Song Siyuan picked up the flashlight and shone the water marks and said: "Judging from the water marks on the wall of the well, this well has definitely been dry for more than a hundred years, and the strangest thing is that there seems to be a culvert under the bottom of the well. ”

Keli stretched out his head and looked at the well, carefully observing the color behind him gradually softening: "It's not a secret passage, this is a unique karez for the people of the territory, and it was also called a well canal in ancient times." ”

What is a qanats?

Karez well, is a kind of Western Regions territory people according to local conditions to develop the well canal technology, Han is not short of groundwater, as long as the well down dozens of meters, there can always appear clear well water, as long as the well here is guaranteed to be deep, can ensure that there is water.

Such a rule for drilling wells is indeed feasible in places with abundant underground river water, but it is completely unfeasible in the northwest region or even in the western regions.

This has to do with climate change in the Great Northwest!

During the Sui and Tang dynasties, the Northwest Plateau was not at all barren and desolate as it is now, it was a world with dense vegetation and abundant water and grass, and the Huns and Turks who went south mostly graze on the plateau, which shows that the climate in the Northwest at that time was humid and the vegetation was rich.

In the Tang and Song dynasties, the rainfall belt gradually shifted, the northwest gradually lacked water and rain, and after the land was drought, the vegetation gradually became scarce, which aggravated the scarcity of tree resources, and when the felling of trees in later generations became more and more serious, the destruction of vegetation was unstoppable.

The occurrence of drought and lack of rainfall and destruction of vegetation will inevitably exacerbate soil erosion in the northwest region, and the soil erosion of thousands of years will eventually promote the northwest plateau to become the current desolate land.

Whether it is in the Western Regions or the Northwest, soil erosion caused by drastic climate change and sparse vegetation has always been a threat to the people, and this threat is concentrated in the scarcity of water.

People in these areas have had to use various ways to conserve fresh water to cope with the prolonged drought.

For example, the people of the Northwest Wilderness like to build water cellars to store water, and whenever it rains, they will open the water cellars and use natural rainwater to store all the fresh water in the water cellars until the water cellars are completely filled.

Eventually, these precious water resources will be stored in cellars to cope with the ensuing drought, when the fresh water will be used as clean drinking water after precipitation to remove impurities.

This is still the case in the Great Northwest Regions, where the people of the Western Regions, faced with increasingly arid deserts, have of course developed their way of preserving fresh water - qanats.

Instead of using groundwater from underground rivers, this kind of qanats use meltwater from snow-capped mountains that melt in the mountains in spring and summer, rainwater from the rainy season, and water from oasis rivers, which will continue to seep into the ground and be drawn out of the surface through the unique structure of the qanats, where they can be used by nearby people to irrigate farmland, drink, cook, or wash their faces.

This kind of well is different from the Handi well, which is built on the ground with long and vertical wells, often into a single well, and a complete qanat is rarely a separate well, including at least four main components: a vertical shaft (draft), a culvert (underground water intake), an open channel (a surface ditch) and a staggered canal (a decentralized reservoir).

The well in front of them is actually one of the shafts of the qanats, and as for the ditches and arches seen at the bottom of the wells, they are the underground culverts of the qanats, and most of the shafts like this are evenly distributed in the city, which is also the reason why their mounds appear regularly - under each mound, there is an underground shaft of the qanats.

Wherever these shafts are dug, they are connected by underground culverts that extend in all directions to form an underground water supply network, and if you follow the underground culverts all the way out of the city, you will inevitably come to the foot of a mountain or near some oasis river.

"In addition to this, there will be small cisterns in the city to receive the usual rainwater, which will eventually seep into the qanats and become part of the water source."

After Keli explained, Song Siyuan looked at these wells and said, "Then does this prove that the construction of these cities was after the climate change in the northwest?" ”

In the Sui and Tang dynasties, the climate in the northwest region, including the Western Regions, was mild and rainy, and there should be no need for qanats.

Her guess was obviously right, and Keli nodded at her: "The rise and fall of groundwater will affect the use of water, and the shortage of water in the northwest region is not sudden, but gradually lacks water for a long time, just like the dry up of Mirandze, which is constantly losing water in every period, and eventually the water volume seems to be completely dried up, judging from the blue brick water marks we see, this town is also abandoned in the gradual lack of water."

"The place where the qanats appeared, at least it was already a dry and rainless climate, and even the draft became a problem, so it can probably be inferred that this city was built at the end of the Tang and Song dynasties, and later, the climate changes intensified, and the groundwater here gradually dried up, and the only qanats could not provide water for the people in the city, so they had to move away one after another, and finally abandoned the city and migrated to other places more suitable for survival."

"Let's go to the center of the old city, and we will probably find the nullah above ground."

After understanding the situation, Song Siyuan covered the manhole cover, followed them to the center of the ancient city to continue to observe the situation, and walked for about half a mile, and the qanats they saw kept appearing, and finally led them to the center of the city and found the nullah of the qanats.

From the end of the Tang and Song dynasties to the present, no matter how short the time is, it has been nearly a thousand years, this nullah has been completely out of shape, the yellow sand and loess that can be seen everywhere completely submerge the bottom of the nullah, forming a loess mound half a meter thick, even the regular pond bank is also submerged by the yellow sand, forming a curved outline, the arch hole originally used for entering and exiting the water is buried in the yellow sand, leaving only a hole gap with a large head.

Song Siyuan wanted to go down to check the situation, but the moment she looked up, she caught a glimpse of the tower building next to the nullah, and her eyes lit up: "These buildings have been corroded into ruins for thousands of years, why is this tower building still intact?" ”

Such a sentence made everyone begin to pay attention to the abandoned pagoda in front of them.

This pagoda-style building is different from ordinary Han-style pagodas, which are mostly wooden and can be used by pedestrians to walk around, and even to carve Buddha statues and paint murals.

The stupa in front of you is closer to the "floating tu" when the Buddhist culture is not sinicized, the overall shape is very similar to the white pagoda of the lama in Tibet, it is composed of the spire, the body of the tower, the foot of the tower, the base of the tower, about five meters high, the base of the tower is slightly wide, it is a square rectangular square, and the position at the foot of the tower suddenly turns into a slightly flattened oval.

On the foot of the elliptical tower, it is the cylindrical tower body that is shaped like a sharp cone, and the position of the spire is suddenly tightened, as if it is like a pointed bamboo shoot rising from the ground, the whole tower body is covered with yellow sand, these sand soil have buried most of the tower base and the tower foot, only the tower body can still rely on the absolute height, break through the yellow sand and reveal the front of people.