Receding Glaciers in Bolivia Leave Communities at Risk

A new study published in The Cryosphere, an European Geosciences Union journal, has found that Bolivian glaciers shrunk by 43% between 1986 and 2014, and will continue to diminish if temperatures in the region continue to increase. "On top of that, glacier recession is leaving lakes that could burst and wash away villages or infrastructure downstream," says lead-author Simon Cook, a lecturer at the Manchester Metropolitan University in the UK.

Receding glaciers also put water supply in the region at risk. Glacial meltwater is important for irrigation, drinking water and hydropower, both for mountain villages and large cities such as La Paz and El Alto. Throughout the year, the 2.3 million inhabitants of these two cities receive about 15% of their water supply from glaciers, with this percentage almost doubling during the dry season. Glacier retreat also means less water is available to supply rivers and lakes, such as southern Bolivia's Lake Poopó, which recently dried up.

The new study is one of the first to monitor recent large-scale glacier change in Bolivia, to better understand how receding glaciers could affect communities in the country. "The novelty of our study lies in the bigger picture -- measuring glacier change over all main glaciated ranges in Bolivia -- and in the identification of potentially dangerous lakes for the first time," Cook says.

The team measured glacier area change from 1986 to 2014 using satellite images from Landsat, the U.S. Geological Survey's and NASA's Earth observation programme. They found that the area of the Bolivian Andes covered by glaciers decreased from about 530 square kilometres in 1986 to only around 300 square kilometres in 2014, a reduction of 43%.

As glaciers recede, they leave behind lakes typically dammed by bedrock or glacial debris. Avalanches, rockfalls or earthquakes can breach these dams, or cause water to overflow them, resulting in catastrophic floods known as glacial lake outburst floods. The team reports that both the number and size of glacier lakes in the study region increased significantly from 1986 to 2014.

In a study, the team also estimated that glacier area will be severely reduced by the end of the century, to about a tenth of the 1986 values. This would put communities even more at risk from water scarcity, Cook says. "We predicted in our study that most glaciers will be gone or much diminished by the end of the century -- so where will the water come from in the dry season? Big cities like La Paz are partially dependent on meltwater from glaciers. But little is known about potential water resource stress in more remote areas. More work needs to be done on this issue."

https://www.sciencedaily.com/releases/2016/10/161020100810.htm