Washington, March 14 : A new study has indicated that without dams and reservoirs, sea levels would have risen 30 percent more than they already have.
According to a report in National Geographic News, dams and reservoirs have stored so much water over the past several decades that they have masked surging sea levels.
Sea levels have been rising for decades, due mostly to global warming caused by greenhouse gases.
The oceans are on average about 6.3 inches (16 centimeters) higher now than in 1930, when they started a noticeable upward climb. Melting glaciers and ice caps, along with ocean warming-water expands as it heats up-are the main culprits behind the increase.
But the new study has shown that reservoirs are also an important factor. Rather than adding to sea-level rise, however, they have counteracted it by storing more water on land.
In fact, since 1930, the storage of water has prevented a total of about 1.2 inches (3 centimeters) of sea-level rise.
"Without dams, sea levels would have risen 30 percent more than they already have," according to a research led by Benjamin Chao of National Central University in Taiwan.
The researchers tallied up the water stored behind nearly 30,000 dams built worldwide since 1900.
The study estimates that human-made reservoirs worldwide store about 2,600 cubic miles (10,800 cubic kilometers) of water-nearly as much as is found in Lake Superior, one of the world's largest lakes.
According to the researchers, water stored in a multitude of smaller reservoirs also adds up. Lots of water also soaks into the ground underneath reservoirs, adding to the amount of water locked up on land.
"The study provides the latest, more accurate estimate of water impoundment by reservoirs," said Vivien Gornitz, of NASA's Goddard Institute for Space Studies in New York City.