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Karez System
Karez System
The Karez System in the Turpan is an irrigation system of wells connected by channels. At its peak, the karez system exceeded 5,000 kilometers (3,106 miles) and was also referred to as "the underground Great Wall." It is among the three ancient major irrigation projects with the other two being Ling Canal and Dujiangyan Irrigation System. Karez system is the crystallization of ancient people's diligence and intelligence.
Karez system is the life source of Turpan. In a sense, without the karez, there would be no Turpan culture. Kareze system has been found in Iran, the Sahara, etc., but the ones in Turpan are the most complete. Currently there are still over 400 systems with the longest is 20 to 30 kilometers while the shortest is only 30 meters.
History of the Karez System
Karez System
According to records, the history of the karez in Xinjiang dates back to 103 B.C.. Originally ancient towns used to depend on the streams and rivers nearby into which glaciers in far-off mountains used to feed. As the time passed the glaciers gradually shrank over the centuries, the streams they fed likewise diminished, resulting in less water flowing downwards.
Then people ingeniously created the Karez system to draw the underground water to irrigate the farmland. Wells begin at the base of the mountains along the contours of the hillside. To keep the underground channels unclogged, two men and a draught animal work as a team - one man is lowered down to clear the tunnel and buckets of mud are hoisted to the surface by the animal. The tunnels slope less than the contours of the geographical depression, so that the water reaches close to ground level. The water in Karez will not evaporate in large quantities.
Features of the Karez System
Karez system is a very delicate irrigation system made up of vertical wells, underground canals, above-ground canals and small reservoirs. Generally, a karez is 3 kilometers (1.9 miles) with the longest being 20 to 30 kilometers (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: 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: The underground canal is about 2 meters (6.5 feet) high and covered with earth to resist the heat.
The above-ground canals: The above-ground 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.
