Dam wall turned waterfall at Mount Bold Reservoir

The water release gates at Mount Bold Reservoir have been opened for the first time in five years, prompted by healthy inflows to the storage from persistent rainfall during recent months.

Since the start of August, more than 30 billion litres of water have flowed into the reservoir to lift its storage level from 30 per cent to just over 94 per cent, which was the trigger point to safely release a controlled flow of water down the Onkaparinga River.

SA Water’s Senior Manager of Wastewater Expertise and Environment James Crocker said proactively releasing water maintains space in the reservoir to help balance the storage level with further inflows.

“Dam walls, gates and spillways are designed to manage water in a controlled manner, and today’s release is an example of the Mount Bold dam wall doing exactly what it was designed and built for,” James said.

“Mount Bold has eight gates that can be controlled to release various volumes of water from the reservoir based on its capacity and inflows from the catchment.

“We’ve worked closely with the Bureau of Meteorology to understand the likely impact of this week’s rainfall on the reservoir’s level, enabling our local team to plan for when and how much water 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.

“At the moment, six gates are open at 20 centimetres in height and two at 10 centimetres, to release water downstream. We will reassess later in the day how long the gates are required to be open for.

“Importantly, the local community downstream of the reservoir can be assured that, based on what we’re expecting to release, there will not be any significant impact.

“This type of gradual and tightly controlled release deliberately aims to manage inflows from the catchment area by moving a small amount of water out of the reservoir when we have the capacity to do so, minimising the impact downstream if we do experience a larger event, while protecting the dam’s structural integrity.

“Visitors can safely watch the cascading water at the new lookout 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 wall and across the wider reserve.”

SA Water’s metropolitan reservoirs are currently sitting at a total capacity of 87 per cent, storing a combined 173 billion litres of water.

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