Xinjiang renovates 2,000-year-old irrigation system

Cultural relics workers in northwest China's Xinjiang Uygur Autonomous Region have spent the past five years renovating an ancient subterranean irrigation system, according to a summary released by a local cultural relics bureau on Monday.

The karez irrigation system was built 2,000 years ago. The karez wells, which convey water from deep underground to the surface, are considered one of China's greatest surviving ancient man-made structures, along with the Great Wall and the Grand Canal.

Renovation started at the end of 2009 and, to date, four stages of renovations, covering 108 karez well systems with a total underground canal length of 18 km, have been carried out in the prefecture of Turpan, said Zhao Qiang, Party head with the cultural relics bureau of Turpan Prefecture.

More than 600 km of the underground canals were desilted and more than 10,000 vertical shafts have been repaired, Zhao said.

Total spending on the restoration has reached 45 million yuan ($7.26 million).

Preparation for the fifth stage, which involves renovation of 15 karez wells, is under way and will start this year.

Traversing more than 5,000 kilometers, the karez wells are known as the "Great Underground Wall."

The karez well systems are composed of vertical shafts, subterranean and ground canals, and small reservoirs. The canals are supplied with water from the melted ice and snow in Xinjiang's Tianshan Mountains.

Turpan, the hottest and driest region in China, has been using the system to avoid water evaporation at the ground surface. Currently, there are more than 1,000 karez wells in Turpan prefecture, most of which have dried up because of groundwater recession and damage to the wells.

Karez wells are also found in nearby countries, including Afghanistan, Iran and Pakistan. In China, they can also be found in the provinces of Gansu, Shaanxi and Shanxi.