The Water Allocation Decision Support System (WAdss) was developed to assess trade-offs associated with different water allocation, access and pricing options for surface and groundwater resources at a catchment or basin scale. The development of WAdss was funded by the Cotton Research and Development Corporation (CRDC) and applications have been developed for the Namoi and Gwydir Valleys. It considers both regulated and unregulated surface waters as well as groundwater concurrently. Following from recent PhD research, future versions have the capacity to consider the interactions between the groundwater and surface water systems. Impacts of changes in allocation, access and pricing are shown as changes to the economic returns to irrigated agriculture as well as impacts on flow (as measured through flow duration curves and hydrographs).

Impacts are shown spatially across the catchment so that users can determine the trade-offs not only between environmental and economic outcomes, but also between users and uses of water within the catchment. The figure below demonstrates how impacts on flow and annual economic return are displayed across the catchment in the WAdss interface.

Display of relative impact of scenario on average annual returns in WAdss interface

The WAdss has been developed to be used by non-technical users (ie. non-modellers). It has been developed with a user-friendly, point-and-click interface. Experience in workshops with state government staff and irrigators has confirmed that it is intuitive and straightforward to use. The model can be run live during meetings (it takes only a couple of minutes per run) and can be used to aid with social learning or group negotiation. It allows for ‘pre-run’ scenarios to be saved and demonstrated as well as for scenarios to be run live. This means that it can be used, for example, during Board meetings when decisions are being made about changes to access rules. Files can be shared between WAdss users so that runs of the model can be disseminated by email or shared between WAdss users.

The WAdss has been developed in such a way as to allow for the development of new applications. All model and interface code can be easily transferred to a new situation (e.g., the Namoi and Gwydir applications use the same code). Stakeholder participation has always been an important part of the WAdss approach. Consultation with irrigators and other water users throughout the model development is essential to ensuring assumptions are accurate and acceptable to the local community. As such it is advised that new applications allow for resources to adequately consult with these groups throughout model development.