Instream Flow Program

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

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) develops river-specific numerical criteria for stream flow protection, and water management plans to implement those criteria, for each Designated River in New Hampshire.

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 pilot program Instream Flow Rules (Env-Wq 1900) effective May 29, 2003 that applied to these two rivers. The rules describe the process for conducting a Protected Instream Flow study and developing a Water Management Plan to implement the study results. Having successfully completed the pilot program, the rules were amended on December 22, 2018 to apply to other Designated Rivers.

Next Instream Flow Study Rivers:
The Instream Flow Program has established that the Cold River, the Warner River, and the upper Ashuelot River are the next Designated Rivers for implementation of protected instream flows. Work on the Cold River is underway, with the study of the Warner River expected to begin in 2020. Please visit the ISF River Prioritization page for more information.

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

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