Alarming trends: rapidly growing and recently formed glacial lakes in the Alaknanda Basin, northern Indian Himalayas

Abstract

Glaciers are retreating worldwide in response to global warming. Glacier retreat can expose over-deepened basins formed by subglacial erosion (e.g., abrasion, quarrying), which may fill with meltwater to form proglacial lakes. Such lakes may also form through moraine or ice damming, depending on local glacial and geomorphic conditions. Glacial Lake outburst floods (GLOFs) cause extensive damage to downstream communities, settlements, and infrastructure. In this study, GLOF hazard assessment using remote sensing is carried out in the Alaknanda Basin in Western Himalayas, India. The study includes mapping of 74 glacial lakes using a time series of LANDSAT and Sentinel-2 data ranging from 1994 to 2023 and assessing rapidly growing and recently formed lakes in the last two decades. The total area of the 24 glacial lakes larger than 0.01 km2 increased from 0.97 +/- 0.03 km2 in 1994 to 1.62 +/- 0.01 km2 in 2023, representing a growth of approximately 67 % over the study period. Between 1994 and 2023, 57 new glacial lakes formed in the basin, increasing the total number to 131; of these, 18 lakes larger than 0.01 km2 account for a combined area of 0.46 +/- 0.006 km2 in 2023, resulting in 42 lakes exceeding 0.01 km2 across the basin. Vasundhara lake and Balbala Lake (4,696 and 5,549 m a.s.l., respectively) expanded by 261 % and 119 % during the same period. A detailed analysis supplemented by a field survey was carried out for one of the rapidly growing lakes with upstream of an important pilgrimage site Badrinath. Observations indicate that 27 glacial lakes in the basin are exhibiting notable growth, which could potentially influence downstream areas and suggest the need for continuous monitoring and further assessment.