What are the geographical locations of the Yangtze River and the Yellow River?
The Yellow River can be divided into three sections: the upper reaches, the middle reaches and the lower reaches, and each section has its own environmental characteristics such as topography and climate. The upper reaches are planned to reach Hekou Town, Inner Mongolia from the source, and the elevation is reduced from 4,500m to 1 1,000m, with a drainage area of 384,000m2, accounting for half of the total drainage area. From Lanzhou City, Gansu Province, the river flows from west to east, and the terrain in the basin is rugged and the flat land is scarce. The annual rainfall is between 300-600 mm. Although the rainfall is not abundant, it has become the main water supply area of the Yellow River because of its sparse population and small water demand. Below Lanzhou, the river turns to the north and enters the desert area. The rainfall decreased slightly and the drainage area was smaller. However, after Qingtongxia (Ningxia) irrigation area and Bameng Yellow River (Hetao) irrigation area, the water consumption in these two areas is extremely high. Based on the average flow of the Yellow River for many years of 5.81100 million cubic meters, the inflow from the upper reaches of Lanzhou is 32.3 billion cubic meters, and the adopted amount is only10.80 billion cubic meters. However, from Lanzhou to Hekou Town, the inflow is 600 million cubic meters, accounting for 1.03 cubic meters, which is the area where the Yellow River benefits the most from water resources.
The middle reaches of the Yellow River are located between Hekou Town and Huayuankou, Henan Province, with a drainage area of 344,000 square kilometers, and the river elevation is reduced from 1.000 meters to 400 meters. The northern section of the middle reaches crosses the Loess Plateau, with dry climate and serious soil erosion. The Loess Plateau is the main sediment-producing area in the Yellow River Basin, with the annual sediment yield exceeding1000 million tons. Details are described below. The main tributaries in the south section of the middle reaches are Fenhe River and Weihe River. The climate and rainfall in these two basins are favorable. Since ancient times, agriculture has developed, population is dense and civilization is prosperous. It is the birthplace of China's ancient culture and economy, and won the title of "cradle of China culture".
The annual inflow of the Yellow River in the middle reaches is 24.7 billion cubic meters, but the adopted amount is only 6.2 billion cubic meters. This is a "supply exceeds demand" water resource area, but it is a sand-producing area. A large amount of sediment flows into the Yellow River, and most of the water resources are wasted on the burden of transporting sand into the sea. It is estimated that the annual water demand for sediment transport is 20-24 billion cubic meters, which is the main part of the current annual flow of the Yellow River into the sea of 32.3 billion cubic meters.
The area of the lower reaches of the Yellow River is very small, only the beaches in the levees on both sides and the highlands at the northern foot of Mount Tai. The areas on both sides of the river basin are densely populated and developed in agriculture, and there is a great demand for river water. At present, the annual water consumption is 2 1 100 million cubic meters, while the used amount is 8.8 billion cubic meters. With the economic development in recent years, the demand for water supply is increasing, and the water resources of the Yellow River have been overwhelmed. If the water use mode is not effectively adjusted, it is estimated that the Yellow River Basin will be short of water by 654.38+0.6 billion cubic meters every year in 2000.
There are frequent floods in the lower reaches of the Yellow River. In the past two hundred years, there have been three devastating floods. 1843, the Yellow River was flooded once in a thousand years and burst its banks and opened. As a result, the Yellow River diverted from Taishan North Road (the so-called "ancient road of Ming and Qing Dynasties") from Taishan South Road to Bohai Bay and became an existing river. Later 1933, 54 places along the extension of the levee were in danger, which flooded 1 1 000 square kilometers and displaced more than 3 million people. Two years later, the Shandong levee burst, flooding 1.2 million square kilometers of land, with 3 million victims.