Chariton River IA 05-CHA-1307

from the Iowa/Missouri state line to the Highway 2 crossing in S27 T69N R17W Appanoose 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
View assessment methodology in new window

Cycle: 2022
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 1/11/2022 12:36:30 PM
Updated: 1/11/2022 12:37:30 PM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2016

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

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 was assessed as “not supported" based on the identification of a bacteria impairment in the adjacent downstream segment in Missouri. This impairment was identified, in part, by using Iowa DNR indicator bacteria data. All other designated uses were "not assessed".

Assessment Explanation

Class A1 - Indicator Bacteria:

The Class A1 use was assessed as "not supported" due to identification of an impairment for indicator bacteria (E. coli) in the adjacent downstream segment by the Missouri Department of Natural Resources. This bacteria impairment covers the entire length of the Chariton River in Missouri. The bacterial impairment for the upper portion of the Chariton River in Missouri was based, in part, on data for E. coli from the Iowa DNR monitoring station downstream from Rathbun Dam (Station 10040001). Thus, identification of an IR Category 5a impairment for the Iowa segment of the river adjacent to Missouri is justified. A TMDL for the bacterial impairment on the Missouri portion of the Chariton River was approved by EPA in December 2010.

Monitoring and Methods

Assessment Key Dates

None listed

Methods

420

Indicator bacteria monitoring

860

Other Agencies/Organizations provided monitoring data