Book excerpt: "The Department of Environmental Resources of Durham, NC, owns and operates two raw water reservoirs: Lake Michie on the Flat River and the Little River reservoir. To ensure that reservoir releases are adequate to meet target demands, Durham has relied on mathematical models developed by Research Triangle Institute and the University of North Carolina. However, most of the modeling work predates the addition of the Little River reservoir in 1988. In 1999, Durham decided to update its decision support system for drought management with a model that includes both reservoirs. This report describes a risk-based simulation model that was developed using 72-years of historical data for reservoir inflows, precipitation, and evaporation. ..." leaf i