In-situ bathymetry and volume estimation of four glacial lakes in western Himalaya

Glacial lakes in the Himalayas have expanded significantly in recent decades, increasing the potential risk of outburst floods. However, limited field surveys and systematic assessments leave downstream communities vulnerable. Accurate volume estimation of glacial lakes is essential for modelling flood dynamics, yet in-situ bathymetric data remain scarce. In this study, we surveyed four glacial lakes - Kya Tso Lake (KTL), Panchi Nala Lake (PNL), Gepang Gath Lake (GGL), and Samudra Tapu Lake (STL) - in the Chandrabhaga basin, western Himalayas. Depth measurements were conducted using a portable inflatable kayak in August 2022 and an echo sounder mounted on a Unmanned Surface Vehicle (USV) in August 2024. Bathymetric modelling revealed maximum depths of 16 m (KTL), 10 m (PNL), 46 m (GGL), and 59 m (STL), with corresponding storage capacities of 0.89, 0.44, 24.12, and 24.69 × 10⁶ m³, respectively. Volume estimates derived from empirical equations showed substantial discrepancies of ±36–1736% compared to in-situ measurements. Despite several operational challenges, this study provides valuable in-situ bathymetric data for future modelling and hazard assessment of rapidly expanding glacial lakes in the region. The findings emphasise the need for robust field-based bathymetric datasets to refine empirical volume estimation models for Himalayan glacial lakes.Here, we present novel In-situ bathymetry datasets for four glacial lakes from western Himalaya.