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Ecological processes at the mouth of the Mary are being heavily impacted by the operation of the barrage upstream, and any further disruption in freshwater flow patterns could have a severe cumulative effect on estuarine processes related to water quality and the limited operation of fishways.
Hypersalinity Ribbe (2006), in a study on hypersalinity in Hervey Bay, has revealed that the lack of freshwater flows from both the Burnett and Mary Rivers has a contributing factor to the cumulative impacts. For the period 1980-2004 it shows freshwater discharges were mostly well below the minimum evaporation rate in June which in turn would lead to persistent hypersaline conditions throughout most of the period.
Studies since 1980 show that runoff from the Burnett and Mary River catchments has declined and is only greater than the minimum evaporation rate for the region, in less than 10% of all instances. This period corresponds to an increase in tidal barrage and dam infrastructure, within both the Burnett and Mary Rivers.
Such preliminary research may be revealing the first impacts on estuarine ecosystems (Ramsar wetlands) from infrastructure related flow reductions to the Great Sandy Strait. These findings also raise serious questions as to what effect further reductions in freshwater flows, under the Mary Water Resource Plan and the Traveston Crossing Dam proposal, will have on Matters of National Environmental Significance within the Great Sandy Strait.
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Barrages, Dams and the Mary’s Environmental Flows |
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PROPOSED MARY RIVER DAM
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‘Big Dams started well, but have ended badly. There was a time when everybody loved them, everybody had them ... There was a time when Big Dams moved men to poetry. Not any longer. All over the world there is a movement growing against Big Dams. In the First World they’re being decommissioned, blown up. The fact that they do more harm than good is no longer just conjecture. Big Dams are obsolete. They’re uncool. They’re undemocratic. They’re a Government’s way of accumulating authority (deciding who will get how much water and who will grow what where) ... They last only as long as it takes Nature to fill them with silt. It’s common knowledge now that Big Dams do the opposite of what their Publicity People say they do—the Local Pain for National Gain myth has been blown wide open.
Arundhati Roy, The Cost of Living, p16-17, 1999. |
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