Page - 360 - in Book of Full Papers - Symposium Hydro Engineering

ABSTRACT Ringlet reservoir is a multipurpose reservoir that is part of Cameron Highlands – Batang Padang Hydroelectric Scheme. The reservoir has the original design storage of 6.7 million m3, of which 2 million m3 is dead storage and 4.7 million m3 is live storage. The catchment is a famous tourist area with active highland agricultural activities. Changes in land use have been significant since 1960’s, showing an increase in agricultural area and reduction of forest cover. A number of studies were conducted in the past to examine the effects of land use changes on the operation of the hydroelectric scheme. Based on survey and sediment monitoring records, the sedimentation rate has increased by 6 times from original design of 25,000 m3/year (in 1960’s) to an average of 139,712 m3/year in 2010, causing a significant reduction of total storage capacity of Ringlet Reservoir from 6.7 million m3 in 1965 to 3.1 million m3 in 2008. Bertam Intake, which is the main power intake is often choked by the sediment built up within the area. To continue the hydropower operation, various mitigation strategies have been implement such as development of an Integrated Lake Basin Management Plan for Cameron Highlands’ catchment to control sediment production at source. At the same time, sediment in Ringlet Reservoir is continuously removed via dredging. The dredged material is dried temporarily at the designated decantation area and disposed at the selected areas. Dredging is not a sustainable solution, mainly due to larger sediment loads entering the reservoir as compared to capacity of removal. Land availability for disposal area is becoming limited in the future and subsequently increase the total cost of removal. Another strategy considered is construction of two (2) check dams and settling basins at the main inlet rivers into Ringlet Reservoir, namely Habu and Ringlet check dams. Mechanical excavation at the check dams is cheaper than deploying dredger to remove sediment from inside the reservoir. In conclusion, managing hydropower operation in rapidly changing land use especially in agricultural area is challenging. Rate of reservoir sedimentation in this area can easily exceed the original design, causing the reservoir operators to carefully plan ahead to manage the potential problems. TNB as the responsible manager, has done extensive works to manage and mitigate the sedimentation problem faced at Ringlet Reservoir. Other options such as controlling the reservoir operating regime and operation of the low level outlet can also be considered. There are still other ways to improve the current sediment management practice and they require extra effort to ensure the sustainability of the operation. 360