2024 RBV Program Report
2024 Riffle Bioassessment by Volunteers Program Report
Two-Tailed Mayfly (Epeorus)
Report Last Updated: September 2025
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.
2024 Local RBV Programs & Leaders
Local RBV Programs ensure that the statewide RBV program is a success each year. Local RBV Coordinators put countless hours into organizing their programs, communicating with DEEP, recruiting and training volunteers, and more.
| Local RBV Program | Coordinators |
|---|---|
| Three Rivers Community College | Diba Khan-Bureau |
| Eightmile River Wild & Scenic Watershed | Pat Young |
| Salmon River Watershed Partnership | Pat Young |
| Vernon Conservation Commission | Carly Andrulat & Jeff Carlson |
| Greenwich Inland Wetlands & Watercourses Agency | Jennifer Urena |
| East Lyme Commission for the Conservation of Natural Resources | Don Danila |
| Bolton Conservation Commission | Rod Parlee |
| The Last Green Valley | Emma MacDonald |
| Trout Unlimited - Candlewood Valley Chapter | Joseph Hovious |
| Pomperaug River Watershed Coalition | Carol Haskins |
| Harbor Watch | Marisa Olivara |
| The Maritime Aquarium | Bridget Cervero |
Saugatuck River, Weston.
Photo courtesy of Harbor Watch.
Welcome New Coordinators!
The RBV Program is excited to welcome new program partners! We welcomed new coordinators from Harbor Watch, The Maritime Aquarium, Vernon Conservation Commission, Greenwich Inland Wetlands & Watercourses Agency and The Last Green Valley!
The new coordinators received training and conducted samples in 2024 and we are happy to welcome them to the program! These partnerships are very beneficial in expanding the program reach to new waterbodies across CT. Thank you to our new and existing partners!
2024 Monitoring Results
The 2024 RBV monitoring program faced numerous challenges, including CT DEEP staffing changes and severe flooding in parts of the state followed by abnormally dry conditions which resulted in variable stream flows. Despite these unpredictable sampling conditions, the program continued to have a positive impact and contributed meaningful water quality data.
RBV volunteers collected 62 vouchers from 54 unique locations on 45 different waterbodies. 35 (56%) of the 2024 monitoring vouchers had 4 or more taxa types in the ‘most wanted’ category, indicating that these stream segments are among Connecticut’s healthiest streams.
Table 1: Summary of Results
| Category | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 |
|---|---|---|---|---|---|---|---|---|---|
| # RBV Samples Submitted | 70 | 78 | 55 | 118 | 47 | 80 | 66 | 59 | 62 |
| # Monitoring Stations | 61 | 74 | 45 | 102 | 41 | 73 | 59 | 55 | 54 |
| # Streams Monitored | 55 | 61 | 43 | 89 | 36 | 65 | 52 | 53 | 45 |
| # Samples w/ 4+ “Most Wanted” Types | 21 | 43 | 23 | 62 | 16 | 52 | 28 | 30 | 35 |
| % of Samples w/ 4+ “Most Wanted” Types | 30% | 55% | 42% | 53% | 34% | 65% | 43% | 51% | 56% |
2024 Results Map
This interactive map depicts the number of ‘Most Wanted’ macroinvertebrate types present in RBV voucher samples from only 2024 samples. Mouse over the site icon to see the monitoring ID, waterbody name, and count of most wanted taxa. To open the full-screen map, click here.
Sites are assessed to be ‘healthy’ (★) if 4 or more ‘most wanted’ macroinvertebrate taxa were present. View the full Volunteer Monitoring Mapping Application to see the results from all 26 years of monitoring.
Table 2: Most Wanted Counts
This table provides a list of most wanted counts by site. The table is sorted according to waterbody name, site ID, and then the date the sample was collected.
A detailed list of all monitoring sites, most wanted counts and the complete RBV taxa list for each can be downloaded from the Water Quality Portal.
*Data collected outside the sampling date range specified in the QAPP (September 1st-November 30th).
Interpreting Your Results
Refer to Table 3 for guidance on how to interpret your monitoring results.
Table 3: Interpretation of RBV Results by Most Wanted Count
| # ‘Most Wanted’ Taxa | What Does it Tell Us? |
| 4+ |
Excellent!! Lots of very sensitive macroinvertebrate types were
present – you found a healthy stream segment! This is a very clear signal of excellent water quality as the ‘Most Wanted’ types cannot survive in degraded streams or otherwise low water quality conditions. DEEP Assessment Decision: The stream containing the monitoring location will be considered for ‘Fully Supporting’ State aquatic life use standards. Fully supporting streams or stream segments will be listed in the next Integrated Water Quality Report (IWQR) and added to the DEEP’s running list of miles of Healthy Waters assessed. Recommended Volunteer Follow-Up Action: Revisit every 2 to 5 years to continue documenting the excellent health of this stream. |
| 3 |
A Very Good Sign – Keep this Site on Your Radar! Three Most Wanted or very sensitive macroinvertebrate types in a sample is a strong signal of good to excellent water quality. Although three most wanted is not statistically enough data for DEEP to list the site as a healthy stream segment this time, this is a great find! DEEP Assessment Decision: No Assessment Made… but consider trying again! Recommended Volunteer Follow-Up Action: If this was the first time the site was monitored with RBV, this site should be a high priority candidate for next season. |
| 0-2 |
Double check whether this is a good spot to be using the RBV
method… More information is needed to determine the water quality at this site. Reasons for few most wanted could include poor water quality; however, few most wanted types should not be interpreted as a proof of degraded conditions. Other factors such as unusual flow conditions and lack of adequate habitat can also result in few most wanted types despite overall good water quality. DEEP Assessment Decision: No Assessment Made Recommended Volunteer Follow-Up Action: Discuss with the State RBV Coordinator whether you should revisit this site in future monitoring seasons. |
2024 RBV Data Impact
The 2024 RBV results will be consolidated into the 2026 Integrated Water Quality Report. A ‘healthy’ river or stream is one that fully supports a variety of uses, including aquatic life use.
In 2024, RBV volunteers monitored 62 waterbodies in Connecticut. Based on the results reported in the previous section, RBV data is likely to generate 4 new listings of Connecticut waterbodies that fully support aquatic life use:
Mill Brook (Woodstock)
Blackmore Brook (Thompson)
North Branch Pootatuck River (Newtown)
NTT to Eightmile River (East Haddam)
In addition, the 2024 RBV data will allow DEEP to propose maintaining
24 existing waterbodies that fully support aquatic life
use.
Appendices
Appendix A: Monitoring Station Details
Appendix B: Most Wanted Taxa by Site
This table provides a list of all the “most wanted” taxa found at each site. The table is sorted according to waterbody name, site ID, and then the date the sample was collected. A full list of all taxa found at each site can be downloaded from the Water Quality Portal.
Appendix C: Presence/Absence of RBV Taxa by Site
To download this supplementary table, click here. Samples are sorted by waterbody name, site ID and then monitoring date. ‘Most Wanted’ taxa confirmed present in the voucher are noted with an “X”. Column numbers correspond to the RBV macroinvertebrate organism ID number on the RBV ID cards and datasheet.
Bold font indicates a site at which four or more ‘Most Wanted’ RBV taxa types were present in the voucher. There are 17 possible most wanted taxa; each miscellaneous small stonefly taxa present (up to 6 types) count as one ‘Most Wanted’ taxa type. The site with the greatest number of ‘Most Wanted’ taxa types is highlighted in green.