Glaciers and water supplies in the tropical Andes:
Over the last decades many of the mountainous glaciers in the tropical Andes have been retreating, a process that can with high likelihood be attributed to global climate change. In particular, countries located in the outer tropics, such as Peru and Bolivia, but also countries in the inner tropics, such as Ecuador, have been affected, above all by the reduction of the glaciers’ capacity to store water in form of ice and release it in drier periods of the year.
In the past this seasonal water storage capacity has been a crucial factor for the provision of a reliable supply of drinking water, as well as for agriculture and the generation of electricity. As a result of the glaciers’ retreat some of the largest cities such as Quito (Ecuador), Lima (Peru), La Paz and El Alto (both Bolivia), as well as rural regions with major agricultural activity have been confronting major difficulties regarding their water supply.
While in some regions the flow of melting water has already decreased, such as in the valley of the Rio Santa in Peru, in most regions the retreat of the glaciers initially enhances the flow of melting water and only in the long run makes it increasingly scarce.
The threat to local hydrological resources, which has been exacerbated by population growth and economic developments, has been addressed with a number of measures including the engineered re-direction of water flowing from the wetter eastern side of the Andes.
It remains to be seen to what extent these and similar measures suffice to ensure a reliable and sufficient supply of water, as scenarios of climate change project that most glaciers will continue to retreat and that presently existing challenges regarding the supply of water will hence be further exacerbated.