This report describes a risk-based decision support system for designing and managing large-scale water resource projects. A model is presented that combines a new risk assessment methodology with traditional decision-making tools to enable systems engineers to capture the full spectrum of operational risks during the design process. Enhancing public welfare through the deliberate management of water resources is vital for every society. Pollution, overuse, and consumption challenge a society's ability to develop and sustain water supplies for municipal, agricultural, industrial, and recreational use while protecting fisheries and wetlands. Water resource management decisions are complex and involve risk. This project identifies a risk taxonomy to help managers identify those risks and their severity. These risk factors provide the foundation for a multi-attribute utility decision support tool for managers and policymakers. Quantifying the risks in competing courses of action is an essential first step. The risk taxonomy identifies 13 risk factors that comprise the physical, logical, and environmental domains. Attributes of the essential risk elements are viewed in terms of utility and drive the decision process through traditional multi-attribute utility analysis. The result is a set of feasible alternatives that is both risk-based and value-focused for the decision maker to consider. The project is presented in the context of the Susquehanna River Basin that spans three states in the United States, with management interests at the state, regional, and national levels. The Susquehanna River is the 16th largest river in the United States and its tributaries drain 27,510 square miles. The project builds on work supporting the Susquehanna River Basin Commission's decision on managing the 14-mile-long Conowingo Pool near the river's terminus. This project was conducted for the NATO Advanced Research Workshop held in Istanbul, Turkey, 12-16 Oct 2006.