Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

North Skunk River IA 03-NSK-863

from confluence with Sugar Cr. (S20 T78N R16W Poweshiek Co.) to confluence with Snipe Cr. in S22 T81N R19W Jasper Co.

Assessment Cycle
2002
Result Period
1998 - 2000
Designations
Assessment Methodology
Assessment Type
Monitored
Integrated Report
Category 0
Legacy ADBCode
IA 03-NSK-0030_0
Overall Use Support
Partial
Aquatic Life Use Support
Partial
Documentation
Assessment Comments

2001 Biocriteria: Fish IBI= 17, 19, 16(poor); BM-IBI= 65, 71, 70(good).

Basis for Assessment

The assessment was based on data collected in 2001 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 2001 Fish IBI scores were 17 (poor), 19 (poor) and 16 (poor); the BM-IBI scores were 65 (good), 71 (good) and 70 (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
8/9/2001 Fixed Monitoring End Date
8/9/2001 Biological Monitoring
8/7/2001 Fixed Monitoring Start Date
Methods
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 3
BioIntegrity Fair
Causes and Sources of Impairment
Causes Use Support Cause Magnitude Sources Source Magnitude
Other habitat alterations Overall Use Support Moderate
  • Agriculture
  • Channelization
  • Hydromodification
  • Moderate
  • Moderate
  • Moderate
Other habitat alterations Aquatic Life Support Moderate
  • Agriculture
  • Channelization
  • Hydromodification
  • Moderate
  • Moderate
  • Moderate