Water Quality

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• Triennial Review Process for Water Quality Standards

  Explanation of the Triennial Review Process for the Connecticut Water Quality Standards.

• Water Quality (305b) Report to Congress

  The DEEP Water Monitoring Group conducts annual water quality monitoring to evaluate the physical, chemical and biological condition of the State’s waters. Group staff collect a wide variety and large quantity of information each year, including water chemistry data, water temperature data, bacteria data, biological community data (fish, macroinvertebrates, diatoms) and tissue contaminant data.

• Cyanobacteria Blooms

  Cyanobacteria, also known as blue-green algae, occur naturally in lakes and ponds throughout Connecticut.  These microscopic organisms often go unnoticed and cause no harm.  However, excessive nutrient pollution and climate change are causing waterbodies to experience more frequent nuisance cyanobacteria blooms that may produce and release toxins.  When cyanobacteria blooms release toxins, people and animals using the water body for recreation can have health effects.  It is important to note that not all algal blooms are harmful algae blooms (HABs), however it is not possible to determine the level of toxins in the water without a more detailed evaluation. Out of precaution it is best to avoid direct contact with water experiencing a bloom.  When in doubt, stay out!   

• Water Quality Reclassification

  Information regarding a request to change the surface or ground water quality classification of a property or area

• Fact Sheet for the Water Quality Standards and Classifications

  The Connecticut Water Quality Standards form the foundation of water quality programs in CT. This fact sheet provides a summary of water quality classification definitions and provides general information.

• Water Quality Standards and Classification

  The Connecticut Water Quality Standards establish the water quality goals of Connecticut's waterbodies and form the foundation of Connecticut's water management programs.

• Proposed Water Quality Standards

  Proposed amendments to Connecticut’s Water Quality Standards 2009.

• Triennial Review of the Connecticut Water Quality Standards

  Topics under Consideration for Revision within the WQS Regulations 2025

• Connecticut Water Quality Standards 2011 Revisions

• Archive of Water Quality Standards Documents

  This archive contains copies of Water Quality Standards which were previously adopted in Connecticut.

• 2013 Proposed Water Quality Standards Regulations

  Previous (2013) proposed changes to the Connecticut Water Quality Standards.