Water and soil loss refers to the phenomenon of simultaneous loss of water and soil due to the impact of natural or human factors, rainwater can not be absorbed on the spot, downflow and soil erosion.The main reasons are large ground slope, improper land use, destruction of ground vegetationfarming techniqueUnreasonable, loose soilDeforestation、OvergrazingEtc.The harm of water and soil loss is mainly manifested in: the soil cultivation layer is eroded and destroyed, making the soil fertility increasingly depleted;Silting up rivers, channelsreservoir, reduce the benefits of water conservancy projects, even lead to floods and droughts, seriously affecting industrial and agricultural production;Soil erosion poses a serious threat to agricultural production in mountainous areas and downstream rivers.[1]The Loess Plateau is one of the key areas for soil erosion control in China.[12]
On June 18, 2024, the Ministry of Water Resources: 620000 square kilometers of water and soil loss have been controlled in the past decade.[15]
Chinese name
soil erosion
Foreign name
water and soil loss
Alias
Water and soil loss
Discipline type
geography
Common types
Water erosion, gravity erosion, wind erosion
Hazards
Destroy land productivity and ecology, and silt up rivers
soil erosion(Water and soil loss) refers to "the destruction and loss of water and soil resources and land productivity, including land surface erosion and water and soil loss, also known as water and soil loss, under the effect of external forces such as water power, gravity and wind power." - (China Water Conservancy Encyclopedia Volume I, China Encyclopedia Water Conservancy Volume, and Water and Soil Conservation Science Wang LixianChina Forestry Press2005）
In 1981, the Science Press, Concise Dictionary of Water Resources and Hydropower, put forward that water and soil loss refers to the phenomenon that surface soil, parent material and rock are subject to external forces such as water power, wind power, gravity, freezing and thawing, resulting in various damages, movements, accumulation processes and water loss itself. This is water and soil loss in a broad sense. Water and soil loss in a narrow sense specifically refers toHydraulic erosionPhenomenon. "
This is the same as the previous onesoil erosionIt is a little similar, so people often compare "water and soil loss" with "soil erosion"”The two words are used together.
According to the second remote sensing survey of water and soil loss in China, at the end of 1980s, the area of water and soil loss in China was 3.56 million km2, including 1.65 million km2 of water erosion area and 1.91 million km2 of wind erosion area. Among the areas of water erosion and wind erosion, the area of water and soil loss in the water and wind erosion crisscross area was 260000 km2.
Among the 1.65 million km2 of water erosion area, 830000 km2 is mild, 550000 km2 is moderate, 180000 km2 is strong, 60000 km2 is extremely strong, and 30000 km2 is severe.
In the 1910000 km2 wind erosion area, 790000 km2 is mild, 250000 km2 is moderate, 250000 km2 is strong, 270000 km2 is extremely strong, and 350000 km2 is severe.
The freeze-thaw erosion area is 1.25 million km2 (based on the remote sensing survey data in 1990), which is not included in the water and soil loss area published in China.
In 1991, the State Council of China promulgated the Law on Water and Soil Conservation, which was the first professional technical regulation on water and soil conservation in China, and ended the long-term inability of Chinese water and soil conservation workers to rely on the law.
In 2005, the Ministry of Water Resources of China carried out a one-year scientific investigation on soil erosion and ecological security in China.
China is one of the countries with the most serious water and soil loss in the world.According to the results of the first national water conservancy survey, China's existing water and soil loss area is 2949100 square kilometers.Serious water and soil loss is a concentrated reflection of China's ecological deterioration, threatening national ecological security, drinking water security, flood control security and food security, restricting mountainous and hilly areas, and affecting the process of building a moderately prosperous society in an all-round way.
The CPC Central Committee and the State Council have always attached great importance to soil and water conservation.At present, the conservation area of national water and soil conservation measures has reached 1.07 million square kilometers, more than 70000 small watersheds have been comprehensively controlled, and more than 800000 square kilometers have been closed for conservation.1991《Water and soil conservation method》Since its promulgation and implementation, a total of 380000 production and construction projects in China have formulated and implemented water and soil conservation plans, preventing and controlling more than 150000 square kilometers of water and soil loss.
However, as an important part of China's ecological civilization construction, the development level of soil and water conservation isCompleting the building of a moderately prosperous society in all respects, as well as a series of new requirements such as urbanization, informatization, agricultural modernization and greening, which still cannot fully adapt to the new expectations of the masses of the people to improve the quality of the ecological environment, and water and soil loss is still a major problem facing ChinaEcological environment problems。
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Water and soil loss caused by wind erosion
According to the "power" of water and soil loss, the most widely distributed water and soil loss can be divided into three types: hydraulic erosion, gravity erosion and wind erosion.
