Cotter Dam now full!

July 7, 2016

The newly enlarged Cotter Dam is now officially full holding 79.4 gigalitres (or 79.4 billion litres)  and has just started to spill following the rainfall events that have occurred over recent weeks. This bodes well for water security for the entire Canberra region as it continues to grow.


The new, Enlarged Cotter Dam was officially opened to the public on Saturday 12 October 2013 with a promise to Canberra that it would bolster the long-term water security for the region and support the economic growth of Canberra for generations. The construction of the Cotter Dam was one of the major water security projects delivered by the Bulk Water Alliance (BWA) following the drawn-out millennium drought.


Managing Director John Knox said that Canberra’s water storage is healthy and brimming, with more water stored in the Cotter catchment than we’ve ever had before, and which prepares the city well as it embraces urban intensification, and the broadening of its regional footprint.


“Our healthy water storage figures are directly owing to the significant investment that has been made over the last decade to ensure Canberra’s water security,” Mr Knox said.


“When we celebrated the completion and opening of the dam in 2013, it was already nearly a third full of water thanks to the better than anticipated rainfall and inflows of 2012. At the time water modelling predicted that the dam would take between two and five years to fill.”


“Today’s brimming dam is a great day for Canberra’s water story and bodes well for future water security for our community, as our population and city grows.”


“Managing the water security for the region takes a range of issues into consideration and sometimes isn’t as straightforward as it might seem. The strategy considers the quality and location of the water sourced; the cost to source and treat; and when to change and move to alternate sources. It also depends on expected climate and rainfall patterns which are sometimes hard to predict in the medium to long term.”


“We know that Canberra values its water greatly and still use it very wisely following the decade of uncertainty for the region. Our community managed to significantly reduce its water usage over that period and we’ve seen very little bounce back since that time. This is a great indication that even as our population increases, we remain steady in our consumption figures as a community.”


Chief Minister Andrew Barr acknowledged the significance of the Cotter Dam to the region.


“The investment in the Cotter Dam was a vitally important project for the ACT. We have gone from being a region often affected by water restrictions to now having long-term water security,” the Chief Minister said.


“With the dam now full for the first time, Canberrans can have confidence that our community will be sustainable now and into the future.”


The Cotter Dam has a rich history in the nation’s capital, being a frequently visited attraction and holds a soft spot in many Canberrans’ hearts.


The original Cotter Dam, a concrete gravity dam, was completed in 1915 and built to a height of 18.6m. It was raised from 1949 – 1951 to a height of 28.5m to accommodate a growing population. It served as Canberra's primary water source until the 1960s, when Bendora and Corin Dams were constructed.


The most recent project has a logbook of interesting achievements that need to be remembered and celebrated:


  • The project was completed in 2013 and was the centrepiece of a suite of water security projects to bolster the ACT’s water supply ensuring it was adequate for future generations.
  • The Cotter Dam construction statistics alone are impressive with a reservoir capacity of 79.4 gigalitres (increased from 4); 341 metres in width and 87 metres high. Construction saw 42 abutment blasts, 34 quarry blasts, 361,000 metres3 of roller compacted concrete; and 1,845 rock bolts installed.
  • There were more than 3,000 workers, providing more than 2.5 million people hours on the job which averaged to 212 people on site per day across the project.
  • Nearly 12,000 hours of formal safety training was undertaken with over 220,000 hours of identifiable safety specific activities delivered. Over the time of the project, the safety aspects of the Cotter Dam project were heavily monitored with 67 regulatory visits to the site, with some taking two inspectors all day to complete. 
  • During the four year construction period, workers experienced temperatures ranging from -10 to 42 degrees.
  • The ACT also recorded its heaviest rainfall period in recorded history with rain recorded on 19.6% of days worked, with an average fall of 13mm recorded on rain days. 


Canberrans will recall that a major flooding event occurred in March 2012 impacting directly on the Cotter Dam site, causing significant damage to some areas of construction. It is estimated that had the dam been complete at the time of flooding, it would have been filled twice over. The recovery following this flood took 9 weeks to clear the debris and damage from th4e site with no recordable injuries occurring. 


The quality of the dam has been recognised through the receipt of ten industry awards including two Engineering Excellence Awards; two institute of Public Works Engineering Australasia awards; an Australian Water Association National Program Innovation Award; an Environmental Excellence Award from the International Erosion Control Australasia.


The timelapse video which provides a photographic illustration of the dam wall construction or visit for more information.  


Statement ends