Using an integrated desision support system (DSS), the water supply system of the City of Colorado Springs, Colorado, is modeled and simulated for various future development scenarios. This paper describes the approaches taken for estimating yields of all existing and potential water supply sources from local and remote river basins, some located as far as 200 miles away. A generalized river basin network model (MODSIM) is used to optimize the City's use of direct flow rights, storage rights, and exchangeable waters from the various sources. Furthermore, the computer model has been extended to incorporate water quality simulation capabilities. This feature is employed to identify and minimize the amount of water entering the system with unfavorable concentrations of TDS, fluoride, and total organic carbon. A user shell is also developed embodying the various program modules in a DSS, which provides the City staff with an intuitive and comprehensive decision support tool. The user interface offers a number of unique features, including a point and click graphical user interface for drawing and editing system features, a digital system map viewer, an object oriented data base management system with spreadsheet style editing environment, an embedded graphical charting capability, file exporting features for generating CADD formatted compatible files, and comprehensive on line help. The DSS is employed for determining how to best utilize and exchange existing and proposed water supplies. In addition, the DSS is used to determine the timing, sizing, and suitability of potential future projects. The results of the study indicate that the City will be able to reliably deliver water to its customers under the current planning horizon. However, proper staging and sizing of proposed projects and maximum synchronization of exchange releases are essential in minimizing possible water supply shortages.