Left over precipitation that has not fallen to bodies of water or the ground cannot soak up more water there is left over water the =flows down to the ocean or lakes, rivers.
This is called the water cycle it is the same process over and over it also cleans our water by this cycle now lets go over the layers.
The first one is the Hydrosphere it comes from the Greek word Hydro which means water and is all water like lakes, rivers, and oceans. It moderates climate and is used for weathering.
Then there is the Atmosphere, this contains all gases around Earth and it transfers heat and is used as blanket around earth as well it protects us from radiation which is called the Ozone that protects us.
The Lithosphere is everything no living this helps the ocean with minerals and salt as well with animal it gives them nutrients.
Lastly the Biosphere is everything that is living so deserts, forest, animals, etc. It helps weather happen as well as the earth's oxegon.