Karez well system is a kind of underground water works invented and built by laboring people of various ethnic groups in our country to adapt to the natural environment in dry region. It is the crystallization of ancient people's diligence and intelligence. In Xinjiang, Karez Wells are mainly in Hami, Turpan and Mori, but most used in Turpan Basin, where there are altogether 1100-odd Karez wells and have the total length of over 5000 km. Some people hold the view that Karez Wells of Xinjiang added Guilin Ling Canal and Dujiangyan Irrigation Project are ancient major irrigation projects; On the other hand, Karez Wells of Xinjiang, the Great Wall and Canal constitute three Ancient Chinese Works. It is called "the underground Great Wall".

Karez well systems are the life source of Turpan. In a sense, without the karez, there would be no Turpan culture. According to records, the history of the karez in Xinjiang dates back to 103B.C. Karezes have been found in Iran, the Sahara, etc., but the ones in Turpan are the most complete. Currently there are still over 400 systems.

Karez well systems are very delicate irrigation systems made up of vertical wells, underground canals, above-ground canals and small reservoirs. Generally, a karez is 3 km (1.9 miles) with the longest being 20 to 30 km (12-19 miles) with several dozen vertical wells. Sometimes the number of vertical wells exceeds 300. Until today, the shortest karez found is only 30 meters (98 feet) long. The vertical wells are for ventilation, digging and maintenance of the karez. The bottoms of all the vertical wells are connected so that water can pass through. The underground canal is about 2 meters (6.5 feet) high and covered with earth to resist the heat. The surface canals, connected to the underground ones, are not more than 1 meter (3.2 feet) wide with trees planted on both sides to prevent evaporation.

Melting snow from the Tianshan Mountain is the water source of the karez. Water is collected by vertical wells and conducted by the underground canals to the oasis, where the water is held in the ground canals for irrigation. The vertical wells near the water source may be 100 meters (328 feet) deep while further downstream they are less than 10 meters (32.8 feet) deep.

A karez reduces evaporation, avoids getting polluted and needs no other power equipment; it runs from high to low ground owing to gravity alone. Turban is the hottest place in China and the arid climate makes water all the more precious. A karez system helps to ideally solve this problem.

Karez systems also functions as the natural air conditioner for the locals because they can sit in one while chatting or doing some chores. When exhausted during the scorching weather, sit in a karez, pick some grapes as they hang over the vertical wells and savour their taste, you will be thoroughly refreshed! Earth in Turpan Basin is solid and good for building well and underground canal.

In Turpan it is very dry and hot in summer, and land here has a high evaporation rate. In wind season, the strong wind here can blow sands into every corner here. After wind, a lot of farmland and water canals are buried by sands. But Karez Wells can supply waters through underground channels and is independent of the effect of season and wind and sand. In addition, Karez Wells have a very low evaporation rate and a stable supply of water, and can irrigate farmland all the year round. The word "Karez" means well.

China tours inclusive of visiting Karez Well, Turpan