This study focuses on how, by 2030, competing demands for scarce water resources can be met and sustained. It is sponsored, written, and supported by a group of private sector companies and institutions who are concerned about water scarcity as an increasing business risk, a major economic threat that cannot be ignored, and a global priority that affects human well-being. After careful quantitative analysis of the problem, this report provides some answers on the path to water resource security. It first quantifies the situation and shows that in many regions, current supply will be inadequate to meet the water requirements. However, as a central thesis, it also shows that meeting all competing demands for water is in fact possible at reasonable cost. This outcome will not emerge naturally from existing market dynamics, but will require a concerted effort by all stakeholders, the willingness to adopt a total resource view where water is seen as a key, cross-sectoral input for development and growth, a mix of technical approaches, and the courage to undertake and fund water sector reforms.