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New Hampshire Department of Environmental Services

Great Bay Estuary


Great Bay EstuaryOften dubbed New Hampshire’s “hidden coast,” the Great Bay is unique because it is both a saltwater and freshwater system, or estuary, set apart from the coastline. The Piscataqua River brings salt water into the bay with the tides, an essential element for the growth of plant and animals that live in estuaries. Water levels in the bay are heavily influenced by these daily tides, which expose mudflats at low tide, providing important feeding grounds for birds. In recognition of Great Bay’s beauty, diversity and productivity, the U.S. Environmental Protection Agency has afforded special protection to it as one of only 28 “estuaries of national significance.”

Seven rivers that carry the pollution from 42 New Hampshire and 10 Maine communities drain into the Great Bay watershed, which comprises of 1,023 square miles. Sadly, the Great Bay estuary is showing signs of a failing ecosystem from this input. The 2018 State of the Estuaries Report, published by the Piscataqua Region Estuaries Partnership, showed 12 of 16 environmental indicators with negative or cautionary trends.

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  • Ted Diers, Administrator
    Watershed Management Bureau
    NH Department of Environmental Services
    29 Hazen Drive; PO Box 95
    Concord, NH 03302-0095
    (603) 271-3289



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NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

copyright 2017. State of New Hampshire