Photo taken on July 28, 2010 shows the sluice of Dujiatai flood diversion project in Xiantao, central China's Hubei Province.  The Dujiatai flood diversion project was prepared to divert flood in an attempt to release the flood pressure for the lower reaches of Han River including Wuhan, capital city of Hubei province. [Xinhua]

Workers are on standby Wednesday to open flood gates on the swollen Han River, the largest branch of the Yangtze River in central China's Hubei Province, to prevent the flooding of provincial capital Wuhan.

About 5,000 residents near an emergency reservoir in Xiantao City, near Wuhan, were evacuated overnight.

A flood peak is expected to arrive at Xiantao Thursday afternoon and raise the Han River's water level to 35.9 meters -- over the danger level of a nearby dike that guards Hanchuan City and one step closer to Wuhan.

Wuhan is a megacity with a population of about 9.1 million.