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Water is the source of life but also a limited resource. Water is not only an essential material to maintain life of all creatures on the Earth， but also impact the survival and development of human society. To conserve water resources and ensure water security is the undeniable responsibilty shared by everyone.
Water and
Water resources
What is water？ How to answer this question？ From the chemistry perspective， water is a kind of compound comprised of two elements： hydrogen and oxygen. From the perspective of life， water is the cradle of life. About 3.8 billion years ago， the most primitive forms of life appeared in the oceans. From the perspective of biological evolution process， liquid water provides the primary prerequisite for the birth and evolution of life. Water is the most widely used solvent， at the same time， it is an important material that contained in various organisms. 70% of the human body is composed of water. From the perspective of social life， agricultural and industrial production cannot operate without water. Water breeds the brilliant human civilization that lasts for several thousand years. Since water is a sensitive factor of environment， the inappropriately use or even pollution of water could cause serious impact on the whole natural system.
Are water and water resource the same thing？ UNESCO and the World Meteorological Organization proposed in 1988： water， as a kind of resource， should be available for use or likely to be used， with sufficient quantity and usable quality and being suitable to satisfy the water need of a certain place for a long-term. While water resource refers to fresh water which can be developed and used.
Knowledge of water on the Earth
Although 70.8% of the Earth surface is covered by water， total volume reaching 1.386 billion cubic kilometers， fresh water resource on the Earth is extremely limited. Of all water resource， water in the ocean takes up 97.2 percent， mainly salt water unsuitable for drinking directly. The remaining 2.8% is fresh water， but 70% of it distribute on polar ice caps， glaciers and permafrost zone alpine snow， difficult to be utilized. Human beings only have access to water from rivers， freshwater lakes on land and water in shallow ground， accounting for less than a million of the total water volume. If all water on the Earth can be described as a large tank， the accessible fresh water is only the equivalent of a small cup， indeed a very small proportion. Water resource on the Earth is in a continuous cycle， primarily because after evaporating， water will rise and form airflow which is taken to the mainland or ocean. Under the right condition， after condensation， it will turn into rain or snow， and fall down. If sea water evaporates， forms water vapor and then falls down on land， the process is called systemic circulation， which provides the major source of fresh water on land. But because of the influence of atmospheric circulation and climatic zone， the precipitation is obviously imbalanced in terms of area and time； when precipitation on land is caused by evaporation from the land or the precipitation in the sea is caused by evaporation of water on the surface of sea， the process is referred to as the minor cycle. Surface water and shallow groundwater can be connect with and complement each other， which is called the hydro-logic cycle. The rational use of systemic circulation and hydro-logic cycle is the basis and premise of rational utilization and management of water resource. Due to the cycle， water resource can be constantly regenerated. However， any problem on a certain link of the water cycle will cause the destruction of the whole cycle， resulting in a variety of natural disasters.
It is generally believed that water is a kind of inexhaustive resource or constant resource， but the constancy is defined in terms of the global scope， which means that the total water volume is constant on the Earth， however， from the point of regional distribution， the problem of water shortage is very prominent. But in terms a region， if the circulating water can be reasonably utilized， the shortage of water resource can be greatly alleviated.
The crisis in the water resource shortage
The shortage of water resources has become one of the major issues currently faced by many societies and countries across the world in the 21st century. Though currently there is no such global event as water resource shortage， an increasing number of areas have been plagued by water shortage for a long time. A report by the UN statistics reveals that about 1.2 billion people， close to 1/5 of the world's population， live in the area naturally lack of water resources， and another 500 million more are about to be exposed to the same situation. Another 1.6 billion people， roughly a quarter of the world's population， confront water resources shortage related to economic mode.
The shortage of water resources is caused not only by nature， but also by human beings. On our planet， there exists enough fresh water for the use of 6 billion people， but it is unevenly distributed， plenty of which is stored in polar ice and snow cover， continental mountain glaciers and in the deep underground permafrost which is very difficult to access. This is a congenital problems. On the other hand， another important reason behind the shortage of water resources is that too much waste， pollution and even the unsustainable way of water use. What’s more， climate warming and trend of rainfall decrease aggravate the crisis of water shortage. It is predicted that as the existing situation of climate change， to year 2030， there will be almost half of the world's population living in regions with high pressure of water shortage. In some dry and semi-arid regions， water resources shortage will force hundreds of millions of people leave their homes and find new ones.
