Global Outlook for Ice & Snow

There is growing evidence that glacier retreat in the tropical Andes has accelerated in recent decades due to atmospheric warming 134 . Ongoing rapid glacier recession was found to have enhanced dis- charge at the expense of catchments storage 138,139 . The recent in- crease in runoff is not likely to last very long 140 . In the long run, changes in runoff may occur which could severely affect the avail- ability of water resources for future generations, particularly during dry periods. Short-term increases in stream discharge with critical long-term loss of storage are likely to be widespread over the Cor- dillera Blanca region. Since glacier melt currently provides a very significant proportion of discharge of the Rio Santa River, the latter is also likely to diminish with continued glacier loss. The melting of glaciers may lead to water shortages for millions of people. Among the Andean countries at risk are Bolivia, Ecuador and Peru, where glaciers feed rivers all year round. On the Pacific side of Peru, 80 per cent of the water resources originate from snow and ice melt. During the dry seasons, glacier-fed surface wa- ters often constitute the sole water resource for domestic, agricul- tural (Figure 6B.17) and industrial uses, not only for rural areas but also for major cities. A reduced glacier runoff will aggravate the problems associated with the water availability, especially if a potential warming leads to earlier snow melt, regional reductions in precipitation and an increase in evaporation 1,141 . Glacier changes and water availability in the tropical Andes Figure 6B.17: Glaciers and irrigation. Irrigation ditches on the slopes of Huascarán, Cordillera Blanca, Peru, support extensive agriculture during the dry season. Most water comes from nearby glaciers. Photo: Michael Hambrey, SwissEduc (www.swisseduc.ch)/Glaciers online (www.glaciers-online.net)

CHAPTER 6B

GLACIERS AND ICE CAPS

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