The recriminations and finger-pointing have not taken long to appear after the Brisbane floods. More than one former dam engineer has gone to the press claiming that mistakes were made by the operators of Wivenhoe Dam, South-East Queensland Water. The claims have been published in major Australian newspapers and run widely by TV and on-line media over the past week.
These claims centre on the emergency release of 645,000 megalitres of water from Wivenhoe Dam on January 11. Massive in-flows over the previous 24 hours had driven dam capacity from 130% to 190%, precipitating the emergency spill. It is claimed that without this discharge the worst of the downstream floods in Brisbane could have been avoided.
As mentioned last week, Wivenhoe Dam has a total storage capacity of 2.6 million megalitres — it is considered 100% full for supply purposes at 1.15 million megalitres, and has an additional flood buffer of 1.45 million megalitres. ‘Critical’ storage capacity in regard to over-topping and heightened risk of dam failure is consequently at c. 220% capacity (a concept that has been difficult for journalists, the public, and I suspect even some in the water industry, to grasp). At 190% capacity, the dam operators must have been very nervous indeed.
The critics seem convinced that the emergency release could have been avoided if the Wivenhoe operators had made higher releases over the 3-4 days prior to January 11. They believe that the dam operators should have been aware of weather forecasts the previous week predicting very heavy rainfalls in the catchment.
Barry Dennien, CEO of SEQ Water, has stated repeatedly in interviews that dam operational rules were followed at all times. Nevertheless, in response to public pressure, SEQ Water this week released the flood manual for Wivenhoe Dam for public scrutiny.
And SEQ Water does have its supporters. Tony Weber, a consulting water engineer from Brisbane, has said in the press “I think the call that we should have had engineering to solve this flood and make it go away is completely unrealistic”.
The truth of the matter will no doubt emerge over the coming months. Queensland Premier Anna Bligh has announced a Commission of Inquiry that will investigate the events leading up to and following the floods, including the operation of Wivenhoe Dam.
Elsewhere in the region, the new Tugun desalination plant on the Gold Coast has been reactivated to help alleviate dirty water problems as sediment transported by the flood continues to affect the quality of water in the Brisbane River. The massive silt load has caused major problems for the Mt Crosby water treatment plant – Brisbane’s main treated water supply. The Tugun desalination plant had been taken out of major service last month in response to the full water storage conditions in Wivenhoe Dam. It is somewhat ironic that a plant built, against much public criticism, to help in drought situations is now assisting with Brisbane’s flood recovery.
Update 27 January (Australian time)
A one-off tax payer levy to help meet the $5 billion cost of this summer’s devastating floods, has been announced by Prime Minister Julia Gillard. See more at: http://www.abc.net.au/news/stories/2011/01/27/3123050.htm