Identification of Glacial Lake and the Potentially Dangerous Glacial Lake in the Himalayan Basin

Glaciers have perennially been the source of fresh water for more than 1.3 billion of people in the Indian subcontinent. The climatic change and variability in recent decades has made considerable impacts on the glacier lifecycle in the Himalayan region. Warmer climates of the past have resulted in glacier retreat and the formation of glacial lakes in many mountain ranges. The lakes, located at the snout of the glacier, are mainly dammed by the lateral or end moraine, where there is a high tendency of breaching. Sudden discharge of large volumes of water with debris from these lakes potentially causes Glacial Lake Outburst Floods (GLOFs) in valleys downstream. A number of hydroelectric (HE) projects in India are being planned in the Himalayan regions. It has become necessary for the project planners and designers to account for the GLOF also along with the design flood for deciding the spillway capacity of projects located in similar hydro-meteorological regions. In order to assess the possible hazards from such lakes it is therefore essential to have a systematic inventory of all such lakes formed at the high altitudes. The hazardous lakes, however, are situated in remote areas and are very difficult to monitor through ground surveys due to rugged terrain and extreme climatic conditions. Monitoring of the glacial lakes and extent of GLOF impact along the downstream can be done quickly and precisely using time series satellite images and aerial photographs. To identify the individual glaciers and glacial lakes, different image enhancement techniques are useful. Besides making a temporal inventory, a regular monitoring of these lakes is also required to assess the change in their nature and aerial extent. In the present paper, identification of glacial lakes has been carried out using IRS LISSIII data. Also criteria for identification of potentially dangerous lake have been discussed.