What is the function of water?

What is the function of water?

The most basic is to quench thirst

How much water is there in the world

There is a lot of water on the earth. It is estimated that the total volume of water is about 1.38 billion cubic kilometers. If these levels are distributed on the surface of the earth, it means that the whole surface of the earth is covered with a layer of water with an average depth of 2650 meters. Unfortunately, 98% of the water is salt water, mainly distributed in the ocean. Fresh water only accounts for 2% of the total water of the earth, about 30 million cubic kilometers, And the 2% of fresh water can not be used by human, because 88% of it is frozen in the polar ice caps and glaciers, and the remaining 12% are rivers, lakes and shallow groundwater that can be exploited. Most of them are groundwater, which can not be used without exploitation. The water in rivers and lakes that can be directly applied only accounts for 0.04% of the total fresh water, It is always changing. The water from the sea and land evaporates into the atmosphere, and then forms rain or snow, which falls back to the earth, nourishes all things, replenishes rivers and lakes, or flows into the sea. Water will also seep into the underground and sink into the underground aquifer. The extremely deep groundwater can not be replenished or exploited, so it is called primary water, so it cannot be regenerated, As a result, there are floods or droughts on land, resulting in uneven distribution of water resources. About 65% of the world's water resources are concentrated in 10 countries every year, while 80 countries with a total population of 40% of the world's total population (including 9 countries in the near and Middle East) are seriously short of water, The other 26 countries (a total of 230 million people) also have very little water resources. We call these countries water deficient countries. The international standard for water deficient countries is based on the definition given by Swedish hydrologists Marin and falcenmark: if the renewable fresh water supply of a country is less than 1700 tons per person per year, At present, there are 15 countries with an average annual water supply of less than 1000 cubic meters per person. Among these countries, the annual per capita water supply of Maltese is only 82 cubic meters, ranking first in the water shortage countries, Qatar (91 cubic meters per capita per year), Kuwait (95 cubic meters per year), Libya (111 cubic meters per year), Bahrain (162 cubic meters per year), Singapore (180 cubic meters per year), Barbados (192 cubic meters per year), Saudi Arabia (249 cubic meters per year), Jordan (318 cubic meters per year), Yemen (346 cubic meters per year), Algeria (527 cubic meters per year) and Brunei are the most water deficient countries It is estimated that by the middle of the 21st century, water in these countries will be more expensive than oil. For example, the annual average per capita in Malta will be 68 cubic meters

Why is there water in the world?

There are more than 30 opinions about the formation of water on the earth, which can be roughly divided into two categories: one is "primary"

Where does the water in the world come from?

There are various opinions about the source of water on the earth, which reflects the diversity of water sources, but it mainly includes two kinds of situations, one is spontaneous, that is, the earth's water comes from the earth's interior; the other is exogenous, that is, the earth's water comes from the space outside the earth