Rising Lake Levels Across High Mountain Asia

Hassan, Javed; Nielsen, Karina; Colgan, William; Kayastha, Rijan Bhakta; Khadka, Mira; Khan, Shfaqat Abbas

doi:10.5194/egusphere-2026-808

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https://doi.org/10.5194/egusphere-2026-808

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02 Apr 2026

| 02 Apr 2026

Status: this preprint is open for discussion and under review for The Cryosphere (TC).

Rising Lake Levels Across High Mountain Asia

Javed Hassan, Karina Nielsen, William Colgan, Rijan Bhakta Kayastha, Mira Khadka, and Shfaqat Abbas Khan

Abstract. High-altitude lakes across High Mountain Asia (HMA) are one of the critical freshwater reservoirs and sensitive indicators of climate change due to their remote locations and limited human disturbances. This study presents continuous water level estimates for 232 lakes across HMA from 2010 to 2024 using CryoSat-2 and ICESat-2 data. We analyzed temporal and spatial variations and inter-mission consistency in the lake water level across HMA. Our results reveal an overall increasing trend (median rate: +0.1 ± 0.01 m yr⁻¹), with 77 % of lakes experiencing rising levels and 91 % exhibiting statistically significant trends. We find a substantial regional heterogeneity with the Tibetan Plateau contributing dominantly to regional increase (0.07 ± 0.001 m yr⁻¹), while Himalayan lakes show persistent decline (0.04 ± 0.001 m yr⁻¹). Water level times series observed with the satellite altimetry missions CryoSat-2 and ICESat-2 intercomparison demonstrates strong consistency (80 % sign agreement, p = 0.013). Lake catchment scale analysis identifies precipitation as the dominant deriver of lakes water level variability (r = 0.42, p < 0.001), whereas lakes in glaciated catchments exhibit weak climate correlations despite significant increases in temperature, indicating nonlinear cryosphere buffering. We find systematic relationships between lake characteristics (area, elevation) and increasing water levels, with larger lakes generally showing more rapid growth. The contrasting hydrological responses with continued rising water levels in cryosphere influenced lakes and accelerating declines in precipitation sensitive lakes in Himalaya highlight divergent lake hydrological regimes. These findings underscore the critical importance of regional differentiation in understanding lake water storage changes and informing climate adaptation strategies for population vulnerable to these changes in the regions.

Received: 10 Feb 2026 – Discussion started: 02 Apr 2026

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Javed Hassan, Karina Nielsen, William Colgan, Rijan Bhakta Kayastha, Mira Khadka, and Shfaqat Abbas Khan

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RC1:
'Comment on egusphere-2026-808', Anonymous Referee #1, 25 May 2026 reply
Reviewer comments on manuscript EGUsphere-2026-808 “Rising Lake Levels Across High Mountain Asia” by Hassan et al.
General comments:
This manuscript analyzes lake-level changes across 232 lakes in High Mountain Asia from 2010 to 2024 using CryoSat-2 and ICESat-2 data. The results show heterogeneous lake-level changes across HMA, with overall increases in the Tibetan Plateau lakes and declining tendencies in the Himalaya. The authors further examine correlations between lake-level changes and ERA5-Land precipitation, temperature, and evaporation to interpret possible hydroclimatic controls. While the dataset and regional synthesis are useful, the manuscript’s current scientific contribution is somewhat limited by a largely descriptive analytical framework. The conclusions regarding climatic drivers, cryospheric buffering, and regional mechanisms are not fully supported by the current analyses. The study would benefit from more robust attribution framework, and a more explicit statement of its novelty relative to previous HMA lake-level studies.
Specific comments:
About innovation. The broader finding on the rising lake-level in the central Tibetan Plateau and declining tendency in the southern Tibetan Plateau/Himalayan region is already well established in the literature. The authors state that the majority of previous studies are confined to the Tibetan Plateau. While, existing studies have either extended the analysis to high-elevation lakes above 2500 m a.s.l. (e.g., Zhang et al., 2020) or to glacial lakes across the entire HMA (e.g., Wang et al., 2025). It is useful that the manuscript extends the lake-level record to 2010–2024, however a 15-year period does not necessarily provide a clear advantage for assessing long-term trends. The manuscript should more explicitly state the knowledge gap, not only in terms of “more lakes and longer time series,” but new process understanding. For example, does the study reveal post-2018 acceleration or deceleration in lake-level changes? Or does it identify regional differences that were not captured by previous TP- or HMA-wide studies?

Wang Y, Zheng D, Zhang G, Carrivick JL, Bolch T, et al. (2025). Patterns and change rates of glacial lake water levels across High Mountain Asia. National Science Review, 12(3): nwaf041.
Zhang, G., Yao, T., Xie, H., Yang, K., Zhu, et al. (2020). Response of Tibetan Plateau lakes to climate change - Trends, patterns, and mechanisms. Earth Science Reviews, 208
About mechanistic interpretation. The manuscript relates lake-level trends to ERA5-Land temperature, precipitation, and evaporation trends. This provides a reasonable first-order analysis, but the Discussion often moves from correlation to mechanistic interpretation. For example, the authors suggest that lake expansion on the Tibetan Plateau is mainly associated with increased precipitation, that glacierized catchments reflect cryospheric buffering, and that declining Himalayan lakes indicate precipitation sensitivity and reduced meltwater buffering. These interpretations are plausible, but correlation analyses alone are not sufficient to infer dominant mechanisms. Lake-level change integrates catchment runoff, direct precipitation over the lake, evaporation, groundwater exchange, glacier and snow melt, and possible outlet dynamics. The authors should therefore either moderate the mechanistic language or strengthen the analysis, for example by introducing a simple lake water-balance framework to guide interpretation.

About uncertainty. The climate-driver analysis is based on ERA5-Land temperature, precipitation, and evaporation. Reanalysis data especially precipitation are highly uncertain in high-mountain regions, and this uncertainty directly affects the interpretation of correlations between climate variables and lake-level changes. The authors should discuss this limitation more explicitly. If possible, comparison with another precipitation product would strengthen the analysis.

About Discussion. The discussion of glacier melt and permafrost contribution mainly relies on previous studies. Some statements on glacier-melt buffering and permafrost-related contributions cannot be directed supported by the lake-level and climate-correlation analyses. The manuscript should make clearer which process interpretations are directly supported by this study and which are inferred from prior literature.

About regional classification. The manuscript groups lakes into Tibetan Plateau, Himalaya, western HMA, and glacierized catchments, however, the criteria are not described explicitly. In particular, “glacierized catchments” overlap spatially with the other regions. It is not clear whether these are treated as an independent category or a cross-cutting classification.

Given the above, I would recommend a major revision.

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Citation: https://doi.org/10.5194/egusphere-2026-808-RC1

Javed Hassan, Karina Nielsen, William Colgan, Rijan Bhakta Kayastha, Mira Khadka, and Shfaqat Abbas Khan

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https://doi.org/10.5194/egusphere-2026-808-supplement

Javed Hassan, Karina Nielsen, William Colgan, Rijan Bhakta Kayastha, Mira Khadka, and Shfaqat Abbas Khan

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Short summary

High-altitude lakes in High Mountain Asia (HMA) are important sources of freshwater and sensitive indicators of environmental change. Using satellite data from 2010 to 2024, we examine water level changes in 232 lakes across HMA. Results show rising lake levels on the Tibetan Plateau, while lakes in the Himalaya are declining. These contrasting patterns highlight strong regional differences and provide valuable information for understanding water availability and associated hazards.


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