# Numerical Modelling on Physical Model of Ringlet Reservoir, Cameron Highland, Malaysia: How Flow Conditions Affect the Hydrodynamics

^{1}

^{2}

^{3}

^{4}

^{*}

## Abstract

**:**

## 1. Introduction

^{3}, after barely 35 years of operation, 52 percent of its storage was already utilised, with 34 percent filled with sediment [10]. Hence, further research and predictions are required for the continuous operation of the current power generation plant. One of the solutions for this is to study the hydrodynamics of the flow velocity in those reservoirs.

## 2. Methodology

#### 2.1. Study Area

^{3}/annum [19]. Tenaga National Berhad (TNB) is responsible for developing and operating most major hydropower projects. At present, TNB is the main operator for three of the largest hydroelectric schemes in Sungai Perak (1249.1 MW), Kenyir (665 MW), and Cameroon Highlands-Batang Padang (622 MW) [20]. A map of Habu is depicted in Figure 2. The Ringlet Reservoir is located within the Bertam catchment, with a combined area of 70.4 km

^{2}. The Bertam Catchment is divided into six sub-catchments: Upper Bertam, Middle Bertam, Lower Bertam, Habu, Ringlet, and Reservoir. Bertam River, Habu River, and Ringlet River are the principal rivers supplying the Ringlet Reservoir. Teh et al. state that most sediment loaded into the Ringlet Reservoir comes from the Habu end [21].

^{2}comprises the upper watershed that feeds the Ringlet Reservoir [22,23]. Electricity is generated from headwater from two main rivers, Sungai Telom and Sungai Bertam. In this regard, even though the Ringlet reservoir had an initial water storage capacity of 6.7 million m

^{3}, it has experienced a loss of operational volume over the years because of accelerated sedimentation [19,24]. This phenomenon is caused by millions of tons of additional sediment mobilized by rapid developments in the upper catchments area. This situation has gradually decreased the reservoir’s capacity for hydro generation and led to a higher risk of downstream flooding [25]. The higher sediment deposition rate would significantly reduce the projected useful life of the reservoir [26]. Additionally, it has a negative impact on the dam’s stability and risks the ability to store water for flood control [27,28].

#### 2.2. Experimental Works

#### 2.2.1. Physical Model Construction

#### 2.2.2. Model Surveying

#### 2.2.3. Flow Measurements

#### 2.3. Numerical Model (HEC-RAS)

#### 2.3.1. Model Setup

#### 2.3.2. Convergence Study and Model Calibration

#### 2.3.3. Model Simulation

## 3. Results and Discussions

#### 3.1. Physical Model

#### 3.2. HEC-RAS

#### 3.2.1. Convergence Study

#### 3.2.2. Model Calibration

#### 3.3. Simulation

#### 3.3.1. Habu Existing Conditions

#### 3.3.2. Habu with Groynes Installed

## 4. Conclusions

## Supplementary Materials

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Flowchart of the study. The major components of the study are the experimental works and validation of the model using a numerical approach.

**Figure 2.**Map area of Habu. Habu is part of the Ringlet Reservoir, Cameron Highland, Malaysia. Hence, the name ‘Habu’ was used throughout.

**Figure 3.**Diagram of the physical model in Habu. (

**a**) existing and (

**b**) with groynes conditions. (

**c**,

**d**) live images of the constructed physical models of (

**a**,

**b**).

**Figure 4.**Velocity points at Habu during; existing condition: (

**a**) 1-year, (

**b**) 5-years and (

**c**) 100-years ARI, Groynes condition: (

**d**) 1-year, (

**e**) 5-years and (

**f**) 100-years ARI, respectively. Display vectors were present with the vector arrow tail at the data location.

**Figure 5.**Velocity distribution comparisons between different ARIs (1-year, 5-years, and 100-years) for (

**a**) existing conditions and (

**b**) with Groynes.

**Figure 7.**(

**a**) River centreline (blue line) and CH (red line) for Habu. WSE plot along the Habu end centreline for different mesh sizes (

**b**) centreline, (

**c**) CH700, (

**d**) CH500.

**Figure 8.**Sensitivity plot of velocity along Habu (

**a**) CH700, (

**b**) CH500 for different mesh sizes. The insets show the enlarged curves to aid comparisons.

**Figure 9.**(

**a**) Observation points from experimental work. Red dots denote the location of sampling used for comparison between experiment and simulation, while green dots denote the additional experimental sampling locations. Water depth and velocity comparison for DWA (

**b**), (

**c**) and SWE (

**d**), (

**e**) between experimental observation and simulation results.

**Figure 10.**Velocity time history at (

**a**) CH750, (

**b**) CH500 for simulation with different Manning’s values.

**Figure 11.**(

**a**) Location of the groynes along Habu catchment and experimental sampling locations. Red dots denote the location of sampling used for comparison between the experiment and simulation, while green dots denote the additional experimental sampling locations. (

**b**) water depth (

**c**) velocity comparison between experimental observation and simulation results (SWE) for a model with groynes installed.

