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.

Children fish in a polluted river covered with algae in Hefei, east China's Anhui province, July 18, 2006. China plans to invest 1.4 trillion yuan ($175 billion) in environmental protection in the next five years, state media said on Tuesday, to curb water and air pollution so severe it causes riots and health problems. (Photo by Jianan Yu/Reuters)

A journalist takes a sample of red polluted water in the Jianhe River in Luoyang, Henan province, on 13 December, 2011. According to local media, the sources of the pollution are two illegal chemical plants discharging their production waste water into the rain sewer pipes. (Photo by Reuters/Stringer)

A boy tries to avoid scattered rubbish floating on a flooded street in Shantou, Guangdong province, on 23 August, 2013. (Photo by Reuters/Stringer)

A fisherman holds his fishing net in his mouth in a polluted river in Wuhan, Hubei province, on 21 June, 2011. (Photo by Reuters/Stringer)

A worker looks at a photographer from a door of a factory manufacturing screws and nuts next to a polluted river in Jiaxing, Zhejiang province March 15, 2012. China's continuing reliance on heavy industry meant it failed to meet its own targets for cleaning its air and water in 2011, the head of the top planning agency told journalists on Monday. (Photo by Reuters/Stringer)

Polluted water in Songhua River reaches Harbin, the capital of northeastern Heilongjiang province November 24, 2005. A stretch of potentially lethally polluted river water headed towards one of China's biggest cities on Thursday after an explosion at a petrochemical plant. China said on Wednesday the blast had caused “major pollution” in the Songhua River from which Harbin and home to nine million people, draws its drinking water. (Photo by Reuters/China Newsphoto Pictures of the Month November 2005)

A man sits atop a drain as he fishes at a polluted canal in central Beijing October 26, 2010. Locals fish in the canals that run through the city before the canals freeze during winter months, making fishing much harder. (Photo by David Gray/Reuters)

Pipes coming from a rare earth smelting plant spew polluted water into a vast tailings dam near Xinguang Village, located on the outskirts of the city of Baotou in China's Inner Mongolia Autonomous Region in this October 31, 2010 picture. The massive Baogang corporation, located on the outskirts of Baotou city, churns out rare earth metals on a vast scale, and villagers living near the smelting plants and a vast tailings dam used to dump the black refuse from ore processing said the rare earths boom was threatening their livelihood and health. Air and water toxins from the plants and dam were poisoning them, their water, crops and children, they said. China supplies 97 percent of rare earths used worldwide, and they go into magnets, bearings and high-tech components that go into computers, vehicles and, increasingly, clean energy technology such as wind turbines and hybrid cars. (Photo by David Gray/Reuters)

A garbage collector walks next to an algae covered beach in Qingdao, Shandong province, July 31, 2014. (Photo by Reuters/China Daily)

A girl collects water from a puddle at a dried-up reservoir as her father stands beside her in Baofeng county, Henan province July 30, 2014. Lingering droughts in most parts of China have affected millions of hectares of agricultural crops, the State Flood Control and Drought Relief Headquarters said on Wednesday. (Photo by Reuters/Stringer)

A boy swims in the algae-filled coastline of Qingdao, Shandong province July 15, 2011. (Photo by Reuters/China Daily)

Dead fish are seen floating on a polluted river in Hefei, Anhui province March 19, 2010. The Earth is literally covered in water, but more than a billion people lack access to clean water for drinking or sanitation as most water is salty or dirty. (Photo by Reuters/Stringer)

Labourers work to drain sewage water from a leaked sewage tank at a copper mine in Shanghang, Fujian province, July 13, 2010. The sewage leak from the copper mine owned by Zijin Mining Group Co, whose shares were suspended from trading in Hong Kong on Monday, has polluted a river and reservoir in Fujian province, Xinhua news agency reported. Xinhua cited environmental authorities as saying the leak from a plant of the Zijinshan Copper Mine had killed or poisoned about 1.89 million kg of fish. (Photo by Reuters/Stringer)

A fisherman wades in Chaohu Lake, covered in blue-green algae, in Chaohu city, Anhui province, July 19, 2013. (Photo by Reuters/China Daily)

A labourer cleans up oil at the oil spill site near Dalian port, Liaoning province July 23, 2010. China's Xingang oil port has resumed some refined fuel loading for the domestic market, but fuel exports remain temporarily halted, industry officials said amid continuing efforts to clean up an oil spill at the country's major port of Dalian. (Photo by Reuters/Stringer)

Gnats, or small biting flies, gather on railings along the East Lake in Wuhan, Hubei province November 26, 2009. Gnats appear in the lake due to water pollution and they will leave once the temperature in the area drops in about half a month's time, according to experts, local media reported. (Photo by Reuters/Stringer)

A child swims in a polluted reservoir in Pingba, southwest China's Guizhou province September 2, 2006. More than a third of China's national nature reserves are sacrificing the environment for profit, a state environmental official said on Friday, Xinhua News Agency reported. (Photo by Reuters/China Daily)

Fishermen walk through the muddy bottom of a polluted canal collecting fish in central Beijing October 21, 2010. The canal has been drained for cleaning, enabling fishermen and local residents to collect the small fish from the thick, black mud lining the bottom of the canal. Earlier this year, data from China's environment watchdog, the Ministry of Environmental Protection, showed almost a quarter of China's surface water remains so polluted that it is unfit even for industrial use, while less than half of total supplies are drinkable. (Photo by David Gray/Reuters)

