The one below is a karez. Viewed from the air, the wellheads are connected in a line, which is very spectacular. It is one of the few projects in the world that has existed for more than 2000 years and is still performing its original function. Many people know about the karez in Xinjiang. It is said that there are more than 1,500 karez in total, with a total length of more than 5,000 kilometers. The engineering difficulty is no less than that of the Great Wall.
Qanat is a water conservancy project in arid areas. It diverts melted water from snow mountains and groundwater to areas where humans cultivate and live. However, it is not only found in Xinjiang. It is believed that the oldest karez is in Iran and has a history of 3,000 years.
These wells we see on the surface are called vertical wells, and their main function is to facilitate the digging of underground culverts, which are the channels for karez to divert water.
When the ancients felt that their area needed more water sources, they would start digging karez. The rich usually hired people to construct a karez. It might take more than ten years to dig a karez. The project was huge and the cost was huge. Therefore, in ancient times, karez was charged, usually based on the head of water used.
When digging, workers determine the direction of the snowy mountain, first dig a shaft, then enter the shaft to dig an underground ditch, and the excavated soil is transported out through the shaft.
Dig all the way toward the snow-capped mountains until you find the melted water that seeps into the ground from the snow-capped mountains. This melted water will flow along the culverts to areas where people live and be used for crop irrigation and daily life.
Because water flows underground and is not easily evaporated, the longest karez is hundreds of kilometers long and can still effectively divert water.
Many people believe that Turpan grapes are the sweetest grapes in the world, but few people know that without irrigation systems like qanat, there would be no Turpan grapes.
However, with the mechanized development of groundwater, karez is gradually withdrawing from the stage of history. The latest karez was dug in 1968, and no one has done this kind of project since then.
It is believed that there are currently less than 200 karez wells with water in Xinjiang, and the annual water flow is about 114 million cubic meters.