Expansion of a moraine‐dammed glacial lake, Tsho Rolpa, in Rolwaling Himal, Nepal Himalaya

Abstract

Across the surface of debris‐covered glaciers in the Nepal Himalayas there are many lakes on the order of 1 km in scale. Some of the lakes, dammed by the end/lateral moraine, have been expanded from ponds on the order of 100 m in length. Tsho Rolpa Glacier Lake in the headwater region of the Rolwaling Valley, Eastern Nepal, was probably a small pond in the early 1950s. The present expansion rate of the glacial lake is unknown. From our investigation of the hydrological and meteorological conditions in 1993–1994, the calculated heat balance in the lake showed a deepening rate of about 1.2 m yr−1 all through the year. This is comparable to the mean deepening rate of the bottom basin since 1952. The vertical expansion thus is still continuing. Annual volume expansion including the calving ice (horizontal expansion) volume was 3% of the present total volume of the lake.