01 March 2011

Wivenhoe Dam release continues

LARGE releases from the Wivenhoe Dam that were due to finish today are now likely to be stopped on Thursday following last week's rainfall.

Dam operators started the releases on February 20, to reduce its drinking capacity by 25 per cent – a full year's drinking supply.

The move to improve flood mitigation led to Colleges Crossing being closed for the seventh time since October last year, funnelling motorists onto the one-lane Mt Crosby Weir crossing.

It was expected to take only nine days but was pushed back after the dam received heavy rainfall early last week.

The media team for the dam's operators was asked yesterday morning for information on when exactly the releases would stop but did not respond before QT's deadline.

SEQ Water Grid chief executive officer Barry Dennien said he had advised Seqwater a reduction to 75 per cent capacity would be manageable from a water security perspective.

Mr Dennien said the January floods also transformed long-term water storage capacity with the recently completed Wyaralong Dam now full, five years earlier than expected.

The Wyaralong Dam was now storing 103,000 megalitres, which was able to be connected to the water grid when required.

"With Wyaralong full, other dams full around the region and the grid in place, Wivenhoe Dam can be operated at a lower level for the rest of the wet season without impacting on water security," Mr Dennien said.

About 40 per cent of the dam's capacity is devoted to storing drinking water and the remaining 60 per cent is for flood mitigation.

The dam is said to be 100 per cent full when the drinking water component is full.

The current release has been made because more rain is predicted for the region until at least April.

"While we can't be certain about what rain is yet to come in this wet season, this measure reflects an abundance of caution," Natural Resources Minister Stephen Robertson said when the release was announced.

About 2.6 million megalitres of water flowed into the Somerset-Wivenhoe system in January's floods, more than double that of 1974.

A Department of Transport and Main Roads official said motorists were being asked to stagger their journeys to help ease the traffic through the weir crossing.

Ipswich City Councillor Paul Tully the dam should be kept at the 75 per cent level as a permanent arrangement.

The role dam operators played in the lead-up to last month's floods will be investigated by the State Government's commission of inquiry.

Release facts

About 290,000 megalitres are being released, equal to a full year's worth of drinking water.

About 380 cubic metres per second was released at the weekend.

The viewing platform at the dam is closed.

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