The brutal oil lakes represent a risk for populations who live downstream, mainly in India, Pakistan, Peru and China.
By clementine Thiberge
Direct consequence of global warming, the melting of glaciers creates more and more glacial lakes in mountain ranges. Today, around 15 million people worldwide could be threatened by floods related to these lakes, according to a study published in the journal Nature Communications, Tuesday, February 7.
When a glacier withdraws, a heap of blocks and rocky debris forms in front of the glacier. This bead, called a frontal moraine, creates a natural dam that holds cast iron water. If there is no outdoor outlet, like a torrent or a cascade, this water turns into a lake. “The problem is that these moraines are not necessarily made of very solid materials, explains Olivier Gagliardini, professor at Grenoble-Alpes University and at Institute of environmental geosciences (IGE), which did not work on this study. These are therefore Lakes that are created, maintained by more or less resistant dams. “
These lakes, made up of a few tens to a few million cubic meters of water, can quickly become threatening. “Floods can occur very quickly when one of these natural dams breaks, explains Tom Robinson, researcher at the University of Canterbury in New Zealand, and co-author of the study. This is the case when an avalanche Or a block of ice falls into the lake and forms a wave or, simply, when the volume of water becomes too large. “
” analyze moraines “
To estimate the overall population subject to this risk, study researchers combined data on the location and size of the glacial lakes with a map of the world’s population. “We then made a cautious estimate that anyone living less than 50 kilometers from a ice lake and less than a kilometer from a river from a glacial lake could be directly or indirectly impacted by a brutal change de lake, explains the researcher. This allowed us to estimate the number of people likely to be in danger in each basin-voor, in each country and on the whole of a mountain range. “
According to the researchers, brutal lake emptying can have consequences up to more than 200 kilometers downstream, depending on the volume of water and the size of the valleys. However, events of this magnitude are rare, and most of the crude damage takes place in the first tens of kilometers.
Today, 15 million people would therefore be threatened by this risk linked to glacial lakes, more than half of which are in four countries: India, Pakistan, Peru and China. But researchers believe that this number could increase rapidly in the coming decades.
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