Frequently Asked Questions:

Why were new Stream Flow Standards and Regulations adopted?

DEEP proposed the Stream Flow Standards and Regulations in response to requirements in legislation approved by the General Assembly and signed into law in 2005 (PA 05-142).  The purpose of the Stream Flow Standards and Regulations is to provide for the protection of Connecticut’s river and streams by establishing stream flow standards that apply to all river and stream systems in the state through a classification process and requiring minimum releases from dams.  These proposed rules add to and eventually replace the existing requirements found in the Minimum Stream Flow Standards and Regulations of the Connecticut Department of Environmental Protection, sections 26-141a-1 to 26-141a-8, inclusive, of the Regulations of Connecticut State Agencies. 

What is the basic regulation framework?

The Stream Flow Standards and Regulations balance the needs of humans to use water for drinking and domestic purposes, fire and public safety, irrigation, manufacturing, and recreation, with the needs of fish, wildlife and other biota that also rely upon the availability of water to sustain healthy, natural communities.  The regulations provide a framework considering the best available science to balance the human and ecological needs for water.  The framework includes: four stream flow classifications; operational rules for each; public notice and input into the classification process; and a phased implementation of regulatory requirements to encourage and support water supply planning and conservation efforts.  These rules help protect Connecticut’s river and stream systems by promoting better, more efficient management of our water supplies, so that all needs, both human and ecological, can be met both today and in the future.

What is the classification scheme?

Stream flow classes range from Class 1 (minimally altered) to Class 4 (substantially altered). The flow standards for each class are based on maintaining, to various degrees, the natural variation in flow expected in Connecticut given seasonal climate and rainfall patterns and human use.

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The stream flow standards incorporate the concept of balancing human and ecological needs for water by establishing different flow standards for each of four classes of waters:

• Class 1- free flowing, priority given to protecting ecological health
• Class 2- minimally altered free flowing stream system
• Class 3- moderately altered, have intermediate balance points between ecological and human uses.
• Class 4- substantially altered, priority is given to human uses

What is the classification process and timeframe?

A public participation process is required that includes a public notice of proposed classifications in the newspaper, opportunity for public comment, State Agency review (including but not limited to the Department of Public Health, Department of Agriculture, Department of Economic and Community Development, Public Utilities Regulatory Authority and Office of Policy and Management), a document summarizing the reasons and support for the stream flow classifications, and notice of adopted classifications in the Connecticut Law Journal.There is no timeframe set in the Stream Flow Standards and Regulations for the classification process to be completed. It is the Department’s expectation that each of the major basin areas will take approximately one year to complete. The DEEP will be issuing public information and notices so the public can comment when river and stream system are classified.

What are the factors used for classification?

Factors that will be considered in the stream flow classification include location of dams, existing diversions, potential water supply, water supply margin of safety, return flows, land cover, planned land use, aquatic resources, aquatic life, anadromous fish runs, trout management areas, and recreational resources.

What happens if there is new information after stream flow classification are established? Is there a procedure to change the stream flow classifications?

Yes, there is a procedure for petition to change a classification that allows for public notice and input prior to the Commissioner making a final determination on the request.

Who must comply and make releases?

Dam owners or operators that impound or divert the waters of a river or stream system or that affect the flow of water in such a system must comply with the regulation and make certain releases.  However there are a number of off ramps in the release rules, and exemptions to that basic applicability.

What are the exemptions?

There are exemptions for safety, emergencies, limited/short term water use, non-consumptive uses, stormwater detention, small watersheds, certain man-made conveyances, and pollution abatement.  Note that some exemptions are subject to conditions.  Key exemptions are listed below:

• hydropower under FERC
• fire emergencies
• flood control dams
• dams not on streams
• permitted diversions
• diversions subject to approved flow management plans, such as special act, or wild and scenic designations

• tidal rivers
• impoundments with no active manipulation or withdrawal, these are typically lakes and ponds used for recreation or other non-consumptive purposes

• small intermittent withdrawals
• draw downs for dam inspection and weed control
• agriculture and golf courses
• dams with watersheds < 3 square miles or naturally limited flows
• certain streams between reservoirs
• man-made conveyances

What are the release rules

There are release requirements in each class for dams to maintain a minimum stream flow, the basic release rules by class are as follows:

