The first natural paragraph of the text The Water of the Earth: Alien Heaven introduces the and

The earth's water resources are distributed in solid, liquid and gaseous forms on the earth's surface and in the atmosphere, lithosphere and biosphere, and their total amount is very large, about 13 861017 cubic meters. However, 97.5% of these water resources are seawater, while freshwater with less than 1 gram of chlorine per liter of water accounts for only 2.5% of the total water volume. Moreover, a large part of the world's freshwater reserves are concentrated in the poles, glaciers and deep subsurface.

Due to economic and technical constraints, the use of ice and snow solid fresh water and deep groundwater has been very limited so far. As a result, only 11 per cent of the total freshwater reserves are easily available and closely related to human survival and livelihood. It can be seen that despite the large amount of water resources in the world, the amount of freshwater resources that can be directly used by human beings is actually very small.

China is a country with severe water shortage, with per capita water storage equivalent to only 1 4 of the world average, and most of the water resources are concentrated in the southern region. Since the founding of the People's Republic of China, the country's water consumption has grown rapidly. Total water use was 103.1 billion cubic metres in 1949 and increased to 554.8 billion cubic metres in 2004.

Of the total water used in 2004, 11.7 per cent was used for domestic use, 22.2 per cent for industry, 1.5 per cent for ecology and 64.6 per cent for agriculture. At present, the utilization rate of agricultural irrigation water in China is only 45%, which is obviously different from the high utilization rate of 70%-80% in advanced water-saving countries. If in 2030, the population of the north and south of China is still distributed according to the current ratio of 53 5 to 46 5, then according to the per capita water demand, the total water demand in the northern region will reach 372 billion cubic meters per year, which has reached more than 90% of the total water resources in the north of China, which means that the northern region will have almost no water available, and the sustainable development of the economy, society and environment in the northern region will not be guaranteed.

Not only has the severe shortage of water shattered the once thought that water was inexhaustible, but it is also replacing oil as one of the main causes of the crisis around the world. According to statistics, more than 2 billion people in the world today are facing a severe shortage of freshwater resources. Already 1 in 4 people around the world are facing a struggle to get enough water for drinking, irrigation and industry.

This battle over water is not only between countries, but also between regions and even between villages. It is expected that by 2025, 2 to 3 people around the world will face instability due to severe water scarcity. The crisis caused by water resources has attracted great attention from countries around the world.

The earth's water resources are distributed on the earth's surface and in the atmosphere, lithosphere, and biosphere in solid, liquid, and gaseous forms.

1 The water on the earth is like a spring ball, and it comes from **.

2 After the formation of the earth, it continued to precipitate water from the interior of the earth and accumulate on the surface. (or that the water on Earth was separated from those cosmic matter when the Earth was formed; After the formation of the earth, water from the interior of the earth continued to precipitate and accumulate on the surface. )

3 Earth 4 categories, column numbers, and comparisons.

5 (Outer Space Acorn) Small puck puck.

6 When the earth was formed, it was separated from the matter of the universe; After the formation of the earth, it is precipitated from the interior of the earth; Ice hockey pucks from space are constantly replenished.