Iowa DNR
Iowa DNR

ADBNet

Water Quality Assessments
Impaired Waters List

West Nishnabotna River IA 05-NSH-1445

from confluence with West Fork West Nishnabotna R. (NW 1/4 S18 T79N R39W Shelby Co) to confluence with Elk Cr. in S36 T81N R38W Shelby Co.

Assessment Cycle
2002
Result Period
1998 - 2000
Designations
Assessment Methodology
Assessment Type
Evaluated
Integrated Report
Category 0
Legacy ADBCode
IA 05-NSH-0090_2
Overall Use Support
Threatened
Aquatic Life Use Support
Threatened
Documentation
Assessment Comments

Assessment is based on results of 1994 Biocriteria sampling: Fish IBI= 33(fair), 28 (fair), BM-IBI= 67(good), 59(good).

Basis for Assessment

[Note:  For the 2002 report, the previous waterbody segment for the West Nishnabotna River (IA 05-NSH-0090-2), which extended 30 miles from the West Fork West Nishnabotna R.  at Harlan to an unnamed tributary NE of Manning in Carroll Co., was split into three subsegments:  (1) West Fork West Nishnabotna R.  to Elk Creek at Irwin (IA 05-NSH-0090-2), (2) Elk Creek to the Crawford-Carroll county line (IA 05-NSH-0090-3), and (3) Crawford-Carroll county line to the unnamed tributary NE of Manning (IA 05-NSH-0090-4).   See above for previous Section 305(b) assessments for the original 30-mile stream segment.]  

SUMMARY:  The Class B(LR) aquatic life uses remain assessed as "fully supported / threatened."  The assessment category, however, is changed from "monitored" to "evaluated."  EXPLANATION:  Continue to use the assessment developed for the 1998 and 2000 reports (see above) that was based on results of the 1994 IDNR biocriteria assessment conducted approximatey 2.5 miles NNE of Kirkman in Shelby County.   However, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is changed from "monitored" (indicating an assessment with relatively high confidence) to "evaluated" (indicating an assessment with relatively low confidence).

Monitoring and Methods
Assessment Key Dates
8/9/1994 Biological Monitoring
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 3
Habitat 3
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 Not Impairing
  • Agriculture
  • Bank or Shoreline Modification/Destabilization
  • Channelization
  • Not Impairing
  • Not Impairing
  • Not Impairing