Abstract: There is no definable recorde about the origin of Karez in ancient chinese articles. Basing on the field work and the historical recordesu The author believed that the construction of karez in Xinjiang derives from the construction of “Well Channel” in the centre of china in West Han dynasty. The＂Beidihou well” recorded in HTSTORY OF HAN DYN-ASTY is the primitive form of karez contruction in the area of Dunhuang, Gansu province. Along with the strength of Han nationality connected with Western Area, the construction of “Well Channel” conducts westforward gradually. The real Karez was constructed by native people using the construction method of “well channel” acorrding to the local hydrological condition.
Karezes distribute mainly in the area of Turpan and Hami. Xinjiang. Karezes had been the main water for irrigation before 1950, the number and the water volume of Karezes increased standingly. Because of the advocating of the rule of “It is useful to whom to build it” in 1957, orginal balance was disasted, meanwill the number of powerful machine wells increased quickly, which made the number and the water volume of karezes decreased obviously, many Karezes dried and discarded. today the ancient water project has faced a serious problem because of its weakness and unjust administration and the allocation disorder of the powerful machine well, etc.
To overcome the weakness of Karez, the main problems are how to enlarge the amount of water and to prevent it from blocking and collapsing. The solutions to the problems are：expending the space about 300-500 meters to left and right on the head of the karez along the underground water vertical line in order to enlarge the area of taking underground water；digging several artesian wells at the lenght to lead the deep pressure water into the karez, concreting the channel and placing pipes, etc.