Managing water resources is a critical challenge in the mountain and hill regions of the Hindu Kush Himalaya (HKH). Not only is demand increasing – for domestic use, irrigation, industry, and energy – the effects of climate change are now being seen in river basins in the form of changes in the hydrological regime and less predictable hydrological cycles. Extreme events such as floods and droughts are becoming more common and affecting communities and their livelihood activities across the region. There is an urgent need to manage the water resources in a more effective and equitable way that takes into account the water needs for all stakeholders and sectors. This resource book provides the broad framework and basic materials needed for developing an IRBM course, serving as a guide to understanding the natural environment and human systems of river basin components.