Dam Consequences

Dams have helped humanity thrive and develop, but such structures have also resulted in unintentional consequences for the environment. 

Now, a new study has found that dams are not just impacting local ecosystems – they are shifting Earth’s poles. 

To arrive at this conclusion, lead author Natasha Valencic and her team from Harvard University analyzed the impact of nearly 7,000 dams constructed between 1835 and 2011, which collectively hold enough freshwater to fill the Grand Canyon twice. 

They said these structures redistributed Earth’s mass in a way that physically altered the planet’s spin – a process known as “true polar wander.” As a result, nearly two centuries of dam building has shifted Earth’s geographic poles by more than three feet. 

“As we trap water behind dams, not only does it remove water from the oceans, thus leading to a global sea level fall, it also distributes mass in a different way around the world,” Valencic explained in a statement. “We’re not going to drop into a new ice age, because the pole moved by about a meter (roughly three feet) in total, but it does have implications for sea level.” 

The researchers found that from 1835 to 1954 – when most dams were built in North America and Europe – the North Pole shifted about eight inches toward the 103rd meridian east, which passes through Russia, Mongolia, China, and the Indochina Peninsula. 

Meanwhile, dam construction in East Africa and Asia from 1954 to 2011 saw the pole swerve 22 inches the other way, toward the 117th meridian west, near western North America. 

Altogether, the planet’s poles moved around 3.7 feet, with most of the movement occurring in the 20th century.  

However, that wasn’t the only planetary nudge: The study also estimated a global sea level drop of 0.83 inches, a subtle but measurable dip. 

While these numbers might sound small, they underscore the astronomical impact of these man-made objects on the world, noted Popular Mechanics. 

For example, NASA scientist Benjamin Fong Chao found in 2005 that when China’s gargantuan Three Gorges Dam became full, it slowed Earth’s rotation by 0.06 microseconds.

The authors said that while these are incremental figures, they matter and can help in better calculating future sea level rise. 

“Depending on where you place dams and reservoirs, the geometry of sea level rise will change,” Valencic added. “These changes can be pretty large, pretty significant.”