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9 Source for every language: www.usgs.gov/special-topics/water-science-school/science/water-cycle-

schools-and-kids
Water returns to the earth's surface by precipitation. On land, some of this water flows over the
surface in streams and rivers into lakes, reservoirs and the oceans.
Understanding how water on land, in the oceans and in the atmosphere is connected in the
hydrologic cycle is essential for the successful management of our water resources, factors affecting
one part the cycle can influence the entire system.

As U.S. Geological Survey (USGS) website mentions, we may think that every drop of rain that falls
from the sky, or each glass of water that you drink, is brand new, but it has always been here and is
a part of the water cycle:

• The heat of the sun provides energy to make the water cycle work.
• The sun evaporates water from the oceans into water vapor.

• This invisible vapor rises into the atmosphere, where the air is colder.
• The colder air causes water vapor to condense into water droplets and clouds.

• Volcanoes can produce steam, which forms clouds.
• Water drops form in clouds, which then fall to Earth as precipitation (rain and snow).
• In cold climates, precipitation builds up as snow, ice, and glaciers.

• Snow can melt, and then flows into rivers, the oceans, and into the ground.
• Some ice evaporates directly into the air, skipping the melting phase (sublimation).

• Rainfall on land flows downhill as runoff, providing water to lakes, rivers, and the oceans.

This project has been funded with support from the European Commission. This communication reflects the
views only of the author, and the Commission cannot be held responsible for any use which may be made of the

information contained therein.