Water Quality at Batang Ai Hydroelectric Reservoir (Sarawak, Malaysia) and Implications for Aquaculture
Ling Teck Yee, Debbie D. Paka, Lee Nyanti, Norhadi Ismail, Justin J.J. Emang

Abstract
Batang Ai reservoir has been an inland aquaculture site. However, little is known about the water quality of the reservoir which is important for aquaculture expansion. Therefore, the objective of this study was to determine the level of dissolved oxygen (DO), biochemical oxygen demand (BOD5) and sulfide in the reservoir. Samplings were conducted at 12 stations and at three different depths. Results show that pH and dissolved oxygen decreased as depth increased. Mean DO at 0.5 m, 14 m and 27 m were 6.4 mg/L, 3.9 mg/L and 2.95 mg/L respectively. BOD5 were 3.9 mg/L, 8.7 mg/L and 8.3 mg/L at 0.5 m, 14 m and 27 m depth respectively. Total sulfide ranged from 0.33 to 32.0 µg/l and the mean at 27 m was significantly higher than 0.5 m depth. Multiple linear regression indicates that BOD5 was the only significant predictor of total sulfide. This study shows that sulfide was much lower than the lethal level and it would only be unhealthy for the caged fish if there were upwelling or mixing where lower DO water with toxic sulfide at and below 14 m depth were to be brought to the culture zone.

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