| 13 May 2026
Multi-Decadal Expansion of Potentially Dangerous Glacial Lakes in Central-Eastern Nepal (1992–2024): Remote Sensing Assessment and GLOF Hazard Implications
Abstract. Glacial lakes in the Himalayan regions are expanding rapidly under ongoing climate change, intensifying the risk of Glacial Lake Outburst Floods (GLOFs). This study quantifies multi-decadal area changes (1992–2024) in four Potentially Dangerous Glacial Lakes (PDGLs), Thulagi, Lumding Tsho, Hongu 2, and Lower Barun, located in central-eastern Nepal, using Landsat 5 and Landsat 8 satellite imagery processed within the Google Earth Engine (GEE) cloud platform. Lake boundaries were delineated from post-monsoon (October–November) median composites using the Normalized Difference Water Index (NDWI; threshold = 0.3), supplemented by manual delineation where topographic shadow conditions compromised automated extractions. Area uncertainties were computed using the standard half-pixel buffer method. Non-parametric Mann-Kendall trend tests with Sen’s slope estimator were applied to all lake area time series to evaluate the statistical significance and rate of expansion. Sub-period regression analysis was used to assess acceleration in lake growth. Empirical area-volume scaling was applied to estimate changes in impounded water volume. All four lakes exhibited statistically significant, monotonically increasing area trends over the 32-year study period (Mann-Kendall tau = 1, p < 0.001 for each lake). Lower Barun exhibited the highest expansion rate (Sen’s slope = 0.063 km2 yr-1), growing from 0.77 ± 0.053 km2 in 1992 to 2.76 ± 0.13 km2 in 2024 (a 258 % increase), with post-2010 expansion accelerating by a factor of 1.35. Lumding Tsho showed a strongly accelerating growth trajectory (R2 = 0.96) with a post-2010 rate that more than doubled. The combined estimated additional water volume stored across all four lakes since 1992 approaches 608.6 × 106 m3, representing a GLOF hazard of exceptional and growing scale. The approach demonstrates a scalable and reproducible framework for long-term glacial lake monitoring and hazard assessment, applicable across data-sparse high mountain environment.
After reading the manuscript by Ghimire et al. carefully, I found that the study, in its current form, provides no new knowledge or scientific insight. The authors selected four previously recognized hazardous glacial lakes in the Nepal Himalaya and primarily evaluated their temporal evolution and rates of expansion. While documenting changes in these lakes is relevant, the analysis remains largely descriptive. I had expected the study had investigated the processes underlying the contrasting expansion rates among the lakes, including the amount of glacier ice lost as a consequence of lake expansion, the relationship between lake expansion and adjacent glacier mass loss, and how glacier dynamics have responded to progressive lake development and also future lake development. Such process-based analysis would have substantially strengthen the scientific contribution of the study.
The assessment of GLOF hazard is also relatively very simplistic. The manuscript estimates lake volume using a single empirical relationship and then infers that increasing lake volume corresponds to increasing GLOF hazard. However, lake volume alone does not adequately represent GLOF hazard. A more comprehensive assessment should consider changes in dam geometry and stability, glacier–lake interactions, surrounding slope and avalanche susceptibility, potential impact zones, and the changing likelihood and magnitude of potential triggering mechanisms. In particular, the authors could examine whether continued lake expansion is bringing the lake closer to potentially unstable probable avalanche source and impact zones, and how such changes may modify future GLOF scenarios. A deeper analysis of the linkage between lake evolution, glacier dynamics, potential triggers, and downstream hazard would provide considerably greater scientific insight than simply documenting lake-area and volume increases.
I also feel authors should read and acknowledge relevant papers of glacial lakes in Nepal Himalaya to built their research and strengthen writings. Some of them are:
1. Khadka, N., Zhang, G., & Thakuri, S. (2018). Glacial lakes in the Nepal Himalaya: Inventory and decadal dynamics (1977–2017). Remote Sensing, 10(12), 1913.
2 .Gouli, M. R., Hu, K., Khadka, N., & Talchabhadel, R. (2023). Hazard assessment of a pair of glacial lakes in Nepal Himalaya: unfolding combined outbursts of Upper and Lower Barun. Geomatics, Natural Hazards and Risk, 14(1), 2266219.
3. Khadka, N., Chen, X., Sharma, S., & Shrestha, B. (2023). Climate change and its impacts on glaciers and glacial lakes in Nepal Himalayas. Regional Environmental Change, 23(4), 143.
4. Khadka, N., Zhang, G., & Chen, W. (2019). The state of six dangerous glacial lakes in the Nepalese Himalaya. Terr. Atmos. Ocean. Sci, 30(6), 10-3319.
5. Furian, W., & Sauter, T. (2025). Assessing economic impacts of future GLOFs in Nepal's Everest region under different SSP scenarios using three-dimensional simulations. Natural Hazards and Earth System Sciences, 25(10), 3779-3802.
6. Khadka, N., Pandey, V. P., Watson, C. S., Zheng, G., Wu, T., Sharma, K., ... & Shrestha, D. (2026). The 2024 cascading glacial lake outburst flood in the Thame Valley of Everest region, Nepal: process, impacts and implications. Natural Hazards and Earth System Sciences, 26(8), 4131-4152.
7. Hu, J., Yao, X., Duan, H., Zhang, Y., Wang, Y., & Wu, T. (2022). Temporal and spatial changes and GLOF susceptibility assessment of glacial lakes in Nepal from 2000 to 2020. Remote Sensing, 14(19), 5034.
8. Rawlins, L. D., Watson, C. S., Bhambri, R., Khadka, N., & Chand, M. B. (2026). Glacial Lake Observatory (GLO): annual dataset of glacial lakes in Nepal and transboundary catchments (2017–2024). Earth System Science Data, 18(7), 5143-5165.
9. Khadka, N., Chen, X., Nie, Y., Thakuri, S., Zheng, G., & Zhang, G. (2021). Evaluation of glacial lake outburst flood susceptibility using multi-criteria assessment framework in Mahalangur Himalaya. Frontiers in Earth Science, 8, 601288.
10. Watson, C. S., Kargel, J. S., Shugar, D. H., Haritashya, U. K., Schiassi, E., & Furfaro, R. (2020). Mass loss from calving in Himalayan proglacial lakes. Frontiers in Earth Science, 7, 342.