09 October, 2010

Irrigation

Now this article from today's SMH is worth repeating. I couldn't have said it better myself!

You can't pay to save the environment if rains fail
Paul Myers
October 9, 2010
THERE is one word that will fix the water problems for which the Murray-Darling Basin Authority believes, incorrectly, it has found the solution: rain.
There is another far more contentious word that would eliminate the claimed need for irrigation water cuts and make more water available to grow food: dams.
And there is a third word that explains why water use has become such a contentious issue: perception.
These three words are the explanation and the answer to eastern and southern Australia's water problems. But don't expect a fourth word - reality - to hold sway in the final basin water plan.
The reason the Murray-Darling Basin's river systems got into strife was a decade of record-low rainfall, not farmers' water extractions. The public perception is otherwise: farmers are widely viewed as having been irresponsibly taking water while the rivers dried up; moreover, once they are stopped from pumping water, the rivers will be automatically "fixed".
How wrong can you be? Irrigators are able to access water only when river flows reach prescribed levels. Little or no water flow means no allocation, as rice and cotton producers know so well. Occasionally, even when rivers flow strongly, farmers are prevented from taking water in deference to the environment.
But has all this "saved" unallocated water made a difference? No, because the water didn't exist and there was no "extra" water to go anywhere, anyway.
A prime example is the much-vilified Cubbie Station in south-west Queensland. This year it has been able to fill its water storages and is about to plant 22,000 hectares to cotton - without a public outcry. Why? Because in a big rainfall year there is plenty of water for everyone; in dry years the water simply can't be extracted.
Quite simply, buying farmers' water entitlements won't fix a problem that the irrigation licensing system didn't create. Rivers rely entirely on run-off and controlled releases from dams. In an average year, if there is such an occasion, there is 21,000 gigalitres of run-off in the Murray-Darling Basin - almost twice the amount of water farmers are entitled (licensed) to extract when there is full allocation.
But in big rainfall years, such as 2010, a million gigalitres of rain can fall across the basin, producing far greater run-off than can be used.
In years like this, water flushes down rivers and excess quantities are held in headwater and other dams.
It is a lesson that should be heeded, because if the several billion dollars to be spent buying farmers' water entitlements was allocated to building one or more headwater dams, food production would be enhanced rather than constrained, there would be more irrigation rather than less, the environment would be protected and the public would receive a return on its investment.
If there is one villain in the water debate it is evaporation. When the water reaches the lower lakes of the Murray fully 50 per cent evaporates. This is precisely what will happen if the water plan is adopted.

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