Globally, over 2 billion people use groundwater as a source of drinking water. In some more arid countries such as Pakistan, Saudi Arabia, and Syria, irrigation accounts for 90 percent of groundwater use. The U.S. Geological Survey publishes data on water use in the United States every five years.

In many parts of Australia, native fauna and flora rely solely on groundwater for their survival. Groundwater also contributes water directly to rivers and lakes as baseflow, often maintaining surface water bodies in times of drought. In the arid zone, groundwater sustains important natural and cultural values.

The Great Artesian Basin is Australia’s largest groundwater system. Comprising around 20% of Australia’s total landmass, the Basin covers most of Queensland, the north western parts of New South Wales, part of the Northern Territory and about half of South Australia.

Groundwater can be found almost everywhere. The water table may lie deep or shallow depending on several factors such as the physical characteristics of the region, the meteorological conditions and the recharge and exploitation rates.

Surface water

There are two main sources of water: surface water and groundwater. Surface Water is found in lakes, rivers, and reservoirs. Groundwater lies under the surface of the land, where it travels through and fills openings in the rocks. The rocks that store and transmit groundwater are called aquifers.

About two-thirds of the Earth’s surface is covered with water. Of this, around 97.5% by volume is held in the oceans as salt water; only 2.5% is fresh water and only a very small fraction of this is accessible as a water source. Surface water, groundwater and rainwater are our main sources of water.

Most groundwater originates as meteoric water from precipitation in the form of rain or snow. If it is not lost by evaporation, transpiration or to stream runoff, water from these sources may infiltrate into the ground.

Potable water means drinking water. Well, river and lake contain drinking water as these all contain either rainwater and groundwater which is suitable for drinking. The sea which contains salty water that is not suitable for drinking is not a source of potable water.

Water is abundant in space and is made up of hydrogen created in the Big Bang and oxygen released from dying stars. Earth was moulded from rocks that came from the inner solar system where the fierce heat of the Sun would have boiled away any water. So, according to the textbooks, water must have come later.