Large-scale algae outbreaks are once again posing a threat to
the drinking water supplies from Taihu and Chaohu lakes.
As the temperature has continued to rise over the past three
days, the blue-green algae has gathered at the western end of
Taihui Lake, which sits on the border of east China's Jiangsu and
Zhejiang provinces, just 11 km from Gonghu water plant, the main
water source for Wuxi, Jiangsu.
And as the mercury climbs above 30 C, the thick blanket of
foul-smelling algae in the 2,400-sq-km freshwater lake - the
country's third largest - will expand rapidly, experts from the
Wuxi agriculture and forestry bureau said.
Winds from the east have been pushing the algae toward the
western part of the lake since Monday.
Zhang Xianzhong, an official with the bureau, said between 1,000
and 2,000 people have been involved each day, trying to clear the
algae from the water.
"We have been pulling out more than 1,000 tons of algae from the
lake every day, first using baskets and then pumps," Zhang
said.
Now, special boats fitted with advanced filtration technology
are being used to clear away the unwanted plant.
More than 100 such boats will be mobilized over the coming
months, Zhang said.
About 300 km to the west of Taihu, Chaohu Lake in nearby Anhui
Province is also under threat of an algae outbreak.
The local environmental protection bureau said dozens of 4- and
5-sq-km "belts" of algae had been seen floating on the 780-sq-km
freshwater lake, the country's fifth largest.
The western part of Chaohu is said to be most at risk, and a tap
water factory 3 km from its western bank stopped using it as a
water source earlier this week.
"Once the conditions for algae growth are ripe, it is very
difficult to effectively control it in the short term," Zhang
Zhiyuan, an engineer with the Anhui environment protection bureau,
said.
"If the situation gets worse, we will divert water from the
Yangtze River to dilute the concentration of algae to prevent a
large-scale outbreak," Zhang said.
As the quality of its water has been steadily degraded, Chaohu
Lake has experienced small- and medium-size algae outbreaks each
June and July over recent years, an expert has said.
Professor Lu Jianjian, a marine expert from East China Normal
University in Shanghai, said: "Excessive nutrients, including
nitrogen and phosphate from fertilizers, industrial runoff and
untreated sewage, combined with the hot weather, provide good
growing conditions for the algae.
"More effort should be made to stop factories discharging
wastewater directly into the lakes," Lu was quoted as saying by
People's Daily.
In May, algae contaminated Taihu Lake leaving some 2 million
Wuxi residents without tap water for more than a week.
(China Daily June 22, 2007)
