The latest Coupled Model Intercomparison Project Phase 5 (CMIP5) projection from the Intergovernmental Panel on Climate Change (IPCC) shows very large uncertainty in climatechange-related risk in the Himalaya region. Inability to plan increases the challenge of water resources management for large river basins, especially in Central and South Asia. This uncertainty is largely attributable to GCMs' poor representation of the snow/glacier melting mechanism and monsoon precipitation prediction. The river basins of the Himalaya region include (from east to west): the Aral Sea basins (Syr Darya and Amu Darya), the Indus Basin, the Ganges Basin and the Brahmaputra Basin. The total population in these basins is about 1.8 billion and is projected to increase faster than other world regions. The increasing population and complex political/socioeconomic conditions make this region even more vulnerable to climate change risks. This study provides a comprehensive summary of the climate change risks in this region and covers topics from climatology and hydrology (natural-system perspective) to water resources system and socioeconomic impacts (anthropocentric perspective). It is expected that this comprehensive knowledge platform will provide guidance for future water-resources-related studies in sub-areas as diverse as energy and food security, infrastructure development, flood and drought management, planning for extreme events, and transboundary water sharing.