Selective dam removal assists in restoring habitat, reducing high temps and protecting communities

Located on a tributary of the Kalamazoo River near Allegan, Michigan, the Swan Creek Dam helps manage water flow and provides residents with recreational opportunities such as fishing and kayaking. But this dam is coming down because the Department of Natural Resources wants the river to be colder. Fish biologist Matt Diana explains why it's a necessary step.

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “Cold water streams in Michigan are imperiled because of global climate change. We're seeing, we've already seen in the last decade over a two degree increase in water temperatures. When there's impoundments on the system that just exacerbates the issues.”

An impoundment is the artificial lake that forms behind a dam. As river water backs up, the sun can heat the water in an impoundment more than it would heat a flowing river and the effect can be surprisingly large.

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “They're creating water temperature warming, in addition to what global climate change is causing. Our monitoring here shows it heats it up about 10 degrees.”

That's enough heat to cause some major stress for certain species of the Great Lakes region, especially for trout.

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “So as the waters warm, we're starting to lose more and more trout. We use a threshold of 68 degrees for trout survival. Above that temperature they don't grow well and they don't survive well.”

And that's not the only trouble dams cause.

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “There's a number of different impacts that dams have on river systems. The most obvious one is fish migration. In the Great Lakes,  we have a lot of fish that rely on river migrations. All salmon and steelhead, lake sturgeon, which are a threatened species. We're seeing lake whitefish have really important migrations in the streams. You know, so if a dam is in place that limits the migration, that limits the habitat that's available to them.”

Dams also block downstream movement of sediment which can deprive the downstream river system of an essential ingredient needed for fish habitats. 

On top of this, many dams around the Great Lakes region have another problem. They're old. In some cases, they've outlived their usefulness and they're expensive to maintain. Swan Creek checks both of those boxes.

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “This particular dam was built in 1937. A lot of dams were built around the early 1800s, mid 1900s, and then a lot of hydro dams were built, associated with kind of World War II. All of those dams are old. The concrete used, the construction used are usually 50-year type construction. So most of them are past their living lifespan. They're either requiring maintenance or constant, kind of Band-Aid fixes in order to keep them in place.”

The hefty cost of maintenance and repairs deters some from taking action. But ignoring aging dams presents enormous risks. When older dams aren't maintained, a breach or a total failure can occur, and that can spell disaster to the surrounding area.

Lynn Coleman: “There it goes. There it goes.”

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “Midland, Michigan is a good example of a dam failure and the kind of impacts that are that happen when a dam fails.”

Gayle King, CBS Mornings: “Breaking news coming from Michigan this morning.” 

The 2020 failure of the Edenville and Sanford dams in Midland resulted in over $250 million in property damage and extensive harm to the fishery. To help prevent disasters of this scale and defend against climate change, a wave of dam removal projects is happening right now in Michigan and across the U.S..

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “As these dams age, they're really not serving a purpose other than creating an impoundment. And, so we're looking at opportunities with these dams instead of repairing them. There's a lot of money out there to do things like removals, through grant programs and state funded programs to try and improve fish habitat.”[[[[[[

A recent influx of state and federal money allows the DNR to remove more dams than previously financially possible. The DNR prioritizes dam removals in a number of different ways.

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “One way we prioritize it is by the risk of the existing dam. Dams are rated as high to low risk based on what would happen if they failed. So a dam in a city might be more high risk because if it failed, it could flood houses and even cause loss of life. So those become high priority dams from a safety aspect.”

The DNR prioritizes low risk dams based on how big of a boost the fishery will get from removing them.

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: So one factor that we use is how many miles of stream is a dam blocking off from fish migration? So in this case, we could remove a dam and, and open up 40 miles of stream that fish moving upstream couldn't access in the past.”

Twenty miles upstream of the Swan Creek Dam,  is where the Otsego Township Dam was removed in 2016 returning this stretch of the Kalamazoo River to its natural state. 

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “This dam was removed because it was failing and because it had contaminated sediments behind it. So if it failed, we would have had contaminant sediments go downstream.”

Since removal of the dam. Researchers from Western Michigan University routinely monitor the area. 

Though their fieldwork isn't complete, the team has seen a clear shift in the types of species present in the water since the dam was removed.

Sara Diller, Ph.D. Student - Western Michigan University: “We see a lot more species we typically see in a river. they're more adapted to riverine conditions, whereas where the dams are in place, we see species that are more adapted to lake-like conditions and where the dams have been taken out, we see more sensitive species. They're intolerant to pollution but where the dam is still in place, we see species that are more pollution tolerant.”

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: We've seen a shift from lake-like fish populations. So things like common carp, largemouth bass, bluegill to more riverine and are what we call lowdic systems, where it's smallmouth bass as pike, which are neonative and more appropriate for a river ecosystem.

And that's good news for the fishery.

Matt Diana, Senior Fisheries Biologist - Michigan Department of Natural Resources: “The kind of information that Western Michigan is collecting here is really valuable to US fisheries managers. We take this kind of information and we use it in order to evaluate these projects and see if there's any need for additional, restoration. My ultimate goal with these projects is to see the river look as natural as it did before the dam was here, restore the fish habitat and really create better fisheries for the public in Michigan.”

contact: miller@iowapbs.org