270 W Amita Shah and Jharna Pathak 10 Sustainable Management and Regional Cooperation for Himalayan Waters Ramesh Ananda Vaidya and Madhav Bahadur Karki  The rapid retreat of the Himalayan glaciers leads to water-related hazards, such as glacier lake outburst floods (GLOFs), and water stress, as a result of the decline in freshwater supplies during the lean season. Thus, there is a need to think and act seriously about cooperation among the countries in the Himalayan region for managing water resources and water-related hazards. According to the Fourth Assessment Report of the United Nations’ Inter- governmental Panel on Climate Change (IPCC 2007), the inci- dence and intensity of floods in the Himalayan region are expected to increase as a result of an increase in extreme precipitation events during the monsoon season and glacial retreat, both, in turn, resulting from global warming. This poses a challenge for reducing the vulnerability of the more than 1.3 billion people living in the major river basins downstream from the Hindu Kush–Himalayan region. The overriding importance of climate change as a driver of environmental change makes it important to address disaster- reduction and water-management concerns in a holistic manner at the river basin level. Such an approach is being considered by the IPCC to be an adaptive measure for tackling the impact of climate change. The economics of water resource management also suggests the need for taking advantage of externalities while planning