Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Walnut Creek IA 02-IOW-708

mouth (S31 T82N R12W Benton Co.) to confluence with North Walnut Cr in S7 T81N R13W Poweshiek Co. trib S24T81NR15W Poweshiek Co.

Assessment Cycle
2006
Result Period
2002 - 2004
Designations
Class B(LR)
Assessment Methodology
Assessment Type
Monitored
Integrated Report
Category 5b
Legacy ADBCode
IA 02-IOW-0187_1
Overall Use Support
Partial
Aquatic Life Use Support
Partial
Documentation
Assessment Comments

Assessment based on 2003 REMAP data: FIBI = 42, 41 (fair), FIBI ave = 41.5; BMIBI = 71 (good), 24 (poor), BMIBI ave = 47.5. FIBI BIC = 36; BMIBI BIC = 51.

Basis for Assessment

The assessment was based on data collected in 2003 as part of the DNR/UHL stream REMAP 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 collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2003 FIBI scores were 42, 41 (fair) and the FIBI average was 41.5.   The 2003 BMIBI scores were 71 (good), 24 (poor) and the BMIBI average was 47.5.   The aquatic life use support was assessed as partially supporting (= PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports.  The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51.

Monitoring and Methods
Assessment Key Dates
9/4/2003 Biological Monitoring
7/30/2003 Biological Monitoring
Methods
220 Non-fixed station physical/chemical monitoring (conventional pollutant only)
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
330 Fish surveys
380 Quan. measurements of instream parms-- channel morphology-- floodplain-- 1-2 seasons-- by prof
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