Maple River IA 06-LSR-1581

mouth (S17 T83N R44W Monona Co.) to confluence with unnamed tributary approximately 1 mile east of Danbury in SW 1/4 NE 1/4 S26 T86N R42W Woodbury Co.

This is a DRAFT assessment

Draft assessments may change without notice

Open Data Collection Period Modal

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 2022 - 2024
Stream/River Water Quality Data	CY 2022 - 2024
Lake Water Quality Data	CY 2020 - 2024
Biological Sampling Data	CY 2020 - 2024*
Fish Kill Data	CY 2020 - 2024
Fish Tissue Sampling Data	CY 2020 - 2024
Continuous Dissolved Oxygen Sampling Data	CY 2020 - 2024
*Biological sites sampled in both 2019 and 2023 were also assessed.

Open Segment Map
View 2026 assessment summary page

Cycle: 2026
Current Phase: Public Comment
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Stable
Created: 10/27/2025 3:09:25 PM
Updated: 2/11/2026 10:59:38 AM

Use Support

Class A1

Recreation - Primary contact

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

Low

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW1

Aquatic Life - Warm Water Type 1

Not Supported

Biological: low fish & invert IBIs- cause unknown

Support Level

Further Investigation Needed

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

2006

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Metals: Selenium

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2020

Impairment Rationale

Violations of chronic criterion

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier IV

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use remains assessed as "not supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use remains assessed as "not supported” due to violations of state water quality chronic criteria for selenium and "WINOFI" based on biological sampling data. The Class HH use was assessed as "fully supported" based on water quality monitoring data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2022-2024	10670002	Maple River at Mapleton
Iowa DNR	6	WQ	CY2020	366	Maple River	Turin (REMAP #21)
Iowa DNR	6	WQ	CY2021	415	Maple River	Castana (REMAP #110)
Iowa DNR	6	BIO	See Below	366	Maple River	Turin (REMAP #21)
Iowa DNR	6	BIO	See Below	415	Maple River	Castana (REMAP #110)
Iowa DNR	6	BIO	See Below	926	Maple River	Mapleton
Iowa DNR	6	BIO	See Below	1208	Maple River	NE of Mapleton (REMAP #447)

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2022/ 2023/2024)

2022 Geometric Mean

2023 Geometric Mean

2024 Geometric Mean

Violates Annual Geometric Mean?

# 2022 SSM violations / SSM Violations needed for impairment

# 2023 SSM violations / SSM Violations needed for impairment

# 2024 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10670002

8/8/8

137

215

326

YES

3 / 3

6 / 3

YES

MONITORED

NOT

Class A1 – 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
10670002	6	36 / 3	7.5	8.5	8.1	0	7	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
10670002	6	Chloride	36 / 3	16	37	23	NA	0 / 0	7	NO	MONITORED	FULL
10670002	6	Dissolved Oxygen	36 / 3	7.7	13.7	10.5	0	NA / NA	7	NO	MONITORED	FULL
10670002	6	pH	36 / 3	7.5	8.5	8.1	0	NA / NA	7	NO	MONITORED	FULL
10670002	6	Sulfate	36 / 3	36	100	68	0	NA / NA	7	NO	MONITORED	FULL
10670002	6	Temperature	36 / 3	0	26.9	12	0	NA / NA	7	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
10670002	6	Ammonia	36 / 3	0.29	0.05	0.02	0 / 0	NO	MONITORED	FULL
10670002	6	Cadmium	18 / 2	0.5	0.5	0.5	0 / 0	NO	MONITORED	FULL
10670002	6	Chromium	18 / 2	4	1.31	1	0 / 0	NO	MONITORED	FULL
10670002	6	Copper	18 / 2	5.7	2.1	1.8	0 / 0	NO	MONITORED	FULL
10670002	6	Lead	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10670002	6	Nickel	18 / 2	2.4	1.7	1.4	0 / 0	NO	MONITORED	FULL
10670002	6	Selenium	36 / 3	10	6	6	0 / 27	YES	MONITORED	NOT
10670002	6	Silver	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10670002	6	Zinc	18 / 2	2.4	0.7	0.5	0 / 0	NO	MONITORED	FULL

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47d/e/m BMIBI BIT	BMIBI Pass/Fail
926	9/12/23	644.0	47m	MO	ArtSub	16	Poor	54	Fail
415	9/20/21	724.4	47m	MO	Floating ArtSub	39	Fair	54	Fail
366	9/1/20	731.8	47d	MO	Floating ArtSub	30	Poor	54	Fail
1208	8/31/20	629.0	47e	MO	Surber	47	Fair	54	Fail

Fish:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	47d/e FIBI BIT	FIBI Pass/Fail
415	9/20/21	724.4	47m	MO	NA	42	Fair	31	Pass
1208	8/31/20	629.0	47e	MO	NA	29	Fair	31	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (0/4)	WINOFI
Fish	Evaluated	Fail (1/2)	WINOFI		Assessment was evaluated because the drainage areas
Overall	Evaluated	Fail	WINOFI	3bu	of the sites were greater than the calibrated range.

Class BWW1- Continuous DO Monitoring:

Site ID	Data Source ID	# Days Monitoring (2020/2021)	DO Criteria Type	# 2020 violations / Violations needed for impairment	# 2021 violations / Violations needed for impairment	Violates Annual Significantly >10% Rule?	Assessment Type	Support Level
366 (2020/			24 hr	0/4	0/5	No
415 (2021)	6	14/19	16 hr	0/4	0/5	No	Monitored	Full

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
10670002	6	Copper	18 / 2	5.7	2.1	1.8	1	NO	MONITORED	FULL
Site ID	Data Source ID	Parameter Name	# Samples per Year (2022/ 2023/2024)	2022 Mean	2023 Mean	2024 Mean	# Non-Detects per Year (2022/ 2023/2024)	Support Level per Year (2022/ 2023/2024)	Assessment Type	Support Level
10670002	6	Selenium	12/12/12	6.583	6.2	6.55	0/0/0	FS/FS/FS	MONITORED	FULL

Monitoring and Methods

Assessment Key Dates

12/4/2024

Monitoring End

9/20/2021

Biological Monitoring

1/11/2022

Monitoring Start

9/1/2020

Biological Monitoring

8/31/2020

Biological Monitoring

9/12/2023

Biological Monitoring

Methods

200

Physical/Chemical Monitoring

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring