Soil Salinity in Australia (2001)
By Steve GartnerJune 1st, 2001
Increasing soil salinity in Australia is a serious land degradation issue. All over the country, salt is rising out of the ground and destroying our farms, homes and towns.
To understand why we have this problem, we need to go way back in Australia’s history.
[Title appears: Soil Salinity in Australia]
[Gloomy music plays and image of a lake with salt damage appears on screen]
Narrator: Salt – white death.
[Camera pans over different areas of salt effected ground]
All over Australia it’s rising out of the ground and destroying our farms, homes, and towns. To understand why we have this problem we need to go way, way back in Australia’s history.
[Image changes to show channels of water and then spirals into a computer generated map of Gondwana, text appears: 360 million years ago]
Australia was once part of a huge super continent called Gondwana. It was joined to Antarctica, India, Africa, and South America. Since then a lot has happened to the land that became Australia.
[A blue shadow appears over an area within the map]
During a severe ice age part of it was covered by an ice sheet. As the ice moved across the land it ground up rock to make new soil. It was the last time new soil was made that way in this continent. Later, India broke away.
[Image changes to show dashes appearing which outlines India, text appears: 160 million years ago]
The climate was much wetter than today, and parts of Australia sank under the weight of river sediments.
[Image changes to show sections of land breaking away, text appears: 118 million years ago]
Still later, when the sea level rose, a lot of the land went under water.
[Image changes to show the map rotating, the outline of Australia can be seen now, text appears: 84 million years ago]
Then the east coast tilted up when it broke from the New Zealand subcontinent, and at the same time parts sank, and continued to sink.
[The computer generated map sinks lower into the ocean, text appears: 60 million years ago]
When Australia finally broke free of Antarctica, large areas were still sinking.
[Image changes to show the clear outline of Australia now, text appears: 45 million years ago]
One of those areas forms the Murray Darling River Basin, which is the site of our biggest river system and major farming lands.
[Image changes to a yellow highlighted section on the map of Australia with blue lines representing the river system appearing in it]
Today the sinking continues, and Australia is shaped like a giant shallow saucer.
[Image changes to an animated cross section of Australia showing the centre as lower than sea level]
If you look at a cross section from east to west you can see that Lake Eyre, near the centre, is well below sea level. This means that rain falling on much of the country drains inwards. For millions of years clouds have dumped salt on the earth in rain.
[Animated clouds move across the picture dumping rain]
Because of the shape of the country the salt hasn’t been able to get back to the sea, it’s had nowhere to go but into the ground. The water that took it there forms a layer of salty underground water. The top of that layer is called the water table.
[Animated trees now appear in the picture coming from a brown level representing soil. Below that is a blue level labelled ‘water table’]
Australia’s native vegetation has evolved in harmony with the water cycle. Many trees and grasses are deep rooted, so they can take up most of the rain that falls on the ground.
[The animated clouds move back over the picture dumping water on the trees. Directional arrows show how the water is absorbed by the roots deep in the ground]
Because they grow all year there’s no time that water isn’t soaked up. Not much water gets through to the groundwater below, so the water table stays at pretty much the same level.
We’ve disrupted the water cycle in two ways, by clearing vegetation, and by pouring more water on the land when we irrigate for farming.
[Animated crops now appear in the picture situated between the native vegetation]
When European farmers cleared the land, they planted shallow rooted crops that grew for only part of the year, taking up a mere fraction of the water falling as rain.
[The animated clouds move back over the picture dumping water on the crops. Directional arrows show how the water is absorbed deeper into the ground this time, in turn making the blue level, or the water table, rise]
The excess water moved down to the subsoil. Eventually the water table rose, bringing salt to the surface. This salt kills most plants, and makes it impossible to grow crops.
[As the blue level, or water table, rises with the salt the plants start to turn brown and fall over]
Without plant roots to hold the soil in place the soil washes or blows away, terrible erosion results.
[The camera pans over different shots of erosion affected areas]
[Image changes to show small planted trees]
One of the ways to reverse the problem is to plant deep rooted trees, grasses, or crops that can suck up the water out of the ground.
[The animated picture of trees and rain falling appears again and directional arrows show the water being absorbed better rather than altering the water table levels]
This will lower the water table and allow the salt to go back down into the ground, below the root zone.
[Image changes to show flowing water]
Irrigation presents another problem.
[Image changes to show irrigation sprinklers in action]
Many of our crops are grown using water that’s poured onto the land. Water seeps from irrigation channels and from over watered crops into the water table. It’s important to add just enough water to the soil to grow the plants, because any extra water causes the water table to rise.
[Image changes to an aerial shot of an irrigation channel]
Every year Australia loses large areas of farming lands to salt.
[Shots of salt affected landscapes followed by sequences of land clearing practices]
If we don’t turn this situation around quickly we’ll have difficulty feeding ourselves. We need to change our land use patterns, and start gaining income from the native plants that grow so well in our landscape.
It’s not only plants that are affected by salt.
[Camera zooms in on bricks at the base of house showing the effects of salt damage]
Homes across Australia are crumbling as salt eats away at the foundations and walls. Houses built to last 25 years are surviving only two years.
[Image changes to show a group of children planting a tree]
By growing native trees and shrubs around homes, and reducing the size of the lawn, the need to water the garden can be reduced.
[Camera zooms out on houses and then zooms in on a salt affected piece of road]
This stops water seeping into the water table. Roads, too, crumble when attacked by salt. Roads need four times the amount of maintenance where water tables are high.
[Camera pans over each of the things mentioned below]
Playing fields, footpaths, swimming pools, and the whole infrastructure of towns and cities, is damaged by salt.
We’re all in this together. Australia was made rich from the agricultural exports of the last two Centuries.
[Different shots of transport and people moving through the main street of a country town]
The wealth in the towns and cities flowed from government initiatives to clear and use the land. History has caused the problem we face – the future is up to us.
[Image changes to a zoomed out shot of Parliament House and then to the fountain on Lake Burley Griffin]
[Music plays and credits roll: Consultant, Dr. Mary E. White. Stock Footage, Murray-Darling Basin Commission CSIRO Land and Water. Camera, David Reid. Animation, Mats Bjorklund. Editor, Shaun Smith. Post Production Supervisor, Robert Kerton. Original Music, Nick Pitsas. Producer, Sandra McEwen, Powerhouse Museum. Production CSIRO Publishing © 2001]