Shanghai is keeping its flood control and drainage system on high alert in a bid to ensure the smooth operation of the long-awaited upcoming World Expo, the city's flood control headquarters said here on Wednesday.

A special center has been established with 24-hour standby emergency facilities to make sure the water in the Expo site can be drained within two hours after extreme rains without causing big accidents, according to Liu Xiaotao, an official with the headquarters.

The official also pledged that the water in the Expo site would be drained timely without affecting the traffic flow under moderate rain.

The expo, to be held from May 1 to Oct. 31, will experience the summer season that is usually plagued by typhoons and rainstorms in the city, Liu said.

More than 500 people in 40 emergency teams and 40 sets of drainage facilities have been prepared, capable of arriving in concerned sites within 30 to 60 minutes, according to Liu.

The six-month event is expected to attract 70 million visitors from home and abroad.