Water Sources: Groundwater

cracked earth

With National Water Week starting on Sunday, here is the next post in our series on ‘Water Sources – there are more than you think’.

What is groundwater?

Groundwater is underground water. Groundwater and surface water are connected as surface water seeps deep into the ground and forms huge underground reservoirs in rock formations called aquifers. We can pump water out of these aquifers for use on the surface, often for agriculture but also for horticulture, domestic use and either direct potable use or treatment for potable use. Around 20% of the Earth’s water is stored as groundwater.

What can groundwater be used for?

Groundwater is used for a variety of purposes around Australia. In Victoria, NSW and SA, 60% of extracted ground water is used for irrigation, while in WA 72% is used for urban and industrial supply.

How is ground water used?

The world’s largest and deepest aquifer is the Great Artesian Basin in Australia supplying plentiful water to some of the driest parts of the country. There are also smaller aquifers across Australia that are shallower and can easily be accessed for agriculture and human use.

According to Craig Simmons, National Centre for Groundwater Research and Training, “Groundwater constitutes around 95 per cent of the nation’s fresh water resource. Besides supporting $34 billion in mining, agriculture and manufacturing industries it also keeps the Australian landscape, including its lakes, rivers and wetlands, alive. It is in short our main water bank.“

Groundwater sources take a long time to replenish. In many cases we are using groundwater at a faster rate than it can be replaced. In Western Australia, they have just completed a groundwater replenishment trial, where recycled water is pumped into the aquifer for later use. Check out this animation for a quick overview.

What are some of the benefits of groundwater?

Recently the water industry has had great success with ‘banking’ water in the wet season by pumping it into shallow underground aquifers, and pumping it out again in the dry season when it is needed. The city of Salisbury in Adelaide is rightly famous for its work in this area.

Craig goes on to say “An underground water bank has one huge advantage – unlike a surface dam, water loss by evaporation is minimal. In a country like ours, where evaporation rates often exceed rainfall, this is a vital consideration. It has the added plus of not drowning landscapes, avoiding the clashes so often seen over surface dams. If ever there was an infrastructure challenge worthy of Australia’s mettle it would be the development of a network of large ”underground dams” to conserve surplus water for the dry times we know are on the way.”

What are some of the issues with groundwater?

Cross section of ground water flow

By T.C. Winter, J.W. Harvey, O.L. Franke, and W.M. Alley [Public domain], via Wikimedia Commons

As shown in the diagram, it can take hundreds, and even thousands, of years to fill a large deep aquifer with water. Water managers need to make sure that where we draw water out we also allow time for aquifers to refill. We also need to be careful that groundwater does not become contaminated with pollutants from other activities, like mining.

Further resources:

Do you use groundwater, for example in a garden bore? How do you think Australia should manage this resource?