1. Hydraulic erosion is most widely distributed in mountainous areashillThe area and all sloping ground will produce water erosion during rainstorm.It is characterized by using the water on the ground as the power to wash away the soil.For example, the Loess Plateau.
2. Gravity erosion is mainly distributed in mountainous and hilly areasgullyOn steep slopes, on both banks of steep slopes and ditches, part of the lower part of the ditch wall is hollowed out by the water flow. Due to the gravity of the soil and its parent material, it cannot continue to remain in the original position and collapse in scattered or in pieces.
3. Wind erosion is mainly distributed in Chinanorthwest, desert, sandy land and hilly sand covered area in North China and Northeast China, followed by southeast coastal sandy land, and then Henan, Anhui and Jiangsu provinces“Yellow River flood area”(In history, sediment was formed due to the Yellow River breach and diversion).It is characterized by that the sand grains are lifted up by the wind, leaving the original position and floating to another place to land with the wind.For example:Hexi CorridorandThe Loess Plateau。
In addition, it can be divided into freeze-thaw erosion, glacier erosion, mixed erosion, wind erosion, plant erosion and chemical erosion.
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Water and soil loss in Hexi Corridor
China is a mountainous country, with mountainous area accounting for 2/3 of the land area;It is also the country with the widest distribution of loess in the world.The terrain in mountainous and hilly areas and loess areas is undulating.Loess or loose weathering crust is vulnerable to erosion in the absence of vegetation protection.Most areas are in monsoon climate, with concentrated precipitation. The precipitation in rainy season often reaches 60%~80% of the annual precipitation, and there are many rainstorms.Geological and geomorphic conditions and climatic conditions prone to water and soil loss are the main reasons for water and soil loss in China.
China has a large population and a large demand for food and civilian fuels. Therefore, under the condition of low productivity, people have implemented predatory reclamation of land, one-sided emphasis on food production, ignoring the comprehensive development of agriculture, forestry and animal husbandry according to local conditions, and turned land only suitable for forestry and animal husbandry into farmland, which has damaged the ecological environment.A large number of steep slopes are reclaimed, so that the steep slopes become poorer and poorer, and the poorer and more cultivated, the vicious cycle of the ecosystem;Deforestation, even digging tree roots and lawns at random, has led to the sharp decline of trees and exposed the earth's surface, which has aggravated the water and soil loss.In addition, some basic construction also does not meet the requirements of water and soil conservation. For example, unreasonable road construction, plant construction, coal mining, quarrying, etc. have damaged vegetation, reduced slope stability, and caused serious geological disasters such as landslides, landslides, debris flows, etc.
1. Natural factors.
It mainly includes climate, rainfall, ground material composition and vegetation.
① Terrain: gully development, steep slope;The steeper the ground slope is, the faster the velocity of surface runoff is, and the stronger the erosion and erosivity of soil will be.The longer the slope is, the more surface runoff is collected and the stronger the scouring force is.
② Rainfall.Rainfall that causes water and soil loss is generally heavy rain. Only when the rainfall intensity exceeds the soil infiltration intensity can surface runoff (over infiltration) be generated, resulting in erosion and erosion of the surface.
③ Ground material composition.
④ Vegetation.The forest and grass vegetation with a certain canopy density can protect the soil from erosion.The higher the canopy density, the stronger the water and soil conservation.
2. Human factors.
The irrational use of land by human beings has destroyed the ground vegetation and stable terrain, resulting in serious water and soil loss.
① Destruction of vegetation.
② Unreasonable farming system.
③ Mining.
