Original text:
Desert is one of the most tenacious natural enemies of mankind. Throughout history, mankind has been fighting against the desert. However, according to ancient legends and historical records, in the past, humans failed to conquer the desert, but some inhabited areas were annexed by the desert.
The Mediterranean coast is called the cradle of western civilization. The civilizations of ancient Egypt, Babylon and Greece all came into being and developed here. But for two or three thousand years, this area has been hit by sandstorms, and some places have gradually turned into deserts.
Yulin City, Shaanxi Province, China is still abundant in rainfall. In the late Ming and early Qing dynasties, it was a natural grassland area with few sandstorms. During the Qianlong period of the Qing Dynasty, many people in Shaanxi and northwestern Shanxi moved to northern Yulin for reclamation. At that time, the government did not care about agricultural production at all, and the production technology was not high. Land reclamation and logging caused the original grassland to expose the soil, the sun and the wind blew, and the dust flew all over the sky. Yulin City was also attacked by the sandstorm outside the Great Wall. Before liberation, 30 kilometers outside Yulin became a desert.
The weapons used in the desert are wind and sand. There are two main ways to deal with sandstorms. A fierce wind that can be called "guerrilla warfare" is blowing hard, and sand flies with the wind. The stronger the wind, the stronger the impact of sand. The seedlings just unearthed in April and May in spring were windy at that time. A big sandstorm may kill all the seedlings or even uproot them. In the sandy areas along the Great Wall, farmers often have to replant two or three times to get a little harvest. One can be called "positional warfare", that is, the wind pushes sand dunes and moves slowly. The heights of sand dunes generally range from several meters to tens of meters, and some are as high as 100 meters. The advance of sand dunes does not move integrally. When the wind speed reaches more than 5 meters per second, the sand grains on the windward side of the sand dunes move with the wind in batches, from the bottom to the top of the sand dunes, and after crossing the top, they fall on the slope on the leeward side due to the weakening of the wind speed. Therefore, although some sand grains move quite fast, ranging from a few meters to tens of meters every day, the whole sand dune moves in waves, and the moving speed is not fast, only 5 meters to 10 meters every year. Several dunes are usually connected together to form a dune chain. Although the sand dunes move slowly, everywhere they go, forests are completely destroyed, villages are completely buried, and battlements become mound ruins.
The way to resist sandstorms is to cultivate shelterbelts. The main function of shelter forest is to reduce wind power. When the wind meets the shelter forest, its speed will be reduced by 70%-80%. When the distance from the shelter forest is equal to 20 times the height of trees, the wind speed returns to its original speed. Therefore, the shelterbelt must be a number of forest belts arranged in parallel, and the distance between two rows shall not exceed 20 times the height of the tree. The second is to cultivate turf. With turf covering the ground, even if there is wind, not much sand can be blown, which reduces the source of sand.
The way to resist sand dune attack is to plant trees and grass. In the desert area of China, some sand dunes have grown turf and shrubs, so they didn't move their positions. This kind of fixed dune can be fixed as long as it can properly protect turf and shrubs and prevent excessive logging and arbitrary grazing. According to the experience of sand control in recent years, the thickness of dry sand layer on the surface of mobile sand dunes in Yulin, northern Shaanxi, Dengkou, Inner Mongolia and Minqin, Gansu is generally less than 10 cm. Below 10 cm, the water content gradually increases, and at the depth of 40 cm, the water content reaches more than 2%, which is a wet sand layer. The moisture in the wet sand layer is enough to supply plants that fix sand dunes. Therefore, planting trees and grass on the flowing sand dunes can survive. When the trees and grass grow, the sand dunes can be fixed.
It is not enough to just defend against sandstorms and fix the position of sand dunes, or just take defense. The main weapon to conquer the desert is water. Whether planting trees or grass, there must be enough water in the soil. Therefore, in order to win the victory of marching into the desert, there must be enough water.
