The Dam Which Slowed Earth’s Rotation

China’s Three Gorges Dam is so massive that it slows the Earth’s rotation, 600 feet / 180 meters high and 7,665 feet/ 2,335 meters long is at capacity. Its reservoir holds 42 billion tons of water.  This shift in mass is actually enough to slow the planet’s rotation, increasing the length of the day by 0.06 microseconds while less than one microsecond may not seem significant. The impact is still remarkable and this is just one example of how dams have reshaped our planets.

                              Few structures can transform a landscape quite like a dam by blocking the flow of the river, dams defy gravity’s pull on water from the mountain to the estuary. This transforms a river’s natural course accruing sediments at the artificial barrier and dampening water’s erosional force downstream. A great example is the Contra Dam also known as the Verzasca Dam in Switzerland. It’s perhaps best known for its appearance in the GoldenEye 1995, James Bond movie. Another awe-inspiring Dam is the Roseland Dam in France.  The Dam is situated in Savoie Valley and offers faithful views of the Rhone-Alpes region. The Monticello Dam in California is a concrete arch dam with a unique feature. A morning-glory-type spillway, “a glory hole”. The last time, reservoir naturally spilled through was in February 2019, loss of life. Unfortunately, people and animals don’t always benefit from Dams between 2000 and 2009. More than 200 dam failures occurred across the globe.  These were triggered by everything from earthquakes and internal erosion to human error and poor maintenance. One of the most deadly failures in history was the Banqiao reservoir dam failure in 1975. The catastrophic collapse of 62 dams including the Banqiao dam killed more than 171,000 and 11 million lost their homes. The Kariba Dam is also on the verge of failure. It suffers from both levels of water that are too high and too low.  If the dam fails it’ll take 40% of Southern Africa’s hydroelectric capacity with it. This would devastate the wildlife in surrounding areas and leave 3.5 million people at risk.

But dams are not always so bleak. Reservoirs created by dams help control flooding by filling valleys in this manner. They can also be used for boating, fishing, and other human recreations.  The largest reservoir in the world, Lake Volta acts as a waterway for ferries and cargo watercraft.

 Dams are also responsible for keeping our landscapes lit. The Gordon Dam is a double curvature concrete arch dam in Tasmania, Australia. It diverts the waters of Lake Gordon to an underground power station and provides approximately 13% of Tasmania’s electricity. The Hoover Dam took five years to build and its construction was a massive effort that involved thousands of workers. The need for a huge workforce created a population spike in nearby Las Vegas. In just one year the population jumped from 5200 to 7500. Soon the government began investing in the city’s infrastructure and Las Vegas continued to grow.  The Dam’s construction brought tourists. In fact, an estimated 75% of those visiting the Dam in the 1930s also stopped in Las Vegas. The Hoover Dam would be responsible for bringing cheap energy to Las Vegas. When the dam started generating power in 1937, the dam also provided water to the developing city. Without the Hoover Dam, Las Vegas wouldn’t be what it is today.

There are more than 100 cases of earthquakes that have been caused by dams. The phenomenon, known as reservoir-induced seismicity, is caused by extra water pressure in the dam’s reservoir resulting in cracks and fissures in the ground below. The water further lubricates the faults which are already in the tectonic strain.  One such example is the 7.9 magnitude Sichuan earthquake which occurred in 2008. The event which has been linked to the Zipingpu Dam killed around 80,000 people.

Dams help to provide water for farming. The Central Valley project in California was devised in 1933. Its 20 dams and reservoirs helped to allow major cities to grow along rivers that previously flooded and transformed desert environments into farmable land. Of course, this can also come at a cost such as desertification due to excessive farming. The future of dams is somewhat uncertain. The rise of popularity in wind and solar power along with the rising costs of hydropower projects will lower hydro’s share of the renewable electricity mix. In fact, global investment in wind and solar energy outpaces investment in hydropower. Still, new dams are on the horizon, for example, China is constructing a controversial new series of dams on the Yarlung Tsangpo River. Once completed, the dams could produce as much as three times the power of the Three Gorges Dam and further contribute to the transformation of our Planet.