27 October, 2010

Murray Darling Basin

There is a very widely held view that we need to "restore the health of our rivers". This statement assumes that they are unhealthy, which might well be the case. However, we have just been through nearly a decade of the lowest rainfall/run-off that has ever been recorded.



Whilst this is extreme, under natural conditions it was not unusual for Australia to have very dry periods and for all of our inland rivers to periodically stop flowing altogether. So we need to be careful that the results of natural dryness are not being branded as "unhealthy". Likewise given this enormous natural variability we need to define just what we actually mean by the term "sustainability". The question asked of CSIRO to determine the "Sustainable Diversion Limits" of our rivers, seems to me to be a question which fails to recognise this variability. If "sustainable"in this sense means "annual" then the answer for even the Murray must be "nil"! We need to be very careful of using average statistics when the spread around the average is so enormous.

I believe we need to closely examine the "unhealthy" notion. What are the specific factors that indicate this apparent lack of health-acid sulphate soils, salinity, blue green algae, river red gum depletion, fish stock depletion, the ravages of carp- seem to me to be the main claims. We need to examine the truth and cause of each of these compared with natural conditions, before we leap to the conclusion that we need to extract less water. Particularly since extractions have been minimal in recent years. Perhaps throwing more water at the issue is not the solution?
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