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 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.

Open Segment Map
View assessment methodology in new window

Cycle: 2022
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Eutrophic
Trend: Stable
Created: 12/30/2021 11:25:55 AM
Updated: 3/23/2022 12:33:22 PM

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

Fully Supported

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 (monitored) as “fully supported.” The Class C use was “fully supported.” 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 2014-2016	21270002	Little River Recreation Area Beach
Iowa DNR	6	WQ	CY 2016-2019	22270001	Little River Lake
Iowa DNR	6	FT	See Below	75	Little River Lake	W of Leon

Class A1 - Indicator Bacteria: Historical 2018 Assessment

Site ID	Data Source ID	# Samples / # Years	2014 Geometric Mean	2015 Geometric Mean	2016 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
21270002	6	40 / 3	12	52	7	No	3	8%	NO	Monitored	Full

In the 2016 assessment/listing cycle, the Class A1 use was listed as "impaired" due to geometric mean and single-sample maximum exceedances. According to DNR's methodology, lakes must meet water quality standards for two consecutive assessment/listing cycles to suggest de-listing. Therefore, the Class A1 use will remain listed as "not supported" for the current cycle.

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

22270001

3/3/0

0 / NA

Evaluated

Full

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	8.1	0	4	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
22270001	6	Chlorophyll a TSI	12 / 4	31	71	55	NO	Monitored	Full
22270001	6	Secchi TSI	12 / 4	42	73	62	NO	Monitored	Full
22270001	6	Total Phosphorus TSI	12 / 4	55	71	67	NA	NA	NA
22270001	6	Inorganic suspended solids	12 / 4	0.3	16	2.6	NA	NA	NA

Class BLW - 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
22270001	6	Ammonia	12 / 4	0.0003	0.152	0.05	NA	0 / 0	4	NO	Monitored	Full
22270001	6	Dissolved Oxygen	12 / 4	1.2	9.5	5.5	5	NA / NA	4	YES	Monitored	Not
22270001	6	pH	12 / 4	7.5	8.8	8.1	0	NA / NA	4	NO	Monitored	Full
22270001	6	Temperature	12 / 4	16	27.7	22.7	0	NA / NA	4	NO	Monitored	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	79.47	100.0%	6.28	70.2%	NO	Evaluated	NA

Class C - Conventional 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)	12 / 4	0.02	0.51	0.14	0.03	0	NO	Monitored	Full
22270001	6	pH	12 / 4	7.5	8.8	8.1	8.1	0	NO	Monitored	Full

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)
75	fillet	2016	channel catfish	4	59.8	0.09	0.02	0.06
75	tissue plug	2019	largemouth bass	10	35.8	0.357
75	tissue plug	2017	largemouth bass	3	39.3	0.357
75	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

5/23/2016

Fixed Monitoring Start Date

8/27/2019

Fixed Monitoring End Date

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

120

Surveys of fish and game biologists/other professionals

222

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

260

Fish tissue analysis

270

PWS chemical monitoring (ambient water)

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring