Glacier Inventories in the Chhombo Chhu Watershed of Tista basin, Sikkim Himalaya, India

Multi-temporal inventory of glaciers compiled for the Chhombo Chhu Watershed (CCW) of Tista basin, Sikkim Himalaya, India. The CCW consists of 74 glaciers (>0.02 km2) with a mean glacier size of 0.61 km2. Change analysis based on the glaciers outlines obtained from declassified hexagon KH-9 (1975), Landsat 5 TM (1989), Landsat 7 ETM+ (2000), Landsat 5 TM (2010) and Sentinel 2A (2018). The total glacier area in 1975 was 62.6 ±0.7 km2; by 2018 the glacier area had decreased to 44.8 ± 1.5 km2, an area loss of 17.9 ± 1.7 km2 (0.42 ± 0.04 km2 a–1). Debris free glaciers exhibit more area loss by 11.8 ± 1.2 km2 (0.27 ± 0.03 km2 a–1) followed by partially debris-covered (5.0 ± 0.4 km2 or 0.12 ± 0.01 km2 a–1) and maximum debris-covered (1.0 ± 0.1 km2 or –0.02 ± 0.002 km2 a–1) glaciers. The quantum of glacier area loss in the CCW of Sikkim Himalaya took its pace during 2000–2010 (0.62 ± 0.5 km2 a–1) and 2010–2018 (0.77 ± 0.6 km2 a–1) timeframes. Field investigations of selected glaciers and climatic records also support the trend in glacier recession in the CCW, as a result of significant increase in temperature trend and more or less static precipitation since 1995. Glacier retreat rates in the CCW were almost similar to the Changme Khangpu basin and other selected glaciers in Sikkim Himalaya. Thus, this glacier inventory and area change analysis will provide valuable information to the glaciological and hydrological community for the future modeling and planning of the water resources in Sikkim state of Eastern Himalaya.