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)

Russian President Vladimir Putin (C) and Defence Minister Sergei Shoigu (back) attend a reception to honour graduates of military academies at the Kremlin in Moscow, Russia, June 28, 2016. (Photo by Alexei Druzhinin/Reuters/Sputnik/Kremlin)

A man lies in the sea grass at a beach on July 18, 2016 in Qingdao, Shandong Province of China. The enteromorpha prolifera spread on the beaches in Qingdao and were under clearing. (Photo by VCG/VCG via Getty Images)

A fan waves a Brazilian flag before the arrival of the Olympic torch ahead of the Rio 2016 Olympic Games on August 2, 2016 in Sao Goncalo, Rio de Janeiro state, Brazil. The torch will arrive in the city of Rio tomorrow and the Games commence on August 5. (Photo by Mario Tama/Getty Images)

An actress dressed as Wonder Woman walks between visitors during the season inauguration of the Madrid Warner amusement park in San Martin de Valdeiglesias, near Madrid, Spain, March 18, 2016. (Photo by Andrea Comas/Reuters)

A giant Iron Man statue stands next to a replica Sphinx in Chuzhou, Anhui Province, China on February 21, 2017. (Photo by Sipa Asia/Rex Features/Shutterstock)

An Indian toddler plays amid marigold flowers at a wasted flowers dumping site, besides a flower market in Mumbai, India, 28 September 2016. Marigold flowers are used in many religious ceremonies in the temples in India. Strung together they make colourful garlands and are used as an offering in temples and to decorate them. (Photo by Divyakant Solanki/EPA)

Riot Police form a cordon as a Police car burns on the opening day of the European Central Bank (ECB) in Frankfurt am Main, western Germany, on March 18, 2015. Supporters of the so-called Blockupy alliance consisting of social movements, activists, workers, trade unions and parties are expected to stage large protests against austerity and the authority of the European Central Bank when the bank's new headquarters officially will be on March 18, 2015. (Photo by Odd Andersen/AFP Photo)