Nantucket watershed map
The Island of Nantucket lies twenty-five miles south of Cape Cod and fifteen miles east of the Island of Martha's Vineyard. The island is 49 square miles in size and is both a county and a town.

The island is hydrologically isolated and receives most of its fresh water from precipitation. There are 28 lakes and ponds on Nantucket, 12 of which are over 10 acres in size. Nantucket's water quality is fundamental to the health and welfare of its residents and to the island's economy. Rising nutrient inputs associated with increased development pose long-term threats to Nantucket's fresh and coastal waters.


Roseate tern
The island is home to 268 species of rare and endangered species, the highest concentration of rare and endangered species in the state. Many terrestrial and marine species, including numerous species of shellfish and birds, considered a threatened species in the Commonwealth find their home in the 13,000 acres of preserved open space on Nantucket. The Island of Nantucket supports a year round population of approximately 8,520 people. In the summer, the population grows to approximately 40,000 people and represents the third fastest growing community in Massachusetts.

Watershed Priorities

  • Improve the quality of marine waters and fisheries habitat by reducing nutrients entering waterways from point and nonpoint source pollution
  • Support a comprehensive water resources management plan to address pollution from wastewater
  • Work to develop a comprehensive wastewater management plan for the island, including sewer for Monomoy and a wastewater facility in Siasconset
  • Identify key parcels of open space for acquisition and/or restriction to protect future water quality
  • Ensure that the watershed has the necessary resources to gain measurable improvements in water quality

Nantucket harbor Watershed Success

Recently, a study of the declining bay scallop population and water quality of Nantucket Harbor was conducted. These locations are currently being examined for growth rate and mortality. A study of the pollution sources to the harbor is also part of this study.

Watershed Links


This information is provided by the Executive Office of Energy and Environmental Affairs, Office of Water Policy