Study of a spill

QUEANBEYAN Council and ACTEW Water have agreed to co-fund a new study to look at possible connections between the management of Googong Dam and flood events downstream in Queanbeyan.

QUEANBEYAN Council and ACTEW Water have agreed to co-fund a new study to look at possible connections between the management of Googong Dam and flood events downstream in Queanbeyan.

QUEANBEYAN Council and ACTEW Water have agreed to co-fund a new study to look at possible connections between the management of Googong Dam and flood events downstream in Queanbeyan.

It follows a $1.3-million repair job to Queanbeyan infrastructure caused by the December 2010 Queanbeyan floods, where the Queanbeyan River burst its banks and water levels peaked at 8.6 metres.

The two parties met last Thursday and agreed to commission an independent study of the Dam's role in flooding events, and whether new management techniques could reduce flood events downstream.

Council has requested ACTEW manage water levels in the dam so that it doesn't exceed around 85 per cent of capacity, creating a flood mitigation buffer in the event of sustained, heavy rain. The dam is currently at 100pc capacity.

However ACTEW Water maintains that a buffer wouldn't have prevented the 2010 floods in Queanbeyan.

ACTEW managing director John Knox said Queanbeyan was already "somewhat protected" by the mere existence of the dam, due to its water-flow attenuation properties.

"Even though the Googong Dam is not, and was not designed to be used as a flood mitigation dam, it does provide a reduction in water flow," Mr Knox said.

"We believe at this point in time that changing the way we manage the dam levels would not have caused any significant change in flooding impact during the 2010 event. However, this doesn't mean that there aren't other feasible options that may present themselves during the study," he said.

Queanbeyan mayor Tim Overall welcomed the co-operative approach between the two organisations.

"The independent review will - among other matters - particularly consider whether the flood risk to Queanbeyan can be reduced by monitoring and managing levels in the reservoirs both during normal and abnormal longer term weather patterns and predictions," he said.

And Cr Overall also pointed out that although Googong Dam was at just 80 per cent in November 2010 prior to the flood, a deluge of around 90 millimetres on December 3 filled it to the point of overflowing. When further heavy rain and flooding commenced on December 9 of that year, the dam was already full, he said.

"At 80pc capacity a very significant rain deluge would be required to fill the reservoir," Cr Overall said.

"As it happened, in late 2010 there were two significant deluges in the catchment within ten days."

The parties will meet again in the coming weeks and draw up terms of reference for the study.

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