Decisions concerning policies and projects related to water infrastructure such as the construction of dams can be prepared in many ways. They can be left to the intuition and interests of market actors or be made the subject of systematic studies at the level of national governments, in state agencies, and even universities. Here the latter idea of of systematic analysis is emphasised. Traditional approaches such as cost-benefit analysis will be compared with more recent proposals such as multi-criteria analysis and positional analysis, which claim to be more in line with mainstream ideas of democracy. Each approach to decision-making has specific philosophical underpinnings and these features are more or less compatible with present ideas about sustainable development. It is concluded that the more disaggregated and ideologically open approaches, MCA and PA, can play a role in guiding us towards sustainable development but that much more is needed. In addition, issues of paradigms in economics, dominant ideologies in society, and institutional arrangements should be scrutinized and be made the subject of dialogue.