Class 1- free flowing

Class 2- 75% of natural inflow

Class 3- this class is where the most balancing of human and ecological needs occurs for water, it establishes baseline release standards as set in the table below

Bioperiod	Effective Dates		Minimum Required Release
			Antecedent Period Dry	Antecendent Period Wet
Overwinter	Dec 1-Feb 28/29		Bioperiod Q99*
Habitat Forming	Mar 1-Apr 30		Bioperiod Q99
Cluepid Spawning	May 1-May 31		Bioperiod Q95
Resident Spawning	June 1-June 30		Bioperiod Q90
Rearing and Growth	July 1-Oct 31		Bioperiod Q80		Bioperiod Q50
Salmonid Spawning	Nov 1-Nov 30		Bioperiod Q90

* These are established by DEEP stream statistics (Stream Stats)

For Class 2 and 3, there are some special provisions for small watersheds, small storage reservoirs and areas between impoundments to make only minimum releases.

There are various operational flexibilities to the Class 3 release rule for public water supplies.

Class 4- these releases are approved individually as a “site specific release” taking into account substantially altered conditions given to human uses.  Releases must be consistent with the Class 4 narrative standard and consider the impact on human uses and ecological benefit of the releases.  The goal is to achieve Class 3 type conditions to the extent practicable.

How can I determine the required “Q” flows that are specified in the Stream Flow Standards and Regulations?

Q stream flows found in the Stream Flow Standards and Regulations can be automatically calculated at any point along a river or stream in the web-based StreamStats application developed by the United States Geological Survey available at USGS Connecticut StreamStats .

References applicable to this work can also be found on the USGS webpage:

Ahearn, E.A., 2004, Regression equations for estimating flood flows for the 2-, 10-, 25-, 50-, 100-, and 500-year recurrence intervals in Connecticut: U.S. Geological Survey Scientific Investigations Report 2004-5160, 62 p.

Ahearn, E.A., 2010, Regional regression equations to estimate flow-duration statistics at ungaged stream sites in Connecticut: U.S. Geological Survey Scientific Investigations Report 2010–5052, 45 p.

Other methods of calculating appropriate Q stream flows may also be considered.

What are the compliance timeframes and reporting requirements?

Generally compliance is required 10 years from river or stream classification date, however there are some reporting requirements ahead of that.  Timeframes are:

• within one year of classification- dam owners and operators subject to the regulations must report, on a DEEP form,  basic information for the dam, such as name of owner and location
• within nine years (unless another date is approved in writing by the commissioner), submit description of methods and locations to be used to calculate release flows and to demonstrate compliance with release flow requirements
• within ten years (unless another date is approved in writing by the commissioner) initiate required releases
• upon initiation of required releases, maintain an operating log

If a release is not required, does a dam owner or operator still have to report information to DEEP?

Generally if you are not subject to the regulation, including meeting exemption provisions, you do not have to report.  However, operation of a dam with no active manipulation of the water storage and no withdrawal of water from within the impoundment, such as recreational lakes and inactive reservoirs, have to report by submitting a certification that such dam is operating, and will continue to operate, as such.

We draw our lake down for maintenance of aquatic plants. What is required under the Stream Flow Standards and Regulations?

Diversion of water caused by drawing down for aquatic weed control, water quality control, seasonal drawdown, or inspection or maintenance are exempt from the Stream Flow Standards and Regulations, provided the surface elevation of the impoundment is lowered only to the elevation and for the amount of time necessary and during drawdown and refilling periods, water is continuously released in an amount no less than the minimum of either the rearing and growth bioperiod Q80 or the natural inflow of water.

Do the Stream Flow Standards and Regulations apply to groundwater?

No, the current Stream Flow Standards and Regulations do not apply to wells.

Data Links

"Stream Stats" Web-based Geographic Information System application developed by the U.S. Geological Survey that computes streamflow statistics for any user defined point along streams in Connecticut.

"Regional Regression Equations to Estimate Flow-Duration Statistics at Ungaged Stream Sites in Connecticut," U.S. Geological Survey Scientific Investigations Report 2010-5052, by Elizabeth A. Ahearn.

