Decision support tools
The terms "Decision Support Tools" or "Decision Support Systems (DSS)" refer to a wide range of computer-based tools (simulation models, and/or techniques and methods) developed to support decision analysis and participatory processes. A DSS consists of a database, different coupled hydrodynamic and socio-economic models and is provided with a dedicated interface in order to be directly and more easily accessible by non-specialists (e.g. policy and decision makers). DSS have specific simulation and prediction capabilities but they are used as well as vehicle of communication, training and experimentation . Principally, DSS can facilitate dialogue and exchange of information thus providing insights to non-experts and support them in the exploration of policy options.
A Database Management System (DBMS): a DBMS collects, organizes, and processes data and information.
Models: different hydrodynamic and socio-economic models are integrated in a DSS to perform optimization, forecasting/prediction, Statistical functions. The type of models included defines the type of support provided and the area of application of a DSS (i.e. erosion or shoreline management, pollution, etc.).
Users’ interface: through the interface helps the users to interact with the system and to analyse its results. Important features if a DSS interface should be its user friendliness meaning its simplicity, flexibility, and capability of presenting data and model output. An effective user’s interface facilitates the communication and increases the acceptability of the tool by intended users (e.g. Coastal Zone Managers as well as Policy and Decision Makers).
Other components: Geographic Information Systems (GIS)' play a significant role in Spatial Decision support systems (SDSS) in which they play the role to organise, present and compare data and information on a visualisation map; Web-Based DSS which are computerised systems that deliver decision support information to managers using a Web browser , Group Decision Support System (GDSS) are common computer tools or networks used to enable collaboration between people to solve complex decision making;
DSS Classification 
A model-driven DSS emphasizes access to and manipulation of a statistical, financial, optimization, or simulation model. Model-driven DSS use data and parameters provided by users to assist decision makers in analyzing a situation; they are not necessarily data intensive.
A communication-driven DSS supports more than one person working on a shared task.
A data-driven DSS or data-oriented DSS emphasizes access to and manipulation of a time series of internal company data and, sometimes, external data.
A document-driven DSS manages, retrieves and manipulates unstructured information in a variety of electronic formats.
A knowledge-driven DSS provides specialized problem solving expertise stored as facts, rules, procedures, or in similar structures.
WHY and FOR WHAT USE DSS?
The database management system component allows the organisation, facilitates access to and the elaboration of time series of raw data.
- The integration of different type of knowledge (e.g. local and expert knowledge), disciplines and perspectives in the development of effective and sustainable water policies can find extremely useful support by the participatory development and implementation of DSS;
- DSS helps multidisciplinary team involved in the analysis of a water problem to establish a common language and think in a structured way. Criteria, objectives and constraints about the problem become more explicit through the whole process of development and application of a decision support system.
- The graphical features of a DSS support communication between stakeholders with different backgrounds. Visual aids in DSS also become more and more important when audiences are composed not only by policy makers but also by citizens. Communication capabilities help in fostering public participation are particularly developed in Deliberation Support Tools. For instance Group Decision Support Systems support collaborative decision making;
Optimisation and simulation capabilities of the integrated help in the analysis of possible trade-offs and conflict situation for the identification of the most suitable within a set of alternative options integrated in the DSS help through the development of “What if…?” scenarios. Specific techniques can be integrated in DSS to help for the selection (“What is best/ what is good enough …?”). For instance multi-criteria decision making for the evaluation, benchmarking and raking of the different options identified. Optimisations models integrated in the systems help to identify the best between the generated alternatives. The use of GIS in Spatial Decision Support Systems allows for the definition hydrological and socio-economic maps that help in the multi-criteria analysis of the problem at hand.. GIS components helps in the visualisation of the location of measures and impacts and facilitate the problem assessment by providing important information for the allocation of water management infrastructures. A DSS help in documenting the decision process that leads to the choice of a particular option thus contributes to its increasing transparency and fairness. In particular, IN COASTAL ZONE MANAGEMENT DSS are developed to help in the investigation of existing gaps on physical processes in coastal zones and their relationships to socio-economic demands and needs. They also support:
- Water quality management (i.e. pollution control strategies, eutrophication management, salt intrusion and surface water quality).
- Erosion management: management of dams and reservoirs operation and forecasting.
- Identification of the location of physical structures (water treatment plants; dams; weirs; uptakes; monitoring stations; ...).
- Risk assessment: flood forecasting, travel-time computations in Early-warning systems in the event of accidental pollution. Floods and drought management under scenarios of climate change. Drought mitigation measures during planning and operation of water systems.
- Enforcement of laws (i.e. the Water Framework Directive – WFD): specifically tailored DSS can help with the implementation of water legislation and guide stakeholders to check on the authority’s performance and agenda management.
- Assessment of the cost-effectiveness, the possible social impacts of the alternatives considered as well as the sustainability of water management measures.
In the Stakeholder analysis section, the Quasta tool is described. This tool can be considered as a qualitative decision support tool, aimed to involve stakeholders in a decision-making process. It is not an optimisation tool, but has a rather deliberative design.
Links to web resources
mDSS (Multi-sectoral Integrated and Operational decision support system for sustainable use of water resources at the catchment scale) - MULINO EU project - 
OPTIMA DSS (Optimisation for Sustainable Water Management) - OPTMA EU project 
RAMCO (Decision Support System for the Integrated Assessment of Sustainable Coastal Zone Management problems) RIKS. 
WMSS (Water Management Support System) Integrated and problem oriented water management system at catchment scale for coastal water resources. -MEDITATE EU project 
TIDDD (Tools to Inform Debates, Dialogues & Deliberations) and DTS (Discussion Support Tools) - GOUVERNe EU project -
NOSTRUM DSS (Network on gOvernance, Science and Technology for sustainable water ResoUrce management in the Mediterranean. The role of Dss tools) gives an overview and discusses on the use of DSS tools in water resources management in the Mediterranean area. 
- Welp M. (2001). The use of decision support tools in participatory river basin management. Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere, 26, 7-8, 535-539.
- Bhargava H. K., D. J. Power and D. Sun (2007). Progress in Web-based decision support technologies. Decision Support Systems, 43, 4, 1083.
- Power D. J. (2003). A Brief History of Decision Support Systems DSS. Resources.COM, World Wide Web, version 2.8, May 31, 2003.
This a revised extract from the Nostrum DSS Guidelines. Please refer to the Nostrum DSS Guidelines  for a complete overview.
Please note that others may also have edited the contents of this article.