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Instream Flow

Ensuring that New Hampshire’s 19 designated rivers have enough water for both people and aquatic life.

screenshot of the title scene to the video
Click on the image to view the program video.

The Instream Flow Program ensures that rivers continue to flow in spite of the uses and stresses that people put on them. Under natural conditions, rivers flow freely with source waters coming from precipitation via lakes, ponds, wetlands, small streams and groundwater. Under human influences, however, river dynamics can change drastically. People frequently withdraw large amounts of water for drinking and irrigation directly from rivers, as well as from the sources that supply the rivers, particularly lakes and groundwater. Land use changes can result in faster runoff and changes to the stream structure. Many rivers have dams that restrict the amount and timing of water flowing downstream. In addition, the loss of wetlands to land development reduces the amount of water that would normally augment rivers during dry periods. These changes in stream flow can impair river habitat. The Instream Flow Program operates within the New Hampshire Rivers Management and Protection Program statute, Section 9-c (RSA 483:9-c) and in accordance with Administrative Rule Env-Wq 1900.

The program determines the seasonal flows necessary to support both natural aquatic habitats and human uses and then works with water users and dam owners to ensure that their water needs are met while maintaining the protected flows during periods of unusually low flow, even during droughts. The program annually performs a wide range of field activities to collect the environmental data necessary to develop protected instream flow values and evaluate the success of instream flow management; the program’s 2021 Work Plan summarizes those field activities.

Currently, two rivers, the Lamprey and Souhegan Rivers, are actively managed under the Instream Flow Program. In addition, protected instream flows are being developed for the Cold and Warner Rivers, and will soon be underway for the Ashuelot River.

Protected Instream Flow Studies In Progress

The protected instream flow studies of the Ashuelot and Warner Rivers are underway, and the draft Protected Instream Flow Study Report for the Cold River has been published. Protected instream flows are criteria that define a stream flow pattern and maintain water for instream public uses and aquatic wildlife, and meet water quality standards. A public hearing on the draft protected instream flows for each river will be scheduled when its draft Protected Instream Flow Study Report is published. NHDES is also working with water users and dam owners along these rivers to determine water use needs and current practices to develop Water Management Plans that balance human needs with the needs of aquatic life identified by each protected instream flow study. A public hearing on each draft Water Management Plan will be scheduled when they are completed.

    a map of the protected area around the ashuelot riverAshuelot River Study

    The protected instream flow study of the Ashuelot River began in 2021. The draft protected instream flows and the draft Water Management Plan for the Ashuelot River are estimated to be complete in 2024.

    Real Time Water Data

    LEARN MORE ABOUT THE ASHUELOT RIVER  

    a map of the cold river watershedCold River Study

    The protected instream flow study of the Cold River began in 2019. A draft Protected Instream Flow Study Report – Cold River is now available for public review. NHDES’ consultant, Gomez & Sullivan Engineers Inc., completed the protected instream flow study of the Cold River and summarized the results in the draft report. The public is invited to review and comment on the report. NHDES held an Informational Meeting describing the report on Monday, September 27. View a recording of the meeting. NHDES held a Public Hearing on the draft protected instream flows on Monday, October 18, at the Alstead Town Hall, in order to solicit comments on the draft study. View a recording of the hearing. The comment period will remain open until November 17, 2021, at 4 PM. The draft Water Management Plan for the Cold River is being prepared, with public review and release planned for later in 2021. Comments may be submitted to Wayne Ives, Instream Flow Program Coordinator, PO Box 95, Concord, NH 03302-0095, or to Wayne.Ives@des.nh.gov.

    Real Time Water Data

    Learn more about the Cold River  

    a map of the Warner River watershedWarner River Study

    The protected instream flow study of the Warner River began in 2020. Public hearings on the draft protected instream flows and the draft Water Management Plan for the Cold River are planned for 2022.

    Real Time Water Data

    Learn more about the Warner River  

    Protected Instream Flow Values Established – Flow Management Underway

    The instream flow pilot study was completed in 2015 on the Lamprey and Souhegan rivers. The Report of the Instream Flow Pilot Program summarizes how the protected instream flows and water management plans were developed for each river, and makes recommendations for applying instream flow management on other New Hampshire rivers designated under the Rivers Management and Protection Program.

    a map of the Lamprey River watershedLamprey River Protected Instream Flow

    The lower Lamprey River, designated in 1990, was the subject of a Protected Instream Flow Study between 2005 and 2009. The upper Lamprey River and five tributaries were added to the Lamprey River designation in 2011, following the protected instream flow study. Protected instream flow criteria for the lower Lamprey River were accepted in 2013. The Lamprey River Water Management Plan was completed in 2013, and applies to only the lower Lamprey River. The remainder of the designated portion of the Lamprey River watershed will be the subject of a future protected instream flow study. Following the additional protected instream flow study, the Lamprey River Water Management Plan will be updated to include the broader Lamprey River designated river.

    Current Lamprey River Instream Flow Conditions 

    Real Time Water Data  

    LAMPREY RIVER INSTREAM FLOW RESOURCES  

    a map of the souhegan river watershedSouhegan River Protected Instream Flow

    The upper and lower reaches of the Souhegan River, designated in 2000 were the subject of a Protected Instream Flow Study between 2005 and 2008. Protected instream flow criteria for the upper and lower reaches of the Souhegan River were accepted in 2008, and slightly modified in 2013. The Souhegan River Water Management Plan was completed in 2013.

    Current Upper Souhegan River Instream Flow Conditions   

    Current Lower Souhegan River Instream Flow Conditions  

    Real Time Water Data  

    SOUHEGAN RIVER INSTREAM FLOW RESOURCES  

    Future River Studies

    Target Fish Communities

    A goal of the Instream Flow Program is to ensure that flows in each river are suitable for the fish that should live in that river. Therefore, there is a target fish community report for each river. The target fish community reports include the fish species population distributions that should be found in each designated river.

    Estimating Historical Stream Flows

    The Instream Flow Program requires at least 30 years of historical stream flow data, but this is not available for every river. Flows can be estimated by comparing nearby gaged rivers and adjusting for watershed area and geography.

    Inforation Icon

     Need more information? 

     Need more information? 

    All of the New Hampshire Instream Flow Program documents available online can be found here. If you still do not see what you are searching for, contact us for more information.

    Watershed-Management
    Instream Flow Program Coordinator
    wayne.Ives@des.nh.gov
    Watershed-Management
    Instream Flow Environmentalist
    joseph.schmidl@des.nh.gov