A storage pond located at the end of the horizontal channel is used for keeping water at night and may also be used as a means for measuring and dividing water among different users. The vertical shafts are located approximately 10 to 20 m apart in the lower reaches and 30 to 70 m apart in the upper reaches for ventilation and maintenance. The size of the tunnels is between 0.5 to 0.8 m wide and 1.2 to 1.8 m high. The length of the horizontal underground tunnels varies greatly, from 3 km up to 50 km. Melted water from glaciers and snowmelts from the northern and western Tian Shan Mountains are their major water source. Karezes in Turpan and Hami are made up of vertical shafts, underground tunnels, and above-ground canals and storage ponds. Karez systems located in Turpan and Hami, Xinjiang Region. Indeed, karezes have been disappearing at a shocking rate of 20 to 30 per year. Unfortunately, only 614 of these karezes were still flowing. Among them, over 97 percent were located in the Turpan and Hami prefectures (Figure 1). In 2003, there were over 1,784 karezes with 5,272 km of underground channels in Xinjiang. The karez system is an important part of the ecosystem as well, as karezes provide water for native vegetation and play an important role for the survival of wildlife by providing habitats through underground tunnels, shafts, and pools. A household’s proximity to the system was a good indicator of the social or economic status of its residents. Essentially, people’s importance and value were judged according to their water ownership rights in the system. In the past, the social arrangements in karez-based communities were directly related to the karez system. Religious beliefs and cultural traditions also helped the karez system to be handed down as a legacy. Karezes have created strong cohesion in their communities owing to the traditions and beliefs attached to them. In most cases, the karez system is not only a structure to extract groundwater, but is also an integration of the history, culture, and unique knowledge of its builders. The karez system has been used to provide water for both domestic purposes and agricultural irrigation because it possesses the following advantages: it is gravity-fed, so it avoids energy requirements its underground transmission reduces evaporation and its underground coverage protects against sediment from wind storms in the desert and assures good water quality. Karezes depend on factors such as climate, topography, hydrology, geology, and nearby agricultural activity. Works have been planned and implemented to revitalize some karezes for use and to preserve some for cultural purposes. In recent years, the United Nations and national governments have raised concerns about and recognized the importance of karez systems. However, karez systems have faced great challenges over the past several decades, including drying up, abandonment, damage, and pollution as a result of over-exploitation of groundwater through deep wells, the construction of reservoirs upstream, the development of oil fields, and other human and natural activities. Because the karez system has provided a safe and reliable water supply over the centuries, the communities that rely on it have referred to it as the “mother river” and “spring of life.” This is particularly true in the Turpan and Hami prefectures in Xinjiang, where most of the region’s karez systems are located.

In China it was recognized as one of three major ancient engineering projects, along with the Great Wall and the Beijing-Hangzhou Grand Canal. The karez is an impressive hydraulic engineering project as well as a cultural achievement. These water systems have also been used in countries in North Africa and West Asia, as well as other Asian countries, including Afghanistan, Iran, and Pakistan.

The water harvesting and underground transmission system called a karez in the Uygur language, or kan er jing in Mandarin, has provided sustainable water supplies in some communities of the Xinjiang Uygur Autonomous Region (Xinjiang), China for over 2,000 years. This essay is part of the Middle East-Asia Project (MAP) series on “Harvesting Water and Harnessing Cooperation: Qanat Systems in the Middle East and Asia.” See Essays and Resources …

Er jing mei