Regional Mountain Conference

Rapid deglaciation and changing climatic regime are altering the hydro-sedimentary properties of the high-mountain lakes, which act as an early indicator of global environmental changes. In this ongoing research, we present the decadal (2016-2025) spatiotemporal suspended sediment (SS) dynamics of eight high-altitude lakes and reservoirs in the Western Alps with different glacier connectivity and various levels of turbidity, situated at an average altitude of 2,000 meters a.s.l. We use reflectance in the red band (B4) as it has already been proven to be a robust proxy for suspended sediment concentration. As Sentinel-2 L2A atmospherically corrected products have limited validity for water analysis, we cross-validated snow, cloud and glint masked Top-of-the-atmosphere (TOA) red band reflectance from the Sentinel-2 L1C product with outputs from the ACOLITE atmospheric correction model and demonstrated good agreement (r²>0.8). Mann-Kendall statistics show that four lakes have an increasing trend, while other four lakes show a decreasing red band signal. Additionally, we employed spectral turbidity indices to substantiate the SS dynamics. Surprisingly, geographically proximal lakes with different glacial connectivity conditions appeared to have similar decadal SS trend. We suggest cryospheric changes, local geomorphology, and anthropogenic factors as controlling factors, which require further in-depth investigation, with an expansion of study area in other parts of the Alps. These lakes have also been chosen as strategic sites for future data sampling and model validation, before implementation to other larger high-mountain regions across the Alps and the Himalayas.