Des Moines River IA 04-LDM-1021

from confluence with South R. (S12 T77N R22W Warren Co.) to confluence with North R. in S36 T78N R23W Polk Co.

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
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Cycle: 2022
Release Status: Final
Overall IR: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Unknown
Created: 1/11/2022 8:43:57 AM
Updated: 1/11/2022 8:47:19 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2002

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Corps of Engineers/ISU/UI

Class BWW1

Aquatic Life - Warm Water Type 1

Not Assessed

Class HH

Human Health -

Not Assessed

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 exceeded state water quality standards. All other designated uses were "not assessed". Note 1: A TMDL for bacteria was approved by U.S. EPA in March 2010. Because this TMDL covers all the impairments in this segment, this segment remains in IR Category 4a (TMDL approved). Note 2: The water quality sites historically used for assessing this segment are actually located in the adjacent downstream segment (Segment 1020). Beginning with the 2020 IR, those sites/data will no longer be used to assess this segment.

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
USACE	12	WQ	CY 2014-2016	17770003	Des Moines River at S35	Site located in Segment 1020 and beginning with 2020 IR will no longer be used to assess this segment.

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
17770003	12	41 / 3	284	357	162	Yes	19	46%	Yes	Evaluated	Not

Class BWW1 – No Data

Class HH – No Data

Monitoring and Methods

Assessment Key Dates

1/5/2012

Fixed Monitoring Start Date

12/8/2014

Fixed Monitoring End Date

3/1/2010

TMDL Completed

Methods

150

Monitoring data more than 5 years old

420

Indicator bacteria monitoring