Water is the basic condition for the reproduction and survival of human beings and other creatures, an irreplaceable important resource for people's lives, the most active and influential factor in the ecological environment, and an important resource for industrial and agricultural production, with unique performance and multiple use functions that many other resources do not have. In industrial production, water has a series of functions such as cooling, processing, boiling, power generation and transportation. Agricultural water accounts for 73% of global water consumption, mainly referring to irrigation water.
There are 654.38+0.39 billion cubic meters in the world, of which 97.3% is salt water. 69% of fresh water exists in the form of ice and snow, or it is as difficult to develop and utilize as ice cubes concentrated in the mountains of the North and South Poles. Only a small amount of water is available for people to use, which has direct economic benefits. Although the water quantity is balanced in a certain period of time, it is very limited in a certain space. At present, there have been countries with water crisis in the world, such as Ethiopia. The United Nations has issued a warning: "Water will become a serious social crisis." Water resources have become a very scarce resource for the sustainable development of a country and region. At present, two-thirds of the countries in the world have reflected the water crisis to varying degrees.
China is a country with very short water resources, and the per capita water resources only account for 1/4 of the world average. Although the total amount of water resources in China is about 2.8 trillion cubic meters, the regional distribution is very uneven, with 80% distributed in the south, while the cultivated land in the south only accounts for about 1/3 of the total cultivated land area in China. The water and soil resources are not matched, and the ecological environment is relatively fragile. China is a vast country with a great span from north to south. The difficulty of long-distance water transfer can be imagined. Therefore, the total amount of available water resources is not very large. China has a per capita water resource of 2,300 cubic meters, and the peak population will reach 654.38+0.6 billion by 2030, with a per capita water resource of 654.38+0.700 cubic meters. Will be close to or reach the world-recognized warning line for water use. The shortage of water resources will increasingly become a serious constraint to the economic and social development of China. The average annual cultivated land area affected by drought in China is about 400 million mu. In normal years, irrigation areas lack 30 billion cubic meters of water every year, and cities lack 6 billion cubic meters of water. The total annual discharge of wastewater in China is nearly 60 billion tons, of which 80% is directly discharged into Shuicheng without treatment. Among more than 700 important rivers surveyed and evaluated in China, nearly 50% reach 90%.
As a result of the imbalance between supply and demand, firstly, the national economy water squeezes the ecological environment water, and secondly, the urban and industrial water squeezes the agricultural water. Excessive discharge of sewage in the southern water network area causes water pollution; A large amount of ecological water is squeezed out in the arid area of northwest China, and the trend of desertification is spreading; The development and utilization of water resources in hilly areas of southwest China is arduous, and the carrying capacity of water resources and ecological environment capacity are obviously insufficient.