‘No trespassing’ signs along a historic ribbon of land from Clinton to Boston will be removed over coming months, after state officials announced Tuesday they would make a network of trails over a century-old system of aqueducts accessible to hikers, bikers, or anyone seeking a stroll in the woods.
The 40 miles of land, long used surreptitiously by residents, will become accessible as the communities are granted permission to share the land with the Massachusetts Water Resources Authority.
“This policy is a great example of promoting multiple environmental goals: clean water supply, open-space access, and connecting people to the outdoors,’’ state Energy and Environmental Affairs Secretary Rick Sullivan said at a press conference in Boston. “We welcome partnerships with local communities to help enhance safety while providing public access to this pristine open space.’’
The trails run atop the Sudbury, Weston, Wachusett, and Cochituate aqueducts. All but the Cochituate aqueduct continue to serve as part of the MWRA’s backup water supply and could be closed to the public in the event of an emergency.
The trails, which are at most 100 yards wide and composed mainly of dirt or grass, run through Berlin, Boston, Clinton, Framingham, Marlborough, Natick, Needham, Newton, Northborough, Sherborn, Southborough, Wayland, Wellesley, and Weston. The trails are not contiguous.
“These aqueducts follow miles of scenic, tree-lined paths across the landscape, which will be a great addition to the open space in these communities,’’ said Fred Laskey, executive director of the MWRA, adding that he hoped the trails would draw leaf peepers in the fall, snowshoers and cross-country skiers in the winter, and bikers and runners throughout the year.
The aqueducts are part of a water system for the Boston area that began in the 1790s, when Jamaica Pond was tapped as a reservoir. As the region grew, officials began looking outside Boston for water.
‘This is an opportunity to allow people a safe place to walk, exercise, and enjoy nature.’Kathleen Bartolini Member of Southborough Planning Board
In the 1840s, they started taking water from Lake Cochituate, and a few decades later they opened the Sudbury system. Water began flowing from the Weston and Wachusett reservoirs around the turn of the century, and the Quabbin Reservoir has been serving the area since the 1930s.
Over the last 20 years, after decades of neglect, MWRA began to modernize the system with a deep rock aqueduct and covered storage tanks, making the aqueducts and reservoirs part of a back-up system.
Ria Convery, a spokeswoman for the MWRA, said the trails have been fenced off for years for security reasons. She said the timing was right to open the land, because the MWRA has created additional reservoirs and water lines.
“However, we will retain care and control, and the needs of the water system will always take precedence,’’ she wrote in an e-mail. “So, if we ever had to reactivate one of the lines, we would have to shut down access during that time.’’
She added there was little risk to the water supply from allowing the public access to the trails. “There’s really no open water along the pathways,’’ she said. “They are more like old railroad beds without the tracks.’’
She said there will be minor costs to the MWRA, mainly from removing fencing and making the trails more accessible. They will remain off limits to cars. She said the agency will trim trees, mow grass, and perform other maintenance a few times a year; the towns will enforce a no-litter policy and conduct other maintenance.
Officials in communities that will benefit from the new trails applauded the decision to open the land.
“This is really a big deal,’’ said state Representative Chris Walsh, a Democrat from Framingham, where the first trail will be inaugurated in the coming weeks. “This will really benefit the quality of life in our community.’’
Kathleen Bartolini, a member of the Southborough Planning Board who more than a decade ago commissioned the first studies that looked into opening the land, said she was elated.
“This is an opportunity to allow people a safe place to walk, exercise, and enjoy nature,’’ she said.
Joel Barrera, deputy director of the Metropolitan Area Planning Council, and one of Governor Deval Patrick’s appointees to the MWRA board of directors, said the valuable land would be protected for perpetuity.
He said each community will seek public input before opening the land, allowing abutters to the trails and others to voice any objections. He said that some communities may choose to keep some of the land restricted from public use and that it would take a few years before permits are granted for all the land.
“We’re talking about using land worth hundreds of millions of dollars for the benefit of the public,’’ he said. “A century from now, people are going to enjoy these trails and for next to no cost. This is now the public’s land.’’Globe correspondent Jaclyn Reiss contributed to this report. David Abel can be reached at email@example.com. Follow him on Twitter @davabel.