Assessment of Glacial Lake Bathymetry and Volume Using Remote Sensing Observations

Reliable estimation of glacial lake bathymetry and volume is essential for Glacial Lake Outburst Flood (GLOF) hazard assessment, as the volume of stored water significantly affects potential flood intensity. However, direct in situ bathymetric surveys are difficult in remote and high-altitude Himalayan regions, necessitating the use of remote sensing-based alternatives. This study evaluates satellite-based bathymetric reconstruction for Panikhar Lake, a moraine-dammed glacial lake in Kargil district, Ladakh, India. Lake bathymetry and water volume were estimated using two independent approaches: a radiative transfer model (RTM) based on multispectral reflectance and the optical properties of water, and a high-resolution DEM-based topographical reconstruction. The estimated maximum depths and lake volumes were evaluated against an in situ echo-sounder survey. RTM underestimated a maximum depth of 77.6% and a volume of 88.7%. This substantial underestimation indicates the limited ability of the optical approach to ascertain depth in deeper parts of the lake. In comparison, the topographical model showed the closest agreement with the field-derived lake volume, with an underestimation of approximately 13.9%, although the maximum depth remained underestimated by about 39.5%. These results demonstrate that DEM-based topographic reconstruction provides a  better representation of basin-scale lake storage than the optical RTM approach. The findings highlight the potential of high-resolution DEM-based topographical reconstruction for estimating glacial lake volume in remote Himalayan regions where direct bathymetric observations are limited.