There is plenty of rainfall in eastern Inner Mongolia, Shaanxi and northwestern Shanxi. Even in the arid areas of northwest China, surface runoff and underground water table are very large. Some desert areas, such as Hexi Corridor, Qaidam, Junggar in northern Xinjiang and Tarim in southern Xinjiang, are all basins, and there is a lot of snow on the surrounding mountains. In this way, as long as we can make full use of these water sources, we will not only be sure to recover lost ground when we enter the desert, but also open up a number of oases in the desert. Downstream of an ordinary river, the more water there is, the bigger the river is. But in the desert, due to the evaporation of air and the infiltration of soil, the river flow is getting smaller and smaller, and finally it dries up and disappears. Part of the water evaporates into the air, and part of it soaks into the cracks in the soil to become groundwater. If the geological structure is a basin, it can be merged into an underground sea as the water source for establishing an oasis. According to the investigation of the Comprehensive Investigation Committee of the Chinese Academy of Sciences, as long as there is water, there are still 654.38 billion mu of wasteland in Xinjiang alone.
The desert can be conquered. Under the leadership of the CPC Central Committee and Chairman Mao, we launched a desert offensive in a planned way and achieved some results. Xinjiang Construction Corps set up state farms in the north and south of Tianshan Mountain, digging ditches and opening canals to plant wheat, cotton and trees. It used to be a barren land, but now it is lush and has become an oasis. Many achievements have also been made in sand control in desert areas of Inner Mongolia.
When we marched into the desert, we not only protected farmland and opened up oases, but also protected traffic lines. The section from Yinchuan to Lanzhou in baotou-lanzhou railway passes through Tengger Desert, during which the sandstorm in Shapotou, Zhongwei County is particularly serious. There are many sandstorms, and a big sandstorm can flood the railway. Relevant departments set up Shapotou Sand Control Station in 1956 for sand fixation and afforestation. The work was finished ahead of schedule. Since baotou-lanzhou railway was opened to traffic, the trains have been running in the desert, and there have never been any accidents caused by sandstorms.
Wind is a weapon for desert to attack human beings, but it can also benefit human beings. The desert area is flat and windy. For example, Xingxingxia, Toksun and Dabancheng in Xinjiang are all famous outlets. Toksun, Institute of Mechanics, Chinese Academy of Sciences, has developed a wind turbine with a radius of 2 meters, which can be used for power generation, water pumping and grinding.
In desert areas, the air is dry and the sunshine is particularly strong. The sunshine time there is particularly long, reaching 3000 hours a year, while the Yangtze River Basin only has 1500 hours and North China only has 2500 hours. Sunlight can be used for generating electricity, heating, boiling water and cooking. Desert lake water contains salt. When sunlight evaporates water, distilled water and salt can be obtained. The best tool to convert sunlight into heat and electricity is semiconductor. It is estimated that it is possible to use cheap semiconductors as roofs in the desert in the future, and people living in it are neither cold in winter nor hot in summer.
Author:
Zhu Kezhen (1890—— 1974) is the founder of modern meteorology and modern geography in China. 1890 was born in Dongguan Town, Shaoxing, Zhejiang Province (now Shangyu). 19 10 to study in the United States at public expense; I studied in the Agricultural College of Illinois University, graduated from 19 13, and then went to Harvard University to study meteorology. 19 18 Dr. returned to China and taught in Wuchang Normal School (predecessor of Wuhan University), Southeast University (predecessor of Nanjing University) and Nankai University. 1928 was the director of the Institute of Meteorology of Academia Sinica (to 1944), and 1936 was the president of Zhejiang University (to 1949). After People's Republic of China (PRC) was born, he served as vice president of China Academy of Sciences, vice president of China Association for Science and Technology, chairman of China Meteorological Society, honorary chairman and chairman of China Geographical Society. He was also elected as a member of the NPC Standing Committee for one to four sessions, and joined the China * * * Production Party at 1962. 1974 passed away in Beijing on February 7th. His main works are: Climatic Regionalization of China (1930), Monsoon and Rainfall in Southeast China (1934), Climate Introduction of China (1935) and Time and Place of the Origin of Twenty-eight Hostels (1944). He Wan, Climatic Characteristics of China and Its Relationship with Food Crop Production (1964), Preliminary Study on Climate Change in China in Recent Five Thousand Years (written by 1966, revised and finalized by 1972).