Methodology and application of Pareto frontier visualization in DSS for the design of water quality improvement strategies in multi-regional river basins

The methodology and real-life application of a new graphic approach to the design of water quality improvement strategies in multi-regional river basins is described. The approach has two main features: (1) it applies a simplified integrated model developed on the basis of diverse data and mathematical models; and (2) it is based on interactive visualization of the Pareto (non-dominated, efficient) frontier in the process of multi-criteria screening of possible decision strategies. The approach is used in the DSS for the design of water quality improvement strategies in large multi-regional river basins. The integrated model used in the DSS consists of three models that describe: (1) wastewater discharge; (2) wastewater treatment; and (3) pollution transport. The first model is based on statistical data and expert estimation of the discharge in the regions located in the basin. The second model was developed on the basis of a database of wastewater treatment technologies. The third model describes the inter-regional pollution transport in the simplified form of influence matrices that were obtained through simulation of a detailed pollution transport model for several types of pollution. The integrated model was studied by the new graphic multi-criteria technique called the Interactive Decision Maps (IDM). The IDM technique helps to explore the Pareto frontier of the feasible criterion set in the case of three to seven decision criteria. The Pareto frontier is displayed in the form of multiple decision maps, which are collections of tradeoff curves for pairs of criteria. The decision maps are provided on-line and animated. Users are informed on feasible combinations of criterion values and on efficient criterion tradeoffs. Selecting of a water quality improvement strategy is based on identification of a feasible goal directly on display. Then, the associated strategy is computed and displayed by a GIS, which informs on spatial aspects of the strategy.