Water is said to have played a key role in the existence of life on earth. In fact, many theories suggest that early forms of life began in oceans and thrived there. With two-thirds of the earth's surface covered by water and the human body consisting of 75 percent of it, it is evidently clear that water is one of the prime elements responsible for life on earth.
We cannot imagine earth without water. The soil, with no water in it and nothing growing on it, would be lifeless, dead, collapsed into dust, sand, clay or rock. The composition of the air would change too. All the methane currently stored in ice and the ocean would be released, thereby increasing the heating effect of the sun.
In fact, the climate of the earth is controlled by oceans. Water cools the earth when it heats up and warms it when it cools down. When the temperature drops low enough, water freezes, releasing its own heat and warming the frigid air. When the temperature rises high enough, water evaporates, taking some of the heat with it and cooling the hot air.
Every year March 22 is celebrated as the World Water Day. The day is celebrated to focus on the importance of water and need to preserve it. The United Nations General Assembly designated 22 March 1993 as the first World Water Day, and this year it's the 25th World Water Day. The theme for World Water Day 2018 is 'Nature for Water' - exploring nature-based solutions to the water challenges we face in the 21st century.
Water and Human body:
Water does more than just quench thirst and regulate body's temperature. The human body cannot carry out and sustain its functions without water. Besides being the basis of saliva and fluid guarding the joint system, water prevents the human body from diseases of different kinds. Each and every human cell needs water for its sustenance, be it the blood cell or neuron the smallest unit of the nervous system. Water has its part to play in the transportation of nutrients. Adequate water intake enables the human body to excrete waste through perspiration, urination, and defecation. The kidneys and liver use it to help flush out waste, as do the intestines.