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'Dammed' If We Do? Gains, Losses in Drive to Remove Defunct Dams

Efforts to remove old dams from America's waterways are accelerating. Native fish stand to benefit, but what are the drawbacks?

'Dammed' If We Do? Gains, Losses in Drive to Remove Defunct Dams

Some dams benefit agriculture by holding runoff for irrigation, but the tradeoff is they present a barrier to natural fish movement. (Shutterstock image)

It was one of those places I could catch a dozen hammer-handle pike on any given day and with just about any method.

Milltown Reservoir, just east of Missoula, Mont., was never intended to be a pike fishery, but it had all the attributes: shallow, weedy water; abundant prey in the form of juvenile trout; and the neglect of fisheries managers.

My main problem was that I couldn’t keep any of my fish. Milltown Reservoir had another distinction: an EPA Superfund cleanup site that trapped tons of poisonous slurry from a century of copper mining upstream.

Those toxins accumulate in the flesh of predatory gamefish. Health officials strongly discouraged anyone from eating any fish from the reservoir or from the miles of Clark Fork River upstream of the dam.

But in 2005, after years of planning, the dam that created the reservoir was removed. The action allowed the Clark Fork and Blackfoot rivers to flow and supercharged the cutthroat and bull trout fisheries. I lost a pike-fishing spot but gained miles of free-flowing trout streams, and vastly healthier fisheries habitat, as a result.

The removal of Milltown Dam was, relatively speaking, a big deal because the river systems it constrained are large in both cubic volume and the lore of the West. The Blackfoot, after all, was the river featured in the seminal novella and subsequent movie "A River Runs Through It."

But across the nation, many less-celebrated dams are removed every year by various local, state and regional agencies and conservation groups. Over the past two decades, the pace of dam removal has accelerated every year, with 69 dams removed just in the past year, according to the conservation group American Rivers, which tracks decommissioned dams.

The group notes that, "Dam removal brings a variety of benefits to local communities, including restoring river health and clean water, revitalizing fish and wildlife, improving public safety and recreation, and enhancing local economies."

Indeed, many of the dams in the American Rivers database—it counts 1,797 dams removed nationwide from 1912 through 2020—were derelict structures, long past their productive lifespan. Many of these were old millwheel dams in the Northeast, stone structures designed to create a millpond and funnel releases through a flume that turned a millwheel to grind grain, sharpen scythes or turn lathes in the decades before readily available electricity. Others, including those in my area of the arid West, were irrigation structures, engineered to hold spring snowmelt and parcel out the water over the summer to grow alfalfa and watermelons.

From a native fish's standpoint, dams are generally not particularly positive. They impede not only spawning migrations, but also movement of individual fish that travel up and down river systems to find suitable seasonal habitat. They tend to accumulate sediment behind the dam, so every year the impounded volume decreases. And, because dams are usually built at the narrowest, most rapid portion of a river, they change the character of entire stretches of formerly free-flowing water.

Defunct Dams
Most old mill dams are no longer needed for diverting water to grind grain but continue to block fish from upstream habitat. (Shutterstock image)

An example of the benefits of dam removal is the Elkhart River Dam in downtown Elkhart, Ind. The dam was built in the late 1890s to divert the river into raceways used to power industry in the gritty Midwestern city. But after a few decades, the raceways were filled and the dam no longer served a purpose.

When the structure was removed in 2020, 40 miles of upstream habitat was reconnected to the Elkhart River and made available to fish migrating out of the St. Joseph River. They comprise 50 species, including the greater redhorse, longnose dace and northern brook lamprey—all listed as endangered or species of special concern in the state—as well as numerous gamefish.


On balance, the removal of dams is a net benefit to native fish. But there are some entries in the liability column. They include access. Dams have historically provided important—and in some cases, sole—recreational access to downstream rivers and upstream reservoirs. It’s important to retain that traditional access any time a dam is removed.

The conversion of free-flowing river to impounded reservoir has benefitted a number of species, including America’s fish—the largemouth bass. Introduced species such as crappie, bluegill and perch have thrived in the reservoirs created by America’s dams, and it’s hard to imagine the Great Plains' walleye fishery without crediting dams.

Many of the West's most consistent trout fisheries are those that thrive in the cool, clear water discharged from the bottom of reservoirs. Among them anglers will find the Bighorn and Missouri rivers in Montana, the South Platte and Yampa in Colorado, and the blue-ribbon North Platte in Wyoming.

Boaters, too, enjoy millions of acres of impounded water for recreational use. Other benefits include flood control, irrigation, reliable water for towns and rural communities, and hydropower generation. As this issue is being produced, water managers on the Colorado River are trying to apportion water behind Hoover Dam in Arizona (Lake Mead), Glen Canyon Dam in Utah (Lake Powell) and impoundments upstream as they figure out how to provide water to a system that has way more demand than supply. Without water-storage dams, their task would be infinitely more difficult.

However, as long as access, public safety and water supply (and water rights) are considered, there are relatively few reasons to prolong the lifetime of derelict dams. They’re expensive and sometimes dangerous to maintain. Because many were built before our knowledge of fish passage and habitat connectivity was well-developed, dams often cut off important headwater habitats to many species of aquatic organisms.

On the Pacific Coast, fisheries managers are increasingly understanding the importance of small headwater streams to the spawning success of salmon and steelhead. Many of these streams have been dammed over the years to provide benefits to timber companies and rural communities, but most low-head dams have been abandoned since their construction.

Fisheries professionals are in the process of identifying dams and working to remove them, opening many miles of high-quality spawning habitat to anadromous species.

Back at the former logging community of Milltown, the Blackfoot River runs wild and frothy at the point where it joins the deeper, moody Clark Fork River. The pike are gone, but it’s a killer spot to catch scrappy cutthroats on streamers twitched in the seam where the two undammed rivers meet.

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