Emerging Role of Remote Sensing For Monitoring Glacial and Surface Water Changes in Nepal

Objectives: This study showcases the use of remote sensing technology for monitoring evolutionary patterns of mountain lakes under climate stress in the mid-hills and hard to reach glacial terrains, ranging about 650-8055 meters above the mean sea level in the Gandaki region of Nepal. Method: Spatiotemporal trends were analyzed from Landsat (Thematic Mapper (TM), Enhanced Thematic Mapper (ETM +) and Operational Land Imager (1988 to 2018) satellite images using Normalized Difference Water Index (NDWI). Surface water content for three mountain glacial lakes (Kapuche, Dona and Tilicho) and two mid-hill lakes (Phewa and Begnas) were evaluated. Findings: Longitudinal data analysis of NDWI surface water pixels between 1988 and 2018 showed contrasting features in the two study terrains – the glacial lakes have expanded (NDWI for Dona and Kapuche increased by 29% and 182% respectively). Over the same period, the mid-hill lakes have receded (NDWI for Phewa and Begnas reduced by 2.05 % and 0.85 % respectively). On the other hand, the annual temperature increased 0.158ºC in the glacial region over the same period. The warmer temperature was considered the driving factor for the melting of glaciers, resulting in increased runoff. The increased surface water in the glacial lakes is attributed mainly to climate change impacts on glacier thickness reduction, whereas the diminishing lake area in the mid-hill belt is attributed mainly to sediment disposition and evaporative losses. Novelty: The study demonstrates the potential global application of remote sensing technology for in situ pervasive monitoring of the spatiotemporal climate change impacts on topographically complex landscapes. Our findings pave the way for the formulation of appropriate policy measures for sustainable management of land resources to reduce the drastic impact on surface water changes. Keywords: Glacier Lakes and Surface Water, Landsat, NDWI, Climate Change, Complex Landscape of Nepal