Rathbun Reservoir - Main Basin IA 05-CHA-1309

Appanoose County approx 6 miles N of Centerville.

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 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.

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Cycle: 2020
Release Status: Final
Overall IR: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trophic: Eutrophic
Trend: Stable
Created: 8/20/2020 1:55:15 PM
Updated: 10/14/2020 2:36:45 PM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Turbidity

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

Moderate

Status

Delisted

Source

Other: Sediment Resuspension

Source Confidence

Moderate

Cycle Added

2012

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Cycle Delisted

2020

Delisting Rationale

TMDL preparation and approval

Data Source

Ambient monitoring: Corps of Engineers/Iowa DNR/ISU

Class BWW1

Aquatic Life - Warm Water Type 1

Fully Supported

Class HH

Human Health -

Fully Supported

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 uses are assessed (monitored) as "not supported” due to high levels of non-algal turbidity that create aesthetically objectionable conditions. The Class BWW aquatic life uses are assessed as "fully supporting" based water quality monitoring. Class HH uses are considered “fully assessed” (“fully supported”) based on fish tissue sampling. Note: A TMDL for turbidity at four segments of Rathbun Lake was prepared by DNR and approved by EPA in 2019. Because all Section 303(d) impairments identified for the current assessment/listing cycle are addressed by the TMDL, this waterbody is placed in IR Category 4a (impaired; TMDL approved).

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 2014-2018	22040001	Rathbun Lake
USACE	12	WQ	CY 2014-2018	99990023	Down lake station (RA-3) near the dam of Rathbun Reservoir
Iowa DNR	6	WQ	CY 2014-2014	14000141	Rathbun Lake RA-7.1
Iowa DNR		FT	See Below	53	Rathbun Lake

Class A1 - Indicator Bacteria: No Data

Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
22040001	6	15 / 5	8.5	8	7.9	0	0%	NO	Monitored	Full
99990023	12	11 / 3	8.65	8.07	8.11	0	0%	NO	Monitored	Full

Class A1 - Lake TSI's

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Median Value	Median TSI Violation	Assessment Type	Support Level
14000141	6	Chlorophyll a TSI	11 / 1	41	72	51	NO	Assessor Discretion	Full
22040001	6	Chlorophyll a TSI	15 / 5	31	62	44	NO	Monitored	Full
99990023	12	Chlorophyll a TSI	24 / 5	37	67	49	NO	Monitored	Full
22040001	6	Secchi TSI	15 / 5	44	77	66	YES	Monitored	Not
99990023	12	Secchi TSI	43 / 5	53	82	69	YES	Monitored	Not
14000141	6	Total Phosphorus TSI	11 / 1	63	84	69	NA	NA	NA
22040001	6	Total Phosphorus TSI	15 / 5	54	71	62	NA	NA	NA
22040001	6	Inorganic suspended solids	15 / 5	0.3	20.99	6	NA	NA	NA

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
22040001	6	Ammonia	15 / 5	0.273	0.04	0.01	0 / 0	0% / 0%	NO	Monitored	Full
22040001	6	Dissolved oxygen	15 / 5	9.9	7.5	8.3	NA / 3	NA / 20%	NO	Monitored	Full
99990023	12	Dissolved oxygen	6 / 1	11.14	8.69	8.83	NA / 0	NA / 0%	NO	Evaluated	Full
22040001	6	pH	15 / 5	8.5	8	7.9	0 / NA	0% / NA	NO	Monitored	Full
99990023	12	pH	11 / 3	8.65	8.07	8.11	0 / NA	0% / NA	NO	Monitored	Full
22040001	6	Temperature	15 / 5	27	22.6	23.9	0 / 0	0% / 0%	NO	Monitored	Full
99990023	12	Temperature	28 / 5	30	21.3	23	0 / 0	0% / 0%	NO	Monitored	Full

Class BWW1 - Lake Planktonic Cyanobacteria:

Site ID	Data Source ID	# Samples	Maximum Cyanobacteria Wet Mass	Maximum Cyanobacteria % Composition	Median Cyanobacteria Wet Mass	Median Cyanobacteria % Composition	Median Cyanobacteria Wet Mass = 75th Percentile	Assessment Type	Support Level
22040001	6	11	8.335	93.3 %	2.311	60.1 %	NO	Evaluated	NA

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
99990023	12	Arsenic	2 / 2	4.3	3.7	3.7	0 / 0	0% / 0%	NO	Evaluated	Full
99990023	12	Cadmium	1 / 1	1	1	1	0 / 0	0% / 0%	NO	Evaluated	Full
99990023	12	Chromium	1 / 1	2.5	2.5	2.5	0 / 0	0% / 0%	NO	Evaluated	Full
99990023	12	Copper	2 / 2	5	5	5	0 / 0	0% / 0%	NO	Evaluated	Full
99990023	12	Lead	2 / 2	80.3	40.9	40.9	0 / 1	0% / 50%	NO	Evaluated	NA
99990023	12	Mercury	2 / 2	2	1.1	1.1	0 / 0	0% / 0%	NO	Evaluated	Full
99990023	12	Nickel	1 / 1	7.5	7.5	7.5	0 / 0	0% / 0%	NO	Evaluated	Full
99990023	12	Selenium	1 / 1	0.4	0.4	0.4	0 / 0	0% / 0%	NO	Evaluated	Full
99990023	12	Zinc	1 / 1	3.5	3.5	3.5	0 / 0	0% / 0%	NO	Evaluated	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
99990023	12	Cadmium	1 / 1	1	1	1	1	NO	Evaluated	Full
99990023	12	Chromium	1 / 1	2.5	2.5	2.5	1	NO	Evaluated	Full
99990023	12	Copper	2 / 2	5	5	5	2	NO	Evaluated	Full
99990023	12	Mercury	2 / 2	2	1.1	1.1	2	NO	Evaluated	Full
99990023	12	Nickel	1 / 1	7.5	7.5	7.5	1	NO	Evaluated	Full
99990023	12	Selenium	1 / 1	0.4	0.4	0.4	1	NO	Evaluated	Full
99990023	12	Zinc	1 / 1	3.5	3.5	3.5	1	NO	Evaluated	Full

Class HH - Fish Tissue Sampling:

Site ID

Date

Species Name

Biopart

# in sample

chlordane result

chlordane violation?

PCBs result

PCBs violation?

Hg result

Hg violation?

Assessment Type

Support Level

6/21/17

largemouth bass

plug

0.223

Monitored

Full

Monitoring and Methods

Assessment Key Dates

4/15/2014

Fixed Monitoring Start Date

9/22/2016

Fixed Monitoring End Date

9/17/2018

Fish Tissue Monitoring

6/14/2019

Fixed Monitoring Start Date

Methods

120

Surveys of fish and game biologists/other professionals

222

Non-fixed-station monitoring (conventional during key seasons and flows)

240

Non-fixed station physical/chemical (conventional + toxicants)

260

Fish tissue analysis

330

Fish surveys

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring