Hidden threats have been found in small glacial lakes, putting thousands of people at risk.

For many years, researchers have been examining the likelihood that populations in mountainous regions are facing an increasing risk of flooding due to meltwater, as melting glaciers release more and more water. A small portion of this meltwater remains in glacial lakes around the world—if their dams fail, glacial lake floods can have catastrophic effects on local communities living downstream, reports PHYS.org.

A team of scientists from the University of Potsdam found that not only the growing number and surface area of glacial lakes determine the risk of such floods. During their study, the researchers analyzed satellite images of nearly 1,700 documented glacial lake floods in 13 glacial regions worldwide from 1990 to 2023. The team discovered that the areas of lakes dammed by ice have decreased, while the areas of lakes dammed by moraines have remained largely unchanged.

According to the lead researcher, Dr. Georg Veha from the Institute of Ecological Sciences and Geography, he and his colleagues also found no trend toward larger lake floods. Some lakes have developed wide outlets over time, allowing rivers from these lakes to efficiently discharge meltwater, but this does not necessarily lead to dam breaches. Other lakes, particularly in the Alps, Peru, and Norway, have been artificially reinforced with dams for intensive hydropower use. The scientists believe that such changes actually contribute to the fact that floods typically occur from smaller lakes, even as lake areas increase worldwide.

The danger lies in the fact that not all lake floods occur under the same scenario. For example, glacial lakes held back by glacial ice do indeed breach more frequently due to increasingly unstable ice masses. However, the resulting floods from these events are on average less extensive due to the smaller volumes of the lakes.

Other lakes are dammed by moraines left over from glacial melt. The researchers found that in the Himalayas, Alaska, and Patagonia, the threat to populations has increased as the volume of lakes continues to grow. However, catastrophic flooding from lakes dammed by moraines, such as in India in 2023 when at least 55 people died, remains rare.

The researchers believe that their findings indicate that climate change, glacial retreat, and natural disasters are closely interconnected and can influence the number and scale of glacial lake floods. The authors of the study argue that continuous remote sensing is essential for monitoring these phenomena.

The scientists believe that remote sensing in the future will enable researchers to track processes in regions previously considered inaccessible.