. Three-fourth of the earth’s surface is covered with water, but only a small proportion of it accounts for freshwater that can be put to use. . The process of hydrological cycle began with the evaporation process due to heat of Sun on all water bodies of the earth including seas and oceans. . These minute particles.of the water then get condensed. In this process of condensation, clouds are formed with dust particles and pollen grains present in the atmosphere. . When saturation takes place, then clouds precipitate in the form of rain or snow. This fresh water then becomes surface run-off water, in the form of rivers, ponds and lakes. This water again gets drained into sea or ocean and forms a hydrological process.