Low-Cost Sonar-Based Bathymetry for Morphometric Analysis of Himalayan High-Altitude Lakes

This study demonstrates the potential of cost-effective sonar integrated with uncrewed surface vehicles (USVs) for bathymetric surveys of high-altitude mountain lakes in the northwestern Himalaya, India. Three lakes were selected as test sites, Deepak Tal (3,770 m), Suraj Tal (4,777 m) near Baralacha La in Lahaul & Spiti, Himachal Pradesh, and a smaller lake near Parashar Lake (hereafter referred to as NP Lake; 2,592 m) in Mandi, Himachal Pradesh, India. The surveys were conducted using a Deeper Pro+ sonar mounted on a USV. The sonar recorded depth measurements at individual points, which were later interpolated using Kriging to generate continuous bathymetric surfaces for each lake.

For Deepak Tal, over 25,000 depth points were collected, yielding a maximum depth of 7.44 m and an estimated lake volume of 41,929.05 m³. For Suraj Tal, more than 5,000 points were acquired, with a maximum depth of 2.56 m and a corresponding volume of 9,400.95 m³. For NP Lake, approximately 1,000 points were recorded, with a maximum depth of ~1.3 m and a volume of 2,947.53 m³. Several empirical  formulas were applied to calculate volume of the lakes and compared with the field-derived volumes, revealing extremely large deviations (up to ~129,908 times), highlighting the limitations of the empirical formulas used for volume estimation of high-altitude lakes.

Overall, this study demonstrates that the Deeper Pro+ sonar mounted on a USV provides an effective, low-cost, and low-risk approach for generating high-resolution bathymetry, accurate volume estimates, and detailed morphometric information for high-mountain lakes.

Keywords: Cost-Effective Bathymetry; High-Altitude Lakes; USV; Sonar Mapping; Lake Volume; Northwestern Himalaya