The water quality of the Huaihe River has returned to normal after a polluted water zone moved away from the Hongze Lake along the lower reaches of the river in east China's Jiangsu Province yesterday.

Earlier this week, unexpected rain storms hit the upper reaches of the river in central China and forced various reservoirs to discharge simultaneously.

As a result, the accumulated foul water created a dirty water zone that contaminated the river and rapidly moved downstream.

Zheng Jianming, an official with Huaihe's monitoring centre, told China Daily the foul water was expected to reach the Yangtze River yesterday but was unlikely to affect nearby residents.

"Thanks to the Yangtze's enormous water volume - more than a dozen times that of the Huaihe's, the dirty water will be greatly diluted," Zheng said.

Pan Yue, deputy director with the State Environmental Protection Administration, urged local governments to clear the pollutants along the river regularly in future.

Huaihe, the country's third largest river, supplies water for some 165 million people in Henan, Hubei, Anhui and Jiangsu provinces in central and east China.

According to Pan, there are about 5,700 reservoirs along the river valley, most of which usually store water to alleviate unforeseen drought. But this summer, the river saw continuous heavy rains in its northern valley and main tributaries.

As it turned out, thousands of reservoirs discharged flood water at the same time, leading to massive pollutants gushing into Huaihe's main course and creating a 30-kilometre belt of contaminated water.

Local media reported the water quality quickly deteriorated as the foul liquid arrived.

In the city of Xuyi, in east China's Jiangsu Province, chemicals in the river once largely surpassed the standard, killing a small amount of living things in the water.

Residents in Bengbu, east China's Anhui Province, could not take drinking water from Huaihe for a few days owing to pollution.

Experts said the problem could have been avoided with more accurate weather forecasts and water treatment plants along the river could play a role.

The river was badly polluted in 1994 when pollutants gushed into its main course as a result of heavy rainfall after a long drought.

A 70-kilometre pollution zone jeopardized the safety of drinking water in some cities.

Then the country started the Huaihe cleaning action and invested almost 20 billion yuan (US$2.4 billion).

As the continuous rainfall hit the river valleys this year, the accumulated foul water - mainly from industrial waste in the cities - created another lengthy pollution zone.

Zheng said a lack of accurate weather forecasts, meant the reservoirs could not plan to prevent the problem.

And effective water pollution treatment could have prevented pollution entering into the river, he said.

The official also said the government should adopt a reasonable project to separate drinkable and polluted water .

(China Daily July 26, 2004)