The karez system, an irrigation system connected by underground channels, is considered as one of the three great ancient projects in China. The other two being the Great Wall and the Grand Canal . There are nearly one thousand karez totaling five thousand kilometers in length in Turpan.
The structure of the karez basically consists of wells, underground channels, ground canal and small reservoirs. In spring and summer, a great amount of melting snow and rainfall flow down from the Bogda and Karawuquntag mountains north and west of the Turpan depression into the valleys and then seep into the Gobi desert. Taking advantage of the mountain slopes, the working people ingeniously created the karez to draw the underground water to irrigate the farmland. The water in the karez will not evaporate in large quantities even under the scorching heat and fierce wind, hence ensuring a stable water flow and gravity irrigation.
坎儿井 - karez