Sustainability has increasingly become a key policy goal, mainly as an answer that the current path of modern societies in not viable in the long term. Several assessment tools have been developed accordingly, especially focusing on the energy sector. This thesis focuses on hydropower, the main source of renewable power worldwide. Hydropower is in this frame explored and analyzed in four steps: 1) Investigation of diversity in water rights, and elaboration of a 9-steps process to overcome this diversity; 2) Exploration of hydropower impacts and building of causal diagrams; 3) Application of MCDA tools and stakeholder survey to analysis the future of existing hydropower installations, based on one case study; 4) Construction of causal diagrams to represents the concerns and expectations of stakeholders, based on two case studies. Globally, our results call for a systematic, early and comprehensive assessment of hydropower impacts, including multiple temporal and spatial scales.