A man pours mud water on the head of his girl friend during the Boryeong Mud Festival at Daecheon Beach in Boryeong, South Korea, Friday, July 18, 2014. The annual mud festival features mud wrestling and mud sliding. (Photo by Ahn Young-joon/AP Photo)

Growing cities, overuse of fertilizers and factory wastewater have degraded China's water supplies to the extent that half the nation's rivers and lakes are severely polluted. China aims to spend $850 billion to improve filthy water supplies over the next decade, but even such huge outlays may do little to reverse damage caused by decades of pollution and overuse in Beijing's push for rapid economic growth. Photo: Fishermen row a boat in the algae-filled Chaohu Lake in Hefei, Anhui province, June 19, 2009. (Photo by Jianan Yu/Reuters)

These two young siblings appear to cling on to a tree for dear life and even hold hands as they learn the ropes of climbing, on June 25, 2013. (Photo by Tim Fitzharris/Minden/Solent)

A Dutch Military Policeman, left inside, guards part of the reconstructed cockpit, right, and forward section of the fuselage after the Dutch Safety Board presented it's final report into what caused Malaysia Airlines Flight 17 to break up high over Eastern Ukraine last year, killing all 298 people on board, during a press conference in Gilze-Rijen, central Netherlands, Tuesday, October 13, 2015. (Photo by Peter Dejong/AP Photo)

Workers from the South Florida Science Center and Aquarium and Imagine Exhibitions put together an animatronic spinosaurus outside the science center in West Palm Beach, Fla., Tuesday, October 27, 2015. The giant spinosaurus is part of the Dinosaurs Around the World exhibit, set to open on November 1. (Photo by Maria Lorenzino/South Florida Sun-Sentinel via AP Photo)

A mother prays for success for her child in the college entrance examinations at a Buddhist temple in Seoul, South Korea, November 12, 2015. About 630,000 students on Thursday sat for the annual exams that could lead them to one of the country's top universities. In South Korea, there is no higher achievement than to be accepted by a prestigious university. As a result, many students prepare for these entrance exams from an early age, often studying up to 16 hours a day for years to take this test. (Photo by Kim Hong-Ji/Reuters)