Diagram The diagram explains the natural process of water circulation in the ground, the oceans and air. Three main stages are shown on the chart. water evaporates the ocean, drops out in the form of a rain, and at last gets back to oceans again. 80 percent of water vapor in air come from the oceans. Heat of the sun forces water to evaporate, and water vapor is condensed with formation of clouds. Then on the chart, water drops out in the form of a rain or snow. And, at last, water which reaches the Earth's surface eventually connects oceans in two various ways. Some of them can get to lakes or return to oceans by means of "a superficial drain" and secondly, it filters in to ground water and gradually mix up with ocean water, accepting some minerals, such as salt from the earth. In summary, the nature carries out regulation of water in continuous process of evaporation, condensation and rainfall.