Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Silver Creek IA 01-TRK-192

mouth (S16 T94N R5W Clayton Co.) to confluence with unnamed tributary in S32 T95N R5W Clayton Co.

Assessment Cycle
2004
Result Period
2000 - 2002
Designations
Assessment Methodology
Assessment Type
Monitored
Integrated Report
Category 5b
Legacy ADBCode
IA 01-TRK-0381_0
Overall Use Support
Not supporting
Aquatic Life Use Support
Not supporting
Documentation
Assessment Comments

Assessment is based on results of IDNR/UHL biological (biocriteria) sampling in 2000 (Fish IBI= 41(fair); BM-IBI=46(fair)).

Basis for Assessment

SUMMARY:  The Class B(LR) aquatic life uses are assessed (monitored) as "not supported" based on results of IDNR/UHL biological (biocriteria) sampling in 2000.   This is the same assessment as that developed for the 2002 reporting cycle.

EXPLANATION:  This assessment was based on data collected in 2000 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 2000 Fish IBI score was 41 (fair) and the BM-IBI score was 46 (fair).  The aquatic life use support was assessed as not supporting (=NS), 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
8/2/2000 Biological Monitoring
8/2/2000 One-time Chemical 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
Organic enrichment/Low DO Aquatic Life Support Moderate
  • Agriculture
  • Grazing related Sources
  • Municipal Point Sources
  • Pasture grazing - Riparian
  • Moderate
  • Moderate
  • Moderate
  • Moderate
Other habitat alterations Aquatic Life Support Moderate
  • Agriculture
  • Grazing related Sources
  • Habitat Modification (other than Hydromodification)
  • Pasture grazing - Riparian
  • Removal of Riparian Vegetation
  • Moderate
  • Moderate
  • Moderate
  • Moderate
  • Moderate
Siltation Aquatic Life Support Moderate
  • Agriculture
  • Grazing related Sources
  • Habitat Modification (other than Hydromodification)
  • Pasture grazing - Riparian
  • Removal of Riparian Vegetation
  • Moderate
  • Moderate
  • Moderate
  • Moderate
  • Moderate