Water moves around the Earth continuously. It evaporates from the ocean, gathers in the atmosphere and falls back down to Earth on the land or into the sea as rain or another form of precipitation, such as hail, snow, sleet, mist.

When water falls on the land it forms rivers and streams, collects in lakes and pools and sinks into the ground.

The Murray-Darling Basin is an area of land in which water falling in mountainous regions then drains away forming rivers and streams, lakes and wetlands, and across flat floodplains.