The water cycle involves evaporation, condensation, and precipitation. Water evaporates from the earth's surface and condenses in the atmosphere to form clouds. The water then falls back to earth as precipitation such as rain or snow. Groundwater is water stored underground in soil and rock, which is recharged through precipitation and runoff infiltrating the ground. Water pollution can occur from air and land pollution being washed into waterways by rain, or from direct dumping of waste into bodies of water.