What are decision support systems?
A decision support system (DSS) is both a process and a tool for solving problems that are too complex for humans alone, but usually too qualitative for only computers. Multiple objectives can complicate the task of decision-making, especially when the objectives conflict. As a process, a DSS is a systematic method of leading decision-makers and other stakeholders through the task of considering all objectives and then evaluating options to identify a solution that best solves an explicit problem while satisfying as many objectives as possible.
As a tool, a DSS consists of mathematical models, data, and point-and-click interfaces that connect decision-makers directly to the models and data they need to make informed, scientific decisions. A DSS collects, organizes, and processes information, and then translates the results into management plans that are comprehensive and justifiable.
Where is a DSS typically used?
Often, water resources stakeholder groups have very diverse goals and values, including environmental, economic, and ecological interests. What complicates this process even further is that water resources managers must try to achieve numerous and often conflicting objectives, such as achieving peak sustainable yield, minimizing environmental impact, managing costs, maintaining adequate water quality, controlling floods, minimizing energy use, and providing recreational opportunities.
DSS programs have been used to develop water resources management plans, adaptable operating rules for water and wastewater systems, and regional policies. Many municipalities and water authorities often derive their water supplies from several sources, which may include surface reservoirs, rivers, groundwater wells or combinations of these sources. To identify the best combination of supply sources in the long term, or to determine the most effective way of managing existing systems, decision-makers need a lot of information to account for all of the hydrologic, hydraulic, water quality, and economic relationships within the system.
What are the benefits of this technology for water resources management?
A DSS is much more comprehensive than traditional methods of decision-making in water resources management. Rule curves, one common traditional method, are discrete and confined to specific conditions, while a DSS can be adapted to any conditions. DSS recommendations are based on scientific data and models and can account for all stakeholder objectives, cause/effect relationships, risks, costs, and reliability, whereas traditional decision processes have had difficulty aggregating all of these considerations.
DSS programs are adaptable; they are custom-designed for specific systems to help achieve system-specific management objectives. And because a DSS is a reproducible method of decision-making, its results are defensible to stakeholders and regulatory agencies.
A DSS is capable of aggregating all competing objectives to identify the best strategy--that is, a strategy that is truly optimal. Moreover, as a process, decision support techniques involve the decision-makers in defining the problems and the objectives. This gives the stakeholders the knowledge that their values are important, and they can see that their qualitative and quantitative input is being used.
What are the challenges of using this technology?
One of the biggest challenges is changing people's perceptions about both water resource management and environmental models. A common misconception is that competing objectives will necessarily result in a stalemate. However, a DSS is designed to consider all objectives and then produce an optimal solution. A computer model is often seen as a black box, but in the case of a DSS, a graphical interface links the decision-makers with the models. Decision-makers can set up scenarios and even view the modeling relationships in familiar formats (spreadsheets or graphical displays). Finally, rather than generating output that is cryptic and disaggregated, a DSS presents management plans graphically or with organized, familiar terminology.
How is CDM helping clients implement DSS tools?
CDM has worked on DSS programs for clients across the country and abroad. We have used these tools to develop long-term regional water supply plans, optimum operational plans for water supply management, and real-time strategies for combined sewer overflow control and water supply withdrawals. Recent examples include the development of integrated water resource plans for San Diego and the Gaza Strip, a source water assessment program and a real-time CSO control program for Philadelphia, and an integrated wastewater and water supply management plan for Los Angeles.
Kirk Westphal, P.E., is a water resources engineer in the firm's Cambridge, Massachusetts office, and has developed decision support systems for clients.