The melting of glaciers in the Himalayas will have varying impact on the waters of the Indus, Ganges, Brahmaputra, Yangtze and Yellow rivers, according to a new Dutch research.

Scientists believe that the changes in the flow of water due to global warming may have a “severe” impact on food security in some areas. However, they also point out that the people living elsewhere are likely to see an increase in food productivity.

Overall, the food security of 4.5 per cent of 1.4 billion people in the region is threatened, the researchers say.

The lives of more than 1.4 billion people are dependent on waters of the Indus, Ganges, Brahmaputra, Yangtze and Yellow rivers. “We show that meltwater is extremely important in the Indus basin and important for the Brahmaputra basin, but only plays a modest role for the Ganges, Yangtze and Yellow rivers,” the BBC quoted the team from the Netherlands, as writing in the journal Science.

The researchers add: “The Brahmaputra and Indus basins are most susceptible to reductions of flow, threatening the food security of an estimated 60m people.” They call mountains the “water towers of the world”. They say: “Snow and glacial melt are important hydrological processes... and changes in temperature and precipitation are expected to seriously affect the melt characteristics.” “The Yellow River, in particular, shows a consistent increase in early spring discharge.

“This is highly beneficial because most reservoirs are empty at the beginning of the growing season. An accelerated melt peak may thus alleviate a shortage of irrigation water in the drought-prone early stages of the growing season.” However, in spite of the projected compensating effects of increased rainfall in the Indus and Brahmaputra basins, the team believes the summer and late spring discharges would eventually dip “consistently and considerably by 2046 to 2065 after a period with increase flows as a result of accelerated glacial melt”. They warn: “These anticipated changes will also have considerable effects on food security.

“By relating changes in upstream water availability to net irrigation requirements, observed crop yields, calorific value of the crops and required human energy consumption, one can estimate the change in the number of people that can be fed.” According to the team’s estimates, about 34.5 million fewer people could be fed in the Brahmaputra basin; 26.3 million fewer in the Indus basin; 7.1 million in the Yangtze region and about 2.1 million fewer around the Ganges. But they also suggest that the changes could witness an increase in food production in the Yellow River basin, sufficient to feed another 3 million people. They write: “In total, we estimate that the food security of 4.5% of the total population will be threatened as a result of reduced water availability.

“The strong need for prioritising adaptation options and further increasing water productivity is therefore ever more eminent.

“We conclude that Asia’s water towers are threatened by climate change, but the effects of climate change on water availability and food security in Asia differ substantially among basins and cannot be generalised. “The effects in the Indus and Brahmaputra basins are likely to be severe owing to the large population and the high dependence on irrigated land and meltwater. In the Yellow River, climate change may even yield a positive benefit as the dependence on meltwater is low and a projected increased upstream precipitation, when retained in reservoirs, would enhance water availability for irrigated agriculture and food security.”