2 October 2020

Dam good news: Cotter to spill and water storage to hit capacity by Christmas

| Michael Weaver
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Cotter Dam

The Cotter Dam close to overflowing Thursday (1 October). Photo: Lucy Cassella, Icon Water.

The Cotter Dam is ready to overflow for the first time since 2016, while recent rains and the declaration of a La Niña event by the Bureau of Meteorology mean the ACT’s four dams could reach capacity by the end of the year.

While some people in regional areas are far from convinced the drought has broken, Canberra’s water supplier Icon Water says the ACT’s four dams could reach capacity by Christmas.

Icon Water’s general manager of infrastructure services Gerard Brierley said their modelling of current forecasts for spring indicate it is very likely that overall dam levels will reach at least 90 per cent by December.

“While it is less likely that combined storages will reach 100 per cent, it is a possibility,” Mr Brierley told Region Media.

Canberra’s combined dam levels are at 85.77 per cent, which is equivalent to 238.30 gigalitres of water. The last time the ACT’s total water storage was at 100 per cent was in November 2016.

Canberra and Queanbeyan’s total potable water demand is approximately 50 GL/year.

Levels dropped below 45 per cent in February this year following a very hot summer, record temperatures and two of the driest years on record. With above-average rainfall during winter, Canberra’s water levels recovered significantly.

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Mr Brierley said Cotter Dam is likely to reach 100 per cent and begin to spill in the coming week, with current levels at 99.1 per cent and increasing by approximately 0.2 per cent daily.

“The water that spills from Cotter Dam will make its way through the Cotter River system contributing to increased flows which are particularly important for endangered Macquarie Perch to feed, breed, migrate and spawn.

“The last time Cotter Dam was at 100 per cent was in January 2018,” he said.

Googong Dam is currently at 84.29 per cent and was last at 100 per cent in December 2016. Corin Dam levels are at 72.34 per cent and were previously at capacity in November 2016.

Bendora Dam filled to capacity of 11,400 million litres and then spilled for several days in late August/early September this year due to high inflows from recent rainfall. The water spilled into the Cotter River and made its way downstream to the Cotter Dam. This along with inflows has contributed to Cotter Dam nearing 100 per cent.

Watch Bendora Dam begin to spill for the first time since 2016.

Mr Brierley said while they were excited to see dam levels increase across Canberra and Queanbeyan’s four water supply dams, it was important the community remains focussed on maintaining its water-wise habits.

“Our team of analysts model literally thousands of potential scenarios to ensure we have the ability to meet the needs of our current and future population,” he said.

“Weather has the greatest influence on our water storage position, with consumption also a contributing factor. Icon Water is continually considering short and medium-term forecasts from the Bureau of Meteorology, which declared this week that a La Niña event is officially underway which makes increased rainfall over spring a high probability.”

The consumption of water by Canberrans has also decreased compared to this time last year. Throughout September, average daily use was 123 megalitres. For the same period in 2019, it was 135.3 megalitres per day.

However, Mr Brierley said the decrease in demand is generally anticipated with cooler and wetter weather and Canberrans should maintain the permanent water conservation measures that have been in place since 2010.

“There are additional measures that commence in spring each year that are specific to when you can and can’t use sprinklers,” Mr Brierley said.

“From 1 September, only a handheld hose fitted with a trigger nozzle can be used during the hours of 9:00 am to 6:00 pm. Outside of these hours, a sprinkler or irrigation system can be used. It is a timely reminder as the community starts preparing their gardens and setting up their automatic sprinkler systems.”

Full details of the permanent water conservation measures, as well as helpful tips for households and businesses, are available on the Icon Water website.

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Andrew Hennell5:06 pm 05 Oct 20

Bendora spilling in 2010 – https://www.youtube.com/watch?v=ucC3DeHRPAU
Cotter overtopping during construction 2012 – https://www.youtube.com/watch?v=S-lvJCJlwm8

Tim Flannery should have his Australian of the Year award taken from him.

The climate alarmist will hate this , what happen to the dams never being back at capacity

No they won’t because those of us who listen to actual qualified experts rather than politicised rants on SkyNews will know that no one said La Nina events will stop happening. What they said is over a long term average our climate will dry, which is exactly what’s happening.


russianafroman7:09 pm 03 Oct 20

I thought we were all going to die of thirst and melt into puddles.

Yep because rain also travels back through time so last year didn’t happen. Well done.

Darryl Lindner3:46 pm 03 Oct 20

Could someone tell Gerard Brierley that the Cotter Dam is at the end if the Cotter River system and that the water that spills only contributes to increased flows in the Murrumbidgee River.

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