Xiaowan hydro station, a keystone power generation project in southwest China's Yunnan Province, became operational Friday, according to a statement from the China Huaneng Group.

Built on the Lancang River since 1999, the first generating unit of the power station is now pumping out 700,000 kilowatts of electricity an hour while five other units of the same capacity are under construction.

The overall investment in the power station is 40 billion yuan (US$5.86 billion). Its six generating units will have an annual capacity of 19 billion Kwh.

Another unit will be put into production by the end of 2009 and the remaining four will become operational in 2010.

The reservoir is designed to provide balance between rain and drought seasons, ensuring a stable output, the group said.

In addition to generating power, the station, whose reservoir will throughput a total of 14.9 billion cubic meters of water a year, will help improve flood control, irrigation and water transportation.

The group said the station's arch dam was the world's tallest and many technical obstacles were tackled during its construction in a quake-prone area but gave no further information.

(Xinhua News Agency September 27, 2009)