What Happens to a Lake When Its Dam is Removed

[Glenn MacGrady]

It depends.

"When engineers pull the plug on a dam, the lake behind it does not just quietly fade away. A reservoir is an artificial, still-water (lentic) system, and removing the barrier that holds it back triggers a rapid shift back into a flowing (lotic) river. Of course the water drains, often in hours rather than weeks, and then the real transformation begins as decades of trapped sediment, submerged tree stumps, and buried riverbed start to reappear. In the United States, more than 2,300 dams have come down since 1912, according to American Rivers . . . . Below, the process is broken down step by step, illustrated with four of the country's largest and most closely studied dam removals."

What Happens To A Lake When Its Dam Is Removed

What Happens To A Lake When Its Dam Is Removed: the reservoir drains in hours, the old river reappears, and sediment, fish, and plants slowly return.

www.worldatlas.com

 

[WoodsNWaters]

Then there are the legal issues. Who owns the land that was under the former reservoir?

A hydro-electric dam in Ellsworth, Maine, has lost it's generating license. One of several reasons is that the dam kills too many fish. The owners may be required to remove the dam. The shore has some public land, but much more private land. Who owned the land under the reservoir and who inherits that land? A recent article in a local newspaper said the resolution can be "very complex".

 

[ppine]

thanks for posting this. Very relevant for all river runners.
I have made runs on the Klamath River in California 3 times, the second largest river in California. Last trip the put in was right below Iron Gate Dam in 2023.
The effects of multiple dam removals has been dramatic in the last 2 years.
The anadromous fishery has responded quickly. Salmon have already traveled up stream past all of the dams and made their way across the enormous Klamath Lake. Fish are already spawning in the Williamson and Sprague Rivers well up into Oregon.

There were plenty of naysayers that said that this would never work. The large winter discharges in a river this big, have moved tremendous amounts of sediment downstream and out into the Pacific past the river mouth. The river already has more or less normal clarity. Big success story. More to follow. The Elwha River in Washington got the ball rolling some years ago.