Blue-green algae in Lake Tai (file photo)

A year after an outbreak of blue-green algae in Jiangsu Province's Lake Tai caused a drinking water crisis in the nearby city of Wuxi, the pollutant algae has returned even earlier than last year, threatening a new natural disaster, warned Lin Zexin, vice director of the Lake Tai Basin Administration, on Monday.

In past years blue-green algae would appear in Lake Tai in July or August but last year it was detected at the end of May.

This year the algae season has arrived even earlier. By the beginning of April, Lin's office had already detected blue-green algae spreading across large areas in the west and south of the lake.

He said the high density of nitrogen and phosphorus in the lake, favorable temperatures and slow moving currents had triggered the growth of the algae.

Lin said Lake Tai would almost certainly be hit by another massive outbreak of blue-green algae this year, adding that his office is closely monitoring the ecological condition of the lake.

In an attempt to defeat the algae, water from the Yangtze River has been diverted to Lake Tai in order to raise the water level and speed up currents. A total of 1.19 billion cubic-meters of water will be diverted to the lake this year.

A protracted battle

Lin said Lake Tai is suffering from eutrophication (an increase in chemical nutrients such as nitrogen and phosphorous), creating a perfect environment for the algae to flourish. He warned the ecological consequences may last another three to five years, or even longer, despite ongoing pollution control measures.

Faced with the impending algae outbreak, the authorities in Wuxi have made plans to guarantee the security of the city's water supply.

According to Lin, measures have been taken to prevent algae from entering drinking water intake pipes and standby sources of water have been made ready.

(China.org.cn by Zhang Tingting April 15, 2008)