Following days of heavy rain, all four Canberra and Queanbeyan dams had reached full capacity on Tuesday, and had overflown - an event which has only occurred once since 2013.
The combined capacities of the regions dams is 277.83 gigalitres, with Googong Dam - the area's largest - accounting for 42 per cent of total capacity.
Managing director of Icon Water Ray Hezkial said he was pleased to see a considerable increase in rainfall considering Canberra's water storage levels in previous years.
In February 2020, capacity across the dams dropped below 45 per cent following a series of extreme dry months.
Current storage levels, according to Mr Hezkial, will now help future-proof Canberra from significant drought.
"[This gives us] a number of viable options to ensure Canberrans have a secure water supply for the future," he said.
Local resident Katie Alsworth was among those who visited the dam on Tuesday after hearing the news from neighbours that it was likely to spill over.
"I've never seen anything like this ... it's beautiful," Ms Alsworth said.
Local resident and bus driver Bimal Gunawara said he was concerned that the Googong Dam spillover would likely contribute to the current floods in Queanbeyan, given the Googong Resevoir connects with the Queanbeyan River.
The river was expected to rise to 6.3 metres through the early hours of Wednesday.
