Physico-chemical Characteristics in the Filling Phase of Bakun Hydroelectric Reservoir, Sarawak, Malaysia
Nyanti Lee, Ling Teck Yee, Jongkar Grinang

Abstract
Since the impoundment of the Bakun Hydroelectric Dam commenced, there have not been any studies on the water quality of the reservoir. As aquaculture is a potential industry to be developed, a study was conducted to determine the water quality of the reservoir fifteen months after the impoundment started at 12 stations. Results show that temperature in the reservoir decreased 5 oC from surface to 20 m depth. At the station nearest to the dam site, thermocline occurred at 5 m depth whereas further away, thermocline occurred at 4 m depth. In the reservoir, DO at the subsurface (5.49 - 8.51 mg/L) dropped drastically to anoxic level at 2 - 4 m. As the distance from the dam site increased, turbidity at the subsurface and at 20 m depth increased indicating the high suspended solids originating from upstream. The present study shows that the newly filled Bakun reservoir is not suitable for aquaculture due to the anoxic condition at such a shallow depth, low pH and high turbidity.

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