Impoundments can lead to decreased abundance and biodiversity of macroinvertebrate
communities. To reverse negative impacts caused by these impoundments, dam removal may be
utilized as a method to restore natural flow regimes and rebalance aquatic ecosystems. In Illinois,
two low-head dams were removed from the Vermilion River (Danville Dam; 2018) and North
Fork Vermilion River (Ellsworth Dam; 2019), reconnecting over a thousand stream miles within
the Vermilion River Basin and restoring connectivity to the Wabash River. To assess
macroinvertebrate communities of the two rivers, pre- and post-dam removal, macroinvertebrates
were sampled using the EPA 20-jab method and Qualitative Habitat Evaluation Index (QHEI)
metrics were recorded. Macroinvertebrate and QHEI surveys were conducted at twelve 100-
meter sites, in the fall of 2014 and 2015 with 4 sites upstream and 2 sites downstream of the dam
locations. Post dam removal, the same sites were sampled in the fall of 2022, 2023 (only North
Fork sites), and 2025. Preliminary results show an increase in QHEI scores, increased diversity
and abundance, increased percent EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa, and
increased abundance of Collector-Filterers, Shredders, and Predators post-dam removal. This
increase in taxonomic and functional diversity in tandem with an increase in proportion of
sensitive taxa collectively demonstrates the improvement observed to macroinvertebrate
communities in rivers following dam removals. Macroinvertebrates provide valuable information
on the health and quality of the stream as they are bioindicators occupying every consumer level
in lotic systems with different functional feeding groups and tolerance values. Thus, it is critical
to monitor these communities to understand holistic impacts of stream restoration efforts like
dam removals.