The Karez System, an irrigation system of wells 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 in the Turpan area nearly one thousand karez totaling 5000 kilometers in length.The structure of the karez basically consists of wells, underground channels, ground canals and small reservoirs. In spring and summer,
a great mount 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
karez will not evaporate in large quantities even under the scorching heat and fierce wind, hence ensuring a stable water flow and gravity irrigation.As far back as the Han dynasty, the karez was recorded in Shi Ji (The Historical Records) and then called "Well- Canals". Most of the existing karezes in the Turpan area were built in the Qing dynasty and in after years. Nowadays, large stretches of fertile land are still irrigated by karezes. The Wudaolin karez and the karez in the Wuxing town are open to visitors. Actually,the Karez is not really a well it is actually a man made underground river that provide tha water for the oasis.As you know Turpan is the second lowest place in the world right next to dead sea in Jordan. so the water always gos down to the lower area. As Turpan is hottest and driest area in China even in the world. To prevent from evaporation,local people invented it to fight agaist the drought.Surprisingly the water can be use as mineral water for people to drink it because the snow covered glacier thawing water seep into the desert and passed through under ground for nearly 60 kilometers and that is why the water here contains so many important elements from the fretiles earth to nourish our body.If you have arrive Turpan do not forget to taste free minaral water from Karez.