Water and
Water resources
What is water？ How to answer this question？ From the chemistry perspective， water is a kind of compound comprised of two elements： hydrogen and oxygen. From the perspective of life， water is the cradle of life. About 3.8 billion years ago， the most primitive forms of life appeared in the oceans. From the perspective of biological evolution process， liquid water provides the primary prerequisite for the birth and evolution of life. Water is the most widely used solvent， at the same time， it is an important material that contained in various organisms. 70% of the human body is composed of water. From the perspective of social life， agricultural and industrial production cannot operate without water. Water breeds the brilliant human civilization that lasts for several thousand years. Since water is a sensitive factor of environment， the inappropriately use or even pollution of water could cause serious impact on the whole natural system.
Are water and water resource the same thing？ UNESCO and the World Meteorological Organization proposed in 1988： water， as a kind of resource， should be available for use or likely to be used， with sufficient quantity and usable quality and being suitable to satisfy the water need of a certain place for a long-term. While water resource refers to fresh water which can be developed and used.
Knowledge of water on the Earth
Although 70.8% of the Earth surface is covered by water， total volume reaching 1.386 billion cubic kilometers， fresh water resource on the Earth is extremely limited. Of all water resource， water in the ocean takes up 97.2 percent， mainly salt water unsuitable for drinking directly. The remaining 2.8% is fresh water， but 70% of it distribute on polar ice caps， glaciers and permafrost zone alpine snow， difficult to be utilized. Human beings only have access to water from rivers， freshwater lakes on land and water in shallow ground， accounting for less than a million of the total water volume. If all water on the Earth can be described as a large tank， the accessible fresh water is only the equivalent of a small cup， indeed a very small proportion. Water resource on the Earth is in a continuous cycle， primarily because after evaporating， water will rise and form airflow which is taken to the mainland or ocean. Under the right condition， after condensation， it will turn into rain or snow， and fall down. If sea water evaporates， forms water vapor and then falls down on land， the process is called systemic circulation， which provides the major source of fresh water on land. But because of the influence of atmospheric circulation and climatic zone， the precipitation is obviously imbalanced in terms of area and time； when precipitation on land is caused by evaporation from the land or the precipitation in the sea is caused by evaporation of water on the surface of sea， the process is referred to as the minor cycle. Surface water and shallow groundwater can be connect with and complement each other， which is called the hydro-logic cycle. The rational use of systemic circulation and hydro-logic cycle is the basis and premise of rational utilization and management of water resource. Due to the cycle， water resource can be constantly regenerated. However， any problem on a certain link of the water cycle will cause the destruction of the whole cycle， resulting in a variety of natural disasters.
It is generally believed that water is a kind of inexhaustive resource or constant resource， but the constancy is defined in terms of the global scope， which means that the total water volume is constant on the Earth， however， from the point of regional distribution， the problem of water shortage is very prominent. But in terms a region， if the circulating water can be reasonably utilized， the shortage of water resource can be greatly alleviated.
The crisis in the water resource shortage
The shortage of water resources has become one of the major issues currently faced by many societies and countries across the world in the 21st century. Though currently there is no such global event as water resource shortage， an increasing number of areas have been plagued by water shortage for a long time. A report by the UN statistics reveals that about 1.2 billion people， close to 1/5 of the world's population， live in the area naturally lack of water resources， and another 500 million more are about to be exposed to the same situation. Another 1.6 billion people， roughly a quarter of the world's population， confront water resources shortage related to economic mode.
The shortage of water resources is caused not only by nature， but also by human beings. On our planet， there exists enough fresh water for the use of 6 billion people， but it is unevenly distributed， plenty of which is stored in polar ice and snow cover， continental mountain glaciers and in the deep underground permafrost which is very difficult to access. This is a congenital problems. On the other hand， another important reason behind the shortage of water resources is that too much waste， pollution and even the unsustainable way of water use. What’s more， climate warming and trend of rainfall decrease aggravate the crisis of water shortage. It is predicted that as the existing situation of climate change， to year 2030， there will be almost half of the world's population living in regions with high pressure of water shortage. In some dry and semi-arid regions， water resources shortage will force hundreds of millions of people leave their homes and find new ones.