The Bartlett Rod Shop Company Dam, built in 1820 on Amethyst Brook in western Massachusetts was removed in November 2012, opening up habitat for trout and creating spawning grounds for sea lamprey. Photo by Alex Hackman/MA Dept of Fish and Game.

In early January, on a visit back to my old stomping grounds in western Massachusetts, I trekked along the snowy banks of Amethyst Brook, a beautiful headwater tributary in the Connecticut River watershed. My mission was to see the site of a dam removed in late 2012.
I’d hiked through this area in the towns of Amherst and Pelham many times before, but had never sought out the stretch of stream blocked by the structure known as the Bartlett Rod Shop Company Dam, after the fly rod manufacturer who began operating alongside the stream in 1864.  The dam itself – a 20-foot (6-meter) tall, 170-foot (52-meter) wide rock structure – had blocked the brook since 1820.

Over the decades, the mill had transitioned through many uses, including a woodworking shop, a machine shop, a maker of boiler tube cleaning equipment, and finally to HRD Press, a provider of products and services for human resources development. While the company owned the dam, it didn’t need it.

After receiving a dam safety order from the state in 2007, HRD Press began working with government agencies and conservation groups to study the idea of taking the obsolete dam down.  In 2010, Massachusetts officials named the dam’s removal a priority project for river restoration – and by late 2012, thanks to a broad partnership of federal and state agencies, the two towns, and conservation groups, the dam was dismantled.

In the months since, Amethyst Brook has begun to heal.

Freed by the dam’s removal, sediment has moved downstream.  So has organic matter in the form of leaves and woody debris, critical to aquatic food webs.  Water temperature has dropped, and oxygen levels have increased.

With the dam gone, trout can now move further upstream to high-quality coldwater habitat.

And below the dam site, a stream bottom of gravel and cobbles has formed – habitat just right for the spawning of the migratory sea lamprey.

A snake-like fish, the sea lamprey (Petromyzon marinus) migrates from the ocean to freshwater to reproduce.  In the Connecticut River system, the fish moves upstream from Long Island Sound in Connecticut, passes Holyoke Dam in Massachusetts with the help of a fish lift, and then travels further north and into side tributaries in search of spawning grounds.

After depositing eggs and milt (sperm) in a protected nest of stones, the adult fish die.  About two weeks later, the eggs hatch.  The larvae then drift downstream and burrow into a sandy stream bottom.  Young sea lamprey will remain in the river system for up to ten years before heading back to the ocean.  After a year or two at sea, it will head up river to spawn, completing its life cycle.

Just six months after the Bartlett Dam was demolished, conservationists were thrilled to find sea lamprey spawning in Amethyst Brook, just below the old dam site.   (You can see a short video of the discovery here.)

Seeing this native fish spawning was “a great sign of improving conditions in the river,” writes Amy Singler, associate director of river restoration with American Rivers, one of the conservation partners involved in removing the dam.

Nothing so exciting as sea lamprey spawning was visible during my visit to the stream on that cold, wintry January day.  But it was fantastic to see the project site – and connectivity restored to the brook.

Removing a dam from a river is like unblocking an artery in the body: the whole system gets healthier and vitality returns.

And the good news is that unsafe or obsolete dams are coming down across the United States, especially in the East, where many old dams that no longer serve their original purpose are badly in need of repair.

Dam owners often find it easier and cheaper to remove an old dam than to fix and maintain it.  The cost of removing Bartlett Dam was estimated at $193,000, compared with $300,000 to repair it.

“If it was just habitat restoration alone, we wouldn’t be doing so many dam-removal projects,” said Brian Graber, senior director of the river restoration program at American Rivers, when I met with him and Singler a couple days after my trek along Amethyst Brook.

Throughout New England, they told me, 80 dam removals have been completed over the last 15 years; 65 removals are now in design or construction phases.
In fact, the widespread dismantling of dams around the United States is one of the surprising success stories of river restoration.

During the last century, some 1200 dams have been removed nationwide, according to American Rivers, which maintains a database on U.S. dam removals.  About three-quarters of them were removed over the past twenty years.

Amy Kober, the organization’s communications director, recently reported in Water Currents, that 51 of those dams, spanning rivers in 18 states, came down in 2013.

The removal of big dams, such as Elwha and Glines Canyon on the Elwha River in Washington State, or the San Clemente Dam on the Carmel River in California, justifiably garner national attention.

But the dismantling of smaller dams is restoring health to many headwaters and tributary streams, like Amethyst Brook, that provide crucial habitats for fish and other aquatic organisms.

Graber and Singler are keeping an eye on an old concrete dam about a half-mile upstream from the Bartlett dam site.

Dam by dam and mile by mile, rivers are getting reconnected and starting to heal.

Originally posted at National Geographic Newswatch.