Instream Flow Program

The Instream Flow Program (ISF) balances the needs of humans and wildlife in rivers and lakes.

Instream Flow Rules:
NHDES is revising the Instream Flow Rules (Env-Wq 1900) and holding a rulemaking public hearing. Please visit the Rulemaking page for more information.

Next Instream Flow Study River:
The Instream Flow Program is proposing the next Designated River for implementation of protected instream flow study. Please visit the ISF River Prioritization page for more information.

NEW! New Hampshire Instream Flow Program Video

This video is a short summary describing the purpose of the program, how the program works, and how NHDES will work with water users and dam owners to implement the program.


The Instream Flow Program (ISF) is developing river-specific numerical criteria for stream flow protection and water management plans to implement those criteria.

In 2002, a broad coalition of New Hampshire business and conservation interests joined together to enact compromise legislation which became Chapter 278, Laws of 2002 that calls for a pilot program for instream flow protection on two of the sixteen designated rivers – the Lamprey River in the coastal watershed and the Souhegan River in the Merrimack watershed. With the advice and input of the statewide Rivers Management Advisory Committee (RMAC), NHDES adopted Instream Flow Rules (Env-Wq 1900) effective May 29, 2003 that apply to the Souhegan and Lamprey Rivers. The rules describe the process for conducting a Protected Instream Flow study and developing a Water Management Plan to implement the study results. If the pilot program is successful, the rules would be amended before they could be applied to other Designated Rivers.

For more information please contact Wayne Ives, Instream Flow Specialist at or at (603) 271-3548.

The following documents represent ISF Program updates starting in January 2011.  Additional ISF materials may be found at the ISF webpage.

Joint Lakes and Rivers Committees’ Recommendations for Comprehensive Surface Water Resource Management Policy Adobe Acrobat Reader Symbol

1/24/2011 RMAC Instream Flow Program Update

For more information please visit the ISF webpage.

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