Instream Flow


The water that ultimately makes its way into the Lamprey comes from several sources: precipitation, overland runoff, and groundwater . On average, 20 inches per year of water comes from overland runoff. About half of this occurs during the months of March, April, and May. While in some watersheds low flows in summer and fall are augmented by adjacent aquifers, the Lamprey watershed contains relatively few aquifers in direct contact with the river. Instream flow, or the amount of water in the river at a given time, is important for several reasons:

  • Low water levels cause a rise in temperature with sometimes severe impacts on aquatic organisms; for example, warm water holds much less oxygen for them than cold water.
  • When flows are low, any contaminants become more concentrated, which can cause wastewater treatment plants to have difficulty meeting their permit requirements.
  • Very low flows cause wetlands to dry up and expose river banks, making aquatic animals more vulnerable to predation by raccoons and other predators.
  • The Lamprey River provides the largest volume of fresh water compared to other sources for and to the Great Bay Estuary. The volume and rhythm of flow to those ecosystems are critical to their health.
  • Finally, humans are affected because a low river means less recreation, poorer water quality for swimming, and shortages for municipal and commercial water supplies.

The Lamprey River was one of the first rivers in New Hampshire to have an instream flow management plan. This plan was based on long-term flow data and was designed to ensure minimal flows to support aquatic life during extended drought. In 2022, NHDES began studying flows in the five main tributaries to determine how those flows might impact the Lamprey River. Near-realtime data for the five tributaries are linked below for those who are interested. 

Little River


North Branch River


Piscassic River


North Branch (02N-NBR) and Pawtuckaway (04-PAR) stations are combined in a single link.


  • Worked to influence water withdrawal policies by the UNH/ Durham Water System, including fact-finding and campus education to promote water conservation.
  • Investigated how efficiently the UNH/Durham Water System is using its water resources and any potential causes of wasted water, such as leaks in the system.
  • Participated in the state’s Instream Flow study by gathering data, identifying important river resources to protect, and reviewing draft documents. LRAC members serve on the Technical Review Committee and the Watershed Management Planning Advisory Committee for the study.
  • Worked with NHDES to establish minimum flows related to withdrawals from the Lamprey by the UNH/Durham Water System. These minimum flow and flow recording requirements became part of the UNH/Durham 401 Water Quality Permit.
  • Assisted in documenting impacts on the river when the Wiswall impoundment was drained for engineering work on the dam in 2006.


Maintain a viable quantity of water in the river during all seasons sufficient to support and sustain the river’s ecological and recreational resources, while considering the need for agricultural and municipal use.

Key Future Actions:

  • Encourage strategies that minimize impervious surfaces in the watershed and allow stormwater runoff to percolate into the soil, recharging groundwater that maintains river flows.
    • Encourage use of impervious surface information contained in the stream buffer study done by UNH and the New Hampshire Estuaries Project (NHEP).
  • Keep water in the Lamprey watershed.
    • Encourage communities with municipal wastewater treatment to return their treated wastewater to the same watershed, whether via surface waters or through land application.
    • Participate in the discussion on the legislative Regional Wastewater Study to assure that options will protect river flows in the Lamprey River watershed.
  • Help ensure NHDES water conservation rules are applied to all new Lamprey withdrawal requests.
  • Promote a NHDES permitting process for currently unregulated users of water from the river.
    • Investigate the potential for lowering the minimum daily quantity of water use that must be reported to NHDES (currently 20,000 gallons per day).
  • Support municipal officials in developing long-range water plans.
    • Encourage the review of existing information about aquifers, including location of water, location of drinking water sources, build-out analyses that include water budgets, and evaluation of existing and new ordinances.
    • Promote watershed-wide water planning including limits on impervious surfaces and water budgets with projected supplies and future needs.
    • Host an annual water forum for Newmarket, Durham, Lee, and Epping.
  • Work with Durham to promote efficient water use, and thereby reduce need to withdraw water from the Lamprey River.
  • Work with the Town of Durham, NHDES, and USGS to develop and implement a plan to measure or estimate outflow from the Wiswall Dam and inflow to the impoundment, as called for in the 401 Water Quality permit for the UNH/Durham Lamprey River withdrawal.
  • Work with the National Park Service to implement its authority under the Wild and Scenic Rivers Act to review and condition federal permits or projects potentially affecting stream flow or the free-flowing character of the Lamprey River.
  • Actively promote water conservation.
    • Encourage communities to consider mandatory conservation measures to augment volunteer efforts during droughts.
    • Develop homeowner incentives to conserve water.
    • Promote the use of gray water systems and drip irrigation systems.
    • Offer information to the public to help users know what their water conservation options are.
    • Encourage the UNH/Durham Water System to reduce unaccounted-for water to less than 15%.
    • Consider partnering with UNH water conservation efforts.
  • Raise awareness about water issues among community residents.
    • Use the internet, LRAC website, public workshops, print media, an advertising campaign, and events such as road races, river rafting, geocaching, and canoeing to focus public attention on wise use of water.
    • Consider hosting an annual river event with water quality and river flow protection as a theme.