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 River 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, establishing Protected Instream Flow values, and developing a Water Management Plan to implement the Protected Instream Flow values. Having successfully completed the pilot program, the pilot rules were amended on December 22, 2018, and now apply to all the state’s designated rivers.

The Next Instream Flow Study Rivers

In 2018, the Instream Flow Program established that the Cold River, the Warner River, and the upper Ashuelot River were the highest-priority designated rivers for Protected Instream Flow Studies. Protected Instream Flow Studies on the Cold and Warner Rivers are underway, and the study of the upper Ashuelot River is beginning in 2021.

With studies now under way for all three of these rivers, the time has come to identify the next priority rivers for implementation of the Instream Flow Program. A proposed 2021 Priority List .pdf Icon of the next rivers to be studied has identified three additional rivers as priorities for studies: the lower Ashuelot, Isinglass and Pemigewasset Rivers. Beginning during Winter 2021, NHDES has been working with stakeholders and the public to confirm these as the next rivers as priorities for protected instream flow studies.  Please visit the ISF River Prioritization page for more information about the process, and feel free to contact us if you have an opinion regarding rivers that you believe should be a priority for instream flow protection.

For more information, please visit the ISF webpage or contact Wayne Ives, Instream Flow Program Coordinator, at or at (603) 271-3548 or Joe Schmidl, Instream Flow Specialist at or at (603) 271-3280.

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