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Science and the Basin Plan

The Murray–Darling Basin is large and complex. The water resources and the communities that depend on them are diverse.

The Basin Plan 2012 (the Basin Plan) requires an understanding of the ecology, hydrology, social and economic factors, and the consequences of different management scenarios for both surface and groundwater systems. There is no single best solution to manage the Basin’s water.

Good science is critical to the success of the Basin Plan. The science is not perfect and expert views are often contested. The views of water users and local communities are many and varied.

The scientific work undertaken to inform the development of the Basin Plan was the best available at the time, however, new work is always becoming available. For example, the Murray–Darling Basin Authority (MDBA) invested in new science and analysis to better understand the ecology and socio-economic situation in the northern Basin. This work informed the Northern Basin Review.

Northern Basin Review

The Northern Basin Review drew together hydrological, social, cultural, economic and environmental investigations over 4 years. The MDBA did this review with the assistance of a consultative body, the Northern Basin Advisory Committee (NBAC). The work also involved collaboration with the New South Wales and Queensland governments.

The responsibility for river operating arrangements in the northern Basin rests with state governments. As a result of the integrated analysis of multiple lines of evidence in the Northern Basin Review, the MDBA sought commitments from the NSW and Queensland governments to implement a range of measures to complement environmental water recovery.

Science Workshops        

The MDBA values the contribution of experts in both developing the science and reviewing the methodology and findings. At times science workshops and meetings are held that include the MDBA, government and external experts.

For example, the Advisory Committee on Social, Economic and Environmental Sciences (ACSEES) hosted a workshop where experts were invited to critique the methods and analysis being used in an independent review of the risks to surface water flows cause by reduced return flows ─ a return flow occurs when water extracted for irrigation is not fully used by crops and instead drains back to the river, either across the surface or underground. The experts also tested the preliminary findings of the independent reviewers.

There was consensus from the workshop that the approach and methodology used for the review was sound. This provides a transparent assurance in regard to the integrity of the work. The detailed findings of this work is published on the MDBA website.

Sustainable Diversion Limit Adjustment Mechanism

The Basin Plan sets sustainable diversion limits (SDLs), which indicate how much water can be used in the Murray–Darling Basin, while leaving enough water to sustain natural ecosystems.

To provide flexibility, the Basin Plan includes the option to adjust the sustainable diversion limits in the southern Basin. Over the coming years, a suite of projects nominated by Basin state governments will be implemented in the southern Basin. The assessment of projects has determined that 605 gigalitres (GL) of water can remain available for communities.

The MDBA administered 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 SDLs. The methodology to assess the projects had been previously agreed by Basin governments. 

The assessment framework includes technical components such as hydrological models, hydrological indicator sites, ecological elements and ecological equivalence scoring. However, the assessment includes much more than modelling—modelling is just one part of the assessment process.

The framework has been trialled and thoroughly reviewed by independent experts and all Basin governments – it was found to be scientifically rigorous and suitable for use in the operation of the adjustment mechanism.

Transparency   

The MDBA engages widely to understand the issues and concerns of stakeholders and how they can contribute to the implementation of the Basin Plan.

The MDBA routinely seeks advice and critical reviews from the independent scientists appointed to its multi-disciplinary Advisory Committee on Social, Economic and Environmental Sciences (ACSEES).  This committee was established to provide strategic advice on science and knowledge to underpin the implementation of an adaptive Basin Plan.

The MDBA exposes its work to peer review as a matter of standard practice. Reviews are carried out by external subject-matter experts, such as an expert panel, academic or other technical experts within other government agencies. The reviews are undertaken by an independent party.

We ensure our work is accessible to interested stakeholders by publishing our findings on the MDBA website – this includes science reports (across a range of subjects), compliance activities and independent reviews of our work.

Examples of independent reviews

SDL Adjustment assessment framework

The framework includes the use of a method independently developed by CSIRO based on scientifically-robust scoring, to test for environmental equivalence of proposed measures relative to benchmark conditions. An Independent Review Panel found the framework and test to be fit-for-purpose.

Independent expert panel Murray–Darling Basin Plan SDL limits of change review

In preparation for the SDL adjustment determination, early MDBA modelling indicated the potential for breaches of a number of ‘change rules’. An expert review panel was commissioned to do an independent ecological analysis and found no material or significant breaches in terms of their likely impact on ecology.

Independent review of social and economic modelling for the Northern Basin Review

This review by the University of New England confirmed the appropriateness and robustness of the socio-economic modelling of Basin Plan impacts in the northern Basin.

Expert panel review of the hydrological modelling framework for the SDL adjustment mechanism and the Northern Basin Review

This review endorsed the use of the modelling frameworks to support each project.