Water changes states between liquid, solid and gas during the cycle. Condensation, evaporation and freezing of water occur in the cycle in response to the earth's climatic conditions. Surface water is evaporated from the Earth by the energy of the Sun. The water vapor forms clouds in the sky. Depending on the temperature and weather conditions, the water vapor condenses and falls to the Earth as different types of precipitation.
Some precipitation runs from high areas to low areas on the Earth's surface.
This is known as surface runoff. Other precipitation seeps into the ground and is stored as groundwater. Some people may be more vulnerable to contaminants in drinking water than the general population. These people should seek advice about drinking water from their health care providers. All sources of drinking water are subject to potential contamination by constants that are naturally occurring or manmade.