A spectacular winter storm has sent billions of liters of water cascading through the Adelaide Hills, bringing local waterfalls to life and delivering the largest single-day inflow to the region's reservoirs in nearly a decade.

Over the weekend, a severe weather system carrying lightning, heavy rain, and small hail swept across the Mount Lofty Ranges. The deluge transformed the usually tranquil waterways of Morialta Conservation Park into raging torrents, mimicking tropical river systems.

A Decade-High Inflow

According to SA Water, a staggering 18 billion liters of water flowed into the metropolitan reservoir system in the 24 hours leading up to Monday morning. This massive influx boosted the state's combined storage capacity by nine percent, bringing the total to 73 percent.

"This was the highest daily volume of combined reservoir inflows we have seen since September 2016," said Ashley Kingsborough, SA Water’s Senior Manager of Water Futures and Security.

Mount Bold, the state's largest reservoir with a capacity of 46.4 gigalitres, was one of the biggest beneficiaries. It received more than 5 billion liters of water, lifting its capacity by 13 percent to a secure 82 percent. Meanwhile, Kangaroo Creek reservoir saw a dramatic 19 percent surge.

"Relative to the size of their catchments, Little Para and South Para reservoirs were also major beneficiaries of this rainfall, with their storage levels increasing by 7 percent and 10 percent respectively," Dr. Kingsborough added.

A Healthy Outlook for Spring

This latest downpour builds on an exceptionally wet winter. Since the start of June, more than 71 billion liters of water have entered the metro reservoirs. At this time last year, storage levels sat at just 55 percent, compared to today’s comfortable 73 percent.

The abundance of water means authorities are closely monitoring storage limits. The last time controlled water releases were required at Mount Bold—typically triggered when capacity exceeds 95 percent—was in November 2022.

"Our reservoirs are in a very healthy position heading into spring," Dr. Kingsborough said. "We will continue to work closely with the Bureau of Meteorology to monitor forecast rain and water levels, ensuring a secure water supply ahead of what is predicted to be a drier-than-average late winter and spring."

Bushwalkers Urged to Keep Distance

While the roaring waterfalls at Morialta Conservation Park make for a stunning spectacle, authorities are urging extreme caution. The park's Fourth Creek, known historically in the Kaurna language as Moriatta ("ever flowing"), has swollen significantly.

Because Fourth Creek flows directly into the River Torrens below the reservoir catchments, the spectacular flow does not add to the drinking water storages, but it does pose a significant safety risk to onlookers.

The Department for Environment and Water has urged visitors to stick strictly to marked trails and stay behind safety barriers. The area has historically been the site of several difficult rescues and tragic accidents.

"Visitors must take responsibility for their own safety, follow the directions of park rangers, and respect all warning signs," a department spokesperson warned.

The wet weekend set several new local weather milestones. Lenswood recorded a massive 110mm of rain, while Coromandel East received 101mm. Unusually high totals were also recorded further north, with some arid regional areas receiving up to 150mm of rain.