The Water Cycle

The Water Cycle

1. How does it work?

   • Energy from the Sun heats the surface of the Earth.
     • Water is evaporated from oceans, rivers, lakes by the sun
       • The warm, moist air rises because it is less dense.
         • Condensation occurs when water vapour is turned back into water droplets as it cools down and clouds are formed.
           • Precipitation occurs as water droplets get bigger and heavier they begin to fall as rain, snow and sleet, etc.
             • Some water will be intercepted by vegetation and then will evaporate from leaves
               • Some of this water will eventually return to the air as vapour through the process of transpiration. This slows down or prevents some water flowing back to the river.
             • Some water flows across the surface of the ground, This is called surface runoff. This happens when water isn't allowed through the surface because it is already saturated or impermeable
             • Some water infiltrates into the soil. This through flow moves more slowly back to the river than surface run-off.
             • Some water percolates deeper into the ground and is slowly transferred back to the river or sea.
               • Percolation ~ When water moves downwards through the soil.

2. Stores and Transfers

   • The major stores of water are the ice caps, land, ocean and the atmosphere. The movement of water between these stores is called transfers.

3. River drainage basins

   • A river basin or drainage basin is an area of land drained by a river and its tributaries.
   • The edge of the drainage basin is known as the watershed
     • This can be compared to a sink or basin, which catches the water falling into it. The water travels towards the centre and leaves the sink through a plug hole.
       • In a similar way, the water flowing through the river will eventually leave the river basin through its mouth and enter the sea or a lake.

Images and files in the map