Glacial lake outburst flood (GLOF) study of Dhauliganga basin in the Himalaya

Abstract

Numerous glacial lakes are forming in high-altitude regions worldwide due to rise in temperature. Some of them may burst i.e. Glacier Lake Outburst Flood (GLOF) may occur causing loss of lives, properties and infrastructures in downstream areas. Thus, GLOF study is necessary to understand its threat and save or minimise the imminent losses. In the present study, the highest dangerous glacial lake of Dhauliganga basin in the Himalaya has been considered with a view to estimate the GLOF hydrograph just downstream of the lake and the routed GLOF hydrograph near Dhauliganga Stage-I Dam. The Glacial lake L2 (Latitude 30^o26′45″ E and Longitude 80^o23′16″ N) is the highest potentially dangerous lake, whose maximum surface area was 132,300 m² acquired on 16 September 2009. GLOF has been simulated for Glacial lake L2 for its maximum volume 2 × 10⁶ m³, by the model prepared with the help of hydraulic software such as HEC-RAS. Results by the model have been compared with the results got by the popular empirical formulae. In average condition, the GLOF hydrograph peak just downstream of Glacial lake L2 is 2,021 cumec and the same is 4,272 cumec in worst condition. The GLOF hydrograph has been routed from Glacial lake L2 to Dhauliganga Stage-I Dam covering a distance around 72 km. In average condition, routed GLOF hydrograph peak near Dhauliganga Stage-I Dam including 100-year return period flood 1,700 cumec is 3,047 cumec at 2 h 01 min and the same is 3,253 cumec at 1 h 46 min in worst condition.