Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Buffalo Creek IA 01-WPS-374

from the Jones/Linn county line (NW 1/4 S19 T85N R4W Jones Co.) to confluence with Boulder Cr. in NE 1/4 S30 T86N R5W Linn Co.

This is a DRAFT assessment
Draft assessments may change without notice
Cycle
2026
Current Phase
Public Comment
Overall IR
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Declining
Trend Comment
New Class BWW1 benthic macroinvertebrate impairment.
Created
10/27/2025 3:09:31 PM
Updated
12/2/2025 8:32:10 AM
Use Support
Class A1
Recreation - Primary contact
Not Assessed
Class BWW1
Aquatic Life - Warm Water Type 1
Not Supported
Support Level
Not Supported
Impairment Code
5b-v - Biological - verified
Cause Magnitude
Slight
Status
New
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2026
Impairment Rationale
Low Biotic Index
Data Source
Biological monitoring: Iowa DNR WQMA
TMDL Priority
Tier IV
Class HH
Human Health -
Fully Supported
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class BWW1 use was assessed as "not supported" based on biological sampling data. The Class HH use was assessed as "fully supported" based on fish tissue 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

BIO

See Below

61

Buffalo Creek

Central City

Iowa DNR

6

FT

See Below

1353

Buffalo Creek

Central City


Class A1 - No Data

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage/ Thermal

BM Sample Gear

BMIBI score

BMIBI Class

47c BMIBI BIT

BMIBI Pass/Fail

61

8/19/24

184.8

47c

MS/WW

Hess

67

Good

70

Fail

61

7/26/21

184.8

47c

MS/WW

Hess

69

Good

70

Fail


Fish:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage/ Thermal

Riffle Site?

FIBI score

FIBI Class

47c FIBI BIT

FIBI Pass/Fail

61

8/19/24

184.8

47c

MS/WW

Yes

74

Excellent

65

Pass

61

7/26/21

184.8

47c

MS/WW

Yes

76

Excellent

65

Pass


Overall Assessment:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Monitored

Fail (0/2)

Not

Fish

Monitored

Pass (2/2)

Full

Assessment was monitored because the assessment was

Overall

Monitored

Fail

Not

5bv

completed using samples collected in a recent five-year period.


Class HH - Fish Tissue Sampling:

Site ID

Biopart

Year

Species

# in sample / # of samples

Avg Length (cm)

(Avg) Hg (ppm)

1353

tissue plug

2016

smallmouth bass

3

33.1

0.05

Support Level

Full

Monitoring and Methods
Assessment Key Dates
8/19/2024
Biological Monitoring
8/3/2016
Fish Tissue Monitoring
7/26/2021
Biological Monitoring
Methods
150
Monitoring data more than 5 years old
260
Fish tissue analysis
315
Regional reference site approach
320
Benthic macroinvertebrate surveys
330
Fish surveys