High-resolution underwater surveys of three major glacial lakes in the Himalayas have revealed that existing geographical and hydrological data on thousands of high-risk glacial lakes is grossly inadequate, limiting the ability of planners and decision-makers to model glacial lake outburst flood (GLOF) hazards, assess risks to downstream populations, and evaluate ecosystem vulnerability, according to a new study by Indian and European researchers published in Nature's Scientific Data on July 6.
Survey Findings Highlight Data Gaps
The researchers used an unmanned surface vehicle (USV) to acquire high-resolution bathymetry for three priority lakes: Gepang Gath, Kadu Nala (both very high-risk pro-glacial lakes), and Chandra Tal, a high-altitude Ramsar wetland. Their findings show that commonly used empirical formulas for estimating glacial lake volume are substantially biased in this region. Bathymetry, the underwater equivalent of topographic survey, measures water depth and creates a 3D map of the lake bed using echo sounders, sonar, and LiDAR systems.
“Due to the scarcity of in-situ measurements, most Himalayan studies continue to rely on area–volume scaling. While remote sensing provides valuable information on lake extent and surface characteristics, acquiring bathymetric data in high-mountain environments remains logistically challenging, costly and hazardous,” the study observed. Consequently, in-situ bathymetry is extremely limited across the Indian Himalaya, constraining accurate reconstruction of GLOF hydrographs, peak discharge estimation, and forward modeling.
Systemic Trans-Boundary Hazard
Across the Himalayan, Karakoram, and Hindu Kush (HKH) mountains, GLOFs constitute a systemic, trans-boundary hazard affecting multiple river basins, infrastructure corridors, and vulnerable mountain communities. Their impacts extend beyond immediate flood zones, disrupting hydropower generation, transportation networks, agricultural systems, and long-term socio-economic stability. The increasing frequency and magnitude of such events underscore the need to assess GLOF hazards at a regional scale rather than through isolated case studies, the study noted.
“This highlights a clear research gap in systematic, field-based data acquisition for glacial lakes, particularly in data-deficient regions of the western Indian Himalaya, where direct measurements remain sparse despite the presence of potentially hazardous lakes,” the researchers said.
NDMA Identified 189 High-Risk Lakes
To address this gap, the National Disaster Management Authority (NDMA) of India has identified 189 high-risk glacial lakes requiring urgent assessment. However, only a small fraction of these lakes has been investigated using direct, field-based bathymetric surveys, underscoring the need for targeted in-situ measurements to complement remote sensing approaches.
The study, conducted by eight researchers from the Birbal Sahni Institute of Palaeosciences (Lucknow), Academy of Scientific and Innovative Research (Ghaziabad), University of Aberdeen (Scotland), Indian Institute of Remote Sensing (Dehradun), and University of Bologna (Italy), was published in Nature's Scientific Data, a peer-reviewed international journal.
Accelerated Glacier Melting and Lake Expansion
The HKH mountains form the core of High Mountain Asia and are widely known as the “water tower of Asia,” containing thousands of glaciers and glacial lakes that feed ten major river systems supporting nearly two billion people. These glaciers are highly sensitive to climate change and are undergoing accelerated melting due to rising temperatures and altered precipitation patterns, which affect snow accumulation, melt rates, and hydrological cycles.
This sensitivity is amplified by elevation-dependent warming, in which higher altitudes experience disproportionately greater temperature increases. Consequently, the HKH region has experienced a rapid increase in the number, area, and volume of glacial lakes, the study observed. “Glacier retreat and lake expansion reinforce each other through a positive feedback mechanism, in which increased melt-water enlarges lakes and expanding lakes enhance glacier calving and retreat. These processes have intensified glacier shrinkage, promoted the formation of new lakes, and increased the likelihood of Glacial Lake Outburst Floods (GLOFs), posing growing risks to downstream communities and infrastructure,” the researchers said.
