The Earth’s water is always moving and changing state from liquid to vapour to ice and back again. This process is known as the water cycle or the hydrologic cycle, it has been working for billions of years and all life on Earth depends on it. The water cycle shows the circulation of water from Earth’s oceans to the atmosphere to the land and back again.
For example, this model outlines the water cycle in the Roscommon area currently under investigation by our Groundwater team (more details, redirect to Groundwater programme).
    

 
Water from the oceans and the land is evaporated by the sun, as it rises it cools and condenses forming clouds, when the clouds get too dense they drop this water as rain. As the rain falls it can either run off the land and return to the ocean or it can soak into the ground and be stored in underground reservoirs known as aquifers.