What’s The Future for Snowpack Water Supply?

In many regions, snow provides water in spring and summer as the snowpack melts. But as climate changes, more winter precipitation may fall as rain rather than snow, and snow may melt earlier in the season

"Snow is important because it forms its own reservoir," said Justin Mankin of Columbia University, US. "But the consequences of reduced snowpack are not the same for all places – it is also a function of where and when people demand water. Water managers in a lot of places may need to prepare for a world where the snow reservoir no longer exists."

The basins at risk lie in the American West, southern Europe, the Middle East and central Asia, Mankin and colleagues from the US, Switzerland and the Netherlands found. The team examined 421 drainage basins across the northern hemisphere, using climate models, water-use patterns and population data. In total, 97 of the basins had at least a two-thirds chance of experiencing water declines if current demand continues.

"We did not know where snow was critical to supplying water for people and thus where people are most likely to be sensitive to projected snow changes," said Mankin. "Many of the basins that are currently snow-dependent have large risks of declines in snow's future potential to supply current demands given both changes in rainfall and snowpack. But despite these risks, innate variations in year-to-year or decade-to-decade climate mean that these same basins have the potential for increases as well, and both of these possibilities are entirely consistent with a warming world."

In many regions, the models showed that changing climate is about as likely to increase water supply, by boosting rainfall, as to decrease it. The Indus and Ganges basins in India, where about 1 billion people live, could see similar levels of water supply, as could the Huai basin in China, home to 130 million. Increased glacier melting in the Himalayas could temporarily boost supplies to Uzbekistan and Kazakhstan.

"We only consider changes in climate, but an even larger source of uncertainty is people and how their consumptive patterns will change," said Mankin. "We know populations will increase and that demand will as well, but that technological and management changes could offset at least some of these increases. So there is some capacity to adapt, but that capacity is going to be different for different places. Water managers need to reconcile these changes against their basin's other vulnerabilities."

Source: Environmental Research

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