Huge algae outbreaks again pose a threat to drinking water
supply from Taihu and Chaohu, two of China's major freshwater
lakes.
Satellite pictures showed blue-green algae covering about a
third of both lakes in the country's densely populated east,
according to the National Satellite Meteorological Center.
In the 2,400-sq-km Taihu Lake, the country's third largest
freshwater lake on the border of Jiangsu and Zhejiang provinces,
about 800 sq km is covered with the fast-growing and foul-smelling
green plant.
A large outbreak a few weeks ago contaminated the lake and
resulted in the shutdown of tap water to about 2 million residents
in Wuxi, Jiangsu Province.
But the latest outbreak has not affected drinking water safety
because the algae is found far from the water intake points, said
Li Jianqiu, a spokesman with Wuxi utilities bureau.
The nearby city of Changzhou, which uses the Yangtze River as
its water source, has also not been affected, said a government
spokesperson.
In the 780-sq-km Chaohu Lake in Anhui, China's fifth largest
freshwater lake, 280 sq km is carpeted by algae.
Last week, the satellite monitoring system showed that patches
of algae had spread over 40 sq km in the lake, a source of drinking
water for some 260,000 people.
Zhang Zhiyuan, a spokesman for the Anhui provincial
environmental protection bureau, said the situation was being
closely watched.
He said the water from the Yangtze River will be diverted to the
lake to improve water quality.
Zhang Bangguo, an expert with the Chaohu bureau of environmental
protection, said excessive nutrients in the lake, including
nitrogen and phosphate from fertilizers, industrial runoff and
untreated sewage, as well as high temperatures, have provided good
conditions for the algae bloom.
"A large algae bloom can break out any time given suitable
sunlight and temperature," Zhang said.
"Once the conditions for algae growth are ripe, it's very
difficult to effectively control it in the short term," Li Yucheng,
a professor at Anhui University's School of Life Sciences, was
quoted as saying yesterday by the Workers' Daily.
"Relief measures can only reduce the harm from an outbreak to a
minimum but cannot solve the problem totally."
(China Daily June 18, 2007)