A dead fish floats in water filled with blue-green algae at the East Lake in Wuhan, Hubei province August 20, 2012. (Photo by Reuters/Stringer)

The river in Xinmeizhou village in eastern China's Zhejiang province quickly filled up with the red colored liquid which had a strange smell, according to villagers, July 25, 2014. (Photo by Reuters/Stringer)

A worker collects catfish for disposal in a polluted pond in Haikou, Hainan province, September 10, 2013. Local government acted to kill all catfish at the fishpond after the water inside the pond were tested below standards, according to local media. (Photo by Reuters/Stringer)

A woman walks on a bridge over a polluted river at a suburban area of Wenzhou, in Zhejiang province February 18, 2011. China is now the world's second largest economy, but hundreds of millions of its people still rely on fouled water that will cost billions of dollars to clean. Growing cities, overuse of fertilisers, and factories that heedlessly dump wastewater have degraded China's water supplies to the extent that half the nation's rivers and lakes are severely polluted. (Photo by Carlos Barria/Reuters)

A worker rows a boat in Chaohu Lake, filled with blue-green algae, in Hefei, Anhui province July 23, 2012. The local environment protection department implemented machines to pump the algae from the lake to a treatment reservoir where it would be decontaminated and recycled, which was the latest solution to fight off blue-green algae on the Chaohu Lake. The new method is able to deal with almost a thousand tonnes of blue-green algae every day, according to local media. (Photo by Reuters/Stringer)

Workers clean up leaked oil after an oil pipeline explosion last week in Qingdao, Shandong province November 25, 2013. Asia's top oil refiner Sinopec has cut production for at least two of its refineries in China's eastern Shandong province after the pipeline blast which killed 55 people on Friday, industry sources said. (Photo by Reuters/Stringer)

A man swims in a polluted canal in the centre of Beijing August 16, 2007. China's capital, host of the 2008 Summer Olympics, warned on Thursday that heat had put some of its lakes at risk of algae blooms, similar to those that have cut water supplies elsewhere in the country. (Photo by David Gray/Reuters)

A worker cleans away dead fish at a lake in Wuhan, central China's Hubei province July 11, 2007. More than 50,000 kilograms (110,000 pounds) of fish died due to pollution and hot weather in the lake, local media reported. (Photo by Reuters/China Daily)

A fisherman fills his cupped palms with water from the algae-filled Chaohu Lake in Hefei, Anhui province, June 16, 2009. The country has invested 51 billion yuan towards the construction of 2,712 projects for the treatment of eight rivers and lakes including Huaihe River, Haihe River, Liaohe River, Chaohu Lake, Dianchi Lake, Songhua River, the Three Gorges region of the Yangtze River and its upstream area, Xinhua News Agency reported. (Photo by Reuters/Stringer)

A man walks by a pipe discharging waste water into the Yangtze River from a paper mill in Anqing, Anhui province, December 4, 2013. (Photo by William Hong/Reuters)

A fisherman jumps from his boat to the bank after fishing in the morning at a polluted river in Hefei, in east China's Anhui province March 8, 2007. (Photo by Jianan Yu/Reuters)

Workers clean up floating garbage on the Yangtze Rive near the Three Gorges reservoir in Fengjie County of China's Chongqing municipality, November 1, 2009. China is facing an arduous mission to improve water quality as 30 percent of the country's major river drainage areas had not met the state required standard by the end of 2008, Xinhua News Agency reported. (Photo by Reuters/China Daily)

Workers collect dead fish at a park in Shenzhen, Guangdong province, November 5, 2013. More than 10,000 fish were found dead in a smelly lake inside a park, near a drain where sewage flowed into the lake, according to local media. (Photo by Reuters/China Daily)

Fishermen row a boat in the algae-filled Chaohu Lake in Hefei, Anhui province, June 19, 2009. The country has invested 51 billion yuan ($7.4 billion) towards the construction of 2,712 projects for the treatment of eight rivers and lakes including Huaihe River, Haihe River, Liaohe River, Chaohu Lake, Dianchi Lake, Songhua River, the Three Gorges region of the Yangtze River and its upstream area, Xinhua News Agency reported. (Photo by Jianan Yu/Reuters)

A child drinks water near a stream in Fuyuan county, Yunnan province March 20, 2009. World Water Day will be observed on March 22. Picture taken March 20, 2009. (Photo by Reuters/Stringer)

Fishermen clean up oil at an oil spill site near Dalian Port, Liaoning province July 27, 2010. Nearly 8,000 workers and hundreds of fishing boats have managed to clean up the oil spill off the major northern Chinese port Dalian, nine days after a pipeline blast leaked 1,500 tonnes of heavy crude into the sea. (Photo by Reuters/Stringer)

A child is reflected in a drainage ditch as he jumps over trash at a village which will soon be demolished, on the outskirts of Jiaxing city, Zhejiang province, January 12, 2013. New residential buildings are seen in the background. (Photo by William Hong/Reuters)

A resident washes clothes in a polluted pond in Xiangfan, Hubei province, March 21, 2010. The Earth is literally covered in water, but more than a billion people lack access to clean water for drinking or sanitation as most water is salty or dirty. (Photo by Reuters/Stringer)