Water for Food

• Why do we need to know how much water we use to grow food? 
• What issues do we face worldwide?
• What is the situation in Australia? 
• How much water is needed to produce food? 
• How is water lost? 
• How is CSIRO Land and Water involved? 
• Where can I get more information on related issues?

Why do we need to know how much water we use to grow food? 

All plants that produce our food and natural fibre need water to grow. This water can come from rain or irrigation, or both.

What issues do we face worldwide? 

Demand on world water supplies is increasing as populations expand. Pressures from urban expansion, agriculture and environmental protection all have an impact on water availability. It is becoming more difficult to provide enough food, water and other necessities for people. Already an estimated 2 billion people worldwide have no access to adequate drinking water.

Although there are more and more people who need water to drink and grow food and other supplies, most of the world's water resources are already being used. Building more dams won't keep pace with estimated demand, even if there is sufficient runoff to fill them all.

We will be forced to use our existing water more efficiently, and investigate options for water recycling and reuse in order to keep up with demand.

What is the situation in Australia? 

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.

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.

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 is CSIRO Land and Water involved?

In Australia we don't have to artificially restrict our choice of crops produced by irrigation. We do need to make sure that we protect our water resources and the public interest. CSIRO Land and Water scientists can use knowledge about water use efficiency to work out the best types of techniques for growing the food, to achieve these aims. From this information we can develop management strategies to maximise water use efficiency in growing food.

We can't avoid that fact that it takes a lot of water to grow food, but we can investigate ways to improve agricultural efficiency to make sure that we only use as much water on crops as the plants can take up. This can have other benefits such as better economic returns for farmers and control of leakage and drainage that can pollute the underground water (groundwater) and water in rivers and lakes.

Where can I get more information on related issues? 

• Latest research (publications), for example:
  • A Bird's Eye View of Australia's Biggest Water User. Irrigation in the Murray and Murrumbidgee Basins 2005
  • Quantifying and Valuing land use change for ICM evaluation in the Murray-Darling Basin 1996/97-2000/01 Executive Summary 2004 (PDF, 196 kB)