Mount Bold spillway reopens as Adelaide Hills floodwaters swell reservoirs

Heavy rains across the Adelaide Hills over the past weekend delivered over 13 billion litres of water into the Mount Bold catchment, pushing the reservoir’s level from 69 % to 95 % of its 46.4-gig litre capacity. In response, SA Water opened four of the eight spillway gates a modest 10 centimetres, allowing a controlled flow toward the Onkaparinga River and onward to the Clarendon Weir, where it can be routed into the Happy Valley Reservoir, which sits at 84 % capacity.

James Crocker, senior manager for Environment and Energy at SA Water, explained that the proactive release creates additional storage headroom for upcoming inflows. The spillway’s last activation was in November 2022, and the current release follows a record-breaking rainfall event that also filled other metropolitan reservoirs to 79 % of capacity. While the dam wall remains off-limits to visitors, a nearby viewing platform provides a view of the temporary waterfall created by the release. The event underscores the ongoing impact of extreme weather on South Australia’s water supply system.