Water flows from Mount Bold after recent record rainfall

Water is now flowing through the spillway gates at Mount Bold Reservoir for the first time in nearly 4 years, after a weekend of record rainfall across Adelaide that prompted significant inflows to the major storage facility.

Entering the weekend at only 69 per cent of capacity, Mount Bold has since captured more than 13 billion litres of water to elevate its storage level to approximately 95 per cent of capacity – which was SA Water’s trigger point to safely release a controlled flow of water down the Onkaparinga River.

Mount Bold’s storage level has more than tripled since the start of winter, with the reservoir holding 44 billion litres of water prior to the opening of its spillway gates this morning.

SA Water’s Senior Manager of Environment and Energy James Crocker said proactively releasing water from the reservoir at certain levels creates additional space to balance natural inflows and protect the dam.

“Dam walls, gates and spillways are designed to manage water within a reservoir in a controlled manner, to ensure we can protect the structural integrity of the dam and its surrounding communities,” James said.

“Proactive water releases such as that now happening at Mount Bold are a perfect example of this type of dam infrastructure in action.
“In the case of Mount Bold, its dam has 8 gates that can be controlled to release different volumes of water from the reservoir based on its storage level and expected inflows from the catchment.

“We have worked closely with the Bureau of Meteorology to understand the likely impact of forecast rainfall this week on the reservoir’s level, enabling our rangers to plan for when and how much should be released.

“Once we reached the trigger point, our on-site rangers operated the gates from our control room, using an electronic panel to open the gates to a certain level.

“We currently have 4 gates open at 10 centimetres in height to safely release a controlled volume of water downstream. We will reassess later in the day how long the gates are required to be open for.

“Water released into the downstream Onkaparinga River travels down to the Clarendon Weir, where some of it can be diverted via an underground tunnel to our Happy Valley Reservoir and we are now transferring as much as possible into this reservoir to maximise the use of this water within our supply system.

“Importantly, based on the amount of water we are expecting to release, the local community downstream of the reservoir can be assured that we do not expect any significant impact from this release on the level of the Onkaparinga River – which is also fed by numerous creeks downstream of the dam.

“This type of gradual and tightly controlled release deliberately aims to manage inflows from the catchment area by moving a small volume of water from the reservoir when we have the capacity to do so, minimising the impact downstream if we do experience a larger rainfall event.

“While the dam wall is currently closed for public access during the water release, visitors can safely watch the pop-up waterfall at the viewing platform within the reservoir reserve, which is a 1.4-kilometre return walk from the car park off Razorback Road and provides spectacular views down towards Mount Bold’s dam.”

More than 85 billion litres of water has been captured by SA Water’s metropolitan reservoirs since the start of winter, with 18 billion litres of this alone flowing into its storages during the 24 hours to 8am on Monday.

SA Water’s metropolitan reservoirs are currently sitting at 79 per cent of capacity, which is compared to only 54 per cent of capacity this time last year.