Where Is Earth's Water?

Water is essential for the survival of all known forms of life. While water covers 72% of the Earth's surface, almost 97% of that water is salt water and so is undrinkable. Of the remaining 3%, only a tiny 1% is accessible, while the other 2% is stored in glaciers and the polar ice caps.

Bodies of water containing low concentrations of salts like those found in ponds, lakes, rivers and streams are referred to as freshwater.

Water is rarely found in its pure form (i.e. containing no dissolved substances), except possibly in laboratories. To support aquatic life, it must contain an adequate level of dissolved oxygen. Water with high levels of dissolved salts and low levels of dissolved oxygen is not very nice to drink.

Where Is Our Water?

Ireland is surrounded by sea and has a 89 million hectare expanse of marine water. Approximately 30% of the country is covered in wetlands - areas of water where the depth does not exceed six metres. This includes all rivers and bogs and some lakes and estuaries. We often see water as an infinite resource when, in fact, it is easily affected by human activity. The need to conserve our water sources and its purity is essential for the benefit of health and life on the planet.

The Water Cycle

The Water Cycle is a key process of the hydrosphere. This cycle describes the continuous movement of water on, above and below the surface of the Earth. It provides a continuous supply of fresh water in the environment and consists of 5 main processes:


1) Evaporation - water is heated and changes from liquid to gas (water vapour).

2) Condensation - vapour rises and condenses into tiny droplets to form clouds.

3) Precipitation - particles of liquid water or ice that fall from the atmosphere as rain, hail or snow.

4) Absorption - the earth absorbs the water.

5) Runoff - when the ground has absorbed water to full capacity, excess water from rain, snow and hail flows overland and eventually flows into streams, rivers and lakes and makes its way back to the sea.

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