The team analyzed Landsat and Sentinel‑2 satellite imagery to track changes in 74 glacial lakes in the Alaknanda River basin in the western Himalayas between 1994 and 2023. Their findings indicate that melting glaciers are forming and feeding high‑altitude lakes that, under certain conditions, can suddenly release large volumes of water.
The combined surface area of the 24 lakes larger than 0.01 km²—the threshold used in the study—expanded from 0.97 km² in 1994 to 1.62 km² in 2023, an increase of 67 percent over 30 years. During the same period, 57 new glacial lakes were identified, bringing the total number in the basin to 131; 18 of these newly formed lakes exceeded the 0.01 km² threshold.
Some lakes grew particularly rapidly. Lake Vasundhara expanded by 261 percent between 1994 and 2023, while Lake Balbala grew by 119 percent. The researchers stress that several lakes require continuous monitoring, as changes in their size and stability may pose risks to downstream communities. A key concern is the possibility of sudden floods triggered by the abrupt drainage of these lakes.
Glacial Lake Outburst Floods (GLOFs) occur when water held back by ice, rock, or sediment is suddenly released, carrying mud and debris with immense destructive force. Experts note that the recent disaster in Nepal was not a classic GLOF, but it illustrates the severe consequences of sudden high‑mountain flooding.
“The recent flood serves as a reminder of the importance of continuously monitoring high‑mountain areas, where hazards such as extreme rainfall, expanding glacial lakes, slope instability, and seismic activity can interact and amplify their impact downstream,” said Dr. Aayushi Pandey of Charles University.
She added that satellite data are essential for studying vast, inaccessible regions, enabling researchers to detect new lakes, measure changes in their size, and identify rapidly expanding bodies of water. However, she emphasized that fieldwork remains crucial for assessing lake depth and volume, slope stability, water outflow paths, glacier‑lake interactions, and improving flood‑risk models.'
(pu)
Source: PAP