Unscheduled repairs to Scrivener Dam worth $20 million have forced the embattled National Capital Authority to delay major capital works at Barton and Regatta Point.
Major engineering work at the dam in the new year will progressively replace 120 anchor bolts, which are part of the flap gate mechanism.
The flap gates are opened in floods to regulate Lake Burley Griffin's water level.
Authority chief executive Gary Rake said the problem was identified during an annual safety audit and surveillance inspection.
The majority of the anchor bolts are encased in steel structures or concrete and were not visible during previous safety audits.
The work will take 50 to 80 weeks and the dam level will be lowered.
It has already been lowered 200mm because of increased inflows from this week's rain.
It will be lowered another 300mm, the same as it was in 2003 during the drought.
The Bowen Place crossing upgrade and renewal of the National Capital Exhibition have been put on hold.
Mr Rake said he understood the community would be disappointed. But the engineering works at Scrivener Dam needed immediate action to complete the work within the recommended time frame.
''We have scheduled the Bowen Place upgrade to recommence in 2014, and the National Capital Exhibition renewal in 2016,'' he said.