Hazard situation of excisting glacier lakes in the Indian Himalayas

Within the HighNoon project, the University of Geneva and Zurich assess the hazard situation of existing glacier lakes in the Indian Himalayas. Moraine-dammed glacier lakes represent significant natural hazards due to potential dam failure and related high-magnitude outburst floods. The hazard situation of moraine-dammed glacier lakes depends mainly on the stability of the moraine dam. Yet, even unstable moraine dams normally need a trigger to induce the dam breach mechanism. Such are for example ice or snow avalanches, debris flows, landslides or rock fall from the flanks above the lake. By reaching and entering the lake tsunami-like waves are produced that can overtop and erode the dam.

Many investigations have been carried out in the Himalayas analyzing the hazard situation of existing glacier lakes, and detailed documentation of past glacier lake outburst floods (GLOF) with partly catastrophic consequences exist. However, so far only few studies focus on the Indian Himalayas and even fewer field studies have been carried out there to analyze systematically the hazard situation of particular lakes.

To fill this gap, we started an intensive field campaign at two different glacier lakes located in Himachal Pradesh and in Ladakh (refer to the map) in September and November 2010. Parameters about the moraine dam, the glacier lake, the retreating glacier behind the lake, and the possible trigger mechanisms were elevated. Working in an altitude of 4’000 and 5’000 m.a.s.l is simply breathtaking – in both meanings of the word. But it was certainly worth it all, as both lakes represent important case studies located in a spectacular mountain environment (see the pictures below).

An explicit post-processing of the in-field collected parameters must now be carried out in order to assess the hazard situation of these lakes. Thereby a dam break and flood routing model will be applied, based on which results decisions for the further advancement will be taken.

The awareness about the existence and the potential hazard of the investigated lakes is hardly present at the village people river downstream. The Buddhists see these mountain valleys as holy places inhabited by their gods, and not all villagers like people going up there. Thus a keen sense is needed to achieve a fruitful cooperation between local population and scientists.

 
Map of North India with the indicated locations of the two investigated glacier lakes in Himachal Pradesh and Ladakh.

Gopang Gath glacier lake in the Chandra Valley (Himachal Pradesh)	Gepang Goh mountain massive surrounding the Gopang Gath glacier lake
Buddhist mountain guide prays to the gods of the Gopang Gath glacier lake	Sissunala river valley, downstream of the glacier lake
The small village of Sissu, downstream of the glacier lake	Another glacier lake in the Chandra Valley (Himachal Pradesh)
Spong Togpo glacier lake in Ladakh, near the small village of Honupatta	The Spong Togpo glacier lake, viewing towards its moraine dam
The downstream valley of the Spong Togpo glacier lake in Ladakh	The small village of Honupatta, downstream of the Spong Togpo glacier lake