Lake water response to the recent megadrought in the Andes of northern and central Chile (18°S-39°S)

Human-induced climate change has led to increased intensity and frequency of dry years, known as megadroughts. These can generate scarcity of water availability which affects natural ecosystems, water security, and quality of life. Mountain lakes are major freshwater reservoirs that can aid in dealing with prolonged periods of hydrological stress. The lack of monitoring systems, however, is a major limitation for future planning. Here, we estimate changes in lake surface area to track the state of Andean lakes from northern and central Chile (18°S-39°S) to assess their response to a recent (2010–2022) megadrought. We mapped 40 high elevation lakes using Landsat satellite images from 1984 to 2021 and compared these results with the available climate data. Lakes in central Chile show a significative decrease in lake surface area up to 45%. A more diverse response occurs in the Altiplano, where several lakes show up to a 19% increase in area, possibly as a response to local factors such as increasing snow melt, especially in northernmost Chile. Further south, many altiplano lakes show a decreasing trend in surface area, which can be linked to variability of rainfall events, an increase in regional temperatures, or a combination of both. To further aid with land management and public policies, our results and database are also available as an online atlas. In the light of ongoing climate change, our results show that we are now at a critical moment regarding water resource management and evidence-based decisions will be key for conserving these threatened lake systems.