According to United Nations statistics, since the beginning of the 20th century, the global consumption of fresh water has increased by 6-7 times, which is twice as high as the population growth rate. At present, there are 65.438+0.4 billion people in the world who lack safe and clean drinking water, that is, 65.438+0 out of every 5 people are 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, the Middle East and India.
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. China's cities lack 6 billion cubic meters of water every year, and the daily water shortage has exceeded 65.438+0.6 million cubic meters. The loss of urban industrial output value caused by water shortage 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 the year 2000, the annual water shortage in China will soar to more than1800 million cubic meters. If we increase the effective utilization rate of water by 10%, we can save more than 40 billion cubic meters of water every year. The reuse rate of industrial water has increased from 20% of 1980 to about 30% now, and some cities have reached 70%. However, the reuse rate of urban water in China has reached 70%.
At present, 40% of the monitored water bodies in China are polluted surface water, 78% of the river sections flowing through the city are unfit for drinking, 50% of the groundwater is polluted, and 64% of the people are using unqualified water sources. According to the results that about 700 large and medium-sized rivers in China are nearly100000 kilometers, nearly 1/2 of the existing rivers in China are polluted. The river in110 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, half of the tributaries in the upper reaches of Huaihe River have completely lost their use value, and the main stream cannot be used at all in dry season, accounting for 62.5%. The Pearl River, which accounts for 0/2% of the whole country, 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 get water from Xijiang and Dongjiang rivers dozens of kilometers away. Since the 1990s, the sewage discharge in the Yangtze River basin has been increasing, with an average annual amount of about 654.38+042 billion cubic meters, accounting for 40% of the national average sewage discharge. At present, the water intake in Shanghai has extended from Huangpu River to the center of the Yangtze River. 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 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.
The ocean is the cradle of life. Before the ocean appeared, the earth, like other planets in the solar system, was lifeless. The warm and humid air flow in the ocean is the main factor for the formation of clouds and rain. Under the irradiation of sunlight, a large amount of water vapor rushes to the sky and drifts to the mainland with the airflow. Under the action of cold air, rainfall is formed, some of which returns to the poles and the ocean through rivers, and the other part penetrates into the ground and becomes groundwater. In the cold regions of the North and South Poles and the mainland, precipitation appears in the form of snow. Because the temperature is too low, it is difficult for a lot of snow to become hard ice, so glaciers are formed. Glaciers on the Himalayas and Kunlun Mountains in China are the main water sources of the Qinghai-Tibet Plateau and Xinjiang, and even our mother rivers, the Yellow River and the Yangtze River, originate from the snow line of the ice peak on the Qinghai-Tibet Plateau. Every summer, when the sun shines on the ice peak, the melted ice and snow flow along the ravine river to Yuan Ye and pasture.
Abundant water resources bring vitality to everything and maintain ecological balance. Seen from space, the earth is a blue planet, and 765,438+0% of the earth's area is covered with water. However, it is hard for people to imagine that the traditional concept of "inexhaustible" water has begun to become a scarce resource, and protecting water resources has become an important issue facing the whole world.
According to scientists' estimation, the total water storage capacity of the earth is 65.438+0.37 billion cubic kilometers, but fresh water only accounts for 2.5% of it. 68.7% of fresh water is sealed in permanent snow in polar glaciers and mountains. As a result, less than 65.438+0% of available fresh water exists in underground aquifers, rivers, lakes, soils, swamps, plants and the atmosphere. According to the United Nations standard, a country whose per capita water supply is less than 1000 cubic meters per year is a water-deficient country. China's population accounts for 22% of the world's total population, while its per capita fresh water possession is only 8% of the world's average. It is a well-known water-deficient country.
The most serious consequence of water shortage is the deterioration of people's health in some countries. According to the survey of the World Health Organization, 654.38 billion people in developing countries have no access to fresh water, and 654.38 billion people worldwide die of diseases caused by drinking unclean or polluted water every year. What is even more disturbing is that in many parts of the world, there is a conflict crisis between countries for water resources. Another aspect of the water crisis that cannot be ignored is the problem of urban water shortage. The list of cities most likely to face water shortage listed by the United Nations includes Beijing and Shanghai in China, as well as Cairo, Mumbai, Jakarta, Mexico and other megacities.
China is a mountainous and watery country, with 1 1,500 rivers and a basin area of over 1 1,000 square kilometers. However, China has a large population and relatively poor water resources. As far as the world is concerned, the high development of industry not only makes the use of fresh water more and more, but also pollutes rivers, lakes and oceans with the discharge of a large amount of sewage, resulting in red tides and fish and shrimp in the sea.
Protecting water resources and preventing water pollution have become the top priority of environmental protection.