2020 Final assessment for Iowa River

Iowa River IA 02-IOW-624

from confluence with Cedar R. to Johnson-Washington Co. line

Assessment Cycle

2020

Release Status

Final

Data Collection Period

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

Overall IR Category: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown

Created: 9/3/2020 6:39:28 AM
Updated: 10/9/2020 8:26:40 AM

Assessment conducted in accordance with Iowa's 2020 IR methodology

Use Support

Class A1

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

Slight

Status

Delisted

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Cycle Delisted

2020

Delisting Rationale

TMDL preparation and approval

Data Source

Ambient monitoring: Iowa DNR-rivers

Class BWW1

Not Supported

Biological: loss of native mussel species

Support Level

Not Supported

Impairment Code

5b - Biological impairment or pollutant-caused fish kill - unknown source. No administrative action.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2004

Impairment Rationale

Loss of >50% of native mussel species

Data Source

Special project/study

TMDL Priority

Tier IV

Biological: low aquatic macroinvertebrate IBI

Support Level

Water in Need of Further Investigation (WINOFI)

Impairment Code

3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2014

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Not Assessed

General Use

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 primary contact recreation use was assessed as “partially supported” due to 2016-2018 violations of water quality criteria for indicator bacteria. The Class BWW1 aquatic life use remains assessed as "not supported" based on results of a 1998-99 statewide assessment of freshwater mussels in Iowa streams and on 2012, 2013 and 2015 biological sampling data. The Class HH (fish consumption) use was assessed as "fully supported" based on 2016-2018 water quality monitoring data. All other designated uses were "not assessed". Note: A TMDL covering the bacteria impairments for all segments, with the segment code prefix "IA 02-IOW" in the Iowa River Basin, was approved by EPA in 2018. Due to the completion of the TMDL, the IR category for the Class A1 use was changed from 5a (impaired; TMDL needed) to 4a (impaired; TMDL approved). Because not all impairments identified for this segment are covered by the TMDL, this segment remains in Category 5 of Iowa's Integrated Report (impaired; TMDL needed).

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2016-2018	10580002	Iowa River near Lone Tree
Iowa DNR	6	BIO	See Below	940	Iowa River	Lone Tree

Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2016 Geometric Mean	2017 Geometric Mean	2018 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10580002	6	21 / 3	461.44	140.56	153.24	Yes	6	29%	Yes	Monitored	Partial

Class A - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10580002	6	36 / 3	9	8.2	8.2	0	0%	No	Monitored	Full

Class BWW1 - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
10580002	6	Ammonia	36 / 3	0.88	0.09	0.02	0 / 0	0% / 0%	No	Monitored	Full
10580002	6	Chloride	36 / 3	52	24	22	0 / 0	0% / 0%	No	Monitored	Full
10580002	6	Dissolved oxygen	36 / 3	15.7	10.6	10.3	NA / 0	NA / 0%	No	Monitored	Full
10580002	6	pH	36 / 3	9	8.2	8.2	0 / NA	0% / NA	No	Monitored	Full
10580002	6	Sulfate	36 / 3	45	26	25	0 / NA	0% / NA	No	Monitored	Full
10580002	6	Temperature	36 / 3	26.9	13.2	13.3	0 / 0	0% / 0%	No	Monitored	Full

Class BWW1 - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
10580002	6	Aluminum	9 / 2	8.7	1.956	1.4	0 / 0	0% / 0%	No	Evaluated	Full
10580002	6	Arsenic	9 / 2	6.1	2.7	2.2	0 / 0	0% / 0%	No	Evaluated	Full
10580002	6	Cadmium	9 / 2	0.06	0.029	0.025	0 / 0	0% / 0%	No	Evaluated	Full
10580002	6	Chromium	9 / 2	1.4	0.79	0.77	0 / 0	0% / 0%	No	Evaluated	Full
10580002	6	Copper	9 / 2	3.9	1.7	1.4	0 / 0	0% / 0%	No	Evaluated	Full
10580002	6	Lead	9 / 2	1.1	0.238	0.13	0 / 0	0% / 0%	No	Evaluated	Full
10580002	6	Nickel	9 / 2	4.5	2.9	2.8	0 / 0	0% / 0%	No	Evaluated	Full
10580002	6	Selenium	9 / 2	2.2	1.23	1.1	0 / 0	0% / 0%	No	Evaluated	Full
10580002	6	Zinc	9 / 2	5	2.53	2.2	0 / 0	0% / 0%	No	Evaluated	Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/ Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47f BMIBI BIT	BMIBI Pass/ Fail
940	8/25/15	4293	47f	MS/WW	Float ArtSub	67	Good	51	Pass
940	10/7/13	4293	47f	MS/WW	ArtSub	23	Poor	51	Fail
940	10/8/12	4293	47f	MS/WW	ArtSub	34	Fair	51	Fail

Overall Assessment:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (1/3)	Partial	3bu	3bu	Assessment is evaluated because samples used to complete assessment were not collected in the last five years and the drainage area of the site is larger than the calibrated range.

Class BWW1 – Freshwater Mussel Sampling:

Freshwater Mussel Survey	Avg. # Freshwater Mussel Species	Avg. # Freshwater Mussel Species Increase/Decrease	Avg % Freshwater Mussel Species Increase/Decrease	Assessment Type	Support Level	IR Category
1984-85 (Frest 1987) 4 sites	8.75
1998-99 (Arbuckle et al. 2000) 4 sites	0.5	-8.25	-94%	Evaluated	Not	5b
As presented by Arbuckle et al. (2000), the potential causes of declines in species richness of Iowa's freshwater mussels include siltation, destabilization of stream substrate, stream flow instability, and high instream levels of nutrients (phosphorus and nitrogen). Their study also suggested the importance of stream shading provided by riparian vegetation to mussel species richness.

Class HH-F - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	Number of Non - Detects	Mean Value > Criterion or MCL	Assessment Type	Support Level
10580002	6	Cadmium	9 / 2	0.06	0.029	0.025	8	No	Evaluated	Full
10580002	6	Chromium	9 / 2	1.4	0.79	0.77	0	No	Evaluated	Full
10580002	6	Copper	9 / 2	3.9	1.7	1.4	0	No	Evaluated	Full
10580002	6	Nickel	9 / 2	4.5	2.9	2.8	0	No	Evaluated	Full
10580002	6	Selenium	9 / 2	2.2	1.23	1.1	1	No	Evaluated	Full
10580002	6	Zinc	9 / 2	5	2.53	2.2	0	No	Evaluated	Full

Monitoring and Methods

Assessment Key Dates

10/8/2012	Biological Monitoring
1/4/2016	Fixed Monitoring Start Date
12/3/2018	Fixed Monitoring End Date
10/7/2013	Biological Monitoring
8/25/2015	Biological Monitoring
3/9/2018	TMDL Completed

Methods

120	Surveys of fish and game biologists/other professionals
150	Monitoring data more than 5 years old
230	Fixed station physical/chemical (conventional plus toxic pollutants)
315	Regional reference site approach
320	Benthic macroinvertebrate surveys
420	Indicator bacteria monitoring

Water Quality Assessments

Impaired Waters List

Iowa River IA 02-IOW-624

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods