Song Siyuan picked up the flashlight and shined the water marks on it, and said: "Judging from the water marks on the well wall, this well must have been dry for more than a hundred years. The strangest thing is that there seems to be an culvert at the bottom of the well. I don't know if it is the owner of the well." Some kind of secret passage darkroom built."
Keli stretched his head and looked down the well. After careful observation, his expression gradually softened: "It's not a secret tunnel. This is a karez unique to the people in the border area. In ancient times, it was also called a well canal."
What is a karez?
Karez is a well technology developed by people in the Western Regions according to local conditions. There is no shortage of groundwater in Han Dynasty. As long as the well is drilled tens of meters down, clear well water will always appear. As long as the well here is drilled deep, it will be fine. Water is guaranteed.
Such well-drilling rules are indeed feasible in places with abundant underground river water. If it is the northwest region or even the Western Regions, it is completely unfeasible.
This has to do with climate change in the Great Northwest!
During the Sui and Tang Dynasties, the northwest plateau was not as barren and desolate as it is now. It was a world of dense vegetation and abundant water and grass. The Huns and Turks who went south mostly grazed on the plateau. It can be seen that the northwest region had a humid climate and rich vegetation at that time.
In the Tang and Song Dynasties, the rainfall belt gradually shifted, and the northwest gradually became short of water and rain. After the land became dry, the vegetation gradually became scarce, which intensified the scarcity of tree resources. When the felling of trees became more serious in later generations, the destruction of vegetation was inevitable. block.
Drought, lack of rain, and vegetation destruction will inevitably intensify water and soil erosion in the northwest. Thousands of years of water and soil erosion will eventually turn the northwest plateau into the desolate land it is today.
Whether it is the Western Region or the Northwest, soil erosion caused by drastic climate changes and sparse vegetation has always been a threat to the people. This threat is concentrated in the scarcity of water.
People in these areas have to use various methods to preserve fresh water to cope with long-term drought.
For example, people in the northwest wilderness like to build water cellars to store water. Whenever it rains, they will open the water cellar and use natural rainwater to store all the fresh water in the water cellar until the water cellar is completely filled. Seal the water cellar.
These precious water resources will eventually be stored in water cellars to cope with the ensuing drought. At that time, after the impurities are removed, the fresh water can be used as clean water for drinking.
This is also the case in the Northwest. Faced with the increasingly arid desert, the people of the Western Regions have certainly developed their own way of preserving fresh water - karez.
This kind of karez does not use the groundwater of underground rivers, but the melted snow mountain water in mountainous areas in spring and summer, rainy season rain and oasis river water. These water resources will continue to seep into the ground and be led to the surface through the unique structure of the karez to be used for nearby People irrigate their fields, drink and cook, or wash and clean their faces.
This type of water well is different from Han Chinese wells. Han Chinese wells are long and vertical wells built on the ground. They are often separate wells. A complete karez is rarely a separate well, including at least a vertical shaft (draught) and an underground channel (underground water inlet). There are four main components: open channels (ground ditches) and cross-channels (distributed reservoirs).
The well in front of them is actually one of the shafts of the Karez. As for the ditches and arches seen at the bottom of the well, it is the underground culvert of the Karez. Most of these shafts are evenly distributed in the city. This is why they The reason why mounds appear regularly is that under each mound is an underground shaft of a karez.
No matter where these shafts are dug, they can be connected by underground culverts extending in all directions to form an underground water supply network. If you follow the underground culverts all the way out of the city, you will definitely reach the foot of a certain mountain, or near some Oasis river channel.
"In addition, there will be small reservoirs in the city to receive daily rainwater. This rainwater will eventually seep into the karez and become part of the water source."
After Keli explained, Song Siyuan looked at the wells and said, "Does this prove that these cities were built after the climate change in the northwest?"
During the Sui and Tang Dynasties, the northwest region, including the Western Regions, had a mild and rainy climate, so there should be no need for karez. Since this kind of installation was created to save water, it must be that the surrounding environment has begun to lack water.
Her guess was obviously correct. Keli nodded to her: "The rise and fall of groundwater will affect water use. The water shortage in the northwest does not appear suddenly, but gradually over a long period of time. This is like drying up." Just like the lost Milanze, it continued to lose water in every period, and eventually the water completely dried up. Judging from the water marks on the blue bricks we saw, this town was also gradually lacking water and was abandoned.
"The place where the karez appeared had at least a dry and dry climate, and even water was a problem. So it can be inferred that this city was built in the late Tang and Song Dynasties. Later, the climate change intensified, and the groundwater here gradually dried up. The only karez could not provide water to the people in the city, so they had to move away one after another, eventually abandoning the city and migrating to other places more suitable for survival."
"Let's walk towards the center of the ancient city. We'll probably find a nullah on the ground."
After understanding the situation, Song Siyuan put the manhole cover on and followed them to the center of the ancient city to continue observing the situation. After walking for about half a mile, the karez they saw kept appearing, and finally led them to the center of the city and discovered the open channel of the karez. .
From the end of the Tang and Song Dynasties to the present day, no matter how short the time is, it is nearly a thousand years. The shape of this open channel has been completely lost. The yellow sand and loess that can be seen everywhere completely submerged the bottom of the open channel, forming a half-meter-thick loess pile. The bank of the pond was also submerged by yellow sand, forming a curved outline. The arch hole originally used for water in and out was buried under the yellow sand, leaving only a hole as big as a head.
Song Siyuan wanted to go down to check the situation. 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 after thousands of years. Why is this tower building still intact?"
Such words made everyone start to pay attention to the abandoned pagoda in front of them.
This pagoda-style building is different from ordinary Chinese-style pagodas, which are mostly wooden structures. At the same time, pedestrians can move around inside the pagoda, and even carve Buddha statues and paint murals.
The pagoda in front of you is closer to the "Buddha" when Buddhist culture was not Chineseized. The overall shape is very similar to the white lama pagoda in Tibet. It consists of the spire, the body, the feet and the base of the pagoda. It is about five meters high. The base is slightly wider, in the shape of a square rectangle, and suddenly changes into a slightly flattened oval at the foot of the tower.
Above the base of the elliptical tower is a cylindrical tower body shaped like a pointed cone. When it reaches the top of the tower, it suddenly tightens, like a pointed bamboo shoot rising from the ground. The entire tower body is covered with yellow sand. These The sand has buried most of the base and feet of the tower, leaving only the tower body that can rely on its absolute height to break through the yellow sand and reveal itself to the public.
