Regulated Release of Water from Bakun HEP Reservoir Minimises Impact of Seasonal Rainfall on Upstream and Downstream Communities

KUCHING, 14 MAY 2020, THURSDAY: Hydropower dams such as Bakun Hydroelectric Plant (HEP) mitigate the impact of heavy rainfall within upstream catchments by storing water in the reservoir, reducing the severity of floods for areas downstream. Recent studies conducted by third party consultants have shown that Bakun HEP has regulated the flow rates in the downstream regions by half.

For Bakun HEP, owned and operated by Sarawak Energy, reservoir levels are managed by releasing water at regulated volumes through the gated spillway. This controlled procedure is conducted on a seasonal basis after permission is secured from the Sarawak River Board and the communities are notified at least two days ahead of the scheduled release.

This is standard practice for hydropower operators worldwide and has been undertaken by the operator of Bakun since it was commissioned in 2010.

The current seasonal release of water through the Bakun HEP spillway commenced on 3 May 2020 and is scheduled to last for three weeks, until water level normalises.

Over this period, the release volume is kept as low as possible, balancing both the upstream reservoir and downstream river levels and will cease once the water level in the reservoir normalises.

The rise in river level and intensity of flowing water will reduce as the distance increases. Areas furthest downstream of the dam will experience a generally imperceptible rise in river level. For instance, the released water is estimated to flow past Kapit town about one day later and Sibu town after three days.

The main contributors to flood situations are natural factors such as heavy rainfall at downstream regions, high sea tides for coastal areas, and water flowing from tributaries of the Rajang River. Spilling by itself does not cause a flood situation, due to the managed volumes.

On top of flood mitigation, the dam also holds back river debris within the catchment, making downstream navigation much safer.

Aerial view of Bakun HEP