Hazard Management of Nathpa Dam (India) from Parechu Lake in Tibet

The Himalayan region contains the largest areas covered by glaciers and permafrost outside the polar region in the world, and is intrinsically linked to global atmospheric circulation, biodiversity, water resources and the hydrological cycle. Being the cradle of nine of the largest rivers in Asia whose basins are home to over 1.3 billion people, the region is susceptible to a whole range of hydro metrological, tectonic and climate induced disasters. With warming in the Himalayas being higher than the global average, climate induced natural hazards are likely to be exacerbated including severe glacial melting and retreat at an average rate of 30 to 60 meters per decade, with rapid accumulation of water in mountaintop lakes. In the face of accelerated global warming, the glaciers in the Himalayas are retreating at a rapid pace leading to rapid accumulation of water in mountain-top lakes. These glacial lakes which form behind moraine or ice ‘dams’ can breach suddenly, leading to floods known as Glacial Lakes Outburst Flood (GLOF). Once breached, millions of cubic meters of water and debris are discharged causing catastrophic flooding up to hundreds of kilometers downstream with serious damage to life, livelihoods, property, forest, farms and high value socio-economic and infrastructure assets. Recurrent flash floods, whether small or large like the ones in the years 2000 and 2005, have left short and long term socioeconomic destruction in their wake. They have also caused losses to economic infrastructure like bridges, roads and power projects. The administration is aware of the needs of the region and is working towards a unified system to manage flash flood risks in a comprehensive manner. This paper presents the hazard and mitigation measures to Nathpa Dam & Downstream area from Parechu lake upstream of Nathpa Jhakri Hydro Project (1500 MW) in Northern, India