Callide Dam Frequently Asked Questions

23 Feb 2015

Here are some answers to frequently asked questions about the unprecedented rainfall event at Callide Dam.

Why did the gates open?

Callide Dam gates opened automatically as they are designed to do once water levels reached a pre-determined level.

The dam is designed to pass on inflows through its gated spillway. Although not designed as a flood mitigation dam, the release of water through the spillway does provide some flood attenuation and providing some more warning time for affected communities.

How much water was released?

The peak discharge from Callide Dam was the equivalent of 3,480 cubic metres per second at around 10:30pm on Friday, 20 February 2015, when the equivalent of approximately 1.8 Olympic swimming pools per second flowed through the dam spillway. The rainfall event upstream of Callide Dam that occurred as part of Tropical Cyclone Marcia is unprecedented with preliminary hydrologic estimates identifying it as a one-in-10,000 year event.

The intensity of the rainfall was extraordinary in that it led to a rapid increase in water levels at the upstream gauging station by more than seven metres in three hours. This compared with Cyclone Oswald in 2013 where the increase in water levels at the upstream gauging station of around 5.5 metres occurred over a period of 18 hours.

Why did SunWater not release water sooner?

SunWater implemented the Emergency Action Plan as soon as possible in response to the severe weather event. The gates released water in automatic mode as it was not possible to commence manual releases on account of the dangerous cyclonic conditions being experienced on site. Priority consideration was given to community safety and to SunWater staff.

Were people warned the gates were opening?

SunWater followed the legislated Emergency Action Plan and advised the Local Disaster Management Group and immediately downstream residents as soon as it became clear that water releases were likely. The warning time was short due to the unpredictability of the severe weather event which produced very intense rainfall in the upstream catchment.


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