Water:

Although two-thirds of the earth is covered with water, 97.5% of it is salt water, and 87% of the remaining 2.5% fresh water is polar ice sheets, glaciers and ice and snow that are difficult for human beings to use. The fresh water available to human beings only accounts for 0.26% of the global total water, and most of these fresh water is groundwater. In fact, the fresh water that humans can get from rivers and lakes only accounts for 0.0 14% of the total water. For example, there is only one tablespoon of fresh water available in the earth's big water tank, and this tablespoon of water has been seriously polluted.

According to United Nations statistics, since the beginning of the 20th century, the global consumption of fresh water has increased by about 6-7 times, which is twice the population growth rate. At present, 1 400 million people in the world lack safe and clean drinking water, that is, on average,1person in every five people is short of water. It is estimated that by 2025, 3 billion people in the world will be short of water. More than 40 countries and regions are affected, mainly in Africa and the Middle East, and parts of India, Peru, Britain, Poland and China will also be affected.

Among the more than 600 cities in China, nearly 400 cities are short of water, among which more than 130 cities are seriously short of water. Cities across the country lack 6 billion cubic meters of water every year, and the daily water shortage has exceeded160,000 cubic meters. The loss of urban industrial output value caused by the shortage of water resources exceeds 654.38+0.2 billion yuan, and it is on the rise.

China is one of 13 water-deficient countries in the world. According to the international standard, the per capita water resource of 2000 cubic meters is the edge of serious water shortage, and per capita 1000 cubic meters is the minimum requirement line. By 2030, the population of China will reach 654.38+600 million ~ 654.38+700 million, including 654.38+650 million.

It is predicted that by 2000, the annual water shortage in China will exceed 654.38 billion cubic meters. If the effective utilization rate of water is increased by 10%, more than 40 billion cubic meters of water can be saved every year, and the reuse rate of industrial water has increased from 20% in 1980 to about 30% now, and some cities have reached 70%. However, the reuse rate of urban water in China is still far lower than that in developed countries, and the unit water consumption of some important products is several times or even dozens times higher than the advanced level abroad.

At present, the surface water that can't be drunk due to pollution accounts for 40% of all monitored water bodies in China, 78% of river sections flowing through cities are not suitable for drinking water sources, 50% of groundwater is polluted, and 64% of people are using unqualified water sources. According to the inspection results of about 700 large and medium-sized rivers in China by the water conservancy department, nearly 10/2 of the existing rivers in China have been polluted, among which110 has been seriously polluted for a long time, and the water has lost its use value, which makes the above water shortage problem more serious. Due to serious pollution, at present, the river water of half tributaries in the upper reaches of Huaihe River has completely lost its use value, and 62.5% of the main stream cannot be used at all in dry season. The Pearl River, which accounts for 0/2% of the national water resources, is also short of water due to pollution, and many rivers are black and smelly. The water quality in the urban reach of Guangzhou is worse than the five standards, and the river water contains more than 20 kinds of toxic substances. As a result, Guangzhou was forced to spend huge sums of money to transfer water from Xijiang and Dongjiang rivers dozens of kilometers away. Since 1990s, the sewage discharge in the Yangtze River basin has been increasing day by day, with an average of about 654.38+042 billion cubic meters per year, accounting for 40% of the national annual sewage discharge. The water intake in Shanghai extends from Huangpu River to the center of the main stream of the Yangtze River. At present, the capacity of using reservoirs as water supply sources in China is 540 billion tons per year. Although the water quality of most water supply sources is good, there are still 1/3 reservoirs whose water quality is polluted to varying degrees.

Water, like air, is necessary for human beings and all living things. People can't live without water, and animals and plants can't live without water. Scientists have long confirmed that early primitive life originated from water. Therefore, we can say that water is the source of life. In nature, oceans, rivers, lakes, glaciers and groundwater constitute a water world, which scientists call hydrosphere. Hydrosphere and atmosphere, lithosphere and biosphere are isomorphic, forming a complete world.