IDENTIFICATION OF GLACIAL LAKES AND GLOF ESTIMATION IN A MOUNTAINOUS WATERSHED IN ARUNACHAL PRADESH

Abstract

Glaciers are the nature's gift to millions of people living in the downstream because they serve as valuable source of fresh water for drinking water supply, agricultural, industrial and hydropower developments for present and future needs. Due to accelerated global warming some of the glaciers are retreating at an alarming rate and thus resulting in formation of glacial lakes. Glacial lakes which are generally adjacent to receding glaciers can lead to a sudden breach of their unstable moraine dams' i.e. Glacial Lake Outburst Flood (GLOF) due to rapid accumulation of water. These floods are very destructive in nature and can release about million cumec of water in few hours. There has been considerable expansion and development of glacial lakes in the Himalayas since last 5 decades. As a result of their expansion, the glacial lakes in the region have become highly unstable, which is posing increased frequency and risks of such flash flood in near future. Most of glacial lakes are inaccessible in nature, so their investigation is a difficult task. The inventories are only possible using time series remote sensing data and geographic information system (GIS) technology. The various satellite images can be used for mapping and monitoring of the glacial lake in the remote regions. Also, various other information which are important for such studies can be extracted from such satellite imaginaries. The present study aim is to understand GLOF phenomenon by creating an inventory of existing glacial lakes in a hilly catchmcnt in high altitude using Geographical InRrmation System (GIS) and remote sensing techniques. Landsat and Indian remote sensing satellite (P6: LISS3) data of 2001, 2005, 2008 and 2010 were used for mapping and monitoring of water bodies. More than 60 water bodies including seasonal and permanent lakes were iden1iled in the catchrnent. One lake was hypothetically considered potentially dangerous from the point of view of failure and generation of GLOF at the outlet. GLOF was computed for this lake using MIKE 11 software. The computed GLOF at the catchment outlet was 729.86 cumec considering a GLOF of 1175.30 cumec at the lake outlet with a travel time of 64 minutes. This study showed that the GLOF results are significant flood at the catchment outlet. It is therefore vety important to consider the impact of GLOF on the downstream projects particularly for the design flood estimation and development of early warning system for flood management