2022 Final assessment for Des Moines River

Des Moines River IA 04-UDM-1214

from upper end of Saylorville Reservior to Fraser Dam in S34 T85N R27W Boone Co.

Assessment Cycle

2022

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 2018 - 2020
Stream/River Water Quality Data	CY 2018 - 2020
Lake Water Quality Data	CY 2016 - 2020
Biological Sampling Data	CY 2016 - 2020*
Fish Kill Data	CY 2016 - 2020
Fish Tissue Sampling Data	CY 2016 - 2020
Continuous Dissolved Oxygen Sampling Data	CY 2016 - 2020
*Biological sites sampled in both 2015 and 2019 were also assessed.

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

Created: 12/28/2021 5:34:26 AM
Updated: 12/28/2021 5:36:09 AM

Assessment conducted in accordance with Iowa's 2022 IR methodology

Use Support

Class A1

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Single-sample maximum criterion exceeded in significantly > 10% of samples

Data Source

Ambient monitoring: Corps of Engineers/ISU/UI

TMDL Priority

Tier III

Class BWW1

Fully Supported

Class HH

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "not supported" based on levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on water quality monitoring data. All other designated uses were "not assessed."

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
USACE	12	WQ	CY 2018-2020	17080001	Des Moines River at E26

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2018/ 2019/2020)

2018 Geometric Mean

2019 Geometric Mean

2020 Geometric Mean

Violates Annual Geometric Mean?

# 2018 SSM violations / SSM Violations needed for impairment

# 2019 SSM violations / SSM Violations needed for impairment

# 2020 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

17080001

10/10/10

227

145

YES

5 / 3

1 / 3

YES

Monitored

Not

Class A – pH:

Site ID	Data Source ID	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
17080001	12	58 / 3	6.07	9.14	8.01	4	10	NO	Monitored	Full

Class BWW1 - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	# Acute / Chronic Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
17080001	12	Ammonia	58 / 3	0.02	0.85	0.12	NA	0 / 1	10	NO	Monitored	Full
17080001	12	Dissolved Oxygen	58 / 3	7.16	16.45	10.15	0	NA / NA	10	NO	Monitored	Full
17080001	12	pH	58 / 3	6.07	9.14	8.01	4	NA / NA	10	NO	Monitored	Full
17080001	12	Temperature	58 / 3	-0.1	27.6	13.5	0	NA / NA	10	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	>1 Acute / Chronic Violation	Assessment Type	Support Level
17080001	12	Lead	5 / 3	0.3	0.1	0.05	0 / 0	NO	Evaluated	Full

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

12/7/2020	Fixed Monitoring End Date
1/8/2018	Fixed Monitoring Start Date

Methods

230	Fixed station physical/chemical (conventional plus toxic pollutants)
420	Indicator bacteria monitoring

Water Quality Assessments

Impaired Waters List

Des Moines River IA 04-UDM-1214

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods