Perth looks back to the day Mundaring Weir last overflowed

When Mundaring Weir came within 30 millimetres of overflowing on Sept. 1, 1996, anticipation was already building across Perth. Two days later, the final three centimetres disappeared and water finally spilled over the dam wall.

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I measured it from the top of the wall. I wasn't supposed to do that, but I dropped a tape down and measured it up.

Jens Jorgensen, who owns and runs the Mundaring Weir Hotel, had tracked the rise for nearly a month. He measured the distance from the top of the wall and recorded each reading on a board that still hangs in the hotel bar. When the overflow arrived, thousands of people drove into the hills to see it, creating what Jorgensen remembered as turmoil and parking trouble.

The water continued flowing into the Helena riverbed for two weeks before the level fell. Almost 30,000 people visited, but they did not know they were watching the final overflow in the dam’s history.

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It was turmoil ... people just started to drive up, and I know the police had quite a few issues with parking.

Mundaring Weir was first built in 1903 to dam the Helena River and supply water for piping to the Goldfields. It overflowed regularly in its early decades, prompting work to raise the wall in the 1940s. The project finished in 1951, but overflows continued through the 1950s and 1960s. Before 1996, the previous overflow had occurred in 1974, while rainfall volumes began declining in the mid-1970s.

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It was something completely different, and you know, I found it very exciting.

Diana Frylinck, who worked at the site in 1996 and remains at the former CY O’Connor Museum, recalled the water coming over the wall gently. She said its lace-like appearance reflected the curved design created by engineer CY O’Connor, which dissipated the energy of the overflow. In September 2026, the water level remained far from reaching the top.

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It came over gently and quietly, and it just looked like lace when it was coming over.