Water is a renewable resource, which is constantly moving between, the lithosphere, the atmosphere and the hydrosphere through the process of water cycle. Three fourth of the earth is covered by water. Out of this 97.3% of water is present in the oceans only. Out of the remaining water, about 2% is in the form of ice-caps. This leaves us with only 0.7% of fresh water to be left for our use.
The process by which water continually changes its form and circulates between oceans, atmosphere and land is known as the water cycle. Water links the atmosphere, oceans and land through energy, and matter exchanges as it evaporates, precipitates and flows. Water can change its state as liquid, vapour and ice in the water cycle.
Salinity is the amount of salt in grams, present in 1000 grams of water. Average density of ocean water is 35 grams salt per 1000 grams of water.
Ocean water is characterized by three types of movements termed as the ocean circulations. These are waves, tides and ocean currents. Waves are the movement of surface ocean water caused by wind movement. The rhythmic rise and fall of ocean water, twice in a day, is referred to as tide. The main cause of tides is the gravitational pull of Sun and Moon. Tides can further be classified as high tides and low tides. The third type of ocean movement is the ocean current. Ocean currents are the streams of water flowing constantly in definite directions on the ocean surface.
Creating awareness among the common people regarding the results of water exploitation and degradation at various levels helps to a great extent in water conservation. One of the most important and effective methods of water conservation is rainwater harvesting.