China's weightless soil and water flow disaster area: the Loess Plateau
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The Loess Plateau in China is now a serious disaster area of water and soil loss. The vegetation on the plateau is scarce, and the ravines are crisscross. The soil lost enters the Yellow River, causing a sharp increase in sediment.But the Yellow River Basin in history is not what it is today. Thousands of years ago, it was densely forested and humid. The original Chinese civilization was born in this area.Since then, on the one hand, due to the change of natural climate, the precipitation has gradually decreased; on the other hand, due to excessive development, the forest and other surface vegetation have rapidly disappeared, and the phenomenon of water and soil loss has become increasingly serious.Because of excessive land development, it has led to serious soil erosion.In turn, the increasingly serious phenomenon of water and soil loss has led to the reduction of cultivated land or pastures.In the long run, overexploitation will not bring more benefits to human beings, but will cause greater ecological environment crisis.At present, excessive land reclamation andOvergrazingThe phenomenon is the main cause of soil erosion in these areas.[2]
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Serious water and soil loss has resulted in the reduction of cultivated land area, soil fertility and crop yield, and the contradiction between man and land is prominent.In order to survive, the local farmers had to cultivate a large number of sloping fields, widely planting and harvesting, forming a vicious circle of "more and more poor, more and more poor", making the ecological environment deteriorating, restricting economic development and exacerbating poverty.In the national "August 7th" poverty alleviation plan, there are 126 poverty-stricken counties in the Loess Plateau, accounting for 21.3% of the total number of poverty-stricken counties in China, with 23 million poverty-stricken people, accounting for 28.8% of the country's poverty-stricken population.After years of poverty alleviation, there are still nearly 10 million poor people, which is one of the areas where the poor people are concentrated in China.The serious water and soil loss also causes the inconvenience of transportation and the difficulty of drinking water for people and animals in this area, which seriously restricts the sustainable development of regional economy and society.[2]
Water and soil loss is very harmful, mainly in the following aspects:
1. Land productivity has been reduced or even lost: the area of water and soil loss in China has expanded to 1.5 million square kilometers, accounting for about 1/6 of China's total, and 5 billion tons of soil is lost every year.The loss of nitrogen, phosphorus and potassium fertilizer in the soil is estimated to reach 40 million tons, which is equivalent to the amount of fertilizer applied in China in the current year, and the economic loss equivalent to 2.4 billion yuan.The Yangtze River and the Yellow River lose 2.6 billion tons of sediment every year.The fertilizer contained in it is about the total amount of fertilizer plants with an annual output of 500000 tons.No wonder some people say that what the Yellow River flows away is not sediment, but the "blood" of the Chinese nation. Such a large area of fertile soil and nitrogen, phosphorus and potassium fertilizers have been washed away, which will inevitably lead to the decline or even complete loss of land productivity.[3]
2. Silted rivers, lakes and reservoirs: Although the water and soil loss in Zhejiang Province is relatively light, the riverbed of eight river systems in the province has generally increased by 0.2-0.1m, and the inland navigation mileage is 1000 km less than that in the 1960s.For example, before 1958, a wooden boat with a load of 10 tons could pass from Shengxian County to Cao'e River.Due to too much silt in the river bed, navigation has been forced to stop. The original water resources have become sand resources, and the aviation construction company has become a "yellow sand" company.
The Dongting Lake in Hunan Province has more than 1400 hectares of sandbanks exposed to the water every year due to too much sandstorms.The lake area has shrunk from 3915 square kilometers in 1954 to 2740 square kilometers in 1978.What is more serious is that the water surface of Dongting Lake is 3 meters higher than the land around the lake, which has lost its role in flood diversion of the Yangtze River.This is a very serious problem.
The Jialing River, Fujiang River, Tuojiang River and other river basins in Sichuan Province also suffer from serious soil erosion, with more than 20% of the sediment deposited in the reservoir.According to the prediction of relevant experts, if this continues, in 50 years' time, some reservoirs in the Yangtze River basin will be silted up or become silt reservoirs.[3]
3. Polluted water quality affects ecological balance: At present, a prominent problem in China is the serious pollution of water quality of rivers, lakes (reservoirs).Soil erosion is an important cause of water pollution.The water quality of the Yangtze River is being polluted, which is a typical example.
It can be seen that soil erosion is not only harmful, but also has long-term effects.The seriousness of the problem must be fully estimated.[3]
China is one of the countries with the most serious soil erosion in the world. Due to special physical geography and socio-economic conditions, soil erosion has become a major environmental problem.
Water and soil loss in China is widely distributed and covers a large area. According to the published results of China's second remote sensing survey, the area of water and soil loss in China is 3.56 million km2, accounting for 37% of the total land area, including 1.65 million km2 of water erosion and 1.91 million km2 of wind erosion.In the area of water erosion and wind erosion, the cross area of water erosion and wind erosion is 260000 km2, with various erosion forms and complex types. Gravity erosion, such as hydraulic erosion, wind erosion, freeze-thaw erosion, landslide and debris flow, has different characteristics, cross each other, and complex causes.Soil loss is serious. According to statistics, the total amount of soil loss in China every year is 5 billion tons.The total annual soil loss in the Yangtze River basin is 2.4 billion tons, of which the total annual soil loss in the upper reaches reaches 1.56 billion tons, and the sediment entering the Yellow River basin and the Loess Plateau reaches 1.6 billion tons every year.
