Author(s): Shanker Kumar Sinnakaudan, Aisah Md Shukor, Mohd Rizal Shukor, Maisarah Abd Ghani, Shahril Mod Husin
Linked Author(s): Shanker Kumar Sinnakaudan
Keywords: In-stream flow analysis, environmental flow, PHABSIM, habitat suitability curve, weighted usable area.
Abstract: A new hydroelectric project (Susu Dam) with a capacity of 372 MW is at the final stage of construction at Ulu Jelai, Cameron Highlands, Pahang, Malaysia. The dam receives its source of water from Sungai Lemoi through underground diversion tunnels. Sungai Lemoi has the significant habitat suitability and is still in pristine conditions. Based on the intake design conditions, 95% of the total flow at Sungai Lemoi will be utilized at all time. 5 % of the total inflow or 1. 31m3/s is considered as environmental flow (EF) and shall meet the 7 days average discharge with ARI 10 years. The feasibility of the suggested EF requirements was further analyzed using PHABSIM habitat simulation model. Detailed river survey was conducted for 2km reach while the hydraulic measurements were carried out at 4 selected reaches (13 transects) that comprises of a series of step pool, deep-pool, cascades and pool which are having a variety of substrate and cover types. Habitat suitability criteria for fish were developed based on fish sampling and riparian observations. Simulated habitat with 10 flow variations were carried out to represent low flow to maximum design EF conditions. The findings indicated that for a typical low flow conditions with an average river discharge of 3. 50m3/s before the dam intake, a minimum EF of 0. 5 m3/s may sustain the existing deep pools with acceptable weighted usable habitat area (WUA) for a required 30 cm flow depth. These conditions may sustain the existing fish (Accroscheilus Hexagonolepis and Accroscheilus Deauratus) and riparian habitat. However, it is also noticeable that on an average, proposed 95 % water withdrawal rate at Lemoi intake may cause water level to drop on average about 22 cm at the deep pools. Any discharges below 0. 2m3/s may disturb the overall river habitat health, thus it is not recommended
Year: 2017