Man-made reasons for the formation of above-ground rivers

A suspended river refers to a river whose riverbed is higher than the ground on both sides of the river. Surface river? . What do you know about rivers on the ground? Let me give you a detailed introduction to the knowledge of the above-ground river.

Man-made reasons for the formation of the above-ground river The loess plateau where the middle reaches of the Yellow River are located is mainly caused by loose loess washed out by storm gullies. Loess is fine in grain, loose in texture, erect (a substance used to build caves in nature), and contains calcium carbonate, which is easily dissolved in water and collapsed. The ground slope is large, the vegetation is sparse, and there are many rainstorms in summer. The sum of precipitation in July, August and September accounts for 80% of the annual precipitation, forming strange peaks, steep walls, caves, Tianshengqiao and other micro-landforms, further contributing to gully expansion and accelerating soil erosion. At the same time, it is also related to the rise of modern crust, which makes the gully bed cut down and eroded laterally, and the erosion of gully source intensifies. Correspondingly, the valley slope is expanding and the gully is more and more broken.

In addition to the above natural factors, it is also closely related to human activities, especially social factors such as the destruction of vegetation, unreasonable farming system and mining. Loess Plateau is the most serious area of soil erosion in China.

Deforestation and reclamation

Since Qin and Han Dynasties, the Loess Plateau has experienced three climaxes of deforestation and reclamation.

The first time was in the Qin and Han Dynasties on a large scale? Reclamation? (Border guards organize large-scale reclamation) What else? What is the true fate of immigration? Reclamation. Big this time? Reclamation? Forests in northern Shanxi and northern Shaanxi have been destroyed on a large scale.

The second time was a large-scale implementation in the Ming Dynasty? Reclamation? The ecological environment in the northern part of the Loess Plateau has suffered an unprecedented catastrophe. According to textual research, it was popularized in northern Shaanxi (Yan 'an, Suide and Yulin) and northern Shanxi in the early Ming Dynasty? Land reclamation? System, actually forced every border guard to complete the task of deforestation. From here, we can easily see that it was implemented in the Ming Dynasty? Land reclamation? Serious damage to the environment.

The third reclamation was in the Qing dynasty, and the system of rewarding reclamation was implemented. The scope of reclamation moved from northern Shaanxi and northern Shanxi to southern Inner Mongolia, and millions of acres of grassland in the northern Loess Plateau and Ordos Plateau were reclaimed as farmland, which made the land desertification and soil erosion intensified.

The evil consequences caused

1, take away fertile soil, make it more difficult for vegetation to survive, and lead to a vicious circle.

2. Increase, expand and deepen the gullies on the Loess Plateau.

3. transport a lot of sediment to the lower reaches of the Yellow River to form the lower reaches of the Yellow River? Surface river? . It has caused harm to the residents in the lower reaches of the Yellow River.

4. deterioration of ecological environment? Restrict social and economic development? Increased poverty? Simply pursuing more food? Deforestation? Increased soil erosion? The ecological environment is deteriorating;

5. The population continues to grow? Per capita arable land decreases and fuel demand increases? Destroy vegetation and reclaim wasteland? Environmental degradation and frequent disasters? Crop yields decline, and then expand wasteland reclamation? The population continues to grow.

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Environmental control problems and control measures of the Yellow River

exist problem

(1) The downstream flood control task is still very arduous. Under the condition that Sanmenxia Reservoir controls the upstream flood, the peak flow at Huayuankou may still be more than 40,000m3/s, far exceeding the capacity of existing dikes to resist 22,000m3/s, so it is necessary to continuously increase the dikes along with the river siltation.

② The ecosystem and economic foundation of the Loess Plateau are weak. It is a long-term and arduous task to prevent soil erosion, develop local resources such as coal and nonferrous metals, and revitalize the local urban and rural economy.

③ Water resources are insufficient. A considerable amount of water in the Yellow River is used to transport sand into the sea, and the amount available for industry and agriculture is limited. The Yellow River has low regulation capacity, and the water quality in some sections is polluted, so the contradiction between supply and demand becomes very acute. In the future, with the increase of industrial and agricultural water consumption, the contradiction between supply and demand of water resources will become more prominent. The degree of development and utilization of hydropower resources in the basin is not high, so it is necessary to rationally allocate and speed up the development process. Some river sections should also consider restoring and developing shipping.

Governance measures

In the past 50 years, great progress has been made in harnessing the Yellow River.

1. More than 3,000 reservoirs have been built in the Yellow River Basin, with the total storage capacity equivalent to the annual runoff of the Yellow River Mother Statue in Lanzhou, and the utilization rate of the Yellow River water resources has reached 60%. The Xiaolangdi project, which was built with the World Bank loan, was closed on schedule on 1998.

2. The dikes in the lower reaches of the Yellow River 1300 km are generally heightened and reinforced for three times.

3. Two fifths of the soil erosion area in the Yellow River Basin has been controlled. During the 48 years from 1950 to 1997, eight provinces (regions) in the Yellow River Basin have completed five major soil and water conservation measures, including terraces, dams, other basic farmland and afforestation and grass planting, reaching 276.5438 billion mu, equivalent to 65.438+0808 million square kilometers, accounting for 8 provinces (. According to the average of 48 years, the average annual progress is 0.83%. In the above-mentioned control areas, there are 46 1.7 1.7 million mu of terraced fields, 5.378 million mu of dam land, 3.381.33 million mu of other basic farmland, 0 1.5094446 million mu of afforestation and 34965438+/kl.

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