2024 Riffle Bioassessment by Volunteers Program Report

Two-Tailed Mayfly (Epeorus)

Report Last Updated: January 2026

Connecticut is fortunate to be a water-rich state, home to over 7,772 miles of rivers and streams. One of the CT DEEP Monitoring and Assessment Program’s (MAP) primary tasks is to conduct water quality monitoring to evaluate the physical, chemical and biological conditions of all waters in the State as part of Clean Water Act (CWA) requirements. Given limited staff resources, this wealth of water resources presents a challenge to achieve this CWA goal. One way MAP has enhanced assessments is by utilizing citizen scientist data to work towards this goal.

In 1999, the MAP developed a citizen science program, called the Riffle Bioassessment by Volunteers (RBV) Program, where trained volunteers collect benthic macroinvertebrate data from wadeable streams. In 2024 we entered the 26th consecutive sampling year for RBV program data. Thank you all for your hard work that allows this program to continue to be a success!


Above: Various 2024 RBV sampling locations (Left: Saugatuck River, Weston, Middle: Jeremy River, Colchester, Right: Eightmile River (West Branch), Haddam). Photos courtesy of Harbor Watch, Salmon River Watershed Partnership & Eightmile River Wild & Scenic Watershed.

A Hunt for CT’s Healthiest Streams!

The CT DEEP Riffle Bioassessment by Volunteers or “RBV” Program is an annual fall ‘treasure hunt’ for Connecticut’s healthiest streams. CT DEEP uses the data collected by RBV volunteers to expand its inventory of excellent small, high gradient Connecticut streams that have excellent water quality – our “Healthy Streams” list.

RBV volunteers examine the water quality of local stream segments by studying the aquatic benthic macroinvertebrate community present in rocky or ‘riffle’ areas of these streams. If volunteers can find four or more pollution sensitive or ‘most wanted’ macroinvertebrates, CT DEEP can use this data to assess that stream as fully supporting water quality standards for aquatic life use – documenting it as one of CT’s healthiest streams!

Because it is a screening approach and not a more in-depth assessment methodology, RBV cannot provide a detailed water quality assessment, nor can it be used to identify low or impaired water quality.