10 February, 2010

River Management

Letter Sent to the Sydney Morning Herald on 10.02.10
Water Management in the Murray Darling Basin


Paul Myers (Only rain can solve riddle of the rivers -SMH 10th February,2010) is so right in his central point that only rain can solve the water shortages in the Murray Darling Basin. The Government buying back water licenses, when there is no water and no allocations, will do nothing to increase water when we are not receiving run-off generating rainfall. When we are receiving such rains, and water supplies are plentiful, the cancellation of these irrigation licenses will only restrict agricultural production so badly needed by a hungry world. We need to remember Dorothea Mackellar's line "droughts and flooding rains" to which we could add "and not much in the middle". The key characteristic of Australia's climate is massive rainfall variability.

Under these highly variable conditions there is something we can do to improve water supplies in dry periods. We need more dams to conserve surplus water in very wet conditions. These can also play a part in flood mitigation. Storages need to be deep so as to minimise evaporation losses - valleys in hilly country are best. The diversion of surplus flows from coastal flowing rivers (eg NSW North Coast), with damming and tunnelling, would not only mitigate floods, but also provide water for food production

The South Australian's claim that the dreadful condition of the Lower Lakes (Alexandrina and Albert) is due to extractions and lack of fresh water from upstream. No mention of the fact that under natural conditions the Lower Lakes were sometimes salty and sometimes fresh depending on fresh water flows, or lack of them, from upstream in Victoria, NSW, and Queensland. No mention of the impact of the building of "The Barrages" at the mouth of the lakes which converted the Lakes to all times fresh with the expectation that there would always be sufficient fresh water flows from upstream.

Under natural conditions with no dams in the Upper Murray catchment and no Snowy diversions, with the minimal run-off of the recent drought years, the Murray would have stopped flowing some three years ago. Salt water would have entered the Lakes and the lower reaches of the river itself as it always did under such dry conditions in the past, prior to the building of the Barrages. So it can be argued that the dire condition of the Lakes is largely a man-made problem.It is only the water stored in the Upper Murray dams, the Snowy diversions and restrictions on irrigation that have enabled the Murray to maintain any flow at all.
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