URUMQI, Dec. 19 (Xinhuanet)-- The number of the wells of a 2,000-year-old karez irrigation system, which is still in use in northwest China's Xinjiang Uygur Autonomous Region, has reduced from 1,784 to 614 during the past half century, according to local water resources department.

    "Declining groundwater levels mainly caused by the sharp rise of motor-pumped wells should be blamed for the ongoing disappearance of the ancient irrigation wells," said Wfuer, general secretary of the Xinjiang Karez Research Association.

    Since the 1950's, 1170 karezs have dried up with annual water provision amount decreased by 381,4 million cubic meters. As a result, some 190.5 thousand mu (12.7 thousand hectares) cannot getirrigation from the ancient water system, said Wfuer.

    Seeing 23 karezs disappear every year, the great irrigation work invented by the ancient local people will die out in 20 to 25years without effective protection, said Wfuer.

    Wfuer called for policies to be issued by the local government for the effective protection of the irrigation system boasting a long history.

    The history of the karez, mainly used in the Hami and Turpan areas in Xinjiang, where it is hot and dry, dates back to the Han Dynasty (206 B.C. - 220 A.D.). It is considered one of the three great projects in ancient China, along with the Great Wall and theBeijing-Hangzhou Grand Canal.

    As an irrigation system using underground water, the karez consists of four parts: a hole as deep as 50 to 60 meters, an underground canal, a above-ground canal and a small reservoir. They have many advantages, such as little evaporation from season to season and little percolation. A karez can provide a stable water supply that does not consume energy or cause pollution.

    Wandering underground over 5,000 kilometers, the karez has alsobe called "the underground Great Wall." Enditem