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Peru has the largest number of tropical glaciers in the world. These water towers are crucial for slowly releasing water, particularly in the dry season. And Peru desperately needs the water all year round. Apart from the need for drinking water, 80% of the country's power has traditionally come from hydro-electricity. And, the current boom sectors of the economy - agro-exports and mining - also absorb huge volumes of water.
The latest figures on glacial melt are alarming. Estimates by a team of Peruvian and international scientists say that Peru and Bolivia, which together account for more than 90% of the world's tropical glaciers, have lost about a third of the surface area of their glaciers between the 1970s and 2006. A lot of attention has been paid to the range known as Cordillera Blanca, home to Peru's largest mountain, Huascaran, at 6,768 metres (22,200ft). Water coming down from the range feeds an array of economic activities in the Rio Santa valley below it. This includes a hydro-electric plant providing 5% of Peru's electricity, drinking water for two cities, and commercial and small-scale agriculture.
"Water from glaciers is absolutely critical for the valley in the six or seven months of the dry season," says Gabriela Rosas, a researcher at the national weather institute, Senamhi. Glacial melt is calculated to provide 10 to 20% of the total annual water run-off in the valley, but it can reach 40% in the dry season. Ms Rosas is part of a team modelling future water availability in Peru.
The models, based on moderate rises in temperature, predict annual water availability will increase slightly as more of the glaciers melt, but that there will be a dramatic decline after 2050 and possibly as early as 2030. Seasonal variations will become more intense, with less water available in the dry season.
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http://news.bbc.co.uk/2/hi/americas/6412351.stm