Relocate, rejuvenate

And outbreak of the foul-smelling algae also triggered a major project to reclaim the aquatic environment in Huzhou, a city of 2.6 million people on Taihu's southern shore. The surfaces of almost all the city's waterways turned an iridescent green, according to Li Dongmin, a retired official with the Huzhou-based Taihu Lake Tourist Resort Administrative Committee. "The stench permeated almost every corner of the city," he said.

In response, Huzhou launched a comprehensive environmental improvement project as part of its goal of becoming a modern, ecologically friendly city. The project has been successful enough for the city to begin promoting lakeside tourism in recent years.

Paper mills, cement plants and printing and dyeing works were closed and the discharge of untreated household and industrial sewage was banned. The lakeside areas were redeveloped and algae outbreaks were closely monitored.

The project also saw the relocation of more than 750 fishermen to new apartments ashore. Their floating homes were moored on a river that fed into the lake, with dire consequences. "These families used to discharge household rubbish and waste water into the river, which then flowed into the lake," Li recalled. "Their vessels were crowded on the river and made the 100-meter-wide waterway so narrow that only one vessel could sail through at a time."

Huzhou also decided to cut off the source of polluted water flowing into the lake, as part of an ongoing program costing 305 million yuan ($49 million) to treat smaller waterways in upstream Deqing county.

The program, which is scheduled for completion in 2016, aims to restore the ecological balance along the 505 km of the county's rivers, by clearing silt deposits, removing garbage and other solid surface waste, dredging and reinforcing the embankments.

Shi Weiqiang, a senior engineer at the county's water resources department, called the drive a clean-up of Taihu's "capillaries". The key is to desilt the rivers, which were contaminated by small dyeing workshops and chemical factories in the 1980s and 1990s, he said. "If left untreated, the pollutants and contaminated silt will flow into Taihu Lake during the flood season. This drive is designed to cut off all the upstream sources of pollution."

Local residents have also benefited; the water quality has improved and their villages look - and smell - much nicer, as desired by the advocates of "beautiful China" in the country's overall development plan.

The program has resulted in improved water quality every year, said Shen Zhihua, director of Huzhou's Water Conservancy Bureau.

Future challenges

However, greater efforts and more time are still needed to fully address the pollution, which is not an overnight phenomenon, but a "slow death" that began in the 1980s when industrial activity and residential development alongside the lake increased dramatically, said officials and experts.

The latest statistics provided by the Taihu Basin Authority under the Ministry of Water Resources indicate that a large swathe of the lake suffered medium-level eutrophication in 2011. Only 446 sq km, less than 20 percent, of the lake was classified as "fourth-class water" in 2011, indicating that it was only suitable for industrial use. Other parts of the lake were classified as "fifth-class water", meaning it is only suitable for agricultural use. If the rating falls any lower, the water will be declared unfit for human consumption.

Adding to the problem, the excessive use of fertilizers and pesticides is one of the biggest threats to the lake. The agricultural sector has outpaced industry to become China's biggest water polluter, one that's difficult to bring under control.

"Ecosystem services", the practice of offering incentives to farmers in exchange for managing their land in accordance with best ecological practice, have been under discussion for some time.

However, the source of the funding remains unclear, as does the means of distributing payments to farmers, said Hu Sunwen, head of the water administration and law-enforcement office under Huzhou Water Conservancy Bureau.

In light of the high level of investment in the control of water pollution, long-term management is now a major part of the effort to control water quality and prevent a recurrence of the problem.

Wuxi has implemented a system to allocate responsibility for the treatment of each river to an individual government official, a measure that's proved effective in reinforcing accountability if pollution occurs. So far, the city has appointed more than 1,200 of these officials, known as "river heads" to take overall control of anti-pollution efforts.

However, even as the authorities try to relieve the problem, the real solution lies with those who live in the areas around the lake, especially the farmers.

"We have been promoting modern agriculture and the correct use of farm chemicals through media outlets, including TV and newspapers, but many turn a deaf ear and just spray every kind of chemical on their plants," said Shen of the Huzhou Water Conservancy Bureau.

Wu Xinqiang, who owns a restaurant in Hongqi village in Daixi township, said the most common chemical used in his village is a herbicide applied to increase bamboo yields. "It's poisonous," he said. "But it is very hard to stop the villagers from using it."

Contact the writer at wangzhenghua@chinadaily.com.cn.