Hundreds of millions of people in developing countries will remain trapped in poverty unless major changes are made to the way water is managed for agriculture, say scientists.
In a report released at this week's World Water Forum in Mexico, they say that global demand for food will double by 2050 and — unless farming is made more efficient — so will the amount of water needed to produce this food.
The report, by the International Water Management Institute (IWMI) and nine partners, challenges researchers to find ways of making farming more water-efficient.
"It takes 70 times more water to grow the food we eat every day than we need for drinking, cooking, bathing and other domestic needs," says IWMI director general, Frank Rijsberman.
The report points out only 40 per cent of rainfall reaches rivers and groundwater.
By focusing on this 'blue water', it says, water managers are ignoring 'green water' — the remaining 60 per cent that is either evaporated directly from the soil or taken up by plants before it reaches rivers and groundwater.
The IWMI says that making better use of green water is essential to meet the UN Millennium Development Goals on poverty, hunger, sanitation and water.
Agriculture can be made more water efficient in developing countries if farmers harvest rainwater or use small scale, inexpensive irrigation technologies, says the report.
For example, perforated plastic tubes laid on the ground can deliver drips of water directly to where it is needed, at the base of planted crops.
The report points out that irrigation systems in Africa and Asia typically take 2,000 litres of water to produce on kilogramme of rice or wheat, whereas the most efficient systems require only 500 litres.
Making fields more efficient at using the irrigation and rainfall they already receive could eliminate the need to irrigate them more, says Rijsberman.
Another "major challenge and opportunity for research" is to find ways of safely using waste-water for farming, says the report.
"Technologies are available but remain largely untested," it adds.
Yesterday (22 March), the United Nations Environment Programme (UNEP) released a report saying that agriculture is the biggest threat to freshwater resources.
"Irrigated agriculture accounts for 70 percent of freshwater used globally, with only 30 percent of this returned to the environment," said Nick Nuttall, a UNEP spokesperson.