream parms-- channel morphology-- floodplain-- 1-2 seasons-- by prof
220 Non-fixed station physical/chemical monitoring (conventional pollutant only)
315 Regional reference site approach
Monitoring Levels
Biological 4
Habitat 4
Physical Chemistry 1
Toxic 0
Pathogen Indicators 0
Other Health Indicators 0
Other Aquatic Life Indicators 0
# of Bio Sites 1
BioIntegrity Fair
Causes and Sources of Impairment
Causes Use Support Cause Magnitude Sources Source Magnitude
Cause Unknown Aquatic Life Support Moderate
  • Source Unknown
  • Moderate