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EGU: World’s “water towers” under threat

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I’m in sunny Vienna this week for the European Geosciences Union general assembly, a yearly gathering where several thousand scientists abandon their field and lab studies for an entire week to get together and talk earth, planets and space.

With over 8,000 participants, this year’s meeting, held at the Austria Vienna Centre on the banks of the Danube, will be the society’s largest yet.

Climate change and energy occupy sizeable slots on this year’s programme; hence my schlep across to Austria to meet with some of the authors behind the 12,000 abstracts.

Following from a spate of recent coverage in Nature and on NRCC, the threat of a warming world on global water resources emerged here today as one of the issues du jour. This time, the question was whether the world’s water supplies from mountains and highlands, known as the world’s natural “water towers”, will still be able to quench our thirst in fifty years.

Speaking at a press conference here this afternoon, hydrologist Daniel Viviroli of the University of Bern in Switzerland explained that these “water towers” supply on average three to five times more runoff to rivers than do lowland areas and are a primary water source for most of the world’s major rivers.

This is especially important in dry regions where water is in short supply and in mountainous regions with glaciers that supply runoff from snowmelt in spring.

On a global level, 7% of mountain regions have a key role in supplying water to lowlands and their dependant populations. From the Rocky Mountains supplying the Colorado River Basin to the Lesotho highlands supplying South Africa, the water runoff from such “hotspots” is likely to diminish in the future, the scientists warned.

A further 37% play a crucial supporting role, said Viviroli, and may also be under threat, though he added that the timescale and nature of such changes are, as of yet, highly uncertain.

One of the issues, highlighted by Bruce Molnia of the US Geological Survey, is that in some regions such as North America and Afghanistan, the period of runoff is now shorter because snow arrives later and melts earlier.

Given that 70% of the world’s population is based in lowland regions with natural “water towers” providing both drinking water and faciliatating food production, many millions could be affected.

Carmen de Jong, a research scientist who works on the Europena Alps, said that in some areas where glaciers are small, the water supply from high elevations could be gone in 30 years time unless there is enough precipitation in summer time to compensate for the loss.

Philip Mote, research scientist at the University of Washington, warned that we need to be careful about specifically attributing all such changes to anthropogenic warming, adding that the most serious human impacts in fifty years time will likely be south of 50 degrees latitude.

I’ll be blogging throughout the week until the conference ends on Friday, so tune in here daily for the highlights on climate change and energy from EGU 2008. My colleague Quirin Schiermeier will also be blogging over on the Nature’s In the Field blog with coverage from the climate and energy streams and more.

Olive Heffernan

Photo: Snowmelt runoff fills a reservoir in the Rocky Mountains near Dillon, Colorado. Credit: Scott Bauer, US Agricultural Research Service.

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