History of Regulation Development (newest first)

• Revised regulations were submitted to the Legislative Regulations Review Committee on November 1, 2011.  The Committee formally approved the regulations with technical corrections on November 29, 2011.  The regulations were filed with the Secretary of State’s Office and became effective on December 13, 2011.
• Revised regulations were submitted to the Legislative Regulations Review Committee on October 4, 2011. The Legislative Commissioner’s office issued a memo on October 13, 2011 which identified several issues in the revised regulations. DEEP requested withdrawal of the proposed regulation from consideration by the Legislative Regulations Review Committee so that the issues could be addressed and to provide an opportunity for stakeholder input on the resultant changes. The changes were made and reviewed by the stakeholder group.
• DEEP and stakeholders engaged in extensive negotiations using the December 2010 version of the regulations as the starting point and in consideration of stakeholder comments. Primary topics of discussion included:
• How to address stream systems that naturally yield a minimal amount of water;
• More certainty in stream flow classification; and
• Additional public water supply considerations, compliance options, and flexibility, including protection of safe yield which is the amount of water available to a water utility to serve customers, protection of an adequate margin of safety (MOS) which is a measure of the reliability of the system, impact to infrastructure investment, recognition of potential sources of supply, environmental benefit, and compliance timeframes.
• The DEEP revised the regulations for resubmission to the Legislative Regulation Review Committee on December 7, 2010. The proposed regulations were rejected without prejudice by the Legislative Regulations Review Committee, on December 21, 2010. The Legislative Regulations Review Committee directed the CT DEEP to continue to meet with stakeholders to resolve the remaining issues.
• The revised regulations received sign-off for legal sufficiency by the Attorney General on August 31, 2010 and were submitted to the Legislative Regulation Review Committee for September 7, 2010. The proposed regulations were rejected without prejudice by the Legislative Regulation Review Committee.
• A Notice of Availability of the revised regulation and the hearing report was issued on August 17, 2010. The hearing report contains a statement of the principal reasons in support of the DEEPs action, and the principal considerations in opposition to the DEEP’s intended action as urged in written or oral comments on the proposed regulation and its reasons for rejecting such considerations.
• The DEEP drafted proposed Stream Flow Standards and Regulations; On October 13, 2009, issued a “Public Notice of Intent to Adopt Regulations and to Hold a Public Hearing.”  The DEEP provided numerous public information meetings from October 13, 2009 – January 21, 2010.  A Public hearing was held on January 21, 2010, and the public comment period was held open until February 4, 2010. 68 individuals provided oral testimony and 380 provided written comment. The extensive public comment was taken into consideration, and revisions were made to the proposed regulations.
• 2005-2009:  The Department initiated a stakeholder process through 3 workgroups (Science & Technical Workgroup; Policy & Implementation Workgroup; and Commissioner’s Advisory Group) that developed the framework of the regulations over a 3 ½ year period;

Stream Flow: The Next Two Decades (PDF) (January 29, 2009)

Balancing Water Use for Future Generations (PDF) (October 13, 2009)

Stream Flow Proposal Timeline (PDF) (October 13, 2009)

Guidelines for Evaluating Streamflow Depletion from Groundwater Withdrawals (PDF) (December 17, 2009) Groundwater withdrawals do not necessarily impact nearby streamflow at a rate equivalent to the well withdrawal rate. Although directly connected, a number of factors influence where along the stream, when, and by how much streamflow will be reduced by pumping groundwater. These draft guidelines were developed to assist water users in evaluating how their individual groundwater withdrawal impacts streamflow. Please note: The US Geological Survey has developed an on-line interface to STRMDEPL08, a software program used in the Guidelines. The interface is discussed in: Internet-Based Interface for STRMDEPL08, by Howard Reeves and A. Jeremiah Asher, USGS Open-File Report 2010-1247.

Documents submitted to the Legislative Regulations Review Committee on November 1, 2011 included:

Revised Small Business Impact Statement, September 6, 2011 (PDF)

Revised Fiscal Note, September 6, 2011 (PDF)

Revised Stream Flow Regulations, November 1, 2011 (PDF)

Redlined Version of Revised Stream Flow Regulations, November 1, 2011 (PDF)

Summary of Changes to Stream Flow Regulations, November 1, 2011 (PDF)

Contact Information:

If you have questions or for further information on the program, please contact us at:

Connecticut Department of Energy and Environmental Protection
Bureau of Water Protection and Land Reuse
Planning and Standards Division
79 Elm Street
Hartford, CT 06106-5127