South Korean soldiers participate in a winter river crossing operation in preparation for a possible North Korean attack on February 8, 2012 in Yeoju, South Korea. The Korean peninsula is the world's last Cold War frontier as stalinist North Korea and pro-western South Korea have been technically at war since the 1950-53 conflict. (Photo by Chung Sung-Jun/Getty Images)

Water gushes out from the Xiaolangdi Reservoir on the Yellow River during a sand-washing operation on June 20, 2012 in Luoyang, China. The sand-washing operation, which started on June 19 and will last for about 20 days, is conducted to clear out the silt deposits at the dam. (Photo by China Foto Press)

“El rio mas bonito del Mundo”, the most beautiful river of the world, the “River of five colors”, the “Rainbow River”, or even the “Escaped from Paradise”, are the shimmering appellations that Colombians give to Cano Cristales, a small stream located in the heart of the Macarena National Park, 150 km (93 miles) south of Bogota. Photo: A waterfall is seen at the end of the rainy season, in August, when the water level finally decreases, in the Cano Cristales RIver in the Sierra de la Macarena in Colombia. It has become covered with a bright pink endemic aquatic plant, Macarenia Clavigera. (Photo by Olivier Grunewald)

A security exercise takes place along the River Thames on January 19, 2012 in London, England. The exercise including around 44 police officers, 94 military personnel, 15 boats and a Royal Navy Lynx helicopter was conducted by both the Metropolitan Police and the Royal Marines and designed to test their joint capability ahead of the 2012 London Olympic Games. (Photo by Dan Kitwood/Getty Images)

This photo taken on July 19, 2020 shows a person taking photos while water is released from the Three Gorges Dam, a gigantic hydropower project on the Yangtze river, to relieve flood pressure in Yichang, central China's Hubei province. Rising waters across central and eastern China have left over 140 people dead or missing, and floods have affected almost 24 million since the start of July, according to the ministry of emergency management. (Photo by AFP Photo/China Stringer Network)

This picture taken on September 3, 2014 shows a man taking pictures of floodwater released from the Three Gorges Dam, a gigantic hydropower project on the Yangtze river, in Yichang, central China's Hubei province, after heavy downpours in the upper reaches of the dam caused the highest flood peak of the year. Eleven people died and 27 others are missing after torrential rains battered southwest China's Chongqing, a municipality in the upper reaches of the Three Gorges Dam, causing thousands of houses to collapse, state media said. (Photo by AFP Photo/Stringer)

This photo taken on July 19, 2020 shows a security guard looking at his smartphone while water is released from the Three Gorges Dam, a gigantic hydropower project on the Yangtze river, to relieve flood pressure in Yichang, central China's Hubei province. Rising waters across central and eastern China have left over 140 people dead or missing, and floods have affected almost 24 million since the start of July, according to the ministry of emergency management. (Photo by AFP Photo/China Stringer Network)