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
1996 - 1998
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 during 2000 & 2001 near Davis City and (2) fish tissue (RAFT) monitoring in 1997.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses remain assessed as "fully supported."  Fish consumption uses remain "fully supported."  EXPLANATION:  The previous assessment of support of the Class B(WW) uses was based, in part, on results of DNR stream use assessments conducted in 1991.   The results of these assessments are now considered too old (greater than five years) for characterizing current water quality conditions.   Thus, the current assessment was based on results of water quality monitoring during the 1996-1997 biennial period at the DNR quarterly monitoring station at Davis City (see assessment for the 1998 report above).   Results from stations monitored monthly or more frequently, however, are preferred for Section 305(b) assessments in order to improve the accuracy and confidence level of the assessment.   As part of DNR's expanded water quality monitoring program, monthly monitoring at the Davis City station began in October 1999.   Fish consumption uses remain "fully supported" based on results of EPA/DNR fish tissue (RAFT) monitoring in 1997 (see assessment for the 1998 report above).

Monitoring and Methods
Assessment Key Dates
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