Against a backdrop of extreme weather wreaking havoc around the world, experts warn that increasingly erratic rainfall related to climate change will pose a major threat to food security and economic growth, especially in Africa and Asia, according to a new report released on Thursday by the International Water Management Institute (IWMI) at the ongoing World Water Week in Stockholm.

They suggest governments increase investment in diverse forms of water storage as an effective remedy.

"Climate change will hit millions of farmers in communities dependent on rainfed agriculture due to decreasing and erratic availability of water," said Colin Chartres, director general of the Sri Lanka-based IWMI in a statement.

The report said that due to the side effects of large dams, one should take an integrated approach that combines large and small- scale storage options, including the use of water from natural wetland, water stored in the soil, groundwater beneath the Earth's surface and water collected in ponds, tanks and reservoirs.

"For millions of people dependent on rain-fed agriculture, reliable access to water can make all the difference between chronic hunger and steady progress toward food security," said Mathew McCartney, the lead author of the report and hydrologist at IWMI.

"Even small amounts of stored water, by enabling crops and livestock to survive dry periods, can produce large gains in agricultural productivity and in the well-being of rural people," McCartney said.

IWMI and its research partners estimate that up to 500 million people in Africa and India can benefit from improved agricultural water management.

In Asia, where irrigation was greatly expanded in recent decades, rainfed agriculture is still extensive, accounting for two-thirds of the total cropped area, according to IWMI's study.

In Sub-Saharan Africa, the proportion is far greater at 94 percent. However, these are precisely the regions where water storage infrastructure is least developed.

The report cited China and India as examples, saying that the construction of more than 90,000 underground water storage tanks in China is benefiting a million farmers while in the northeast of India's Rajasthan state, the construction of about 10,000 water harvesting structures -- intended mainly to recharge groundwater -- has made it possible to irrigate about 14,000 hectares, benefiting some 70,000 people.

In Sri Lanka, the construction of a large water storage reservoir which was then linked to five previously created small reservoirs brought about a 400-percent increase in crop production, the report added.