**Figure 12.**(

**a**) Water Surface Elevation (WSE) along the Habu centreline. Simulated water depth at the end of the simulation for (

**b**) 1 year (

**c**) 5 years, and (

**d**) 100 years ARI.

**Figure 13.**Velocity magnitude at a time step, t = 10, 20 and 30 min, for 1-year, 5-years and 100-years ARI. The arrow represents the flow direction of the water and is applied to all cases.

**Figure 14.**Particle tracing at time step, t = 30 min, for (

**a**) 1-year, (

**b**) 5 years and (

**c**) 100-years ARI. The arrow represents the flow direction of the water and is applied to all cases.

**Figure 15.**Velocity comparison between 1-year, 5-years and 100-years ARI during steady-state conditions at (

**a**) CH650, (

**b**) CH500 and (

**c**) CH350.

**Figure 16.**Water depth at Habu with groynes installed for (

**a**) 1 year (

**b**) 5 years, and (

**c**) 100 years ARI.

**Figure 17.**Velocity magnitude comparison between 1-year, 5-years and 100-years ARI for Habu with groynes installed at a time step, t = 10, 20 and 30 min. The arrow represents the flow direction of the water and is applied to all cases.

**Figure 18.**Particle tracing comparison between (

**a**) 1-year (

**b**) 5-years, and (

**c**) 100-years ARI for Habu with groynes installed. The arrow represents the flow direction of the water and is applied to all cases.

**Figure 19.**Velocity comparison between existing condition (black line) and groynes installed (red line) at CH 600 (

**a**–

**c**), CH 500 (

**d**–

**f**), CH400 (

**g**–

**i**) for 1-year, 5-years and 100-years ARI.

Location | Conditions | ARI (Year) | Test Series | Flow Rate | |
---|---|---|---|---|---|

Prototype (m ^{3}/s) | Model (l/s) | ||||

Habu | H1 Existing | 1 | H1-1 | 23.5 | 4.7 |

5 | H1-5 | 34.5 | 7.0 | ||

100 | H1-100 | 55.5 | 11.3 | ||

H2 with Groynes | 1 | H2-1 | 23.5 | 4.7 | |

5 | H2-5 | 34.5 | 7.0 | ||

100 | H2-100 | 55.5 | 11.3 |

Condition | $\mathbf{A}\mathbf{R}\mathbf{I}$ (Years) | $\mathbf{Flow}\mathbf{Rate},\mathbf{Q}$ (L/s) | ${\mathbf{U}}_{\mathbf{m}\mathbf{i}\mathbf{n}}(\mathbf{m}/\mathbf{s})$ | ${\mathbf{U}}_{\mathbf{m}\mathbf{a}\mathbf{x}}(\mathbf{m}/\mathbf{s})$ | ${\mathbf{U}}_{\mathbf{a}\mathbf{v}\mathbf{e}}(\mathbf{m}/\mathbf{s})$ |
---|---|---|---|---|---|

H1 Existing | 1 | 4.7 | 0.062 | 0.622 | 0.180 |

5 | 7.0 | 0.044 | 0.793 | 0.181 | |

100 | 11.3 | 0.021 | 0.899 | 0.188 | |

H2 Groynes | 1 | 4.7 | 0.038 | 0.608 | 0.161 |

5 | 7.0 | 0.034 | 0.729 | 0.195 | |

100 | 11.3 | 0.026 | 0.874 | 0.248 |

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**MDPI and ACS Style**

Mat Desa, S.; Jamal, M.H.; Mohd, M.S.F.; Samion, M.K.H.; Rahim, N.S.; Muda, R.S.; Sa’ari, R.; Kasiman, E.H.; Mustaffar, M.; Ishak, D.S.M.;
et al. Numerical Modelling on Physical Model of Ringlet Reservoir, Cameron Highland, Malaysia: How Flow Conditions Affect the Hydrodynamics. *Water* **2023**, *15*, 1883.
https://doi.org/10.3390/w15101883

**AMA Style**

Mat Desa S, Jamal MH, Mohd MSF, Samion MKH, Rahim NS, Muda RS, Sa’ari R, Kasiman EH, Mustaffar M, Ishak DSM,
et al. Numerical Modelling on Physical Model of Ringlet Reservoir, Cameron Highland, Malaysia: How Flow Conditions Affect the Hydrodynamics. *Water*. 2023; 15(10):1883.
https://doi.org/10.3390/w15101883

**Chicago/Turabian Style**

Mat Desa, Safari, Mohamad Hidayat Jamal, Mohd Syazwan Faisal Mohd, Mohd Kamarul Huda Samion, Nor Suhaila Rahim, Rahsidi Sabri Muda, Radzuan Sa’ari, Erwan Hafizi Kasiman, Mushairry Mustaffar, Daeng Siti Maimunah Ishak,
and et al. 2023. "Numerical Modelling on Physical Model of Ringlet Reservoir, Cameron Highland, Malaysia: How Flow Conditions Affect the Hydrodynamics" *Water* 15, no. 10: 1883.
https://doi.org/10.3390/w15101883