Glacier meltwater provides a steady source of water for communities that would otherwise lack access during the dry season, but melting glaciers can cause problems beyond raising the sea level and endangering coastal communities. Meltwater forms lakes below the glaciers, and this water is often held in place by natural dams. Rock slides or avalanches can weaken or destroy these dams, causing the lakes to burst and flood the mountain-side. These flooding events are called glacial lake outburst events (GLOFs). Countries like Nepal and Bolivia provide the opportunity to study the development and characteristics of GLOF-prone glacial lakes.
Scientists from the UK and Bolivia used Landsat satellite imagery to monitor glacial size between 1986 and 2014. They found that the glaciers have seen a 43.1% reduction in area. The number of glacial lakes has also increased from 38-72% depending on the area. The researchers used specific and somewhat simplistic criteria such as proximity to glaciers, geographical slope, water volume, and dam type to assess the glacial lakes. They found that of the 137 lakes that fit their criteria, 25 lakes pose a serious risk to Bolivian populations and infrastructure should they flood.
While the first assessment of its kind and the identification criteria might be over-simplistic, this study does provide solid estimates of potential dangers. Preparing for these disasters by breaching the lakes in a controlled way or rebuilding current infrastructure to withstand floods, for example, would be expensive solutions. However, the results can at least inform the communities about the most at-risk areas to avoid.
Acknowledgements: Many thanks to Christopher Horvat in the EPS department at Harvard University. Chris is currently studying climate science, applied mathematics, and science policy.
Managing correspondent: Zane Wolf
Original Article: Glacier change and glacial lake outburst flood risk in the Bolivian Andes -The Cryosphere
Media Coverage: Melting glaciers are threatening to wash away mountain villages in Bolivia
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Image Credit: Glacier Ancohuma
