Water quality at Bakun HEP reservior, Belaga, Sarawak

Koh, Willie (2016) Water quality at Bakun HEP reservior, Belaga, Sarawak. [Final Year Project Report] (Unpublished)

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Abstract

Since the water supply at Bakun Hydroelectric Dam reached its full supply level, only one previous study has been done during the filling phase of the dam which was 3 years and 10 months earlier than this study. As water in the reservoir is very important for the aquatic organisms in the reservoir and downstream of the dam, a study was conducted at 3 stations to determine the selected water quality parameters 5 years 6 months after impoundment started. At each station, water in triplicate samples were collected at 6 levels, which is the subsurface, at 10m, 20m, 30m, 40m and 50m depth. Results showed that thermocline occurred at 3m to 10m depth at all stations. DO at the subsurface (4.99 -6.10 mg/L) dropped drastically to anoxic level starting from 2m to 10m depth at all stations. Water conductivity and turbidity increases while pH decreased as depth increased. The highest chlorophyll-a (11.68 J-lg/L) was recorded at 10m depth with positive correlation with turbidity. Increasing levels of ammonia-nitrogen (0.0533 -0.6400 mg/L), total suspended solids (3.30 -63.06 mg/L), and five-day biochemical oxygen demand (1.86 -4.30 mg/L) were observed while depth increases. Nitrate (0.01 -0.22 mg/L), nitrite (0.0020 -0.1170 mg/L), silica (0.39 -1.54 mg/L) and orthophosphate (0.0900 -1.7067 mg/L) showed different variations with depth. This present study showed that the water quality at Bakun Hydroelectric Dam was improving and still changing compared to the previous study during the filling phase and has not stabilize even after 5 years 6 months after impoundment started.

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