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Regulated Release Of Water From Bakun HEP – Impact On Downstream Regions

In addition to generating electricity, hydropower dams such as Bakun HEP mitigate the impact of heavy rainfall on downstream flow by holding back large volumes of water in its reservoir.

When the reservoir level exceeds a certain point, water is released through a spillway specially designed for this purpose. This is a standard practice undertaken by hydropower operators worldwide.
 
This controlled procedure ensures water is released at regulated volumes through the gated spillway over a duration of time, to achieve the required level in the reservoir, and to minimize the impact to the downstream regions.

Nevertheless, over the release period, downstream towns are expected to experience minimal rise in river levels. Hydropower dams are capable of mitigating impacts from heavy rainfalls within the upstream catchment, but other factors such as high sea tides, heavy rainfall downstream into catchments and tributaries of the Rejang can still result in floods, unrelated to the scheduled release.

Since the completion and impoundment of Bakun HEP in 2010, Sarawak Energy’s HEP operator Sarawak Hidro Sdn Bhd (SHSB) has managed the reservoir water level in this manner – holding back water throughout the year and slowly releasing the water in a regulated procedure when the need arises, in the process helping to reduce major flooding downstream in areas such as Sibu.

Over the period of release scheduled to commence on 12th February 2018, the release will be kept as low as possible, and will cease once the water level at the reservoir normalises.

The released water is estimated to flow past Kapit town about two days after the release and Sibu town after four days. The rise in river level and intensity of flowing water will reduce as the distance increases.

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