The Three Gorges Reservoir on the Yangtze River might be taken as an additional source for the mammoth South-North Water Diversion Project, due to a declining water reserve in the original one, according to some deputies attending the ongoing annual session of the Chinese legislature.

"It is an imperative need to channel in water from the Three Gorges Reservoir, but the plan is being examined for approval," said Yu Xuexin, a deputy to the Tenth National People's Congress (NPC) that is in a ten-day annual session in Beijing.

According to the original plan for the unprecedented water diversion project, 9.5 billion cubic meters of water will be diverted from the Danjiangkou Reservoir in Hubei Province through the central route to the arid northern part of China between 2002 and 2010.

However, the rainfall on the upper reaches of the reservoir decreased at an average annual speed of 15 percent in the past few years, said Yu, also director of the Beijing Municipal Development and Reform Commission.

The Three Gorges Reservoir will ensure the water supply to the central route for a long term, and it is a better choice than some other suggestions, said Lei Hengshun, an environment professor with Chongqing University.

Upon completion of the entire Three Gorges Project in 2009, the reservoir, with a storage capacity of 39.3 billion cubic meters of water and annual inpouring runoff of 451 billion cubic meters of water, will provide sufficient freshwater as a backup for the South-North Water Diversion Project, said Wu Gang, an NPC deputy and also the vice director of the Beijing Municipal Development and Reform Commission.

Administrative regulations should be enacted particularly to ensure security, environmental protection and water quality of the Three Gorges Project, the world's largest hydropower program with a designed annual generating capacity of 84.7 billion kWh of hydro-electric power, Wu said.

China's per capita fresh water is barely a quarter of the world average.

The south-north water diversion project was first imagined by former Chinese leader Mao Zedong in 1952. After protracted debates that lasted nearly a half century, the State Council sanctioned the ambitious project in December 2002.

It plans to divert 44.8 billion cubic meters of water annually from the Yangtze River, China's longest river, through eastern, middle and western routes to relieve water shortages in North China by 2050.

The construction of the project's eastern route began in December 2002 and is expected to supply water to Shandong Province by 2007. The central route began in December 2003 and is due to supply water to Henan and Hebei provinces, Beijing and Tianjin by 2010. The western route is scheduled to begin construction in 2010. The massive water diversion project will cost 500 billion yuan (61.65 billion US dollars).