Adelaide Hills Reservoirs Surge to Near-Decade High After Spectacular Weekend Deluge

A spectacular deluge has brought Adelaide Hills' waterfalls to life, following a historic 24-hour period that delivered the region's highest reservoir inflows in almost a decade.

A combination of lightning, heavy rain, and small hail swept through Morialta Conservation Park east of the city at around 2:30pm yesterday. The weather event transformed the park's usually gentle waterway into a roaring torrent reminiscent of tropical Queensland.

Massive Inflows for Metro Reservoirs

Data from SA Water reveals that approximately 18 billion litres of water flowed into the metropolitan reservoir network in the 24 hours leading up to 8am today. This massive influx boosted the combined storage levels by 9 per cent, bringing the system to 73 per cent of its total capacity.

"This was the highest daily volume of combined reservoir inflows since September 2016," Water Futures and Security senior manager Ashley Kingsborough said.

Mount Bold, which is the network's largest reservoir with a capacity of 46.4 gigalitres, took in more than 5 billion litres of water. This boosted its storage by 13 per cent to reach 82 per cent capacity. Meanwhile, Kangaroo Creek reservoir experienced a 19 per cent increase in its storage levels.

"Relative to the size of their catchments, Little Para and South Para reservoirs were some of the main beneficiaries of this rainfall, with their storage levels increasing by 7 per cent and 10 per cent respectively," Dr Kingsborough said.

Since the start of winter, over 71 billion litres of water has poured into Adelaide's metro reservoirs. This places the system well ahead of the 55 per cent storage level recorded at the same point last year.

"A wet start to winter laid the groundwork by helping increase soil moisture across our catchments, and we're now seeing the benefit of this on our reservoirs, through the cumulative impact of rainfall events like yesterday," Dr Kingsborough said.

Monitoring and Safety Warnings

The last time water releases were required at Mount Bold—which can hold up to 46.2 gigalitres and typically triggers releases when storage exceeds 95 per cent capacity—was in November 2022. Officials are closely monitoring the situation.

"We will continue working in partnership with the Bureau of Meteorology [BOM] to monitor forecast rain and water levels in our reservoirs, to guide any potential releases of water from Mt Bold," Dr Kingsborough said.

"Our reservoirs are in a healthy position heading into spring, and we will keep a close eye on our storage levels to ensure a secure water supply for our customers in advance of what the BOM is forecasting to be a dry late winter and spring."

In light of the heavy flows, authorities are urging bushwalkers to exercise extreme caution. Morialta Conservation Park's Fourth Creek is named "Moriatta" by the Kaurna people, which means "ever flowing", though upstream dams and agriculture have changed that. The creek carries water through Morialta and into the River Torrens system, which occurs below reservoir catchments and therefore does not impact storage levels.

Because the site has previously been the scene of several rescues and fatal accidents, visitors must adhere strictly to safety guidelines.

"Visitors are responsible for their own safety and should follow advice from park rangers, comply with all warnings and other park signage, stay on marked trails, and remain behind safety barriers that are installed to protect the public," a Department for Environment and Water spokesperson said last month.

The surging waterways follow record-breaking August rainfall across several South Australian towns on Saturday and yesterday, with Lenswood recording 110 millimetres, Coromandel East receiving 101mm, and some far north regions of the state logging up to 150mm.