Our planet also has water on its surface, which is something very unique. In fact, Earth is often called the 'Blue Planet' because most of it is covered in water. This water is made up of freshwater in rivers and lakes, the saltwater of the oceans and estuaries, groundwater and water vapour. Together, all these water bodies are called the hydrosphere. The term hydrosphere (Greek hydro means "water") describes the collective mass of water found on, under, and over a planet's surface.
The hydrosphere considered as the Earth's water budget is about 97% saltwater while the remaining 3% is freshwater. Among the freshwater on Earth, 2.59% is in the form of ice caps, glaciers, ice bergs and deep ground water which are difficult to obtain.Conversely, just a mere 0.41% of all waters on Earth are readily available for use for drinking, bathing, cooking and for man's survival.
You might wonder that since that there is a a very small amount of fresh water available, there will be not enough for man, plants, and animals. But remember that there is a continuous cycle of water or the hydrologic cycle.
* Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air.
* Water vapor in the air gets cold and changes back into liquid, forming clouds. This is called condensation.
* Precipitation occurs when so much water has condensed that the air cannot hold it anymore. The clouds get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.
It is so easy sometimes to take our hydrosphere for granted and we seldom take the time to really think about the role that this part of the planet plays in keeping us alive. Below are just some of the very important functions of water in the hydrosphere:
- Water is a part of living cells. Each cell in a living organism is made up of almost 75% water, and this allows the cell to function normally. In fact, most of the chemical reactions that occur in life, involve substances that are dissolved in water. Without water, cells would not be able to carry out their normal functions and life could not exist.
- Water provides a habitat. The hydrosphere provides an important place for many animals and plants to live.
- Regulating climate. One of water's unique characteristics is its high specific heat. This means that water takes a long time to heat up and also a long time to cool down. This is important in helping to regulate temperatures on earth so that they stay within a range that is acceptable for life to exist. Ocean currents also help to disperse heat.
- Human needs. Humans use water in a number of ways. Drinking water is obviously very important, but water is also used domestically (e.g. washing and cleaning) and in industry.It is essential to life, without water humans would die in a week. In addition, the human body is mostly water. Approximately, the human body is made up of 60% water, blood about 50% while the brain is 77% water ,
- Water can also be used to generate electricity through hydropower.
These are just a few of the very important functions that water plays on our planet.
Hydrosphere is very important in our daily life. We need water to live. All living things like animals, plants need water to survive. And all these things can be useful to us but we shouldn’t abuse but conserve this instead. Use water wisely and properly.
