Connecticut State Council on Environmental Quality

2025 CEQ Annual Report


Water


The Water of Long Island Sound               Warming and Rising Waters                Swimming              Clamming and Oystering               Drinking Water

Rivers, Lakes, and Estuaries

the sun, earth and a thermometer that identifies indicators that are affected by a warmer climate or those that affect the climate

quick summary box indicating that the most recent year's data improved from the previous year, improved from the previous ten-year average and not applicable to meet goal.

 

 

 

Rivers

The total length of assessed rivers that fully support the designated use for aquatic life (1,999 miles) increased by about 1.6 percent and the total length of assessed rivers that fully support the designated use for recreation (487 miles) decreased by approximately eleven (11) percent since 2022. The Department of Energy and Environmental Protection (DEEP) assesses water quality for each designated use (aquatic life, recreation, and fish consumption) for some waterbodies in the state, which characterizes whether the water is suitable for that designated use. Waters designated as habitat for aquatic life are suitable for the support of a viable community of fish and other wildlife. Waters designated for recreation can support activities like swimming or boating. 

 

 

Lakes

The total area of assessed lakes that fully support the designated use for aquatic life (23,543 acres) increased slightly since 2022, while the total area of assessed lakes that fully support the designated use for recreation (16,281 acres) remained unchanged since 2022. 

Estuaries

The total area of estuaries assessed that fully support the designated use for aquatic life (252 square miles (M2)) increased by about one (1) percent, while the total area of estuaries assessed that fully support the designated use for recreation (26 M2) decreased by approximately 8.7 percent since 2022.32

Goal: Section 101(a)(2) of the Clean Water Act (1972) established a national goal for “water quality which provides for the protection and propagation of fish, shellfish, and wildlife, and recreation in and on the water, wherever attainable”.
 

Combined sewer overflows

Combined sewer overflows (CSOs) are discharges of untreated sewage from combined sewer systems, and sanitary sewer overflows (SSOs) are discharges of untreated sewage from separate sanitary sewers and are sometimes referred to as spills or bypasses. 


The occurrence of CSOs and SSOs increases when significant rainfall occurs, particularly from extreme weather events. During heavy rains, untreated stormwater and wastewater, which can contain pathogens, excess nutrients, and chemicals, may be discharged. The discharge of untreated or partially treated sewage can adversely impact water quality, which affects recreational and economic opportunities, such as swimming and shellfishing. As depicted in the chart, more than 600 million gallons of CSO volume and over 840 million gallons of SSO volume were released to waterbodies in Connecticut in 2025. * Over 86 percent of the total CSO volume and 72 percent of the total SSO volume released in 2025 was attributed to the Metropolitan District (MDC) treatment facilities.33

Technical Note: *For 2024 (most recent data available), approximately 543 million gallons of CSO volume was discharged to the Connecticut River from facilities in Massachusetts. 

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32 DEEP, 2024 Final Integrated Water Quality Report to Congress; portal.ct.gov/-/media/deep/water/water_quality_management/305b/2024/final-2024-iwqr.pdf.

33 DEEP, CT Sewage Right-to-Know webpage 2026 Annual Report (Due February 1, 2026), accessed March 4, 2026; portal.ct.gov/deep/municipal-wastewater/ct-sewage-right-to-know. Frequently Asked Questions about Combined Sewer Overflows (CSOs); portal.ct.gov/deep/municipal-wastewater/combined-sewer-overflows-frequently-asked-questions.

34 Massachusetts Department of Environmental Protection, Annual Sewage Notification Report 2024, May 15, 2024, Table A7; www.mass.gov/doc/2024-sewage-notification-annual-report/download.