Loess Plateau: The next rain, you have to peel off a layer of skin? Ninety percent of the Yellow River sediment comes from here!
The yellow of the Yellow River is said to be silt, so the ancient saying has clouds: "The Yellow River doushui, mud giant seven", although this is not accurate, but in the past, the yellow river main stream averaged 1.6 billion tons of sediment per year, which is higher than the sediment content of any large river in the world, on average: 1 cubic meter of Yellow River water, there are 70 pounds of sediment!
In the Loess Plateau, there is such a folk song: "The next rain, peel off a layer of skin, tired and tired and hungry belly", which is not only a true portrayal of the desolate and barren Loess Plateau decades ago, but also a vivid reflection of the serious erosion of local soil and water. It should be known that the yellow river has so much sediment, about 90% of which is entered from the Loess Plateau, and it is mainly concentrated in the flood season with heavy precipitation, that is to say, when the Yellow River has a lot of water, it is also the time when the sand is the largest.
Although there is evidence that the Loess Plateau a thousand years ago was also a place with lush vegetation, but since we saw this place, it is loose soil, easy to erode and easy to disperse, so when the rainstorm comes, a large amount of loess will be washed into the Yellow River, and over time, there will be almost no soil in many places, becoming stony and sandy, planting trees in such a place, of course, the survival rate is much lower!
Plant a tree and "feed" 60 pounds of water! How difficult is it to plant trees on the Loess Plateau?
In order to improve the ecology of the Loess Plateau and greatly reduce the amount of yellow sediment, the only roads in front of us are afforestation, returning farmland to forests, and wind and sand fixation. If you have time, you can go to the Meridian Ridge on the border between Gansu and Shaanxi to see the grass and trees, and go to the Pengyang Rice Terrace in Ningxia to see the apricot blossoms.
The ecological environment of the Loess Plateau has become better with the naked eye, which can be seen from the increase in forest coverage and the significant reduction in the amount of yellow sediment, like qinyuan county's forest coverage rate has exceeded 50%, Shanxi's forest coverage rate has increased from 18.03% in 2010 to 23.18% in 2019, but do you know how difficult it is to plant trees under the Yellow River rolling under your feet, the tip of your nose sticking to the cliff, and people hanging upside down in mid-air at a height of 20 meters to plant trees?
The cliffs on the banks of the Yellow River in Yan'an Yanchang County have changed from bare to lush, and Li Feng, who has been in the local daily tree planting team for 15 years, said that there are now more than 300,000 cypresses on the yellow river cliffs and Yanhe river walls, and these places were originally stony mountains with only 10 cm thick surface soil, so when planting saplings before, the survival rate could not even be done. Moreover, it is difficult to plant trees on such a stony mountain, first of all, the mountain stone is broken to build a stone pit more than half a meter high, and then fill it with loess, because the annual rainfall in these places is only 200 mm, so when planting saplings, you have to feed the saplings with 60 pounds of water!
And the sand control people are also continuing from generation to generation, so we can see the great changes that have taken place in the Yulin Desert, and millions of acres of shifting sand have been fixed, or semi-fixed, to achieve more than 60% of the vegetation coverage of the sand area.
Qingyang City's location is in the hinterland of the Loess Plateau, which is notoriously low vegetation coverage, but since the "Rebuild a Meridian Ridge" project was launched, more than 1 million mu of barren mountains have been used for afforestation every year, and by the end of 2020, more than 7.3 million mu of afforestation area has been completed. Once, 86% of Qingyang's land area was plagued by soil erosion, but by the end of 2021, 1,543 square kilometers of land had been treated and protected.
Why would Shaanxi, Gansu, and Ningxia guard the Yellow River to "cry thirst"?
Located in the northern region of China, the Yellow River has a total length of 5,464 kilometers and a basin area of 795,000 square kilometers, making it the second longest river in China and a world-class river.
