The design and operation of water treatment and distribution systems are also complex tasks in which the experience of the designer or operator is critical. Typically, models of these systems have sacrificed physical accuracy so that solutions could be obtained in a timely manner. Pingry et al. [1991] presented a DSS which allowed the user to evaluate the trade-offs between model solvability and accuracy in the design of water supply and distribution systems. The DSS was applied to a case study of the upper main stem subregion of the Colorado River, which had high salinity levels. A number of investment options were evaluated, and the interaction between water quantity and quality was demonstrated. Orr et al. [1992] addressed the trade-offs between flexibility and accuracy. They outlined a scheduling and control methodology for water distribution systems which included the use of general network simulation and optimization models, a database management system, and a graphic user interface. The methodology was applied to a large urban distribution system in the United Kingdom, and it was shown that structural changes to the system could be handled relatively easily. Deininger et al. [1992] presented a system for animation and visualization of water quality changes in distribution systems. Two applications were discussed in which the disappearance and reappearance of fluoride, as well as slow changes which occurred in several dead ends, allowed insight into the system dynamics which would be unlikely from conventional simulation models.