Wivenhoe Dam reached its highest-ever stage on January 11, 2011 – a day like no different for the primary provider of Brisbane’s consuming water.
On that fateful day, Seqwater, the supervisor of Wivenhoe and Somerset dams, was urgently juggling the speed of dam water releases to forestall a significant flooding drawback for Ipswich and Brisbane.
Seqwater believed water was coming into Wivenhoe Dam quicker than it might be safely launched and the integrity of the dam was severely questioned.
A day earlier, water was being launched at a rate of 2044 cubic metres of water per second from the five huge gates, in accordance with the Queensland Floods Fee of Inquiry.
Nevertheless, regardless of this, the dam reached 191 per cent of its water storage the subsequent day – that’s, 91 per cent of the flood storage capability excessive of the 100 per cent water storage capability.
In 2011, the dam’s administration staff confronted the state of affairs of the dam receiving twice the volume of water received during south-east Queensland’s 1974 floods.
“On the morning of Tuesday 11 January 2011, water ranges in Wivenhoe Dam started rising quickly in response to very heavy localised rainfall on and near the Wivenhoe Dam lake space,” the Seqwater report of March 2011 says.
“The amount of complete influx into Wivenhoe Dam in the course of the Occasion was 2,650,000 megalitres.
“This quantity is sort of double [190 per cent] the comparable quantity of influx from the January 1974 flood occasion, and comparable with the flood of 1893.”
General there have been two large inflows to Wivenhoe Dam – 30 hours aside – near January 11, the report says.
“The influx into Wivenhoe Dam in the course of the occasion was characterised by two distinct flood peaks, with every peak separated by about 30 hours,” it says.
Within the aftermath, Justice Holmes discovered “even a big dam equivalent to Wivenhoe has a restricted flood mitigation capability when the amount of water coming into it’s considerably bigger than its storage capability”.
“Its flood-mitigation impact for Brisbane was additional restricted by the truth that floodwaters from different elements of the Brisbane River catchment entered the river downstream of the dam, by the Bremer River and the Lockyer Creek.
“The flooding in Brisbane and Ipswich might have been lowered to some extent had the dam had its capability lowered to 75 per cent previous to the December rains, however to understand what the magnitude of the rain could be and that it might fall within the dam space would have required a greater than human capability of prediction.”
Seqwater declined to remark.
Tony Moore is a senior reporter on the Brisbane Instances