Soil erosion in the downstream area only has an impact on the upstream

When you think about it, basically the likelihood of an impact is very small.

From the perspective of physical geography, there is basically no soil erosion downstream, but mainly sediment accumulation. Even rivers with serious soil erosion in the upper reaches of the Yellow River, when they reach the lower reaches, sediment accumulation is mainly occurring (hence the "above-ground rivers"). As the river reaches the lower reaches of the river, the flow of water slows downstream, and the thrusting effect of the high tide of the sea and the increase in the salinity of the fresh water into the sea, it usually accumulates gradually.

Taking the lower reaches of the Yangtze River as an example, Chongming Island is basically completely stacked in this way. Nowadays, Rudong and other counties on the north bank of the Yangtze River in the north of Chongming Island have even gradually piled up sand since the late Qing Dynasty.

It can be seen that most of the lower reaches of the river have very little soil erosion due to the imminent entry into the sea.

As for inland rivers, some rivers that flow through the desert will evaporate and disappear when the water leaks downstream, but the water is gone, and the soil cannot be lost, so it will not have any impact on the upper rivers.

So, what if serious soil erosion does occur downstream? It really depends on how we define "downstream". If "downstream" does not refer to the place where the river flows into the sea (into the lake) or disappears, but only in relation to the watercourse of the previous section, then such a situation is not unthinkable

Usually rivers originate in the mountains. We all know that due to the gravity of the earth, the river will continue to cut down, forming river valleys, so the higher the mountains, the deeper the valleys. Deep valleys are formed by the undercutting of rivers.

Therefore, in the upper reaches of the river, you can always see high mountains and gorges. Compared with the previous section of the waterway, because the potential energy of the high water level is continuously converted into the kinetic energy of the low water level, therefore, the depth of the lower cut of the latter section of the channel will always be greater than that of the previous section, and the deepening speed of the latter section of the channel will be greater than that of the previous section of the waterway.

"Tracing the source of erosion" may be similar to the landlord's statement of "downstream soil erosion". Under the continuous action of the process of "tracing the source of erosion", the upstream river valley has gradually deepened, and at the watershed, there is a possibility of river "raiding". That is, on either side of the watershed, there were originally two rivers A and B flowing to each side.

However, one of the rivers, A, has a stronger role of "traceable erosion", and its upstream source continues to move backwards, and finally crosses the watershed first and invades the source of river B on the other side. And because the valley of river A is deeper, the flow of water from river B on the other side also flows into this river A. This is probably an example of "soil erosion downstream" affecting "upstream" at a relatively close distance, right?

In fact, such river raids only occur in the upper reaches of the entire length of the river.

Above, I hope it will be helpful to the landlord.

There will be a certain impact on the upstream. Soil erosion downstream can cause silting up of downstream rivers and upstream water levels**.

Theoretically, there are positive significance and effects such as regulating water resources (spatio-temporal allocation), power generation, shipping (only beneficial to the upstream), flood control, etc., but I think that from the perspective of natural ecological maintenance and actual utilization effect, the negative effects are even greater

1. In terms of water resource allocation, the rainy season (China's monsoon climate characteristics are usually manifested as seasonal or short-term heavy rainfall) usually does not play an effective role in flood discharge, and flood discharge usually aggravates the damage to the middle and lower reaches of the river; During the dry season, stakeholders usually need to store water for their own economic interests, causing water difficulties for life, production (mainly agricultural irrigation) in the middle and lower reaches of the river (there are many relevant examples in China, including some well-known water conservancy projects);

2. Cause sediment accumulation and riverbed elevation in the middle and lower reaches of the river, and aggravate flood disasters under monsoon climate conditions;

3. Artificially cut off and destroy the living environment of river organisms (mainly fish), and fish resources are increasingly depleted (many fish have migratory spawning habits, and the reservoir dam body largely cuts off the migration route of fish);

4. If it is a large-scale reservoir, especially a super-large reservoir, it will also strongly change the landform because of the huge water conservancy project, which is easy to cause landslides, debris flows, ** and other geological disasters (related examples are the same as 1).

Reasons: 1. There are many plains in the middle and lower reaches, and the terrain is low and flat, which is not conducive to flooding.

