Soil erosion in China

-

[Author: He Wenshe/Fang Duo/Yang Jurui/Li Changzhi/Cao Shuyou]

[Date of Issue: 200 108 13]

[Source: World Science and Technology Research and Development, Volume 23, No.2, 200 1]

The deterioration of water environment is harmless to aggravate soil erosion, which is the root cause of poor mountains and rotten waters and alternating floods and droughts. The existing soil erosion area in China is 3.67 million square kilometers, including 6.5438+0.794 million square kilometers of hydraulic erosion and 6.5438+0.876 million square kilometers of wind erosion, accounting for 38.7% of the national territory. According to the statistical calculation of China Soil Erosion Intensity Map, the annual soil loss in China is about 80-1200 million tons. According to incomplete statistics, in the past 40 years, the cultivated land area lost by soil erosion in China is 2.67× 106 square meters, with an average of 6.67× 104 square meters per year. Southwest and northwest regions are the two regions with the most serious soil erosion in China, and the soil erosion area of cultivated land accounts for 24.85% and 22.39% of the whole country respectively. Since the founding of New China, 86,000 reservoirs have been built in China, with a total storage capacity of more than 400 billion cubic meters, with a storage capacity of110, and 22 key reservoirs for siltation and waste disposal. In addition, due to the siltation of rivers, the navigable capacity of rivers in China has decreased from1720,000 km in 1960s to1080,000 km. Sediment is one of the main factors that aggravate river flood disasters. The middle and upper reaches of the Yellow River with the most serious soil erosion have a total area of 6.0× 105 square kilometers, and the loss area has reached 4.5× 105 square kilometers. The average soil erosion modulus of the Yellow River Basin is 3,700 tons/km2, and the annual sediment input below the Three Gorges is 1.6× 1.09 tons. At present, sediment deposition makes the riverbed in the lower reaches of the Yellow River rise by 8- 10 cm on average every year, resulting in local "suspended river" in the lower reaches. Less water and more sediment is one of the hydrological characteristics of the Yellow River. The annual average soil sediment yield of the Yellow River is 5.8× 10 10 cubic meter. In order to prevent and reduce sediment deposition, it is necessary to dump 2.00-4.00×10/0 cubic meters of runoff into the sea every year for sediment transport, accounting for 34? 4 1%, which is equivalent to the sum of water consumption in the upper and lower reaches of the Yellow River. The farmland in eastern Qinghai reduces nearly 10,000 mu of cultivated land and loses more than 230,000 tons of nitrogen, phosphorus and potassium fertilizer every year due to soil erosion. Therefore, soil erosion is the fundamental reason for the alternation of mountains and rivers and drought. The country loses more than 5 billion cubic meters of topsoil every year, and the riverbed in the lower reaches of the Yellow River deposits 400 million cubic meters of sediment every year. Due to sediment deposition, since 1949, the storage capacity of reservoirs and ponds in China has reached 20 billion cubic meters, resulting in direct economic losses of 1000 billion yuan. At present, the desertification area in China has reached 2.26× 106 square kilometers, that is, more than14 of the land is desertification land, and the annual direct economic loss reaches 540× 10 100 billion yuan, and the desertification is still expanding. The loess plateau in the western region covers an area of about 6.4× 105 square kilometers, and the soil erosion area reaches 4.5× 105 square kilometers, accounting for 70% of the loess plateau area. A large number of soil erosion makes the vegetation in the upper reaches in a state of reverse succession, and the frequency of summer drought in the reservoir area is as high as 80-90%. Due to sediment deposition and land reclamation around the lake, the lake has been reduced by tens of thousands of square kilometers. This extinction has been accelerating in the past 50 years, especially in the past 20 years. 1949, there were 25,828 square kilometers of lakes in the middle and lower reaches of the Yangtze River. To 1977, only 14074 square kilometers, a decrease of nearly 50%. The original 22 large Tongjiang lakes in the Yangtze River have lost 56.7 billion cubic meters of volume due to a large number of unreasonable development and construction. In the early 1950s, there were 332 lakes in Hubei, covering an area of over 333 square kilometers. Now there are only 125 lakes with a total area of 2,520 square kilometers, which is less than 1/3 in the early 1950s. Due to the above reasons, the surface of Poyang Lake, the largest freshwater lake in China, has also decreased sharply, and the lake bed has increased by an average of 3 cm per year.

[opinion]

[All comments] [Visits: 600] [More exciting in science and technology]

Dazhong Xiao print