Perth residents are recalling the dramatic moment Mundaring Weir last overflowed in 1996, an event now deemed impossible to repeat. This past spectacle contrasts sharply with the dam’s current critically low levels. The region has experienced one of its driest winters in over a decade.
Thirty years ago, anticipation mounted as water levels in the dam steadily rose. Jens Jorgensen, owner of the Mundaring Weir Hotel, meticulously recorded the daily increase. He measured the water’s proximity to the dam wall’s summit, documenting it on a board in his bar.
Strong rainfall caused the levels to climb rapidly. On September 1, 1996, the water was just 30 millimetres from the top. Two days later, on September 3, the weir finally spilled over. This created a local sensation.
Thousands flocked to the hills surrounding the dam to witness the rare sight. Mr. Jorgensen described the scene as “turmoil” due to the immense crowds and parking challenges. He found the entire experience exceptionally exciting.
For two weeks, water cascaded into the Helena riverbed. Officials estimate nearly 30,000 people visited the site. Few, however, realised this would be the final time the Mundaring Weir last overflowed.
Diana Frylinck, then working on-site for the Water Corporation, vividly remembers the 1996 event. She praised engineer C.Y. O’Connor’s design, noting how the wall’s curve allowed for a calm, gentle overflow. Her role granted special access, though the public walkway was closed for safety reasons.
The museum, where Ms. Frylinck still works, extended its hours to accommodate the influx of visitors. She even recalls a notable guest: Alan Bond, visiting shortly before his court sentencing. Despite the excitement, Ms. Frylinck admits staff prepared for future overflows, unaware it was the last.
Historically, the weir, built in 1903 to supply the Goldfields, often overflowed. Its wall was even raised in the 1940s, finishing in 1951. Overflows continued through the 1950s and 60s, a testament to steady winter rains. Rainfall volumes, however, began declining in the mid-1970s; the previous overflow before 1996 was in 1974.
Today, the situation is drastically different. Mundaring Dam is only 42 percent full. Streamflow into Perth’s dams this year totals just over 12 billion litres, a stark contrast to the average 75 billion litres over the last decade. This figure is far from the 420 billion litres that flowed annually before the mid-1970s.
Michael Wiltshire, Water Corporation manager, suggests only a cyclone could now fill the dam. Even then, he states, an overflow would likely be prevented. He considers it a waste of a precious resource and an “operational nightmare” given modern population density. Upgrades to the integrated water supply system also play a role.
Damien Postma, a Waterwise programs manager, reinforces the focus on preservation. He stresses the need for residents to use water wisely. Rainfall now provides only 15 percent of Perth’s drinking water, with desalination and groundwater making up the rest. Officials do not expect to see Mundaring Weir last overflowed ever again. They encourage simple conservation habits like shorter showers and turning off taps while brushing teeth.
