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

Thompson Fork - Grand River Davis City

Analysis Summary for Series #2637

Benthic Macroinvertebrate Index of Biotic Integrity (BMIBI)

Metric Name Value Score
MH Total Taxa 31 5.96
SH Total Taxa 15 6.61
MH EPT Taxa 15 5.56
SH EPT Taxa 10.67 7.26
MH Sensitive Taxa 5 4.55
SH Ephem % 18.44 2.36
SH EPT % 81.37 8.52
SH Chiron % 11.43 8.95
SH Scraper % 4.29 0.96
SH Top3Dom % 52.57 7.53
SH Dom FFG % 60.7 6.55
MHBI 4.99 7.44
*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 8/3/2022
Sampling Series Series #2637
Drainage Area (mi2) 701
Log(DA) 2.84571801796666
Calculation Last Updated 10/10/2025 8:07:52 AM
Sampling Gear Surb
BMIBI Score
60
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 survey site. Survey sites are compared to reference sites within the same ecoregion. A reference site represents natural stream qualities that are least disturbed by human activities within the watershed. Reference sites are grouped by ecoregion to establish a benchmark against which these survey streams are compared.

EcoRegion Comparison

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

Loess Flats and Till Plains

This site is in the Loess Flats and Till Plains ecoregion.

Ecoregion Map
Max 78
75th Percentile 58
Median 52
25th Percentile 42
Min 14
This Session's Score 60
Total Reference Site Samples 49
Mean 49.84
Standard Deviation 13.11