Abstract
Reservoir sedimentation adversely affects both operation and safety of dam. It is important for reservoir manager and operator to predict the incoming sediment inflow into a reservoir to develop sustainable sediment management plan. Continuous sediment monitoring is preferred to estimate total sediment load but it is labor intensive and costly. To cope with these limitations, total sediment inflow into a reservoir is predicted by coupling the runoff from hydrological model and sediment rating curves derived from field sampling dataset. In this research, MIKE NAM rainfall runoff model is used to simulate runoff in Cameron Highlands’ catchment, using hydrological data from 1999 to 2012. This model is calibrated and validated using the flow data of Sg Bertam. Field sampling is conducted to measure the Total Suspended Solids (TSS), Bed Load and grab samples at major rivers namely Sg Telom, Sg Habu, Sg Ringlet and Sg Bertam. Sediment rating curves using power function are used to describe the relationship between the total sediment load and discharge. Using this concept, annual total sediment inflow into Ringlet Reservoir from 1999 to 2012 is estimated in the range of 100,000 m3/year to 270,000 m3/year, agreeable to the survey records previously.
Highlights
Reservoir sedimentation is a common problem faced worldwide
Results are divided into three main components; 1) derivation of inflow hydrographs at main rivers feeding into Ringlet Reservoir and 2) derivation of sediment rating curves for each rivers and 3) calculation of annual sediment load
The calibration and validation results for continuous period of 1999 to 2006 and 2010 to 2012 using stream flow data at Sg Bertam is illustrated in Fig 5 and Fig 6 respectively, with Nash-Sutcliffe Efficiency (NSE) value of 0.663 and 0.569 respectively
Summary
Reservoir sedimentation is a common problem faced worldwide. A comprehensive reservoir sedimentation management requires good understanding on the incoming sediment inflow rate. Using two consecutive survey information, difference in storage indicates sedimentation rate provided that information on sediment removal via dredging, flushing or others is known This method does not provide temporal variation of sediment inflow, but useful for long term sediment management and planning. Main limitation of this method is frequency of survey record, as it is costly to conduct every survey. Another common method to predict reservoir sedimentation rates is using the trap efficiency, which is defined as the ratio between sediment deposition inside the reservoir and sediment inflow into the reservoir. Using the trap efficiency curves, annual sediment inflow can be estimated based on the capacity to annual inflow ratio and type of the reservoir [1] [2]
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