Little River Watershed Lake IA 05-GRA-1358

Decatur County S19T69NR25W approx 2 mi NW of Leon.

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 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

Open Segment Map
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Cycle: 2024
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Eutrophic
Trend: Stable
Created: 11/1/2023 8:13:19 AM
Updated: 2/5/2024 11:00:28 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5* - 303(d)-impaired last cycle; fully supporting this cycle; potential de-listing.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2014

Impairment Rationale

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

Data Source

Beach monitoring: Iowa DNR city/county

TMDL Priority

Tier II

Class BLW

Aquatic Life - Lakes and wetlands

WINOFI

Algal Growth: Cyanobacteria

Support Level

Further Investigation Needed

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Slight

Status

New

Source

Agriculture

Source Confidence

Low

Cycle Added

2024

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Ambient monitoring: Iowa DNR-lakes

Class C

Drinking Water -

Fully Supported

Class HH

Human Health -

Not Supported

Fish Consumption Advisory: Mercury

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

2020

Impairment Rationale

Fish consumption advisory in effect: no more than 1 meal/week

Data Source

Fish contaminant monitoring: Iowa DNR

TMDL Priority

Tier IV

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use remains assessed (monitored) as “not supported” due to violations of the state's water quality criteria for indicator bacteria. The Class BLW use was assessed (evaluated) as “WINOFI” due to frequent cyanobacteria blooms. The Class C use was “fully supported” based on water quality monitoring data and drinking water compliance monitoring required by the DNR. The Class HH (fish consumption) use was assessed (monitored) as "not supported" based on fish tissue sampling data and due to the existence of a one meal/week mercury consumption advisory for largemouth bass on this segment. Note: A TMDL for turbidity and total phosphorus at Little River Watershed Lake was prepared for and approved by EPA in March 2014. Because the indicator bacteria and mercury impairments at Little River Watershed Lake were not addressed in this TMDL, it will remain listed in category 5a; impaired - TMDL needed.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2018-2022	22270001	Little River Lake
Iowa DNR	6	FT	See Below	1075	Little River Lake	W of Leon

Class A1 - Indicator Bacteria: No Data. See Historical 2018 assessment.

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
22270001	6	12 / 4	7.5	8.8	8.2	0	4	NO	Mon	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
22270001	6	Chlorophyll a TSI	12 / 4	31	79	66	YES	Mon	Not
22270001	6	Secchi TSI	12 / 4	42	70	64	NO	Mon	Full
22270001	6	Total Phosphorus TSI	12 / 4	55	72	68	NA	NA	NA
22270001	6	Inorganic suspended solids	12 / 4	0.6	12	2.5	NA	NA	NA

Class BLW - Binomial 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
22270001	6	Dissolved Oxygen	12 / 4	3.4	9.2	6.1	5	NA / NA	4	YES	Mon	Not
22270001	6	pH	12 / 4	7.5	8.8	8.2	0	NA / NA	4	NO	Mon	Full
22270001	6	Temperature	12 / 4	17.2	27.7	23.9	0	NA / NA	4	NO	Mon	Full

Class BLW - 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 Concentration = 75th Percentile	Assessment Type	Support Level
22270001	6	6	79.47413446	100%	13.77826627	79%	YES	Evaluated	3b

Class C - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	Median Value	# Violations	Violates Significantly >10% Rule?	Assessment Type	Support Level
22270001	6	Inorganic nitrogen (nitrate and nitrite)	11 / 4	0.02	0.51	0.15	0.1	0	NO	Mon	Full
22270001	6	pH	12 / 4	7.5	8.8	8.2	8.1	0	NO	Mon	Full

Class C - Iowa Drinking Water Compliance Report:

Compliance monitoring required by the Iowa DNR Water Supply Operations and Engineering Sections did not show violations of finished water that were caused by source water at the Leon Water Supply facility during the 2020-22 monitoring period. The violations reported were related to plant operations. The results of compliance monitoring as reported in annual compliance reports are available at the following location at the Iowa DNR’s home page: https://www.iowadnr.gov/Environmental-Protection/Water-Quality/Water-Supply-Engineering/Annual-Compliance-Report.

Class HH - Fish Tissue Sampling:

Site ID	Biopart	Year	Species	# in sample / # of samples	Avg Length (cm)	(Avg) Hg (ppm)	Chlordane (ppm)	Sum PCBs (ppm)
1075	fillet	2016	channel catfish	4	59.8	0.09	0.02	0.06
1075	tissue plug	2019	largemouth bass	10	35.8	0.357
1075	tissue plug	2017	largemouth bass	3	39.3	0.357
1075	tissue plug	2016	largemouth bass	3	39.5	0.453
Support Level	Not	A one meal/week mercury consumption advisory for largemouth bass exists on this segment. Based on IR Methodology, the Class HH (fish consumption) use was assessed as “not supported.”

Monitoring and Methods

Assessment Key Dates

5/21/2018

Monitoring Start

9/5/2022

Monitoring End

3/27/2014

TMDL Completed

7/18/2016

Fish Tissue Monitoring

6/29/2016

Fish Tissue Monitoring

5/23/2017

Fish Tissue Monitoring

7/1/2019

Fish Tissue Monitoring

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

260

Fish tissue analysis

275

Drinking water compliance reports

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)