Recently, a piece of news about the unexpected discovery of an ancient river bed in the Han River has spread like wildfire, attracting many citizens, tourists and photography enthusiasts to visit and take pictures in the ancient river bed. Why does the magical and spectacular ancient river bed appear here? What is the relationship between it and the Han River that has been flowing for thousands of years? With these questions in mind, the reporter followed Du Jiankuo, a Ph.D. in science from the School of Humanities of Shaanxi University of Science and Technology, and Wu Jie, a Ph.D. in geology from the School of Humanities of Shaanxi University of Science and Technology, to conduct a field visit to the ancient river bed.
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On the afternoon of January 11, the reporter saw this ancient river bed about two kilometers east of the Hanjiang Bridge Gate. The ancient river bed is about 800 meters long from east to west and 200 meters wide from north to south. It runs parallel to the direction of water flow from east to west. The ravines are evenly distributed, and the deepest groove at the center of the river is up to 2 meters. The main body of the ancient river bed is yellow-brown, with a small amount of bluish-gray. It is spectacular from a distance.
This "wonderful scene" attracted many citizens and photography enthusiasts to visit. While everyone marveled at the miraculous workmanship of nature, they used mobile phones, cameras, small aerial photography equipment, etc. to record this magnificent scenery. "I saw this ancient river bed on Douyin. I found it very shocking and beautiful. I made a special trip to see it. Growing up by the Han River, I never knew there was such a river bed." Citizen Zhang Xinlan told reporters to his own amazement.
"I posted the video of the ancient river bed on WeChat Moments and Douyin on January 9th. Unexpectedly, it became popular immediately. Many friends left messages asking me for the specific location. I discovered this place when I came here recently. There are already a lot of tourists, and at the most, there are more than 200 people on the river beach," photographer Hanzhong Yemao told reporters.
How was the magical ancient river bed formed?
Ancient riverbed refers to the riverbed left after rivers were diverted or abandoned for other reasons during the geological historical period. They are mostly distributed in alluvial plains and floodplain areas. The sediment that makes up the ancient riverbed is relatively coarse and the groundwater is rich. It is closely related to production. The reporter saw that the ancient river bed was mainly composed of gravel mixed with small pebbles. The ravine was the deepest at the center of the river, and gradually became shallower from the center to both banks.
Dr. Du Jiankuo told reporters that it can be observed from satellite remote sensing images that the ancient river bed is located in the downstream area where the Lengshui River merges into the main stream of the Han River. The Lengshui River channel is narrow and the Han River channel is wide. After the Lengshui River merges into the Han River, the river flow rate gradually slows down. Under such circumstances, after the turbulent Lengshui River carried a large amount of sediment and merged into the Han River, the water flow slowed down and its sand-carrying capacity decreased. Therefore, a large amount of sediment was formed here. Over the years, an ancient river bed was formed. Most of the north bank of this ancient river bed is an abandoned channel that does not flow through the river. It also belongs to the floodplain area, so it can be called an ancient river bed.
Why is the river bed suddenly revealed? The reporter called the Shimen Reservoir Management Bureau of Hanzhong City. Li Pingwen, director of the Flood Control and Dispatch Office, checked and compared the flow from the reservoir to the Han River during the same period over the years. He said that in addition to the ancient river bed being exposed due to the drop in the water level of the Han River during the dry season, there was no difference between the flow of flood peaks in the summer and autumn last year and It is also related to the fact that the No. 3 bridge gate lifts and releases water so that the silt and other coverings are washed away.
Dr. Wu Jie sampled the soil layer at the ancient river channel site. She said that although it can be determined that this is an ancient river bed, how "ancient" it is cannot be determined. Sample collection and professional carbon 14 dating are needed. Only by testing can we know whether it is a thousand-year-old river bed or a ten-thousand-year-old river bed. "We can clearly see that the gravel deposited at the bottom of the river bed is wrapped with small pebbles and arranged horizontally layer by layer, and is pressed very tightly. This shows that it must have been formed after a long period of baptism."
These different shades How is the ravine of One formed? Dr. Du Jiankuo said that the reasons for the formation of gullies are more complicated. For example, during floods, river water carries away large rocks, causing damage to the river bed and forming grooves, which ultimately present the landscape we see.In addition, differences in the properties of river bed sediments and differences in kinetic energy in different parts of the river are also responsible for the formation of gullies. Dr. Wu Jie added: "The reason why the gully in the center of the river is the deepest and the two banks are shallower is mainly because the water velocity in the center of the river is the largest, and the erosion of the center of the river is also the most obvious."
