Robert Neil (“no wasted water in delicate balance of habitats, June 1 p15) argues for the retention of environmental flows policy.
Critics of the regime are not calling for the removal of environmental flows and are not suggesting that stopping environmental flows will solve the current problem.
They are asking that the regime for environmental flows in years of high rainfall be reexamined and that low flows should be monitored for effectiveness.
The present environmental flow rules means the dams are unlikely to fill.
The policy says that large quantities of water are to be released when dams reach a certain capacity. The release in 2000, 2001 and 2002 below Cotter and Googong totalled about 120 gigaliters.
This is two years consumption at current rates. It is obvious now that this water should not have been released. The reason for the release of large quantities stated in the environment report was to scour the river with large flows and remove sand. If this is the reason then it was not the best environmental strategy. The best strategy to get the occasional scouring is to try to keep the dams full and when there is a rain event to supplement spillway floods with the release of water. This will give less frequent but larger floods and create greater scouring.
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There would have been an event in 2000.
There is nothing in the reports that I can find that measure the effectiveness of the current low level flow regime. Perhaps an approach of setting objective measures of “health” such as the number of species of different types in the water ways would give more reassurance that the river health was good. Perhaps a better environmental flow policy would be to keep the flows at a minimum during the “good years” because there would be some natural “side” inflows and to release more in the bad years.