DRAFT 2026 assessment for Catfish Creek

Catfish Creek IA 01-TRK-125

from S. Fk. Catfish Cr. (S2 T88N R2E Dubuque Co.) to south line of S9 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

Stable

Current Phase

Public Comment

Created

10/27/2025 3:11:07 PM by

Updated

1/30/2026 11:44:18 AM by

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.

Cause Magnitude

High

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2012

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Watershed project monitoring

TMDL Priority

Tier III

Class BWW2

Aquatic Life - Warm Water Type 2

Not Assessed

303(d) Delistings for this Cycle

Cycle Added	Class	Cause	Data Source	Rationale
2016	Class BWW2	Fish Kill: Due To Unknown Toxicity	Biological monitoring: Iowa DNR fish kill follow-up	New data: recovery of fish community from pollutant-caused fish kill

Documentation

Assessment Summary

The presumptive Class A1 use was assessed as “not supported” due to violations of Iowa water quality criteria for indicator bacteria (E. coli). The Class BWW2 use was "not assessed" based on 2023 fish kill follow-up sampling that indicated fish community recovery from the fish kill. According to IR fish kill follow-up methodology, the previous 5b fish kill impairment was de-listed.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2024-2024	14000622	Catfish Creek
Iowa DNR	6	BIO	See Below	1426	Catfish Creek	Dubuque

Presumptive Class A1 - 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
14000622	6	10	416	YES	8 / 3	YES	MONITORED	NOT

Class BWW2 – Fish Kill Assessment:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/ Thermal	Fish per mile	52b REMAP 25 % fish per mile	>52b REMAP 25 % fish per mile?	52b expected fish taxa	Fish Taxa Present % (>50% to pass)
1426	9/21/23	19.3	52b	MS/WW	4002	1502	Yes (Pass)	9/12	75% (Pass)
The Class BWW2 use previously resided in Category 5b based on a fish kill that occurred in 2014. This segment’s fish community was sampled in 2023 as part of the DNR fish kill follow-up sampling program. The results from this follow-up sampling and comparison to ecoregion averages suggest that the fish community of this segment is similar to non-fish kill impacted streams. Based on the fish kill follow-up sampling results, the Category for the fish kill assessment was changed from 5b to 3a (not assessed).

Details about the 2014 fish kill can be found here:https://programs.iowadnr.gov/fishkill/Events/879

Monitoring and Methods

Assessment Key Dates

4/17/2024

Monitoring Start

11/13/2024

Monitoring End

8/31/2014

Fish Kill

9/21/2023

Biological Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

140

Incidence of spills and/or fish kills

330

Fish surveys

420

Indicator bacteria monitoring