2021 CEQ Annual Report

Water Quality

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

Rivers, Lakes, and Estuaries

Climate Change Indicator


Water quality shows little signs of improvement.

There are estimated to be 7,772 river miles, 72,509 acres of lakes, and 611.91 square miles of estuarine waters in Connecticut.31 Connecticut’s waterbodies provide several key functions, such as the redistribution of sediment and nutrients vital to aquatic habitats; provision of water for drinking, power, and irrigation; and essential habitat for an abundance of diverse plants and animals.32

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 as either fully supporting, not supporting, insufficient information, or not assessed, which characterizes whether or not the water is suitable for that use. While there has been an increase in the miles of rivers assessed to all those tracked by DEEP, there has been little improvement in the miles of assessed rivers that fully support aquatic life and recreation for 2012 through 2018. Conversely, the lakes identified in assessments from 2006-2014 declined, while the lakes assessed in 2016 and 2018 remained neutral.33

Impervious cover, wastewater treatment outflows, stormwater drainage systems and over land flow are primary factors in the transport of pollutants to surface waters!

The Council assessed the relationship between the percent of impervious cover (2012 data**) and the stream/river miles (2020 data) that do not support aquatic life or recreation for each impervious cover grouping. The ratio of the number of impaired stream/river miles divided by the total area of drainage basins for each impervious cover grouping highlights the relative impact that impervious cover has on water quality.

Goal: Attainment, wherever possible, of “water quality, which provides for the protection and propagation of fish, shellfish and wildlife and provides for recreation in and on the water”.

Technical Note: *Analysis of water quality is the net difference in river miles, and area of lakes and estuaries for aquatic life and recreation only. Apparent fluctuations in year-to-year water quality results may be due to limitations in data collection and study design and not to widespread changes in water quality. Section 305(b) of the Federal Clean Water Act (CWA) requires each State to monitor, assess and report on the quality of its waters relative to designated uses. ** Based on data from the Connecticut Environmental Conditions Online (CT ECO).


31 DEEP, 2020 Integrated Water Quality Report - September 2020; portal.ct.gov/DEEP/Water/Water-Quality/Water-Quality-305b-Report-to-Congress.

32 DEEP, GC3 Final Report: Working & Natural Lands Working Group - Rivers Sub-Working Group; portal.ct.gov/-/media/DEEP/climatechange/GC3/GC3-working-group-reports/GC3-WNLWG-Rivers-Final-Report-11-20-20.pdf.
33 DEEP, Integrated Water Quality Report to Congress; portal.ct.gov/DEEP/Water/Water-Quality/Water-Quality-305b-Report-to-Congress.