Planet Earth is unique. It is the only planet that can support life.The Earth is just the right distance from the sun to have temperatures that are suitable for life to exist. The earth has four physical systems namely the the atmosphere (air), lithosphere (land), hydrosphere (water) and biosphere (life). Earth's atmosphere has exactly the right type of gases in the right amounts for life to survive.

On the other hand, hydrosphere refers to that portion of Earth that is composed of water. 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 vapor.

         The term hydrosphere comes from the Greek word hydro means "water" that describes the collective mass of water found on, under, and over a planet's surface. It includes oceans, but technically includes clouds, inland seas, lakes, ponds, streams, rivers, and underground waters.

         The hydrosphere covers about 70% of the surface of the Earth and is the home for many plants and animals. We live in a world of water, but approximately 97% of it makes up the oceans.  Ocean water is too salty to be used for drinking water, farming, or manufacturing.  Only 3% of the world's water is fresh, and 2% of this supply is frozen in glaciers and ice caps. And there are only 0.41% of all waters on Earth which are available for use for drinking, bathing, cooking and for man's survival.

       Sometimes it is so easy to take our hydrosphere for granted and we really didn't think about the role that this part of the planet plays making life possible. Knowing its importance help humans to be inform on how Earth's hydrosphere makes life possible. Some of the important functions of Earth's hydrosphere are:

        One of 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 suitable for life to exist. Ocean currents also help to scatter heat.

      
     Many early people used the water in cooking, cleaning, and other aspects of living. They also used the fish and seafood from the nearby bodies of water for their daily food. 

     
     Hydrosphere also plays an important role for transportation. Rivers and ocean currents were the original highways of mankind. Rivers helped people to travel quickly from one place to another and to move large quantities of goods from where they were obtained or made to the market place.

     Moving water can also be used for power. Today large dams are built on rivers, and the release of the water produces large quantities of hydroelectric power used by many cities. In addition, the large lakes that form upstream of the dam provide large recreational areas.

     Hydrosphere which includes river, stream, sea, or ocean is very useful especially for the people living close to it. Particularly the fishermen who depend on the this for their livelihood.

     Scientists, engineers, and farmers are also interested in the hydrosphere. Farmers are interested in the hydrosphere for the reason that it contributes to the irrigation of their crops.

     Water is important. With two thirds of the earth's surface covered by water the human body is mostly water. Approximately, the human body is made up of 60% water, blood about 82% while the brain is 70% water. Just like the circulation of water to the land, it also circulates to the human body by transporting, dissolving, replenishing nutrients and organic matter, while carrying away waste material. It also regulates the activities of fluids, tissues, cells, lymph, blood and glandular secretions. Without water, cells would not be able to carry out their normal functions and life could not exist.

     Water is the best medicine for all diseases and illnesses and its not costly like some healthy product and nutrition products, if you drink water you will be healthy and energized, you will be very active and fast, you will never feel dullness and weakness and your body will grow well.

     Water also provides a habitat. The hydrosphere provides an important place for many animals and plants to live such as the fishes and coral reefs. In addition, various animals that live on land can only procreate if there is sufficient water like frogs.

     Human needs water. Humans use water in a number of ways. Drinking water is obviously very important, but water is also used in washing, cleaning and in industry. 

     The movement of water around, over, and through the Earth is called the water cycle, a key process of the hydrosphere. Water evaporation helps plants and animals to cool down their bodies. The process of exchanging gases when breathing takes place is only possible if the surface is moist.

     Speaking of Earth's hydrosphere, there are really many benefits that it gives to living things. Therefore we have to give importance to it for hydrosphere makes life possible on earth. Conservation of water is one way of giving importance to the hydrosphere and to ensure availability for future generations.