Junior high school geography examination paper protects water resources.

Although two-thirds of the earth's surface 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.

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 to form clouds and rain. Under the irradiation of sunlight, a large amount of water vapor rushed into the sky, drifted to the mainland with the airflow, and under the action of cold air, rainfall was formed, some of which returned to the poles and the ocean through rivers, and the other part infiltrated into the ground and became groundwater. However, 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 in Himalayas and Kunlun Mountains in China are the main water sources in Qinghai-Tibet Plateau and Xinjiang. Even our mother rivers, the Yellow River and the Yangtze River, all originate from the ice peaks and snow lines on the Qinghai-Tibet Plateau. Every summer, the sun shines on the ice peak, and the melted ice flows along the gully river to Yuan Ye and pasture, which becomes the main water source for local people and animals to drink water and irrigate agriculture and animal husbandry.

Abundant water resources bring vitality to everything and maintain ecological balance. Seen from space, the earth is a blue planet, and 7 1% of its 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 654.38+0.37 billion cubic kilometers, of which fresh water only accounts for 2.5%. 68.7% of fresh water is sealed in permanent snow in polar glaciers and mountains. Therefore, less than 65,438+0% of available fresh water exists in aquifers, rivers, lakes, soils, swamps, plants and the atmosphere, and a large part of it is difficult to obtain. According to the United Nations standard, a country is considered as a water-deficient country if its per capita annual water supply is less than 1000 cubic meters. China's population accounts for 22% of the world's total population, while its per capita freshwater possession accounts for only 8% of the world's total, and its per capita freshwater possession is only 1/3 of the world 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+0 billion people in developing countries can't drink fresh water, and 654.38+0 million 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 that can't be ignored in the water crisis 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 more than 1500 rivers, and the basin area exceeds 1000 square kilometers. However, China has a large population and relatively poor water resources. As far as the whole world is concerned, the high development of industry not only uses more and more fresh water, but also pollutes rivers, lakes and oceans day by day, leading to marine red tides, the extinction of fish and shrimp in rivers, and some even become smelly rivers and dead rivers.

Protecting water resources and preventing water pollution have become the top priority of environmental protection.