Lake Oelwein IA 01-WPS-6461

Lake Oelwein at south edge of Oelwein in W1/2 S33 T91N R9W 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: 3 - Insufficient data exist to determine whether any designated uses are met.
Trophic: Unknown
Trend: Unknown
Created: 1/5/2024 8:51:11 AM
Updated: 2/5/2024 1:08:22 PM

Use Support

Class A1

Recreation - Primary contact

Not Assessed

Class BLW

Aquatic Life - Lakes and wetlands

WINOFI

Fish Kill: Due To Natural Causes

Support Level

Further Investigation Needed

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Slight

Status

New

Source

Natural

Source Confidence

Moderate

Cycle Added

2024

Impairment Rationale

Potential Impairment

Data Source

Fish kill investigation: Iowa DNR

Class HH

Human Health -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class BLW use was assessed (evaluated) as "WINOFI" due to a fish kill. All other designated uses are “not assessed.”

Assessment Explanation

Class A1 – No Data

Class BLW - Fish Kill:

The Class BLW use was assessed (evaluated) as “WINOFI” due to fish kill that occurred in April of 2022. Because the cause of the fish kill was not identified, or the fish kill was attributed to a non-pollutant cause (e.g., winterkill), the assessment type is “evaluated.” Segments assessed using “evaluated” assessments are placed in Category 3b and are added to the state list of waters in need of further investigation. If no additional fish kills are reported in the segment for a 5 year period, the Category will be changed from 3b to 3a (water not assessed).

Details about the 2022 fish kill can be found here:https://programs.iowadnr.gov/fishkill/events/1017

Class HH: No Data

Monitoring and Methods

Assessment Key Dates

None listed

Methods

120

Surveys of fish and game biologists/other professionals

140

Incidence of spills and/or fish kills