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The Sustainable Diversion Limit Adjustment Mechanism – reports and business cases

The Murray–Darling Basin Authority (MDBA) has assessed a suite of projects to determine an adjustment to the sustainable diversion limits.

These reports outline the assessment framework, designed in collaboration with Basin governments, to assess the state projects and calculate how much water these projects will contribute towards any change in sustainable diversion limits. This includes modelling a fully implemented Basin Plan, modelling different scenarios under the adjustment mechanism framework and independent assessments of the MDBA’s modelling and limits of change assessment.


Assessment report
Sustainable Diversion Limit Adjustment Mechanism: Draft Determination Report 2017
Notification of supply measure projects

The MDBA has determined the proposed adjustment to sustainable diversion limits based on a package of projects agreed and notified by Basin state governments.

Basin state governments notified the MDBA of the final package of projects in June 2017, to allow the MDBA to complete its modelling assessment.

The current notification documents for each supply measure project are provided below.

Some personal information, detailed cost estimates and other commercial-in-confidence information has been deliberately omitted from these documents at the request of Basin state governments. This information has been withheld to ensure that individuals’ privacy is protected and that value for money is achieved when these projects are issued for tender.

Summary of feedback report
Summary of Public Feedback: Sustainable Diversion Limit Adjustment Mechanism – Draft Determination

This report highlights the issues and opportunities raised by stakeholders on the Sustainable Diversion Limit Adjustment Mechanism and the package of projects. The MDBA has provided recommendations on the issues and opportunities raised during consultations and the public comment period.

Supporting documents
Benchmark conditions of development for assessment of the SDL supply contribution

Outlines a model of a fully implemented Basin Plan. The report describes how changes included to the Basin Plan Benchmark scenario to produce the Sustainable Diversion Limit Benchmark scenario. This represents the implementation of the Basin Plan to achieve 2750 GL of water recovery for the environment. This model was agreed to by all Basin governments.

Modelling assessment to determine SDL Adjustment Volume

This  report describes the implementation of the supply measures package in the modelling framework. It explains how the model represents and assesses the supply measures to achieve maximum supply contribution. The report lists the results of three equivalence tests (ecological elements score tests, limits of change in environmental outcomes, and reliability of supply targets) to compare environmental outcomes and reliability of the Sustainable Diversion Limit Adjustment scenario to the Sustainable Diversion Limit Benchmark scenario.

Independent Review of Hydrologic Modelling for SDL Adjustment (by Bewsher Consulting)

The report gives a detailed evaluation of the modelling framework, outlining the methodology and criteria used to assess the Sustainable Diversion Limit Benchmark and Adjustment scenarios. The independent audit lists a number of suggested improvements to ensure the modelling framework is an appropriate representation of the system and remains fit for purpose.

Independent Expert Panel Murray–Darling Basin Plan SDL Limits of Change Review

Prior to the Sustainable Diversion Limit adjustment determination, early MDBA modelling indicated the potential for a number of limits of change rules to breach. The MDBA commissioned an expert review panel to undertake an independent ecological analysis of the potential breaches likely to occur across several possible Sustainable Diversion Limit adjustment model runs. This report outlines the independent expert panel's assessment.

Advice from the Basin Officials Committee

The Basin Officials Committee reviewed the draft determination and provided its advice to the MDBA on the proposed adjustment to Sustainable Diversion Limits. This includes advice from the New South Wales, Victorian and South Australian governments.

Adjustment assessment framework for supply measures
Sustainable Diversion Limit adjustment mechanism assessment framework for supply measures

The Murray–Darling Basin Authority has developed and trialled the way it will assess projects under the Basin Plan's Sustainable Diversion Limits adjustment mechanism in 2016. The framework explains the key concepts, how the Sustainable Adjustment Limit adjustment mechanism works, and results for trialling the method using 7 of the 27 supply projects submitted by Basin State governments for this purpose. The framework includes the use on an independently developed (by the CSIRO), scientifically robust scoring method (test) for environmental equivalence. An independent review panel has found the framework and test to be fit for purpose.

CSIRO summary of the scoring method
Summary of the Independent Panel's method review
Independent Review Panel's letter
Updated: 23 Oct 2018  •   MDBA reports