Iowa DNR
BioNet
River & Stream Biological Monitoring
Fish and Benthic Macroinvertebrate Surveys
Physical Habitat Assessments

Onion Creek Ames (Timber HWCRS)

Analysis Summary for Series #939

Benthic Macroinvertebrate Index of Biotic Integrity (BMIBI)

Metric Name Value Score
MH Total Taxa 28 7.06
SH Total Taxa 11.67 7.49
MH EPT Taxa 12 6.43
SH EPT Taxa 8.33 7.92
MH Sensitive Taxa 5 5.99
SH Ephem % 30.23 3.87
SH EPT % 87.42 9.15
SH Chiron % 10.2 9.07
SH Scraper % 6.21 1.39
SH Top3Dom % 61.74 8.51
SH Dom FFG % 59.93 6.68
MHBI 5.36 6.07
*Mouse-over metric for full name
**Final IBI is sum of scores multiplied by 0.8333

Analysis Factors

Factor Value
BMIBI Type Warm Water
Sample Date 7/25/2007
Sampling Series Series #939
Drainage Area (mi2) 18.841
Log(DA) 1.2751039495692
Calculation Last Updated 7/22/2025 3:35:34 PM
Sampling Gear Hess
BMIBI Score
66
Warm Water
Good

BMIBI Score Explained

This site was analyzed using the BMIBI-Warm Water assessment methodology.

Sites that score between 56 - 75 are considered good. A slight reduction in number (Ephemeroptera, Plecoptera, Trichoptera) of taxa; however, good numbers of taxa are present, including several sensitive species, EPT taxa are fairly diverse and dominate the community. The most sensitive taxa and some habitat specialists may not be present and/or are reduced in abundance. The community is balanced, with no taxon excessively dominating in abundance. One functional feeding group, often collector filterers or collector gatherers, may be somewhat dominant.

This location has been classified as a Candidate Reference Site. Further study is required to determine if this site represents natural stream qualities that are least disturbed by human activities within the watershed.

EcoRegion Comparison

Scores for a sampling session are compared against reference sites within the same ecoregion:

Des Moines Lobe

This site is in the Des Moines Lobe ecoregion.

Ecoregion Map
Max 84
75th Percentile 68
Median 59
25th Percentile 51
Min 10
This Session's Score 66
Total Reference Site Samples 162
Mean 58.11
Standard Deviation 13.08