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The Murray-Darling Basin Plan (MDBA, 2012a) defines a new sustainable diversion limit (SDL) for the Murray-Darling Basin. Schedule 6 of the Basin Plan identifies the default method by which supply measures can be used to increase SDLs. The SDL adjustments are based on achieving the same environmental outcomes as defined by the Basin Plan using less environmental water by the implementation of supply measures. Such a mechanism would allow the SDL to be increased, whilst achieving equivalent or improved environmental outcomes. Schedule 6 of the Basin Plan provides the default method for assessing the environmental equivalence between two model scenarios; one that defines the environmental outcome of the Basin Plan (Benchmark scenario), and the other that defines the increase in the SDL that can be achieved through the inclusion of supply measures while still achieving the same environmental outcome score (Supply contribution scenario). The default method specifies that the method will use preference curves, metrics for weighting environmental significance and a rules-based approach for combining these curves to determine an environmental outcome score.

This project provides the Ecological Elements of the default method (preference curves, weightings, combinations) for assessing environmental outcomes for supply measures. The defined method is based on best available science and is compliant with the Basin Plan’s default method. The method is also compatible with the models and tools applied for determining the Environmentally Sustainable Level of Take (ESLT) and with Schedule 6 specifications …