Society’s large dependence on water, in combination with climate, socio-economic and demographic changes, places a massive pressure on our freshwater resources. As a result, water crisis, defined as a significant decline in the available quality and quantity of freshwater, is now considered to be among the most critical global risks to society. The overall aim of this thesis is to increase the understanding of how decision support methods based on risk, cost-benefit and multi-criteria decision analyses can be used to facilitate our collective action towards water security. In the thesis, a sustainability assessment model is presented which can rank alternative drinking water options from the most preferred to the least preferred within each of the social, environmental and economic sustainability domains and with regards to all domains. The thesis further presents a marginal abatement cost curve to provide a common starting point for cross-sectoral dialogue on water scarcity mitigation. It enables a comparison of the cost-effectiveness of alternative mitigation measures, providing guidance for businesses, households, farmers and water utilities. Furthermore, a scenario-based risk assessment approach is presented to enable a comprehensive view on risk when evaluating water supply systems and risk reduction options. The approach allows for thorough analyses of economic losses under a range of water supply disruption scenarios, facilitating prioritizations on measures that aim to reduce the overall risk rather than individual risks. The provided methods are all exemplified in Swedish case studies, demonstrating different ways of evaluating and comparing management responses to the water-related challenges we face. In conclusion, the methods can help us strengthen the ongoing discussions regarding challenges and opportunities while providing structure and transparency to decision-making, and by that contribute to an enhanced water security.