However, the average annual runoff of the Yellow River over the years is actually only about 58 billion cubic meters, and there are 21 billion cubic meters of water, which is called sand transport water.
That is to say, the amount of water in the Yellow River is really not large, and it can even be said that the water shortage is serious, especially in the upper and middle reaches of Lanzhou to Sanmenxia River, if you per capita, it is only about one-eighth of the national average. Nearly 15% of the mainland's arable land area, nearly 12% of the total population, and more than 50 large and medium-sized cities rely on it for water supply, so it will not be only Shaanxi, Gansu, and Ningxia that guard the Yellow River to "shout thirst".
As we all know, the Yellow River flows through 9 provinces (autonomous regions), of which in addition to Gansu, Shaanxi and Ningxia, there are also Qinghai, Sichuan, Inner Mongolia, Shanxi, Henan and Shandong. In addition, there can be no less Tianjin and Hebei, which are also allocating Yellow River water, these places should be allocated together in addition to sand transport water, the remaining 37 billion cubic meters of Yellow River water, and in the actual distribution is not directly divided, such as Shanxi in the early days because of the development needs of energy bases, so the water consumption increased by more than 50%, but because the tenth in this area is high and low, so although more than four billion cubic meters of Yellow River water is allocated, the actual consumption is only more than one billion cubic meters.
There should be many people who know the introduction of the Hanjiwei Project, the purpose is to let the Wei River into the Yellow River, can be replenished through the water in the upper reaches of the Han River in southern Shaanxi, which is equivalent to a "south-to-north water diversion" project in Shaanxi Province, by replacing the Yellow River water to solve the problem of water shortage in the energy base in northern Shaanxi, and the situation in Ningdong can be said to be similar to that of northern Shaanxi, they are all energy golden triangles.
Changes in the Loess Plateau
The length of about 270,000 ditches is more than 500 meters, and the annual precipitation of the Loess Plateau is mainly concentrated in those months, and the loess itself has large porosity, strong permeability and poor erosion resistance, so in the mainland and even the world, the Loess Plateau is one of the most serious areas of soil erosion, and even has been evaluated by Snow (a well-known American journalist) as the most unsuitable place for human beings to live.
But have you ever wondered why the earlier flourishing ancient civilizations began on the Loess Plateau? Originally, during the Western Zhou Dynasty, the forest coverage rate of the Loess Plateau was as high as 53%, but later with the development of human society, the level of agricultural productivity did increase, but the population became larger and larger, which meant that the demand for food and housing was also getting bigger.
Then, the vegetation on the Loess Plateau slowly began to decrease, especially after iron tools were widely used in the Spring and Autumn period and the Warring States Period, such as the middle and lower reaches of the Fenhe Plain and the Guanzhong Plain, which were the first to bear the brunt of the grasslands and forests in these places, and then turned into arable land. After entering the Qin and Han Dynasties, a large number of woodlands and grasslands in the western and northern parts of the Loess Plateau were gradually transformed into farmland to meet food needs.
Although the Loess Plateau still had a forest cover of about 40% during the Southern and Northern Dynasties, it gradually dropped to 33% during the Tang and Song dynasties. If you want to say that the period of rapid vegetation destruction on the Loess Plateau is the period from the Ming and Qing dynasties to the early 20th century, during which the forest coverage rate directly fell to about 6.1%.
The vegetation on the Loess Plateau has become less, and the sediment entering the Yellow River has naturally become more, which can also be seen from the amount of yellow sediment in each period: from the Western Zhou To the Sui and Tang Dynasties, the amount of yellow sediment into the Yellow Plateau was about 200 million tons per year, but by the time of the Ming and Qing Dynasties, the amount of yellow sediment into the Yellow River reached an average of 600 million tons to 1 billion tons per year, and after entering 1800, the Loess Plateau reached the highest level of soil erosion in history, and the amount of sediment entering the Yellow River in one year was about 1.6 billion tons!