2. It belongs to the monsoon climate, with a lot of precipitation and concentration, and a lot of heavy rain in summer.

3. The north and south tributaries flow into more.

4. The upstream area has serious damage to vegetation, resulting in soil erosion, and the downstream riverbed is raised, and sediment is silted up, forming an above-ground river (the Jingjiang River section is particularly prominent, known as the "Jiuqu ileum").

5. People surrounded the lake to create farmland, which reduced the area of the lake, and weakened the lake's ability to regulate and store floodwaters.

The hazards are mainly in the middle and lower reaches.

Soil erosion in the middle and upper reaches increases the sediment content of rivers, and the middle and lower reaches enter the plain area, the river channel widens, the flow rate slows down, and the sediment accumulates into the rivers and lakes, which reduces the flood storage capacity of rivers and lakes, resulting in floods.

Upstream: Soil erosion, insufficient nutrients required for plant growth, reduced vegetation coverage, and decreased stabilizing effect of plant roots on mountain soil and rock, which is easy to cause natural disasters such as debris flows and landslides, which affect people's production and life.

Middle and lower reaches: Because the middle and lower reaches of rivers are usually relatively gentle, the water flow speed is slow, resulting in the weakening of the carrying effect of the water flow on the soil, and the deposition of the soil, resulting in the elevation of the river bed, which is easy to cause flooding disasters and reduce the navigation value of the river.

The destruction of vegetation and soil erosion in the middle and upper reaches of the river lead to silt in the lower reaches of the river.

In recent decades, due to the increase in population and industrial development in the upper and middle reaches of the Yangtze River, people have indiscriminately deforested, steep slopes have been cleared, and the arbitrary use of production and living energy has led to a great reduction in vegetation coverage in the middle and upper reaches of the Yangtze River, resulting in serious soil erosion

1. Human causes. There are two main aspects of unreasonable use of land by human beings, destruction of ground vegetation and stable topography, resulting in serious soil erosion.

1.Deforestation and grass destruction, steep slopes have cleared land, destroying ground vegetation.

2.The lack of attention to soil and water conservation in production and construction projects destroys the ground vegetation and stable terrain, and at the same time, waste soil and rocks are dumped into the ditch at will, resulting in a large amount of new soil erosion.

2. Impact on downstream river sections:

1 The increase in sediment content causes siltation of the river, which is not conducive to navigation.

2. The increase of sediment content, due to the wide downstream river channel, the water speed slows down, resulting in sediment deposition and elevation of the river bed, which is easy to cause flooding.

3 Reducing the area of downstream waters, such as the large reduction of the area of Dongting Lake4 Destroying the ecological environment and affecting the ecological balance.

Vegetation destruction, soil erosion.

runoff decreases and groundwater levels fall; Seawater intrusion, soil salinization intensifies, and water quality deteriorates; The decrease of water and sediment has reduced the fertility of coastal land and the fishery resources in the sea near the estuary. seawater intrusion and increased coastline erosion; Wetland reduction, affecting the growth and habitat of animals and plants; Evaporation is vigorous, the climate is drier, and the continentalism is stronger; Desertification is intensifying, and the downstream ecological environment tends to deteriorate.

runoff decreases, recharge groundwater decreases, and groundwater levels fall; The water volume at the estuary decreases, the seawater backs up into the river, the water quality decreases, and the water with higher salinity seeps into the ground, resulting in the secondary salinization of the soil, and the salinization of the soil leads to the decline of soil fertility. The amount of water entering the sea is reduced, the nutrients entering the sea are reduced, and the fishery production is reduced; The sediment carried by the river decreases, the sediment weakens, the seawater erosion intensifies, and the coastline retreats. Deltas are decreasing, wetlands are decreasing, biodiversity is decreasing; The water of the river is decreasing, the regulating effect on the climate is weakened, the climate becomes arid, and the ecological environment deteriorates.

The decrease in the flow of the upper reaches of the river is prone to the following impacts on the physical geographical environment of the downstream

When the flow of rivers decreases or stops, various ecological balances will be lost, the land will dry up, the grass and trees will shrink, the trees will grow slowly, and people and livestock will have difficulty drinking water, and other undesirable natural disasters will gradually appear.

The decrease in the flow of the upper reaches of the river is easy to cause the flow of the river to decrease or cut off the flow of the downstream natural geographical environment, and various ecological balances will be lost, the land will dry up, the grass and trees will shrink, the growth of trees will be slow, and the difficulty of drinking water for people and livestock will gradually appear.