North Skunk River IA 03-NSK-859

from the Mahaska/Poweshiek line to confluence with Sugar Cr. in S20 T78N R16W Poweshiek Co.

This is a Legacy Assessment. Prior to 2004, assessments were developed under a methodology that pre-dated the Integrated Report guidelines.

Assessment Cycle

2002

Result Period

1998 - 2000

Designations

Assessment Methodology

2002 Methodology Document

Assessment Type

Monitored

Integrated Report

Category 0

Legacy ADBCode

IA 03-NSK-0020_2

Overall Use Support

Partial

Aquatic Life Use Support

Partial

Documentation

Assessment Comments

2001 Biocriteria: Fish IBI= 15(poor), BM-IBI= 76(excellent).

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 score was 15 (poor) and the BM-IBI score was 76 (excellent). 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

8/6/2001	Fixed Monitoring Start Date
8/6/2001	Fixed Monitoring End Date
8/6/2001	Biological Monitoring

Methods

330	Fish surveys
375	Visual observation-- may not quantify some parameters-- single season-- by prof.
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
320	Benthic macroinvertebrate surveys

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
Other habitat alterations	Overall Use Support	Moderate	Agriculture Bank or Shoreline Modification/Destabilization Channelization Grazing related Sources Habitat Modification (other than Hydromodification) Hydromodification Pasture grazing - Riparian	Moderate Moderate Moderate Moderate Moderate Moderate Moderate
Other habitat alterations	Aquatic Life Support	Moderate	Agriculture Bank or Shoreline Modification/Destabilization Channelization Grazing related Sources Habitat Modification (other than Hydromodification) Hydromodification Pasture grazing - Riparian	Moderate Moderate Moderate Moderate Moderate Moderate Moderate
Siltation	Overall Use Support	Moderate	Agriculture Bank or Shoreline Modification/Destabilization Grazing related Sources Pasture grazing - Riparian	Moderate Moderate Moderate Moderate
Siltation	Aquatic Life Support	Moderate	Agriculture Bank or Shoreline Modification/Destabilization Grazing related Sources Pasture grazing - Riparian	Moderate Moderate Moderate Moderate
Suspended solids	Overall Use Support	Moderate	Agriculture Grazing related Sources Pasture grazing - Riparian	Moderate Moderate Moderate
Suspended solids	Aquatic Life Support	Moderate	Agriculture Grazing related Sources Pasture grazing - Riparian	Moderate Moderate Moderate