Walnut Creek IA 05-NSH-1449

mouth (S8 T69N R41W Fremont Co.) to confluence with unnamed tributary at the S30/31 line in T73N R38W Montgomery 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 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.

Open Segment Map
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Cycle: 2020
Release Status: Final
Overall IR: 3 - Insufficient data exist to determine whether any designated uses are met.
Trend: Unknown
Created: 9/18/2020 7:18:17 AM
Updated: 10/19/2020 8:30:55 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class BWW1

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low fish & invert IBIs- cause unknown

Support Level

Further Investigation Needed

Impairment Code

3b-c - Use potentially biologically impaired based on calibrated IBI metrics.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2010

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class BWW1 use remains assessed as “partially supported” based on biological sampling data. All other designated uses were "not assessed".

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	BIO	See Below	80	Walnut Creek	Red Oak - Downstream
Iowa DNR	6	BIO	See Below	81	Walnut Creek	Red Oak - Upstream
Iowa DNR	6	BIO	See Below	989	Walnut Creek	W of Red Oak

Presumptive Class A1 - No Data

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	BM Sample Gear	BMIBI score	BMIBI Class	47e BMIBI BIT	BMIBI Pass/ Fail
80	10/11/96	108	47e	MO/WW	ArtSub	54	Fair	54	Pass
80	10/11/96	108	47e	MO/WW	Hess	52	Fair	54	Fail
81	10/11/96	108	47e	MO/WW	ArtSub	46	Fair	54	Fail

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	Riffle Stream?	FIBI score	FIBI Class	47e FIBI BIT	FIBI Pass/ Fail
989	8/24/98	139	47e	MO/WW	NA	29	Fair	31	Fail
80	10/14/96	108	47e	MO/WW	NA	23	Poor	31	Fail
81	10/14/96	108	47e	MO/WW	NA	20	Poor	31	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (1/3)	Partial
Fish	Evaluated	Fail (0/3)	Partial
Overall	Evaluated	Fail	Partial	3bc	3bc	Assessment is evaluated because it was based on samples not collected in the last five years.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

10/14/1996

Biological Monitoring

10/11/1996

Biological Monitoring

8/24/1998

Biological Monitoring

Methods

150

Monitoring data more than 5 years old

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys