This book analyses the effectiveness of reservoir based hydropower as an energy source for the PR China and Japan regarding the countries' self-proclaimed goals of improving social and environmental performance while increasing electricity production. It builds upon the classic (three pillar) Sustainability approach of a combined social, economic and environmental analysis. The novelty of this book lies in its approach thereafter: it argues that - similar to established small scale assessments - the sustainability performance on a country scale will differ according to geographical, social, economic and other features of each country. This book is a fresh approach to the idea of Sustainable Development and takes the classic model to a new level by developing country level indicators for a comparative and sector specific assessment of hydropower.