Rapid growth of a glacial lake in Khumbu Himal, Himalaya: prospects for a catastrophic flood

The growth of a lake on the Imja Glacier, Khumbu Himal, was traced from maps and photographs supplied by several sources. There were five small ponds in the 1950s. A single lake with islands formed by 1975. A small island existing in 1978 had disappeared in 1980. The lake area was in 1984, and had become slightly larger by 1991. The comparison of the lake water volumes of "Imja Glacier Lake" and of the lakes which burst in 1977 and 1985 suggests that future outbursts of "Imja Glacier Lake" may cause catastrophic damage below. Today, the spillway morphology at the surface of the debris-covered ice near the glacier terminus is changing noticeably, indicating rapid expansion of the lake toward the west. As this proceeds, the possibility for catastrophic outburst will become greater, even if the lake level is lowered. Recent observations indicate a maximum depth of more than 90 m and an average depth of 40-50 m; thus the potential for a major outburst is much higher than previously anticipated. Glaciological and hydrological investigations and a monitoring program should be undertaken in order to mitigate potential catastrophic damage at the lower elevations.