Asian farmers need to modernise their irrigation methods
Asia must reform its water use to feed 1.5 billion extra people by 2050, says a new report.
The authors warn that without big changes to irrigation many nations will have to import food.
The report says that 94% of suitable land in South Asia is already being used for growing food.
According to their computer model the continent could obtain three quarters of the additional food it needs with better irrigation systems.
The report will be presented on Tuesday to the World Water Week conference in Stockholm.
The study was carried out by the International Water Management Institute and the United Nations Food and Agriculture Organization (FAO).
The researchers warn that some developing nations will have to import more than a quarter of the rice, wheat and maize they will need by 2050 and that this prospect will be politically risky.
They outline three options for meeting the food needs of Asia's population.
The first is to import large quantities of cereals from other regions, the second to improve and expand "rain-fed" agriculture and the third is to focus on irrigated farmlands.
The report warns that the first option is too politically risky and the second is impossible as suitable land is already in use in many areas.
Lead author Aditi Mukherji of the International Water Management Institute said: "Today, the option of expanding irrigated land area in Asia to feed a growing population is becoming increasingly problematic due to land or water constraints."
The scenarios presented in the report do not factor in climate change which is likely to make rainfall more erratic.
The report recommends modernising the region's large scale irrigation systems which rely on surface water but have fallen into disrepair through lack of investment.
Another suggestion is for governments to help individual farmers use cheap pumps to extract ground water for irrigation.