Algae spread over 40 sq km floats on Chaohu Lake, Anhui Province, yesterday but officials ruled out a serious outbreak.

A serious outbreak of algae in Anhui's Chaohu Lake is unlikely mainly due to imminent rains which dilute the concentration of the fast-spreading, foul-smelling plant, a senior environmental official said yesterday.

The threat to drinking water has greatly decreased as the current bed of algae "is moving away from the drinking water source," said Zhao Yingmin, head of science, technology and standards department affiliated to the State Environmental Protection Administration.

The forecast up to Friday is for regular showers.

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Cool weather on Monday and yesterday also helped constrain the growth of algae, Zhao told China Daily after inspecting the country's fifth largest fresh-water lake. The outlook for the week is an average temperature of 21 C.

According to Zhang Zhiyuan, spokesman for the Anhui provincial environmental protection bureau, an outbreak of the blue-green algae occurs only when the weather is warm and sunny.

A recent serious algae outbreak polluted Taihu Lake in East China and affected drinking water supply to about 2 million people in Wuxi, Jiangsu Province.

The satellite monitoring system yesterday showed patches of algae spread over 40 sq km floating on the 820-sq-km Chaohu Lake, a source of drinking water to some 260,000 people.

Zhang Bangguo, chief engineer of the Chaohu environmental protection bureau, however, warned that the possibility of an outbreak could not be completely ruled out.

The provincial environmental watchdog issued an emergency notice last Monday, warning of a possible threat of algae and ordering close monitoring every hour.

All enterprises around the lake are under strict surveillance to ensure that they do not discharge pollutants.

Algae appears on the lake each year but usually disappears with wind and rain. The most serious outbreak was in 2004.

(China Daily 06/13/2007 page1)