Because the ecological environment of the Han River is good
The ancient river bed may disappear in the future
In the central area of the ancient river bed, there is an obvious layering at a distance of 1.7 to 1.8 meters from the top. This phenomenon attracted the attention of Dr. Wu Jie. Wu Jie said: "This is a sedimentary discontinuity with very obvious characteristics. The lower part is dominated by coarse sand and gravel deposits, and the upper part is deposited with silt sand and clay. The texture of these sediments is relatively loose and has not been consolidated into rocks."
Why does this phenomenon occur here? Dr. Du Jiankuo explained: "This is related to changes in the hydrological environment of the Han River. Many years ago, the water flow of the Han River was larger and it was feasible for boats. This means that the river has a strong sand-carrying capacity and larger particles can be transported farther. And In recent years, with the development of water conservancy projects Due to the interference of human factors such as construction, the water flow has become smaller, the river's sand-carrying capacity has weakened, and relatively stable water environments such as reservoirs have accepted more sediment deposition, resulting in changes in the sediment environment of the river. In addition, water and soil erosion in the upper reaches of the Han River have occurred. The situation continues to improve, These are the reasons for this phenomenon. "
Data from the Hantai District Water Conservancy Bureau show that the water environment quality of the Han River has improved significantly, and the outbound water quality has stabilized at Class II standards. At the same time, in recent years. In recent years, the Han River has been continuously implementing comprehensive improvement actions such as "clearing", "restoring" and "beautifying" the Han River. Building new embankments, closing sand beaches, restoring beaches, and releasing various types of fish fry have all contributed to increasing species and protecting water sources, improving the water environment of the Han River and restoring important role of water ecology.
Dr. Du Jiankuo said that based on this situation, it can be inferred that the river water cannot provide a continuous supply of raw materials for the continuous sedimentation of the ancient river bed. After a few years, it may disappear because the sedimentation rate of the ancient river bed cannot keep up with the erosion and weathering of nature.
Here we also call on the general public to pay attention to protecting the ancient riverbed during the tour and reduce trampling, so that this magical and magnificent landscape can be preserved on the land of Tianhan for as long as possible.
Hanzhong Daily reporter: Wang Qian
Editor: Ziliang
In addition, differences in the properties of river bed sediments and differences in kinetic energy in different parts of the river are also responsible for the formation of gullies. Dr. Wu Jie added: "The reason why the gully in the center of the river is the deepest and the two banks are shallower is mainly because the water velocity in the center of the river is the largest, and the erosion of the center of the river is also the most obvious."Because the ecological environment of the Han River is good
The ancient river bed may disappear in the future
In the central area of the ancient river bed, there is an obvious layering at a distance of 1.7 to 1.8 meters from the top. This phenomenon attracted the attention of Dr. Wu Jie. Wu Jie said: "This is a sedimentary discontinuity with very obvious characteristics. The lower part is dominated by coarse sand and gravel deposits, and the upper part is deposited with silt sand and clay. The texture of these sediments is relatively loose and has not been consolidated into rocks."
Why does this phenomenon occur here? Dr. Du Jiankuo explained: "This is related to changes in the hydrological environment of the Han River. Many years ago, the water flow of the Han River was larger and it was feasible for boats. This means that the river has a strong sand-carrying capacity and larger particles can be transported farther. And In recent years, with the development of water conservancy projects Due to the interference of human factors such as construction, the water flow has become smaller, the river's sand-carrying capacity has weakened, and relatively stable water environments such as reservoirs have accepted more sediment deposition, resulting in changes in the sediment environment of the river. In addition, water and soil erosion in the upper reaches of the Han River have occurred. The situation continues to improve, These are the reasons for this phenomenon. "
Data from the Hantai District Water Conservancy Bureau show that the water environment quality of the Han River has improved significantly, and the outbound water quality has stabilized at Class II standards. At the same time, in recent years. In recent years, the Han River has been continuously implementing comprehensive improvement actions such as "clearing", "restoring" and "beautifying" the Han River. Building new embankments, closing sand beaches, restoring beaches, and releasing various types of fish fry have all contributed to increasing species and protecting water sources, improving the water environment of the Han River and restoring important role of water ecology.
Dr. Du Jiankuo said that based on this situation, it can be inferred that the river water cannot provide a continuous supply of raw materials for the continuous sedimentation of the ancient river bed. After a few years, it may disappear because the sedimentation rate of the ancient river bed cannot keep up with the erosion and weathering of nature.
Here we also call on the general public to pay attention to protecting the ancient riverbed during the tour and reduce trampling, so that this magical and magnificent landscape can be preserved on the land of Tianhan for as long as possible.
Hanzhong Daily reporter: Wang Qian
Editor: Ziliang
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