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Sucking out the Poison in Lakes

Dining tables may be missing a few mitten crabs of late but behind the delicacy's shortage lies an epic battle involving man, chemicals and nature.

Authorities have closed down many of the farms along a lake in Jiangsu province where the hairy crustaceans are nurtured because of fears that it could become polluted by a blue-green algae outbreak affecting a connecting lake.

The crabs are traditionally bred in Yangcheng Lake, which offer ideal conditions for their development. But just along the connecting Yangtze River is Taihu, a lake badly affected by poisonous algae, a scum that floats atop the water.

More than 86 percent of 50,000 mu (3,330 hectares) of crab farms were removed from Yangcheng Lake by June in order to reduce the amount of fertilizer dumped into the water, which would otherwise provide an ideal environment for the algae's growth.

Suzhou, the city with jurisdiction over Yangcheng Lake, has spent around 220 million yuan (US$30 million) to relocate 700 families who, for generations, had been crustacean farmers, according to local government figures.

But it is just a small percentage of the price paid by the cities near Taihu, principally Suzhou and Wuxi, to treat water pollution and ensure clean drinking water.

Authorities have devised an estimated 1,600 environmental projects aimed at restoring the ecosystem in Taihu, China's third largest freshwater lake, with an investment of 80 billion yuan before 2012 and a further 28 billion yuan between 2012 and 2020.

It is considered a small price to pay for clean drinking water for millions in the Yangtze River Delta.

Zhang Jing, a 26-year-old from Wuxi, said she will never forget the day two years ago when she awoke to find her tap water has been badly contaminated.

"It stank," she said. "It was summer and the day was so hot and humid. What was worse, I really needed to feed my five-month-old baby."

She later discovered the city's water intake from Taihu had been contaminated with blue-green algae and, along with 3 million fellow residents, was forced to rush out and buy bottled water before they all disappeared from the shelves.

The desperate mother even had to wash her baby in bottled water - an extra expense and heavy burden for a family with a monthly income of just 3,000 yuan.

"It was the first time in my life I realized how precious clean water is," she said. "Now I always store bottled water in time for summer, in case it happens again."

Along the shore of the lake today, in both Suzhou or Wuxi, children laugh and play, anglers are fishing and young couples are having their wedding photos taken in front of reed marshes.

It is hard to believe only two years ago there was a 30-50 cm layer of blue-green algae and debris floating on the water, giving out a foul stench. The only reminders are the men on boats working to remove algae or silt.

Latest research by the National Development and Reform Commission shows the blue-green algae has been reduced by 73 percent from the level in 2007. Now about 20 million algae organisms live in every liter of lake water, compared to more than 100 million two years ago.

Pollutants such as hypermanganate, nitrogen and phosphate have been reduced 20 percent since last year.

Although the water in Taihu is safe to drink once it has been processed, water experts said it has become prone to algal outbreaks in warm weather and is in serious danger if the level of pollution increases. Keeping the lake clean will be a long-term process.

The State Council, the nation's cabinet, recently released a general plan for comprehensively treating the Taihu basin, which was approved by Premier Wen Jiabao. It requires surrounding communities, such as those in Shanghai municipality and provinces of Jiangsu and Zhejiang, to submit detailed proposals for action.

The plan mapped out short- and long-term targets to ensure the quality of water and set 2012 as the target date to finally rid the lake of nutrients that lead to excessive algal growth.

By then, it states, the water quality should be improved from being "worse than Grade V", the highest level of poisoning and when the lake has no biological function, to Grade V, which means the lake water is able to be processed for agricultural irrigation.

By 2020, it adds, the water quality should be improved to Grade IV, when it is able to be processed for industrial use, or Grade III, when it can be processed for drinking, swimming or aquatic farming.

The Taihu basin, the core area of the Yangtze River Delta, is the country's richest region, with a high population density, as well as a high level of industrial development.

Wuxi alone has 1,500 people per sq km, 10 times more than the national average. About 60 percent of industrial ventures contribute to its gross domestic product (GDP) and the city has 10 plants per sq km, meaning its GDP per sq km is more than 57 million yuan, 57 times more than the national average.

The ecosystem of Taihu has borne the brunt of its fast economic development. But now the focus is on creating sustainable development, even if it slows the high rate of growth.

"The period since May 2007, when the blue-green algae outbreak hit Wuxi, has been the hardest time in my 20-year career," said Liu Yajun, director of Wuxi environmental protection bureau.

The authority had to move the intake point in Taihu by 3,000 m to the lake's center, where the water is less polluted, to ensure clean drinking supplies, while the city also started to take water from the Yangtze River.

It now receives 800,000 tons of water from both Taihu Lake and the Yangtze River every day, with every drop first undergoing 106 strict quality tests. It previously went through only 35 tests.

Wuxi has also implemented the most stringent waste treatment standards in China. It boasts 68 waste treatment plants and has updated more than 6,000 km of pipelines.

In addition to organic pollutants, levels of nitrogen and phosphate, the main causes of algal growth, have also been reduced, while real-time and online monitoring systems have been improved.

More than 1,400 small factories that consumed high levels of energy, or released a lot of pollution but produced little in the way of economic advantage, have already been closed down.

Neighboring cities have cooperated in a biological approach to the pollution, with more than 10,000 mu of wetlands recovered with the planting of reed marshes and a forest belt 200 m wide planted along the shore.

Water farms and floating restaurants have been permanently removed.

Meanwhile, the blue-green algae has been put to good use by the Wuxi authorities as a biomass for electricity generation and fertilizer for the young trees.

The Taihu basin has become almost a pilot experiment in introducing market instruments to reduce pollutants, such as cap and trade, paid emission rights and a biological compensation system.

Some measures, though, have aroused controversy, including the introduction of water from the Yangtze River to dilute the pollution, which experts claimed could transfer pollution into the Yangtze.

Plans to dump silt dredged from the lake was also heavily criticized as environmentalists said it would lead to soil pollution.

"It's impossible to get everything right," said bureau chief Liu. "The priority is to ensure an adequate supply of clean drinking water and prevent an outbreak of poisonous algae."

Given the size of the task, cutting a few mitten crabs from the menu is not such a big sacrifice.

Source:China Daily

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