According to the results of the first national water conservancy census on soil and water conservation, China's current total area of soil erosion is 2.949 million square kilometers, accounting for 31.1% of the total area of the census.Among them, hydraulic erosion is 1.293 million square kilometers, and wind erosion is 1.656 million square kilometers.There are 666719 erosion gullies in northwest loess plateau area and 295663 erosion gullies in northeast black soil area.[4]
The problem of man-made soil erosion caused by large-scale development and construction is still very prominent.Serious water and soil loss is a concentrated reflection of China's ecological deterioration, threatening national ecological security, drinking water security, flood control security and food security, restricting economic and social development in hilly areas, and affecting the process of building a well-off society in an all-round way.
On March 5, 2023, Premier Li Keqiang pointed out in the government work report that in the past five years, the area of soil erosion land has decreased by 106000 square kilometers。[11]
On December 12, 2023, the State Council Information Office held a press conference.According to the latest monitoring results of the Ministry of Water Resources, the area of water and soil loss in China has dropped to 2.6534 million square kilometers, 83500 square kilometers less than that in 2018, showing two good trends: the first trend is the "double decline" of the area and intensity of water and soil loss, and the other trend is the "double decline" of water and wind erosion.[13]
Regional comparison
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The Loess Plateau:
1. Natural causes: loose soil and concentrated precipitation.
2. Human factors: human overexploitation (overgrazing, mining, deforestation) [mainly water erosion].
Remedial measures: the loess plateau is not as good as the south in terms of water and heat conditions, and it is in a transitional zone, so it is necessary to plant trees and grassReturning farmland to forests and grasslandsAnd other biological measures;Engineering measures such as building reservoirs, damming and silting up land, and building horizontal terraces are comprehensively managed in small watersheds to improve the ecological environment of the Loess Plateau and develop regional economy.
Southern hills:
1. Natural causes: the undulation of the surface is conducive to water scouring, and the precipitation is large and takes a long time;
2. Human factors: human overexploitation (overexploitation, woodcutting) [mainly precipitation erosion].
Rectification measures: due to the good water and heat conditions in the low mountains and hills in the south, the effective measures are to close the mountains for afforestation and vegetation restoration, to develop new small hydropower, and to do a lot of biogas (to effectively solve the problem of rural energy consumption is the basic guarantee to seal the mountains and forests).
The impact of water and soil loss in low mountain and hilly areas in the south is far more serious than that in the north:
1、 From an economic perspective
The water and heat conditions are better in the southern low mountain and hilly areas, the biomass and output value of unit land are higher, and the loss caused by soil erosion per inch of land is greater.
2、 From an ecological perspective
The southern low mountain and hilly areas are mostly rocky mountains with thin soil layers. Once the topsoil is eroded, it is easy to form rocky desertification, and it is more difficult to recover.
3、 From a social perspective
Low mountain and hilly areas in the south are densely populated, and most of them are important industries in the lower reaches of riversAgricultural production baseAs well as the economic center, water and soil loss has a greater impact on society and causes greater losses.
Governance and development
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chemical treatment
applicationAnionic polyacrylamide(PAM) prevention and control of water and soil loss has become a chemical treatment measure widely adopted internationally.In 2003, soil and water conservation in the United States reported that DC. Flangan et al. conducted an experimental study on the application of PAM to prevent and control water and soil loss in the multi disturbance farmland by using the simulated rainfall device, and obtained the experimental results of the application of PAM to prevent and control water and soil loss in the areas with abundant rainfall.After the first rainstorm event, 20kg/h ㎡ PAM can reduce the leaching amount of soil solid particles of agricultural silty loam by 60%, and can also slow down the erosion of 60 L/min high-intensity water.The soil treated with PAM in areas prone to serious erosion can effectively control erosion.The study of initial dry soil simulated rainfall shows that 80 kg/h ㎡ PAM can reduce 86% of surface runoff and 99% of soil loss of silty soil embankment in 69mm/h rainfall.In topsoil, air dried soil sprayed with PAM liquid mist can control erosion more timely and effectively than that treated with dry PAM particles directly.It is believed that this study can be used as a reference for the experimental study on the application of PAM to prevent and control soil erosion in China.
comprehensive control
Principle: adjust the land use structure and combine governance with development.
