By Cam Walker, based on research by Naomi Schwartz.

Australia is, for the most part, a dry continent, with erratic weather and often un predictable rainfall. The community is keenly aware of the threats to our inland rivers, and water shortages in the cities. Many people are taking action: changing behaviour, installing water tanks, and reducing personal use of water, buying more efficient appliances and so on. But a huge element is missing from the debate at present – that of water use in agriculture. And a big part of this is because there is so little information available on the topic.

Agriculture accounts for much greater water usage than households and all other sectors combined, and is therefore the area where smart water management policies can have the greatest effect. In Victoria, for example, only 8% of water use is domestic whereas agriculture is responsible for 66%.

Many farmers are seeking to become more efficient in their production – costs of water and limited availability as well as concern about being good land stewards being key factors driving this innovation. However, without eco-labelling that gives a sense of the water intensity of various food products, it is impossible for consumers to be able to help drive this innovation, or reward the producers who are working smartest and most efficiently when it comes to water consumption.

Most people have heard of shopping organic, or paying attention to food miles. But what about shopping for water intensity? It seems clear that this will be the next stage in eco-labelling because it will allow us to take action on water stress and reduce our personal water footprints.

Beyond picking the more efficient producers within a particular product range, water intensity labelling would also allow us to consider the categories of food we eat, with a view to reducing the more intensive products. Obviously, some products require a lot more water than others. In an environment with such scarce supplies of water as Australia, the amount of irrigation a crop receives has a huge effect on the environment. Removing water from rivers, streams, and other natural bodies of water throws off the delicate balance of their ecosystems. Excess irrigation can leach nutrients into our water supply, and cause salinisation of land and water. Therefore, it is important to encourage farmers both to take as little water from the environment as possible, and when they do extract water, to use it in an thoughtful way and return it in good condition.

In the future, we hope that products will be labelled for their water intensity. That way, every time you shop you will be able to judge products for their water intensity and compare individual producers' water use practices. The label would take into account both the average water intensity of a product and a producer's individual water use efficiency. This should encourage farmers to improve their irrigation practices for the water intensive products they are already growing as well as to switch to growing foods that require less water. It would also give consumers considerable power to minimise their impacts and support those farmers who are the most efficient.

There is currently very little research on the water intensity of different foods. Hopefully, as the water shortage becomes more serious, a larger body of information will become available. In the meantime, you can use the accompanying table as a guide when you go shopping, and there is a lot of good information at <www.waterfootprint.org>.

Water intensity and food categories

Processed foods

In general, processed foods have high water intensities. Many industrial food processes use a lot of water, and although they are becoming more efficient, they tend to produce a lot of waste water. So the virtual water content of processed foods include not only the water required to grow the ingredients, but also the large amounts of water used in their manufacture.

Fruits and vegetables

The best products to eat for low water intensity are fruits and vegetables. They have a high yield per water input and require little processing. Pumpkin and squash, tomato, sweet potato, lettuce, and strawberries are some of the fruits and vegetables with the lowest water intensity. Grapes, oranges, bananas, and stonefruits have high water intensity in comparison.

Grains, legumes, and cereals

Grains, legumes, and cereals have higher water intensities than fruits and vegetables, largely because they are usually processed before they arrive on our plates. Among grains, rice has one of the highest water footprints. Many Australian rice growers are amongst the most efficient in the world. It takes 1,176 litres of water to grow one kilogram of rice in Australia—which is small compared to the global average of 2,300 litres. Even though we live on the driest inhabited continent in the world, we are growing enough rice to feed 40 million people daily. This makes a huge dent on our water supply.

Animal products

Animal products are uniformly more water intensive than plant products. This is because the water footprint of an animal product includes the water content of their feed, servicing, and drinking. Beef products are the worst due to the long life span of cattle. They consume a lot more in their average three years of life before slaughter than a sheep does in 18 months or a chicken does in ten weeks. In terms of water intensity, it would be best to avoid meat altogether, but if you must eat meat, try to stick to chicken or lamb and steer clear of beef.

Drinks

Coffee has a very large water footprint due to the water intensive processes required before we drink it. Tea, by comparison, has a very small water intensity. The virtual water content of a cup of coffee is 140 litres while that of a cup of tea is only 30 litres. The virtual water content of a 250 ml glass of beer is 75 litres, while it takes 120 litres of water to produce a 125 ml glass of wine. However, beer production is more land intensive than wine.