Willow Creek IA 01-VOL-312

mouth (S32 T93N R6W Clayton Co.) to spring source in S13 T92N R7W Fayette 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 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

Open Segment Map
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Cycle: 2024
Release Status: Final
Overall IR: 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
Trend: Unknown
Created: 11/1/2023 8:12:38 AM
Updated: 12/19/2023 3:13:38 PM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class BWW2

Aquatic Life - Warm Water Type 2

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class BWW2 use was assessed as “fully supported” based on biological sampling data and on the trout reproduction in Iowa streams summary prepared by the DNR Fisheries Bureau. All other designated uses were "not assessed." Although not designated for the coldwater aquatic life use in the Iowa Water Quality Standards, part of this segment is identified as a trout stream by the DNR Fisheries Bureau.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	BIO	See Below	901	Willow Creek	Volga

Presumptive Class A1 - No Data

Class BWW2 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	52b BMIBI BIT	BMIBI Pass/Fail
901	7/31/18	3	52b	MS	Hess	81	Excellent	61	Pass
901	7/22/14	3	52b	MS	Hess	81	Excellent	61	Pass

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Site?	FIBI score	FIBI Class	52b FIBI BIT	FIBI Pass/Fail
901	7/31/18	3	52b	MS	NA	73	Excellent	52	Pass
901	7/22/14	3	52b	MS	NA	80	Excellent	52	Pass

Overall Assessment:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (2/2)	Full
Fish	Evaluated	Pass (2/2)	Full		Assessment was evaluated because the watershed above the
Overall	Evaluated	Pass	Full	1	sampling site was smaller than the calibrated range.

Class BWW2 – Trout Natural Reproduction:

Based on the January 2024 trout reproduction in Iowa streams summary prepared by the DNR Fisheries Bureau, the Class BWW2 coldwater aquatic life use of Willow Creek was assessed as "fully supported." According to the updated summary, this stream was placed in both Category I: streams that exhibit consistent natural reproduction and maintain a wild population of one or more trout species without any stocking and Category II: streams that exhibit recent but inconsistent reproductive success and occasional stocking may be needed to maintain the trout population.

Monitoring and Methods

Assessment Key Dates

7/22/2014

Biological Monitoring

7/31/2018

Biological Monitoring

1/1/2024

Biological Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

150

Monitoring data more than 5 years old

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys