Monitoring glacier evolution and evaluating glacial lake outburst flood hazard in the Bolivian Andes: A GIS approach

This research focuses on changes to glaciers and glacial lakes across the Bolivian Andes between 2016 and 2022. During this period, the total glaciated area of the Bolivian Andes decreased by 9.1%, from 316.6 ± 3.2 km2 to 287.8 ± 2.9 km2; a rate of loss of 4.8 km2 a-1. Larger glaciers, and those at higher altitudes, lost a smaller proportion of their surface area than smaller and lower glaciers. Lake-terminating glaciers did not exhibit greater losses than their land-terminating counterparts, contrary to findings from other parts of the world. As glaciers continued to retreat across the region, the number and surface area of glacial lakes increased. The number of lakes grew by 2.6%, from 704 in 2016 to 770 in 2022. Over the same period, the total surface area of glacial lakes expanded by 1.9%, from 37.1 ± 0.7 km2 to 37.8 ± 0.8 km2. A comprehensive glacial lake outburst flood (GLOF) hazard analysis was undertaken for the 2022 lake inventory. The results of this identified nine lakes as ‘high hazard’, sixteen as ‘medium hazard’ and fourteen as ‘low hazard’. A previously unreported GLOF event was discovered to have taken place in late 2019 or early 2020. One of the smaller lakes left behind by this event was amongst those categorised as ‘high hazard’ by the GLOF hazard analysis. Subglacial topographic analysis was undertaken to predict potential future sites for lake formation. Sixty new lakes, with a surface area of ~8.5 km2 are expected to form given continued deglaciation. The model was tested by applying it to areas where glaciers retreated between 2000 and 2022. Forty-four (46%) of the ninety-six lakes predicted by the model existed in 2022. This is the first time that an inventory of potential future lake sites has been produced for the region.