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)

Two Bulgarian tourists pose in front of the Eiffel Tower in Paris on their last day in the capital on March 24, 2014. (Photo by Franck Fife/AFP Photo)

A handout photograph provided by Brian Kubicki of Costa Rican Amphibian Research Center on 26 April 2016 shows a “Crystal frog”, Hyalinobatrachium dianae (H. diane). This frog was discovered by US biologist Brian Kubicki and Costa Ricans Stanley Salazar and Robert Puschendorf in a rainy forest of Costa Rican caribbean after 40 years without notice of any new example of this kind. (Photo by Brian Kubicki/EPA/Costa Rican Amphibian Research Center)

Auto worker Christopher Brower screws a component into the cab of a four-door F150 at Ford's Kansas City Assembly Plant where new aluminum intensive Ford F-Series pickups are built in Claycomo, Missouri May 5, 2015. (Photo by Dave Kaup/Reuters)

Mercedes driver Nico Rosberg, right, of Germany steers his car in front of Mercedes driver Mercedes driver Lewis Hamilton of Britain, center and Ferrari driver Sebastian Vettel of Germany during the Austrian Formula One Grand Prix race at the Red Bull Ring in Spielberg, southern Austria, Sunday, June 21, 2015. (AP Photo/Kerstin Joensson)

In this June 29, 2015 photo, hairdresser Loavia Bienaime, 30, sits on her bed as she prepares to begin her day in the room her family occupies in an government office building that was damaged in the 2010 earthquake in Port-au-Prince, Haiti. Bienaime's husband, Jimmy Bellefleur, used his skill as an electrician to connect the abandoned building to the power grid, and has repaired broken televisions, fans, and a blender for the family to use. (Photo by Rebecca Blackwell/AP Photo)

Kung Fu master Li Liangui practices “Suogugong” Kung Fu and his wife Liang Xiaoyan (R) practices Qigong at a park in Beijing, China, June 30, 2016. For 50 years, kung fu master Li Liangui has been contorting his body into eye-watering positions while practising one of the more unusual and less popular Chinese martial art forms. The 70-year-old is an expert in suogugong, or body shrinking kung fu, where practitioners dislocate their bones to help them achieve unlikely positions and feats. (Photo by Kim Kyung-Hoon/Reuters)

A man carries a woman across a river at Petit Goave where a bridge collapsed during the rains of the Hurricane Matthew, southwest of Port-au-Prince, October 5, 2016. (Photo by Hector Retamal/AFP Photo)