LONDON - Increasingly erratic rainfall patterns related to climate change pose a major threat to food security and economic growth, water experts said on Monday, arguing for greater investment in water storage.

In a report by the International Water Management Institute (IWMI), experts said Africa and Asia were likely to be hardest hit by unpredictable rainfall, and urged policymakers and farmers to try to find ways of diversifying sources of water.

The IWMI research estimates that up to 499 million people in Africa and India could benefit from improved agricultural water management.

The U.N. panel of climate experts has projected more extreme weather such as droughts, floods and heatwaves this century, caused by global warming.

The report said that, despite a great expansion in irrigation in recent decades in Asia, around 66 percent of agriculture there is still dependent on rainfall.

In sub-Saharan Africa, the proportion is even greater at 94 percent, it said. These are the regions where water storage infrastructure is least developed.

The report cautioned against over-reliance on single solutions such as big dams, and said an integrated approach combining large- and small-scale storage was a better strategy.