The last minute decision to include an additional 450Gl in the Murray-Basin Basin Plan was based on a ‘blue sky thinking’ workshop, undertaken by experienced river operators and the Murray-Darling Basin Authority, modelling a relaxed constraints 3200Gl scenario, using flows that have since been significantly reduced due to the impacts that would have resulted from the subsequent major flooding.
In early 2012 a workshop of experienced river operators was requested by the basin official committee ‘‘to embrace blue-sky thinking, and not to be constrained by current arrangements’’.
The workshop focused on investigating how to increase the frequency of over-bank flows in the Lower Murray to achieve a target event of up to 80000Ml/day downstream of Euston for up to 30 days every one-to-four to one-to-five years.
To achieve this target event, the workshop analysis stated the key features required were significant inflows from at least three of the four major river systems, relaxation of constraints and pre-wetted or primed catchments with timing of inflows from each catchment being crucial.
As ‘blue sky thinking’ is ‘‘not grounded or in touch with realities of the present and does not include the necessity of dealing with practicality’’, the workshop concluded that increased environmental flows were feasible if constraints were relaxed, but in reality had no knowledge if constraints could in fact be relaxed, only noting socio-economic impacts would increase with higher flows.
The MDBA, in its hydrologic modelling of the relaxation of operational constraints in the southern connected system (October 2012), assumed a relaxed constraints scenario was possible and used flow levels that have since been abandoned due to the severe impacts that would be caused by the major flood flows that would be needed to achieve a flow of 80000Ml/day at the South Australian border.
To achieve this flow, the MDBA modelling used a flow of 40000Ml/day in the Lower Goulburn now reduced to 20000Ml/day and 40000Ml/day in the Yarrawonga to Wakool constraints area, now reduced to 30000Ml/day.
Despite this reduction in flows there has never been any revised modelling or analysis to assess the fact that these reduced flows mean the 450Gl can not be delivered in the initial proposed large volumes to SA.
The Experienced River Operators workshop did, however, note that a cost/benefit analysis would be needed.
Six years later, despite the MDBA also stating in 2012, that ‘‘a cost/benefit analysis (including assessments of any third party impacts)’’ would be required, there has been no cost/benefit analysis undertaken.
None of the above issues have been resolved, but the Federal Department of Agriculture and Water Resources is rushing forward with the attempted recovery of the 450Gl, despite the fact it has no certain knowledge or scientific grounds to show that this water can be delivered downstream within the legislated guidelines.
—Jan Beer, Yea