The project is designed to divert at least 50 billion cubic metres of water from the Yangtze River into North China through its middle, east and west routes.

The middle line will transfer water from the central section of the Yangtze in Sichuan or Hubei Province to North China via Henan Province.

For the east line, water from the Yangtze will be lifted up through the Grand Canal to the northern parts of Jiangsu, Anhui and Shandong provinces and then to the north of the Yellow River.

The west line will connect the Tongtian River, Dadu River and Yalong River, all tributaries of the Yangtze, to the Yellow River from upper streams in the Qinghai-Tibet Plateau.

The three lines all have their own difficulties and advantages.

On the west line, which experts only conducted an on-the-spot survey and did not make feasibility studies, the Yangtze and Yellow river area is separated by Mount Bayankala and the water must be lifted through a huge tunnel across the mountain to provide water to Northwest China's semi-arid areas.

Although the quality of water from the west line might be almost pure, its construction may be too difficult, involving technical problems still unsolved.

Water can easily flow to Tianjin along the east line after an estimated 18 billion cubic metres of water were lifted gradually via the Grand Canal from the Yangtze to the Huaihe and Yellow rivers. But water pollution remains a key threat in the area.

In the middle line, the project entails raising the current Danjiangkou Dam on the Hanjiang River in Hubei Province to 175 metres, then building a 1,240-kilometre-long channel crossing more than 360 various rivers to Beijing and Tianjin.

The biggest advantage of the line is the water's natural flow to the north and the high quality of water.

(China Daily)