South Australia’s science analysis of MDBA modelling and draft plans

This page explains how South Australia carried out science reviews of the different models and draft versions of the Murray-Darling Basin Plan (see the final plan). It is presented in reverse chronological order, starting with the most recent activity.

South Australian analysis of additional water recovery modelling for the draft Basin Plan

SA Government analysis – August 2012

Scientists from the SA Government analysed the 3200 GL scenario modelling prepared by the Murray-Darling Basin Authority (MDBA) and compared outcomes for key environmental and water quality indicators against the draft Basin Plan scenario of 2750 GL. The analysis focused on the South Australian River Murray floodplain (including the Riverland-Chowilla Floodplain Ramsar site) and the Coorong, Lower Lakes and Murray Mouth Ramsar site.

A summary of the science analysis of the additional modelling is available. 

View the full technical report on the science review of MDBA modelling of relaxing constraints for basin scenarios.

Murray-Darling Basin Authority modelling – June 2012

In June 2012, the Murray-Darling Basin Ministerial Council requested that the MDBA model and assess the benefits of recovering 3200 GL of water for the environment when key constraints on delivering overbank flows to environmental sites are relaxed.   

View the full technical report on the MDBA's science analysis of the additional hydrologic modelling.

Goyder Institute for Water Research peer review of SA Government analysis

The Goyder Institute for Water Research undertook a comparative analysis of the SA Government’s work which found that the analysis and interpretation was fit-for-purpose and scientifically defensible.

See the full report.

SA Government science analysis of the draft Basin Plan – April 2012

SA Government scientists completed an analysis of the MDBA’s proposed 2750 gigalitre (GL) water recovery scenario to identify the potential hydrological and ecological implications for key environmental assets in South Australia. The analysis was based on modelling data provided by the MDBA that underpinned its proposed 2750 GL water recovery target.  

The analysis focused on two Ramsar sites in South Australia - the Riverland-Chowilla Floodplain and the Coorong, Lower Lakes and Murray Mouth - and also considered the potential implications for the broader floodplain environment in South Australia.

Where possible, the MDBA’s sensitivity analysis of 2400 GL and 3200 GL was also examined to determine what outcomes could be expected from these environmental water recovery volumes.  

Key findings

The draft Basin Plan 2750 GL water recovery scenario showed an improvement in the frequency of flow events delivered to meet environmental water requirements for key environmental assets and functions when compared with current conditions. 

While the analysis identified potential for benefits to be achieved relative to the baseline under the 2750 GL scenario, the actual benefits would be fundamentally dependent on the way in which water is delivered and used. As a result, the benefits forecast represented only one possible outcome of the delivery of an additional 2750 GL on average per annum.  

It was clear that the return of 2750 GL of water would not meet many of the environmental water requirements for key assets in South Australia:

  • Environmental water requirements of key vegetation communities, such as red gum, lignum and black box, were not met for significant areas of the floodplain including the Riverland-Chowilla Ramsar site. These assets would remain at risk of continued decline.
  • The Coorong, Lower Lakes and Murray Mouth Ramsar site would remain at risk from low water levels and high salinities during dry periods, which would adversely affect the health of plants and animals, particularly in the South Lagoon and Lake Albert.
  • The MDBA’s salt export target of two million tonnes per year was not met, especially during dry periods.
  • Periods of constriction of the Murray Mouth would still occur and could require dredging to ensure the mouth is kept open during periods of low barrage flows, such as during drought.

The delivery of overbank flows required to water floodplain environments was shown to be limited by constraints on water delivery, such as limits on channel capacities and operating rules.

The analysis showed that removal or relaxation of these constraints would be necessary to deliver flow regimes that would significantly improve ecological benefits for floodplain environments in South Australia.

The MDBA had not assessed climate change impacts and hence this was considered by the science analysis.

The MDBA had changed its modelling approach from that used in the Guide to the proposed Basin Plan (see below for a link to the guide). As a result, it was not possible to directly compare outcomes from the 2750 GL water recovery scenario with the outcomes from the 3000, 3500 and 4000 GL scenarios presented in the guide.

View full technical reports of the science reviews: 

Goyder Institute expert panel review – April 2012

The Goyder Institute: 

  • convened an expert panel review of the SA Government’s work
  • undertook further assessment to evaluate the potential ecological consequences for key River Murray environmental assets and functions in South Australia
  • provided advice on mitigating ecological risks.

The expert panel considered the initial hydrological and ecological analysis undertaken by scientists from the former Department for Water and Department of Environment and Natural Resources and found it to be fit-for-purpose, but subject to the limitations of the MDBA modelling on which the SA Government’s work was based.

Key findings from the Goyder Institute expert panel supported the findings of the SA Government scientists.

The Goyder Institute expert panel concluded that while there was potential to deliver some improved outcomes, the ecological character of key environmental assets was unlikely to be maintained under the 2750 GL scenario.

SA science review of the Guide to the Proposed Basin Plan - 2011

The Goyder Institute released a high-level science review of the proposals in the MDBA’s Guide to the proposed Basin Plan, which was released in October 2010.  

The review examined the implications for South Australia of three environmental water recovery scenarios of 3000 GL, 3500 GL and 4000 GL, as proposed by the MDBA in the guide.

View the synthesis report of the Goyder Institute’s science review

View the full technical reports of the Goyder Institute’s science review:

Environmental water requirements

Work was undertaken to specify the environmental water requirements of the Coorong, Lower Lakes and Murray Mouth region. View the full technical reports:

Drafts of the full reports were independently reviewed by Professor Ed Maltby of Liverpool University and Dr Dugald Black of CSIRO Land and Water, as part of the Goyder Institute’s Science Review. View the synthesis peer review of the draft reports. See also the author’s response to the peer review.

There's also the Goyder Institute science review background paper.