2020 Final assessment for Little Sioux River

Little Sioux River IA 06-LSR-1565

from confluence with Maple R. (S17 T83N R44W Monona Co.) to confluence with Big Cr. in Anthon in S4 T87N R43W Woodbury Co.

Assessment Cycle

2020

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 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.

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

Created: 9/21/2020 2:13:13 PM
Updated: 10/19/2020 7:46:34 AM

Assessment conducted in accordance with Iowa's 2020 IR methodology

Use Support

Class A1

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially 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

Fully Supported

Class HH

Fully Supported

General Use

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use remains assessed as "partially supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on biological sampling data and water quality monitoring data. The Class HH use was assessed as "fully supported" based on water quality monitoring data.

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 2014-2016, CY 2016-2018	10970001	Little Sioux River near Smithland
Iowa DNR	6	BIO	See Below	845	Little Sioux River	Smithland

Class A1 - Indicator Bacteria:

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
10430001	6	24 / 3	386	335	480	Yes	13	54%	Yes	Evaluated	Partial

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
10970001	6	33 / 3	8.6	8.2	8.3	0	0%	No	Monitored	Full

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
10970001	6	Ammonia	33 / 3	0.66	0.05	0.02	0 / 0	0% / 0%	No	Monitored	Full
10970001	6	Chloride	36 / 3	25	21	22	0 / 0	0% / 0%	No	Monitored	Full
10970001	6	Dissolved oxygen	36 / 3	15	10.4	10.8	NA / 0	NA / 0%	No	Monitored	Full
10970001	6	pH	33 / 3	8.6	8.2	8.3	0 / NA	0% / NA	No	Monitored	Full
10970001	6	Sulfate	36 / 3	88	58	57	0 / NA	0% / NA	No	Monitored	Full
10970001	6	Temperature	36 / 3	27.7	12.2	9.8	0 / 0	0% / 0%	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	% Acute/ Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
10970001	6	Aluminum	9 / 2	5.3	2.78	3.5	0 / 0	0% / 0%	No	Evaluated	Full
10970001	6	Arsenic	9 / 2	3.5	2.2	1.8	0 / 0	0% / 0%	No	Evaluated	Full
10970001	6	Cadmium	9 / 2	0.025	0.025	0.025	0 / 0	0% / 0%	No	Evaluated	Full
10970001	6	Chromium	9 / 2	1.4	0.68	0.77	0 / 0	0% / 0%	No	Evaluated	Full
10970001	6	Copper	9 / 2	3.7	1.27	1.2	0 / 0	0% / 0%	No	Evaluated	Full
10970001	6	Lead	9 / 2	0.17	0.076	0.07	0 / 0	0% / 0%	No	Evaluated	Full
10970001	6	Nickel	9 / 2	4.8	2.9	2.8	0 / 0	0% / 0%	No	Evaluated	Full
10970001	6	Selenium	9 / 2	4.5	2.7	2.6	0 / 0	0% / 0%	No	Evaluated	Full
10970001	6	Zinc	9 / 2	2.9	1.39	1.3	0 / 0	0% / 0%	No	Evaluated	Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47m BMIBI BIT	BMIBI Pass/ Fail
845	8/14/18	2687	47m	MO/WW	Float ArtSub	54	Fair	54	Pass
845	8/18/14	2687	47m	MO/WW	Float ArtSub	54	Fair	54	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (2/2)	Full	1	1	Assessment is evaluated because the drainage area of the sample site was larger than the calibrated range.

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
10970001	6	Cadmium	9 / 2	0.025	0.025	0.025	9	No	Evaluated	Full
10970001	6	Chromium	9 / 2	1.4	0.68	0.77	0	No	Evaluated	Full
10970001	6	Copper	9 / 2	3.7	1.27	1.2	0	No	Evaluated	Full
10970001	6	Nickel	9 / 2	4.8	2.9	2.8	0	No	Evaluated	Full
10970001	6	Selenium	9 / 2	4.5	2.7	2.6	0	No	Evaluated	Full
10970001	6	Zinc	9 / 2	2.9	1.39	1.3	0	No	Evaluated	Full

Monitoring and Methods

Assessment Key Dates

1/8/2014	Fixed Monitoring Start Date
12/7/2016	Fixed Monitoring End Date
8/18/2014	Biological Monitoring
8/8/2018	Biological Monitoring
1/5/2016	Fixed Monitoring Start Date
10/5/2018	Fixed Monitoring End Date

Methods

230	Fixed station physical/chemical (conventional plus toxic pollutants)
315	Regional reference site approach
320	Benthic macroinvertebrate surveys
420	Indicator bacteria monitoring

Water Quality Assessments

Impaired Waters List

Little Sioux River IA 06-LSR-1565

Assessment Summary

Assessment Explanation

Assessment Key Dates

Methods