Water is the world's most important resource, without it life on Earth would not exist. We rely on it for everything from drinking supplies, to its use in agriculture, to supporting animal and plant life around the world (i.e. to sustain our ecosystems). Approximately 71% of the Earth's surface is covered by water but not all of it is available to us for use.

Over 96% of the world water is held in our oceans and only 2.5% of Earth's water is freshwater. Of this 2.5% of freshwater the majority is trapped in glaciers and ice-caps with the remainder being groundwater or surface water such as lakes and rivers. 

In Ireland we rely heavily on groundwater, it supplies 20-25% of our drinking water supplies and in some counties it supplies up to 50%. In rural areas not served by water schemes it is the only source of drinking water with these areas relying on wells and springs. 

In this section you will learn about onshore and offshore water.

Onshore water includes things like groundwater, which is important for our drinking water and surface water, such as lakes and rivers.
Offshore water refers to the oceans and the seas. Did you know that from being able to map the seabed, the INFOMAR programme (a collaboration between Geological Survey Ireland and Marine Institute) has been able to determine that the Irish territory still continues kilometres out to sea and that the Irish landmass only makes up 10% of Ireland's territory.

The Water Cycle

Water continuously changes state from liquid to vapour to solid, and these changes, and the relationship between them are linked by what is called The Water Cycle, a cycle which has been around for billions of years and which, as stated above, all life depends upon. 

In oceans, lakes, rivers and other bodies of water, water is in its liquid form. With the sun, the water evaporates (turns into its vapour form) from the surface of these water bodies and rises upwards into the sky. As it rises, the difference in temperature causes the water vapour to cool and condense, forming clouds. When these clouds become too dense, the water drops, back in its liquid form, as rain. When rain falls, it can either run off the land and return to water bodies or it can soak into the ground and be stored as groundwater in underground reservoirs known as aquifers. When it is cold, and temperatures fall below 0°C, water freezes into its solid state, ice. When it warms up and melts, evaporation occurs and the process of evaporation occurs again, and the water cycle continues. The water cycle is continuously circulating water from Earth's water bodies, to the atmosphere, to the land and back again.