The Strategic Environmental Assessment process initiated by DWAF is expected to provide both information and tools to support decision making at the scale of the Water Management Area (WMA). The aim of this project is to design a Decision Support System (DSS) which links a set of modelling, manipulation and display tools to a structured database that has the facility to store both observed and simulated data. It was suggested that the purpose of a DSS is a function of

• the type of concern, problem or question being addressed; and
• the scale at which the solution needs to be met.

The structure of the document is based on a modified representation of the generic decision making process developed by Stewart et al., (2000) incorporating the following steps, process and activities:

• Acquiring information to identify the problem

• Problem structuring

• Defining the problem framework
• Identification of information requirements

• Model requirements
• Data requirements
• Stakeholder participation

• Supporting the process of obtaining and including necessary data and information
• Identification of alternatives, criteria, stakeholders and constraints

• Evaluation of and choosing between alternatives

• Visualisation
• Ranking and scoring (aggregation, integration, discussion)
• Supporting the trade off process

• Making provisional decisions.

In the DSS design the problem definition has been structured in accordance with the NWA (1998) guidelines and particularly Section 27. Information requirements were therefore addressed on two different levels:

• those required to implement the catchment management strategy (CMS); and
• those required to assess the individual license applications.

In establishing the information requirements the modelling, data and stakeholder requirements are identified. The modelling requirements could be defined as a set of modelling tools that are able to generate hydrological, economic, social and environmental information that is required to achieve equitable, efficient and sustainable solutions within a WMA. The hydrological modelling component is looked into in more detail with the need for a physically based process model being emphasised. The ACRU model is highlighted as perhaps the best tool to perform the majority of the hydrological modelling. The data required to feed the modelling tools and to make decisions are described. The necessity for stakeholder interaction is highlighted in terms of both the model and data requirements.

The database requirements are then described in an attempt to support the process of obtaining and including necessary data and information. It is concluded that a relational database linked to the ArcView GIS would be the best option in terms of efficient data storage, manipulation and query options. The necessity to store both observed and simulated data along with the requirement of linking spatial, attribute and time series data into a single database was the driving force behind this suggestion.

The identification of alternatives, criteria, stakeholders and constraints is addressed in the scenario generator section. The main objective of developing a hydrologically focussed Scenario Generator (SG) is to have a tool that can easily be used to generate water related scenarios, which broadly include scenarios influencing the demand for water and/or changes to the supply of water. The reason for developing this tool is relatively straightforward. The SEA is tasked to assess the current and potential water use and supply conditions. The value of the SG is to assist in the generation of accurate, meaningful water use and supply scenarios.

It is suggested that the SG be developed with the following capabilities:

• Credible scenarios need to be scientifically translated into changes on the GIS map.
• The SG must automatically translate the scenario into the correct model configuration.
• The SG must either automatically provide the required model parameter information, or must query the user through the SG for the appropriate information.
• The scenario/s may then be processed through the model/s.

In the evaluation of alternatives section the need to refine the information generated using the DSS into quantities that can easily be used and interpreted by model users and decision makers is highlighted. The necessity of discussing and identifying the critical information requirements to make certain sets of decisions with stakeholder and decision makers is emphasised. Visualisation of information is seen as a critical component of the DSS as it is the basis upon which the final decisions are made. Visualisation can take the form of graphical output at specific points of interest within the catchment, spatial output that shows descriptions of various critical indicators in a GIS format giving an idea of the spatial distribution in a particular area; and specific indicator output at critical points in the catchment.

In the design and implementation plan section the more specific options of setting up the DSS are discussed. In this section the three main components required to set up and integrate the all the decision making tools required in the DSS are discussed. The components consist of

• a database that is able to store both simulated and observed data as well as combining spatial, attribute and time series information into a single framework by coupling a GIS with a relational database;
• a processing component that consists of a set of modelling tools that could produce hydrological, economic, social and environmental information; and
• a visualisation component consisting of a processing phase to translate variables produced by simulation scenarios and base data into indicators and a display system used to display the different indicators in a suitable format that can be used by the decision maker.

The DSS developed should be a set of tools which can be used by decision making bodies (typically planners and those responsible for water licensing) to assess the impacts of various scenarios (e.g. change in land use or engineering structures) on the catchment system and to review the costs and benefits of decisions to be made. The tools developed need to offer means of entering, accessing and interpreting the information for the purpose of sound decision making. Thus, the overall objectives of this project are the development of a set of tools aimed at transforming data into information and to aid decisions at different scales within the WMA.

The following summary of requirements is provided with emphasis been placed on the different tools used to perform the various functions in the DSS.

• Develop a database that conforms with the DWAF standards that links spatial, attribute and time series data by coupling a GIS with a relational database. The ArcView/Oracle link is suggested as the most promising option at this stage. The Regis system used by the Geohydrology section of DWAF will be investigated to see if it can perform this task.
• The ACRU hydrological model should be used to perform the hydrological modelling in the processing component of the DSS. The model is a physically based conceptual model that allows for the analysis of different scenarios and can be used with reasonable confidence in ungauged areas. The new developments currently being added to the model will allow it to analyse flow networks with realistic simulations of the operational hydrology. Water quality routines are also been added which will increase the flexibility of the model. The model is also locally developed and able to handle local conditions and data with the minimum of data manipulation needed.
• The system should not be restricted to the use of one particular model. Although the ACRU model has been suggested as the model of preference the system should be able accommodate the use of other models reasonably easily.
• The ArcView GIS should be used as it is the most widely used and accepted GIS available both locally and internationally. Its full range of manipulation abilities is required in the manipulation and display of information in the DSS.
• Economic, social and environmental modules should use simplified weighting and regression techniques a well as more complicated simulation modelling which can be coupled with the ArcView GIS to manipulate and display the outputs.
• The system will need to be seamlessly integrated to simplify the user requirements, making the system more user friendly and hence easier to use. The Visual Basic programming language could be used for this purpose. The scenario generator will essentially fulfil this requirement, giving the user the ability to test and query scenarios with relative ease.
• The information produced by the model needs to be credible and the assumptions made explicit to enhance stakeholder buy in and understanding.

This system has the potential to be a powerful tool to aid in decision making by Catchment Management Agencies in their WMAs. It needs to be easy to use, have the facility to simulate a range of possible scenarios in the catchment, allow easy interpretation of outputs and have the facility to assess not only hydrological information but also economic, social and environmental aspects of water resources management.