Frequently Asked Questions
In Australia, as in many other countries, there is an imbalance in the availability of water and the concentration of population. Most of Australia's water resources are in northern Australia and Tasmania, but most of our population lives in the south eastern mainland.
Most of the water resources where we live are already being used. The Murray-Darling Basin is Australia's most important agricultural production area, but water use has been capped in the area and there is no extra water available.
In Australia we are moving away from notions of drought-proofing the land, and becoming more aware of our physical environments in which droughts are a natural feature. We are aware that water is a finite but renewable resource.
What are the issues of the Murray-Darling Basin?
There are several issues concerned with the Basin:
Land issues
Irrigation salinity and waterlogging
Soil structure and fertility decline
Wind and water erosion
Soil acidification
Dryland salinity
Pest plants and animals
Water issues
Deterioration of groundwater resources
Over-commitment of water resources
Deteriorating quality:
- salinity
- turbidity
- pesticides
- bacteria and viruses
- nutrients
Other environmental issues
Clearance and decline of native vegetation
Habitat destruction/ modification
Destruction of natural heritage sites
Species decline and extinction
Degradation of wetlands
Cultural issues
Deterioration of aboriginal heritage sites
Deterioration of historic heritage sites
Degradation of tourist and recreation sites
Management issues
Uncoordinated and inappropriate policies
Failure to apply existing regulations and policies
Technical knowledge gaps
Lack of community education/ information
Inappropriate management practices and land use
Where does water come from?
97% of the world's water is contained in the oceans as saltwater. The remaining 3% is fresh water made up in the following parts: 2.25% in polar ice caps and glaciers; 0.6% in underground water; and 0.15% in streams, lakes, and the atmosphere. During the hydrologic cycle water undergoes a continual change of state between liquid, solid and gas in four distinct processes.
These processes are:
- evaporation and transpiration
- precipitation (rain, hail, sleet or snow)
- infiltration
- runoff
How is water lost?
All plants, whether irrigated or rain fed, transpire water from the leaves to reduce the temperature when exposed to the sun. If crops are irrigated then a lot of water that is taken from a river or dam can be lost through seepage, evaporation and transpiration, before it actually gets to the farm.
Recent documentation of the effectiveness of water conveyancing in the Murray-Darling Basin from river to farm gate shows that up to 85% of water can be lost when open earthen channel supplies are used. On the other hand, as little as 5% can be lost when new fully piped systems are used and managed well.
How much water is needed to produce food?
CSIRO Land and Water scientists have used precision weighing systems to measure water use by various crops, and the yield from the crops. The following approximate figures were revealed:
- To produce one kilogram of oven dry wheat grain, it takes 715 - 750 litres of water
- For 1 kg maize, 540 - 630 litres
- For 1 kg soybeans, 1650 - 2200 litres
- For 1 kg paddy rice, 1550 litres
- For 1 kg beef, 50,000 - 100,000 litres
- For 1 kg clean wool, 170,000 litres
These figures were determined in very controlled conditions. They can vary with the environment and with the methods of water delivery and harvesting used.
Although many people react with amazement at these figures, we should be cautious about interpreting them. The numbers don't necessarily imply that some types of food are better than others. They do emphasise the large amount of water that is needed to grow food, and demonstrate that we should be investigating ways to conserve and improve water use efficiency.
If you have any questions please go to the Enquiries page and send in your question.