Water or Oil 水与油

The Present Situation of Water
• Water Resource Distribution and Desalination
• Water uses
• Water pollution
1.Water Resources
Water covers 71% of the Earth's surface and is vital for all known forms of life. On Earth, 97% of the planet's water is found in oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds, and precipitation. Only 3 % of the Earth's water is freshwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products.
3. Water pollution
Water crisis Disproportion in distribution Increase in population Pollution intensify … Water is considered polluted if a substance or condition is present that renders the water useless for a particular purpose. e.g. drinking water for humans is considered polluted (non-potable) if it contains pathogens or toxic substances. Analysis from source, pollutant and water body.
The Additional Effects
Agriculture
Crops needs the irrigation of water , which is a key component to produce enough food. Irrigation takes up to 90% of water withdrawn in some developing countriesand significant proportions in more economically developed countries (United States, 30% of freshwater usage is for irrigation).
Heat exchange
Water and steam are used as heat transfer fluids in diverse heat exchange systems, due to its availability and high heat capacity, both as a coolant and for heating. Cool water may even be naturally available from a lake or the sea. Condensing steam is a particularly efficient heating fluid because of the large heat of vaporization.
Water or Oil
Which is more important?
Water-the first national agenda
• As we all known,water is the necessity of our daily life,no one can stay alive without water for a long time.But with the increase of population,the drinkable water cannot satisfy the great demands.So,we are facing a severe problem of water shortage.Although oil is important,and oil crisis is also serious today,we can find some reproducible energy to substitute it,while it is impossible to find some other things to replace the function of water.In a word, we should put water into the first national agenda.
In-stream Uses Non-consumptive. Major in-stream uses are hydroelectric power, recreation, and navigation. Presently, hydroelectric power plants produce 2.5% of world energy.
Chemical uses
Water is widely used in chemical reactions as a solvent or reactant and less commonly as a solute or catalyst. In inorganic reactions, water is a common solvent（普通溶 剂）, dissolving many ionic compounds(离子化合物）
Other Effects
Washing
The propensity of water to form solutions and emulsions is useful in various washing processes. Many industrial processes rely on reactions using chemicals dissolved in water, suspension of solids in water slurries or using water to dissolve and extract substances. Washing is also an important component of several aspects of personal body hygiene.
So Many People
More than 1/3 people all around the world is suffring lack of water!
2. Water uses
Domestic use Agricultural use Industrial use In-stream use
Four common irrigation methods: Surface / Flood (地面灌溉) Requires extensive canal systems. Spray (喷洒灌溉) Mandates use of pumps. Trickle (滴水灌溉) Strategically placed openings. Sub-Irrigation (地下灌溉) Pipes can be used for drainage as well.
Toxic and overload wastes lead stream and lake degradation
protect waters from pollution.
Setting water quality standards for surface water. Limiting effluent discharges into the water.Biblioteka Transportation
The use of water for transportation of materials through rivers and canals as well as the international shipping lanes is an important part of the world economy.
Desalination: a costly option
Two major problems: High cost. Desalination produces large quantities of briny wastewater that contains lots of salt and other minerals.
Life Comes From Water
Food comes from water
The Effects of Water
drinking
The human body contains from 55% to 78% water, depending on body size.To function properly, the body requires between one and seven liters of water per day to avoid dehydraton(脱水）