Glaciers, lakes and the global hydrological cycle.




To understand the fate of lakes, we need to zoom out to the global hydrological cycle – the invisible thread linking glaciers, rivers, wetlands, aquifers and seas. Glaciers, often called “water towers of the world”, feed many of the planet’s lakes and rivers. Nearly 1.9 billion people depend on these frozen reserves for drinking water, irrigation and hydropower.



But climate change is melting glaciers at unprecedented rates. Recognizing this, 2025 marks the United Nations International Year of Glaciers’ Preservation. The year 2024 was the warmest year on record, and in 2023 alone, glaciers lost more than 600 gigatons of ice – the greatest loss in five decades. As they retreat, a new phenomenon is reshaping mountain landscapes: the explosive growth of glacial lakes. These lakes can be both lifelines and risks. They store meltwater, acting as buffers during drought. But they also pose catastrophic risks through glacial lake outburst floods (GLOFs), which can devastate entire valleys.



Inger Andersen, Under-Secretary-General of the United Nations and Executive Director of the United Nations Environment Programme (UNEP). UNEP/Natasha Sweeney

Inger Andersen, Under-Secretary-General of the United Nations and Executive Director of the United Nations Environment Programme (UNEP).

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