科学与发展网络(SciDev.Net)

A farmer in Bangladesh. Asian irrigation needs an overhaul.

Flickr/IRRI

Asia's run-down irrigation systems need to be updated if the continent is to meet the challenge of feeding an extra 1.5 billion people by 2050, according to a new report.

It's a case of adopting existing rather than new technologies, says Colin Chartres, director general of the International Water Management Institute (IWMI), one of the organisations behind the report, presented today (18 August) at the World Water Week conference in Sweden.

Without improvement in irrigation, many countries in Asia might have to import more than a quarter of their maize, wheat and rice, the report adds.

Researchers from IWMI and the UN Food and Agriculture Organization modelled the water requirements of three different ways of feeding the booming population: importing food, expanding and improving rain-fed agriculture, and enhancing irrigated agriculture.

They describe a significant rise in cereal imports as "politically untenable", and Chartres says expansion of rain-fed agriculture is a not an option. "There's very little land … it's all being used. You can't expand laterally, therefore you've got to increase productivity on existing land and it's easier to increase productivity with irrigation than it is by rain-fed [agriculture]," he told SciDev.Net.

However, increases in irrigation productivity could produce as much as three-quarters of the additional food required, the researchers estimate.

Asia accounts for 70 per cent of the world's irrigated land. Most irrigation systems were constructed in the 1970s and 1980s and helped boost food supplies in Asia during the Green Revolution. The systems have since fallen into a poor state.

"The water delivery systems need rehabilitation. The way they're managed means they're supply driven — farmers are given water when it is available, not when they want it. Farmers might be getting a good crop, but then the water fizzles out and they get a bad yield. There are also a lot of water losses through evaporation and drainage," says Chartres. 

Improving productivity won't require "a rocket science solution", he adds. Surface irrigation could be used to fill intermediate storage containers to give farmers more control over their own water supply. Properly governed and managed schemes could also pump groundwater to individual farms, without exhausting resources, as has occurred in some areas (see Thirsty Indian farming depleting water resources).

But investment is needed to encourage farmers to use new technologies, says Chartres.

"The farmers themselves are using old-style systems, there's very little adoption of high-tech or efficient irrigation systems, such as drip irrigation or sprinklers … there's a lack of capacity for the adoption of new technologies across the whole farming system."

Other new technologies could help.

"There's a tremendous need for knowledge. But most farmers have a mobile phone in India and China   and more and more have access to the Internet, so there's much more opportunity to get information out there."

Link to full report from the IWMI [6.20MB]