by Mike Young and Ken Jury
5th December 2009
Regarding the ABC Stateline program of November 13, 2009. titled, "Dramatic fall in bird numbers on the lower Murray". We believe it is necessary to provide a counterpoint to some of the comments made during this recent television segment.
Presenter, Ian Henschke correctly recognised problems concerning the disappearance of thousands of water birds from the Coorong and Lower Lakes. He reported how aerial surveys have revealed a drop in bird numbers with fears for the lower end.
A guest environmental scientist discussed the system and said that wrong decisions now could be terminal and it “would be difficult to recover from.” When discussing bird surveys of the Murray Darling Basin, the scientist touched upon major changes to the wetland systems at the end of the rivers - like the Coorong and the Lower Lakes.
Coorong only marginally influenced by the river
His statement suggests that the Coorong is being supported by water from the River Murray. This is not correct. A world acclaimed wetland scientist, Professor Gell of Ballarat University, recently told how his core sampling evidence concluded that the Coorong was only marginally influenced by the river, with the exception being that the river kept the Murray Mouth clear for tidal flows.
While the availability of freshwater and its decline is understood, the issue here concerns the statement of freshwater for the Coorong. Since the barrages have been in place, the primary source of fresh water for the Coorong is not from the river, but from the upper South East drainage. Importantly, the decline of fresh water resulted from mismanagement of the South East drainage system many decades ago when fresh water ordinarily destined to reach the Coorong through Salt Creek was turned towards the ocean. Today, some work is being done to turn that situation around but it will be a slow process to return suitable flows through Salt Creek into the Coorong.
During the interview, Minister Weatherill said (in part) that the Lower Lakes and Coorong were compromised by a lack of fresh water flows. Assuming he meant River Murray flow, again this is not correct as the only freshwater flows entering the Coorong recently have come from the South East, out of the SE drainage, through Salt Creek and into the lower Coorong. View a map of the area here.
What about the Lower River Murray below Lock One?
Minister Weatherill agreed that damage in the Lower Lakes and Coorong has occurred and it is damage that should be compensated for. The minister said how (the government) doesn’t think it’s gone past the point of no return although he told how “we have gone horribly close.”
This statement ignores the damage now done to riverine backwaters and lagoons as a habitat for freshwater birds. Damage has been done by the insistence of letting freshwater out of the river into the lake instead of holding it in the river by means of a weir containing a lock.
The Minister then commented how water birds were not getting enough water and how these birds are showing major changes and declines in numbers.
None of the comments in this segment recognised that “water birds” fall into a number of categories, and subsequently use different habitats. Freshwater lakes and lagoons of a reedy nature are generally dominated by a group of sedentary freshwater birds. This is the situation along the River Murray where these habitats must be maintained along its entire length.
However, sedentary, nomadic and migratory waders and open water fishing birds all make use of tidal flats and/or estuarine systems. Assured feeding and resting areas for migratory waders are internationally important when it comes to estuarine habitats such as the Coorong.
Weir, estuary and no dredging
When discussing birds and other marine or aquatic life found in the Lower Lakes and Coorong, if we had gone along a path of a permanent weir with a lock to stop tidal water going up into the River Murray beyond Wellington, and properly managed the lakes as a tidal system when it was first generally recognised as the best long term solution by many, it would now be a viable working estuarine system with tidal feeding flats for waders, with no acid sulphate issues and no commitments to have to dredge the mouth for the next four years.
220 GL not enough to make a difference
Minister Weatherill said that three hundred and fifty gigalitres each year should flow past Wellington. The minister said that 220 gigalitres had been secured by the government to bring down river throughout the course of this summer. He continued that this is a substantial additional flow that will make a ‘big step’ to keeping those acid sulphate soils covered while replenishing the lakes.
We contend that this amount of freshwater wouldn’t even reach the amount of the annual evaporation rates from the 800 sq km lakes (at full surface level) where evaporation loss is in the vicinity of 750 gigalitres a year.
Mike Young & Ken Jury.