DRAFT 2026 assessment for Catfish Creek

Catfish Creek IA 01-TRK-126

south line of S9 T88N R2E (Dubuque Co.) to west line of S30 T88N R2E Dubuque Co.

This is a DRAFT assessment

Draft assessments may change without notice

2026
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 2022 - 2024
Stream/River Water Quality Data	CY 2022 - 2024
Lake Water Quality Data	CY 2020 - 2024
Biological Sampling Data	CY 2020 - 2024*
Fish Kill Data	CY 2020 - 2024
Fish Tissue Sampling Data	CY 2020 - 2024
Continuous Dissolved Oxygen Sampling Data	CY 2020 - 2024
*Biological sites sampled in both 2019 and 2023 were also assessed.

Open Segment Map
View 2026 assessment summary page

Overall IR

5 - Water is impaired or threatened and a TMDL is needed.

Trend

Declining

Trend Comment

New presumptive A1 and A3 impairments.

Current Phase

Public Comment

Created

10/27/2025 3:09:01 PM by

Updated

2/11/2026 9:31:20 AM by

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

303(d) Listing Status

New

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2026

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Special project/study: Iowa DNR

TMDL Priority

Tier II

Class A2

Recreation - Secondary contact

Fully Supported

Class A3

Recreation - Children's contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

303(d) Listing Status

New

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2026

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Special project/study: Iowa DNR

TMDL Priority

Tier II

Class BCW1

Aquatic Life - Cold Water Type 1

WINOFI

Biological: low aquatic macroinvertebrate IBI

Support Level

Further Investigation Needed

Impairment Code

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

Cause Magnitude

Moderate

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2012

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

Not Assessed

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 and A3 uses were assessed as "not supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class A2 use was assessed as "fully supported" based on indicator bacteria monitoring data. The Class BCW1 use was assessed as "WINOFI" based on biological sampling data. All other designated uses were "not assessed."

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2024	14000623	Catfish Creek
Iowa DNR	6	BIO	See Below	23	Catfish Creek	Swiss Valley Park

Presumptive Class A1 & Class A3 - Indicator Bacteria:

Site ID	Data Source ID	# Samples per Year (2024)	2024 Geometric Mean	Violates Annual Geometric Mean?	# 2024 SSM violations / SSM Violations needed for impairment	Violates Annual SSM Significantly >10% Rule?	Assessment Type	Support Level
14000623	6	10	339	YES	4 / 3	YES	MONITORED	NOT

Class A2 - Indicator Bacteria:

Site ID	Data Source ID	# Samples per Year (2024)	2024 Geometric Mean	Violates Annual Geometric Mean?	# 2024 SSM violations / SSM Violations needed for impairment	Violates Annual SSM Significantly >10% Rule?	Assessment Type	Support Level
14000623	6	10	339	NO	1 / 3	NO	MONITORED	FULL

Class HH - No Data

Class BCW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	BM Sample Gear	CBI score	CBI Class	CBI BIT	CBI Pass/Fail
23	8/21/24	12	52b	MS/CW	Hess	36	NA	60	Fail

Overall Assessment:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (0/1)	WINOFI	3bc	Assessment was evaluated because it was based on a single sample.

Aquatic Life Use - Trout Natural Reproduction

Based on the latest trout reproduction in Iowa streams summary prepared by the DNR Fisheries Bureau, the aquatic life use was assessed as "fully supported." According to the summary, a portion, or all, of this assessment unit was placed in Category I: streams that exhibit consistent natural reproduction and maintain a wild population of one or more trout species without any stocking.

Monitoring and Methods

Assessment Key Dates

1/1/2025

Biological Monitoring

8/21/2024

Biological Monitoring

4/17/2024

Monitoring Start

11/13/2024

Monitoring End

Methods

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring