EASTHAMPTON — The city is joining forces with Southampton to protect a critical 25 acres of land above the Barnes Aquifer from development of as many as 14 homes.

The move, part of a larger conservation effort above the aquifer since 1989, will help protect the only supply of drinking water for Easthampton and the only active backup water supply for neighboring Southampton.

The slightly more than $1 million needed to buy the 25 acres straddling both communities near Cook and County roads is coming from three sources. Easthampton’s City Council on Nov. 16 OK’d spending $343,762 in Community Preservation Act funds; Southampton at a Town Meeting in May voted to contribute $386,862 of its own CPA funds; and the balance is expected to come from a $400,000 Local Acquisitions for Natural Diversity grant that Easthampton is seeking from the state. The latter grant awaits approval by the end of the year.

Once the transaction is complete, Southampton will own the land and Easthampton will obtain a conservation restriction to protect it from development.

The Barnes Aquifer extends about 12 miles beneath portions of Westfield, Holyoke, Southampton and Easthampton. More than 60,000 people depend on the aquifer for drinking water and it is the sole source of water for Easthampton’s public wells. In 2015, the Easthampton’s public water supply was named best in the nation by the National Rural Water Association.

“The aquifer is our water supply and we have some of the best water in the world,” City Councilor Daniel Rist said. “This must be protected against development.”

Purchase of a conservation restriction will prevent construction of new houses on the property, officials said.

Mark Wamsley of Kestrel Land Trust has been working on the project and said the process has been challenging.

“If this land isn’t protected now, it will be developed into 14 house lots,” Wamsley said. “The land is so valuable from the development perspective.”

Such development could damage the aquifer, Wamsley said, noting that chemicals used around homes, such as pesticides and fertilizers, can increase the risk of contaminating the drinking water.

Though the appraised value of the land is higher, the owners have agreed to sell it at less than market value.

“We are very grateful to property owners who take this route rather than selling it for a higher price,” Mayor Karen Cadieux said.

Barbara LaFlam, 74, of Southampton, is one of the 11 heirs to the land. LaFlam said her grandfather purchased the parcel in 1896 and farmed cows, pigs, chickens, potatoes, tomatoes and other vegetables.

“I grew up on the land and loved it and respected it,” LaFlam said.

The property will become publicly accessible conservation land with the possibility of being used as a town park. LaFlam said she plans to visit often.

“The land was good to my grandfather,” she said. “It’s been good to the rest of us as well.”

Caitlin Ashworth can be reached at cashworth@gazettenet.com.