More crops per drop

Water efficiencies can even be obtained from international trade. Harvested Australian wheat exported to water scarce regions such as Iraq can in fact be regarded as “virtual water” exported from Australian rain-fed agriculture to regions with a water deficit. The concept of global trade in virtual water (pdf file 3.02MB) has been used to explain how food production can be shifted from water-rich regions such as North America to contribute to the water-deficient economies in Asia and the Middle-East.

Green water is invisible - as we actually cannot see the water transpiration stream emerging from a leaf, but there is much more of it than blue fresh-water. Water savings from improved green water productivity emerge from numerous changes in global agriculture where savings are achieved by trade in “virtual water,” and by options taken up by farmers that minimise irrigation by enabling farmers to operate more profitably without using irrigation.

An emphasis on improving green water productivity may well have more impact on ensuring sustainable use of water resources (pdf file 430KB) than investment in irrigation: it does not necessarily require heavy local capital investment, relies on technologies all farmers are familiar with, and, in the case of more water efficient crop varieties, has the potential to be distributed widely at low cost.

The green water concept helps highlight potentially overlooked opportunities for water conservation and improvement to water productivity. Sixty per cent of the world food production is rain-fed and totally dependent on green water and this rain-fed agriculture will remain the dominant food production resource for the foreseeable future. Green water savings are a major driver for reduced use of water in agriculture, and make possible both future food security and sound management of river catchments during the coming decades of this century.

Direct scientific approaches to improve crop water efficiency are still very much in their infancy; as with most agricultural innovation, there is a long lag time between basic science and the economic and environmental benefits and time is need to make sure innovation works effectively in the challenging context of farming.

The DELTA carbon technique, for instance, has yet to bear full fruit with other crops than Australian wheat varieties 25 years after its inception. Molecular genetics also is yet to be fully exploited for the options it promises for reducing crop loss from water stress, although there is a lot of promise in the pipeline. But because knowledge and seeds can easily spread from farmer to farmer, and farmers are using a technology they already are deeply familiar with, the benefits can be huge, and green water technological innovation by teamwork between scientists, farmers, and breeders, is living up to its name - it’s the green way to save natural resources.