Details: 1. Compress agricultural land, focus on the construction of Sichuan land, tableland, dam land and gentle slope terraces, fully tap water resources, adopt modern agricultural technical measures, improve land productivity, and gradually build basic farmland with high and stable yield and drought and waterlogging (basic premise).
2. Expand the area of forest and grass planting;
3. Improve the vegetation of the natural grassland, and appropriately reduce the number of livestock, improve the quality of livestock, and implement rotation grazing in places with overloading and overgrazing;
Key points: conserve water and soil, develop and utilize water and soil resources, and establish an organic and efficient production system of agriculture, forestry and animal husbandry.
Policy: tableland protection, slope protection and ditch fixation
Mode: engineering measures (dam construction, land leveling, basic farmland construction, water pumping and irrigation).[5]
Biological measures
Agricultural technical measures (deep ploughing and soil improvement, scientific fertilization, breeding of improved varieties, plastic film mulching, rotation and multiple cropping).[5]
Current situation of prevention and control
At present, the conservation area of national water and soil conservation measures has reached 1.07 million square kilometers, more than 70000 small watersheds have been comprehensively controlled, and more than 800000 square kilometers have been closed for conservation.1991《Law of the People's Republic of China on Water and Soil Conservation》Since its promulgation and implementation, a total of 380000 production and construction projects in China have formulated and implemented water and soil conservation plans, preventing and controlling more than 150000 square kilometers of water and soil loss.[6]
In 2015, 74000 square kilometers of comprehensive prevention and control area of water and soil loss were completed nationwide;Among them, the comprehensive treatment area is 54000 square kilometers, the ecological restoration area is 20000 square kilometers, the slope transformation is 4 million mu, and more than 300 ecological clean small basins are built.In 2015, an additional 54000 square kilometers of water and soil loss control area and 20000 square kilometers of water and soil loss areas were closed for conservation.[7]
Issued in December 2015《National Water and Soil Conservation Plan (2015-2030)》It is proposed that the short-term goal is to basically build a comprehensive prevention and control system of water and soil loss compatible with China's economic and social development by 2020.The newly increased area of soil erosion control nationwide is 320000 square kilometers, including 290000 square kilometers of newly increased area of water erosion control, with an average annual decreaseSoil loss800 million tons.Long term goal: by 2030, build a comprehensive prevention and control system of water and soil loss that is compatible with China's economic and social development, and increase 940000 square kilometers of water and soil loss control area nationwide, including 860000 square kilometers of water erosion control area, with an average annual reduction of 1.5 billion tons of soil loss.[6]
In 2021, ChinaannualNewly increased control area of soil erosion is 62000 square kilometers[8]。
In 2022, China will complete 63000 square kilometers of soil erosion control.[9-10]
On March 14, 2024, the State Council Information Office held a press conference to introduce the progress of national water security.The area of water and soil loss in China has decreased to 2.6276 million square kilometers, and the rate of water and soil conservation has reached 72.56%.[14]
On June 18, 2024, the State Council Information Office held a series of press conferences on the theme of "promoting high-quality development".Chen Min, Vice Minister of the Ministry of Water Resources, said that we should adhere to systematic governance and maintain the healthy life of rivers and lakes at a higher standard.In the past ten years, 620000 square kilometers of water and soil loss have been controlled.[15]
Preventive measures
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The application of anionic polyacrylamide (PAM) to prevent and control soil erosion has become a chemical treatment measure widely adopted internationally.In 2003, soil and water conservation in the United States reported that DC. Flangan et al. conducted an experimental study on the application of PAM to prevent and control water and soil loss in the multi disturbance farmland by using the simulated rainfall device, and obtained the experimental results of the application of PAM to prevent and control water and soil loss in the areas with abundant rainfall.After the first rainstorm event, 20kg/h ㎡ PAM can reduce the leaching amount of soil solid particles of agricultural silty loam by 60%, and can also slow down the erosion of 60 L/min high-intensity water.The soil treated with PAM in areas prone to serious erosion can effectively control erosion.The study of initial dry soil simulated rainfall shows that 80 kg/h ㎡ PAM can reduce 86% of surface runoff and 99% of soil loss of silty soil embankment in 69mm/h rainfall.In topsoil, air dried soil sprayed with PAM liquid mist can control erosion more timely and effectively than that treated with dry PAM particles directly.It is believed that this study can be used as a reference for the experimental study on the application of PAM to prevent and control soil erosion in China.[2]
