The water cycle, also known as the hydrological cycle, is maintained by the processes of evaporation, condensation, and precipitation.
Water from oceans, lakes, rivers, and other bodies of water evaporates due to the sun's heat. This water vapor then rises into the atmosphere, where it cools and condenses to form clouds.
As these clouds become heavier, the condensed water droplets fall back to the earth as precipitation in the form of rain, snow, sleet, or hail. Some of this precipitation infiltrates the ground to replenish groundwater supplies, while the rest flows over the land into rivers, lakes, and oceans, completing the cycle.
Therefore, the water cycle is maintained mainly by the processes of evaporation and condensation of water in the environment, which constantly move water between the earth's surface and the atmosphere.