Scientists stunned by unexpected side effects in rivers after knocking down dams: 'The other experts in the field were also surprised'

There are times when a dam has a purpose and then times when that becomes a burden. Dams effectively store water for flood control, irrigation, and other functions. However, dammed rivers disrupt the natural habitat of existing fish and wildlife.

"Rivers are a transport system, and if they are to fulfill their ecological function, they need to move water, sediments, nutrients, and living beings," explained researcher Askoa Ibisate in a EurekAlert news release.

Fortunately, European Union policies have encouraged the restoration of rivers with disused dams. The Olloki dam in Spain's Basque Country is one such case under a study performed by fluvial geomorphology geographers.

The research group monitored 1,800 stones in the Leitzaran River between 2016 and 2022, embedding a code inside the stone samples. They distributed them at three points in the river: upstream, downstream, and at a control site. They then scanned the river from bank to bank with a detector.

"When the device detects a code, it informs us which stone it is and gives us the GPS coordinates," Ibisate explained.

The process enables researchers to understand the function of rivers and their sediment flow, providing a better prediction of the demolition of dams. The researchers discovered that some stones in the river traveled over 5 miles.

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"We didn't think the sediments would move so much," Ibisate stated, "and the other experts in the field were also surprised."

There are roughly 500,000 dams in the United States, and 85% are over 50 years old and no longer serve a purpose. However, around 900 dams were removed by 2015, and an additional 50 to 60 per year thereafter.

The continued effort to remove disused dams restores the natural water flow of rivers necessary for wildlife to flourish. Salmon, sturgeon, and other migratory fish can travel up and down the river during their lifecycle. Also, the free-flowing rivers improve water quality, leading to a healthier ecosystem for both people and nature.

How often do you worry about the quality of your drinking water?

Never 👎