Iowa DNR

Water Quality Assessments

Impaired Waters List

Iowa River IA 02-IOW-622

from south corporate limit of Wapello (S35, T74N, R3W, Louisa Co.) to Long Cr (S1, T74N, R4W, Louisa Co.)

Assessment Cycle
Release Status
Result Period
2004 - 2006
Class A1 Class B(WW-1) Class HH
Assessment Type
Integrated Report
Category 2a
Legacy ADBCode
IA 02-IOW-0010_2
Overall Use Support
Aquatic Life Use Support
Fish Consumption
Primary Contact Recreation
Not assessed
Assessment Comments

Assessment is based on: (1) results of ambient water quality monitoring at Wapello conducted from January 2004 to September 2006 as part of the USGS NAWQA program, (2) results of biological monitoring conducted in 2002 as part of the IDNR/UHL REMAP project, (3) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2005 and 2006, and (4) results of REMAP fish contaminant monitoring in 2006.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses remain not assessed due to the lack of information on levels of indicator bacteria upon which to base an assessment.   The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient physical/chemical water quality monitoring from 2004-2006 and on results of biological (fish) monitoring conducted in 2002.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2005 and 2006.   Sources of data for this assessment include (1) results of ambient water quality monitoring at Wapello conducted from January 2004 to September 2006 as part of the USGS NAWQA program, (2) results of biological monitoring conducted in 2002 as part of the IDNR/UHL REMAP project, (3) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2005 and 2006, and (4) results of fish contaminant monitoring conducted in 2006 as part of the Iowa DNR's REMAP project (Site 45).

EXPLANATION:  The Class A1 (primary contact recreation) uses remain “not assessed” due to lack of data on indicator bacteria upon which to base an assessments.   The monitoring conducted on the Iowa River at Wapello from 2004 through 2006 by USGS (station 05465500) did not include analysis for indicator bacteria.   Thus, due to this lack of information, an assessment of support of the Class A1 uses was not developed.  

Regarding support of the Class B(WW1) uses, results of the USGS/NAWQA monitoring from January 2004 through December 2006 showed no violations of Class B(WW1) water quality criteria for dissolved oxygen (29 samples) or ammonia-nitrogen (40 samples).   Two of 41 samples (5%) did violate the Class B(WW1)/A1 criterion for pH.   Both violations were 9.1 units, thus exceeding the Class B(WW1)/A1 criterion of 9.0 units.   According to U.S.  EPA assessment guidelines, however, if less than 10% of samples exceed state criteria for conventional parameters such as pH, the primary contact (Class A) and aquatic life (Class B) uses should be assessed as fully supported (see pgs 3-17 of U.S.  EPA 1997b).   Violations of pH in ambient waters tend to reflect high levels of primary productivity and do not typically reflect the addition of pollutants to surface waters.  

Results of this monitoring also showed no violations of the Class B(WW1) chronic water quality criteria for DDE (12 samples analyzed) or dieldrin (38 samples analyzed).   Note:  the assessment of aquatic life uses developed for the 2000 report ("partially supported”) was based on two violations of the Class B(WW) chronic water quaity criterion for dieldrin in the 52 samples collected between March 1996 and August 1998.   Because no dieldrin was detected in the 34 samples collected between October 1998 and September 2001, this assessment was changed to "fully supported" for the 2002 report.   USGS monitoring conducted from September 2001 through December 2006 has shown no levels of dieldrin above the level of detection (0.005 ug/l) thus confirming the lack of violations of dieldrin criteria in this river reach.

Results of biological monitoring also suggest full support of the aquatic life uses designated for this river segment.   The biological assessment was based on data collected in 2002 as part of the IDNR/UHL stream REMAP project.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological sampling data.   The biological metrics are based on the numbers and types of fish species collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (FIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 FIBI score was 40 (fair).   The aquatic life use support was assessed (evaluated) as Fully Supporting (=FS), based on a comparison of the FIBI score with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 36.   This assessment is considered “evaluated” (i.e., of lower confidence) because the drainage area (12,490 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site passed the FIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.

Fish consumption uses are assessed (monitored) as "fully supported" based on fish contaminant monitoring near Wapello conducted (1) in 2005 and 2006 as part of the EPA/IDNR fish tissue (RAFT) program and (2) in 2006 as part of the IDNR REMAP project (Site 45).   This site has been sampled for whole-fish common carp since 1995 on an every-other-year basis as part of RAFT trend monitoring.   Due to a change in the design of the RAFT program, this site was sampled in the consecutive years of 2005 and 2006.   The 2005 composite whole-fish samples of common carp had low levels of the primary contaminants:  mercury: 0.111 ppm; total PCBs: 0.193 ppm; and technical chlordane: 0.051 ppm.   The 2006 composite whole-fish samples of common carp had similar levels of these contaminants:  mercury: 0.196 ppm; total PCBs: 0.223 ppm; and technical chlordane: 0.043 ppm.  

The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.   Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa.   In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol.   This protocol went into effect in January 2006 (see for more information on Iowa’s revised fish consumption advisory protocol).   Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses.  

Although assessed as “fully supported” for this reporting cycle, the level of at least one contaminant does, however, exceed one or more advisory trigger levels:  the level of PCBs in the 2006 sample of whole-fish common carp (0.223 ppm) slightly exceeds the one meal per week trigger level of 0.20 ppm.   According to the IDNR/IDPH advisory protocol, this single result from the 2006 sampling neither warrants issuance of an advisory nor indicates impairment of fish consumption uses:  two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.  Fish contaminant monitoring conducted as part of the IDNR REMAP project in October 2006, however, suggests that levels of PCBs in the edible portion of common carp are well-below the advisory trigger level for PCBs.   Results of this monitoring showed low levels of the primary contaminants in the samples of common carp fillets:  mercury: 0.183 ppm; total PCBs: 0.1 ppm; and technical chlordane: <0.03 ppm.  These results suggest that PCB levels in the edible portion of bottom feeding fish are below advisory trigger levels for PCBs as well as those for mercury and chlordane.   In addition, RAFT monitoring will be conducted in 2007 to better define contaminant levels in fish from this river segment.

Monitoring and Methods
Assessment Key Dates
12/6/2006 Fixed Monitoring End Date
10/23/2006 Fish Tissue Monitoring
8/16/2006 Fish Tissue Monitoring
8/22/2005 Fish Tissue Monitoring
1/8/2004 Fixed Monitoring Start Date
9/24/2002 Biological Monitoring
220 Non-fixed station physical/chemical monitoring (conventional pollutant only)
315 Regional reference site approach
330 Fish surveys
380 Quan. measurements of instream parms-- channel morphology-- floodplain-- 1-2 seasons-- by prof
230 Fixed station physical/chemical (conventional plus toxic pollutants)
260 Fish tissue analysis
Monitoring Levels
Biological 4
Habitat 4
Physical Chemistry 3
Toxic 3
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