Iowa DNR

Water Quality Assessments

Impaired Waters List

Thompson River IA 05-GRA-1351

from the Iowa/Missouri state line to confluence with Long Cr. in SW 1/4, S8, T69N, R26W, Decatur Co.

Assessment Cycle
Release Status
Result Period
1994 - 1996
Assessment Type
Integrated Report
Category 0
Legacy ADBCode
IA 05-GRA-0040_0
Overall Use Support
Aquatic Life Use Support
Fish Consumption
Assessment Comments

Assessment is based on results of (1) IDNR monthly monitoring near Davis City and (2) fish tissue (RAFT) monitoring in 1997.

Basis for Assessment

Upgraded the assessment of support of the Class B(WW) aquatic life uses from FST to FS due to (1) results of quarterly monitoring between Oct.95 & July 1997 at the DNR quarterly station nr Davis City showed no violations of Class B(WW) WQ criteria for either toxic or conventional pollutants in the 8 samples collected over the two-year period, (2) a review of the field sheets from the July 1991 DNR stream use assessments near Terre Haute and Decatur City showed a relatively diverse fish community (15 species from 4 families at the Terre Haute site) and the presence of nearly all of the expected fish taxa (7 of 8) for streams in the Central Irregular Plains (40) ecoregion, and (3) presence of the expected game fish species (channel catfish, reported as "common" at the Terre Haute site; several YOY & larger adults present up to 18" TL).   Habitat assessments at both assessment sites show above average aquatic habitats and do not indicate any significant threats to the continued support of the Class B(WW) uses.   Support of the fish consumption uses was assessed as FS due to results of fish contaminant monitoring conducted as part of the 1997 DNR/U.S.  EPA RAFT program that showed levels of all contaminants below 1/2 the respective FDA action levels in the composite sample of fillets from channel catfish.

Monitoring and Methods
Assessment Key Dates
10/17/2001 Fixed Monitoring End Date
9/30/1997 Fixed Monitoring Start Date
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)
230 Fixed station physical/chemical (conventional plus toxic pollutants)
260 Fish tissue analysis
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
Monitoring Levels
Biological 4
Habitat 4
Physical Chemistry 3
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