DRAFT 2026 assessment for Crawford Creek Impoundment

Crawford Creek Impoundment IA 06-LSR-1583

Ida County S10T86NR41W 2.5 mi. S of Battle Creek.

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.

Trophic

Eutrophic

Trend

Stable

Current Phase

Public Comment

Created

10/27/2025 3:10:21 PM by

Updated

11/21/2025 3:39:08 PM by

Use Support

Class A1

Recreation - Primary contact

Not Supported

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2024

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier II

Class BLW

Aquatic Life - Lakes and wetlands

Not Supported

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2024

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier II

Class HH

Human Health -

Not Assessed

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed (monitored) as “not supported” due to violations of the Class A1 criterion for pH. The Class BLW use was assessed (monitored) as “not supported” due to violations of the Class BLW criterion for pH. 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 2020-2024	22470001	Crawford Creek Lake

Class A - Indicator Bacteria: No Data

Class A1 - pH

Site ID	Data Source ID	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
22470001	6	15 / 5	7.7	9.9	8.7	4	4	YES	MONITORED	NOT

Class A1 - Lake TSI's

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Median Value	Median TSI Violation?	Assessment Type	Support Level
22470001	6	Chlorophyll a TSI	15 / 5	39	75	56	NO	MONITORED	FULL
22470001	6	Secchi TSI	15 / 5	40	77	63	NO	MONITORED	FULL
22470001	6	Total Phosphorus TSI	15 / 5	37	75	62	NA	NA	NA
22470001	6	Fixed suspended solids	15 / 5	0.7	10	1.9	NA	NA	NA

Class BLW - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	# Acute / Chronic Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
22470001	6	Dissolved Oxygen	15 / 5	4.3	13.7	8.3	1	NA / NA	4	NO	MONITORED	FULL
22470001	6	pH	15 / 5	7.7	9.9	8.7	4	NA / NA	4	YES	MONITORED	NOT
22470001	6	Temperature	15 / 5	16.5	30.1	23.2	0	NA / NA	4	NO	MONITORED	FULL

Class BLW - Lake Planktonic Cyanobacteria:

Site ID	Data Source ID	# Samples	Maximum Cyanobacteria Wet Mass	Maximum Cyanobacteria % Composition	Median Cyanobacteria Wet Mass	Median Cyanobacteria % Composition	Median Cyanobacteria Concentration = 75th Percentile	Assessment Type	Support Level
22470001	6	5	10.84500067	73.66%	2.387613971	8.45%	NO	EVALUATED	NA

Class BLW - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
22470001	6	Ammonia	15 / 5	0.0856	0.03	0.03	0 / 0	NO	MONITORED	FULL

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

5/26/2020

Monitoring Start

9/3/2024

Monitoring End

Methods

200

Physical/Chemical Monitoring

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)