Water allocation and access arrangements affect the livelihoods and well-being of a diverse range of water users, including irrigators and the environment increasing pressures on surface and groundwater resources have seen a shift in water management towards decision Processes that attempt to represent the interests of these diverse groups. Decision makers are increasingly being asked to take account of trade-offs between different users of water so as to make fair, equitable and/or efficient decisions that achieve a balance of social, economic and environmental outcomes.

In NSW, changes to water allocations and access through the design and implementation of Water Sharing Plans, involved negotiation between stakeholders representing many different interests and concerns. A key gap identified by many stakeholders involved in these negotiations was open access to integrated, scientifically sound and generally agreed upon information on the socioeconomic trade-offs likely to result from changes in access, allocation ~d pricing. In addition, estimates of impacts on the flow regime and on river health are also required. The Water Allocation Decision Support System (WAdss) has been

Developed and applied to two NSW catchments the Namoi and Gwydir River catchments for considering the trade-offs between environmental and socioeconomic outcomes resulting from changes in water allocation, access and pricing in the unregulated and regulated surface water systems and the groundwater system of these catchments.

The WAdss has been developed to be used in a workshop situation, allowing for analysis of a library of pre-run scenarios, sharing of scenarios between users, and creation of new scenarios live in meetings and workshops. I t also allows for reports to be generated which can be accessed from outside the system. The system has been tested in workshops situations with a broad range of potential users and found to have potential for considering water allocation issues.

Development of the WAdss has involved substantial stakeholder involvement. This has been aimed at giving stakeholders a greater sense of ownership of the models, results and WAdss, by incorporating their comments and ideas into the system. It was also important for obtaining information and data necessary for ground-truthing or calibrating the models in the system and for increasing the awareness of stakeholder groups of the existence of WAdss, its potential uses and limitations.

Overall the development process of the WAdss has been successful, given the maintained engagement of stakeholders in its development and support for its continued use and development. Initial development of the WAdss is complete. The WAdss is now moving into an adoption, extension and reapplication phase. Success in this phase will depend on the maintained engagement of stakeholders and the enthusiasm and input of researchers or other champions within Agencies or Catchment Management Authorities. With this support and adoption of the system by these groups for policy and planning processes it is hoped that the WAdss will lead to greater communication between irrigators and catchment management authorities and the development of policy options that lead to improved environmental outcomes at the least cost to production. The WAdss provides an important opportunity to

incorporate the opinions and knowledge of irrigators in the water allocation decision making process and debate. The potential of WAdss for use in other catchments and for incorporating the investigation of other issues (wetland ecology, salinity, vegetation change) is very high. WAdss has the framework and the analytic tools to examine trade-offs in these cases.