Key Issues: 4-Reservoir Sedimentation Climate Zone: Subjects

IEA Hydropower Implementing Agreement Annex VIII - Hydropower Good Practices: Environmental Mitigation Measures
and Benefits Case study 04-03: Reservoir Sedimentation - Cameron Highlands Hydroelectric Scheme, Malaysia
Key Issues:
4-Reservoir Sedimentation
Climate Zone:
Af: Highland Tropical Humid
Subjects:
- Sediment Management
Effects:
Sultan Abu Bakar Dam
- Prevention of sediment entering into the Telom Tunnel
- Prevention of sediment accumulation in Ringlet Reservoir
Project Name:
Country:
Cameron Highlands Hydroelectric Scheme
Pahang, Malaysia (Asia)
Implementing Party & Period
Tenaga Nasional Berhad (TNB)
- Project:
- Good Practice:
1978 (Completion of construction) Tenaga Nasional Berhad (TNB)
1970’s -
Key Words:
Sediment, Land Use Change, Desilting Work, Desander (Settling Basin)
Abstract:
Since the early 1970s, mitigation measures for sedimentation have been carried out
periodically at various locations in the Cameron Highlands Scheme to minimize its impact on
the operation and maintenance of the five hydro stations. These measures include construction
of a silt retention weir, pumping of sediment, and de-silting of tunnels, and have successfully
reduced sediment inflow into the reservoir.
1. Outline of the Project
The Cameron Highlands Hydroelectric Scheme is situated in the northwest of the state of Pahang,
Malaysia. It was constructed in the period between 1957 and 1964. The scheme consists of four small
run-of-river and one storage hydro projects and has five power stations.
The main features of the storage project beside the 100 MW underground power station are a 40-m high
concrete buttress dam with gated spillways, four side-stream diversion schemes of Sg. Plau’ur, Sg. Kial,
Sg. Kodol, and Sg. Telom, some 20 km length of tunnels, the Bertam Intake and other appurtenant
structures. The major specifications and the layout plan of the scheme are shown in Table 1, Table 2 and
Figure 1 respectively.
Table 1 Specifications of the Sultan Abu Bakar Dam (the Ringlet Reservoir)
Gross Storage
[MCM]
6.7
Usable Storage
[MCM]
4.7
Dam Height
[m]
40
Dam Type
[m]
Concrete & Rockfill
Normal Water Level
[EL. m]
1,068.3
Low Water Level
[EL. m]
1,065.3
item
Max. Output
Max. Discharge
Rated Head
Gross Head
Annual Generation
Operational Year
Intake Water Level
Tail Water Level
Catchment Area
Generation Type
Turbine Type
Table 2 Specifications of the Hydro Projects
Kampung
Kuala Terla
Robinson
Raja P/S
P/S
Falls P/S
[MW]
1 x 0.8
1 x 0.5
3 x 0.3
3
[m /sec]
1.253
1.718
0.173
[m]
80
37
235
[m]
83.8
39.3
243.7
[GWh]
6
5
7
1964
1964
1959
[EL. m]
1,378.3
1,284.7
1,410.6
[EL. m]
1,296.3
1,245.62
1172.0
[km2]
30.8
43.3
21.4
Run-of-river Run-of-river
HF
Habu P/S
2 x 2.75
4.347
91
97.5
32
1964
1,165.7
1,071.2
132.7
Run-of-river Run-of-river
HF
HP
HF
Sultan
Yussuf P/S
4 x 25.0
5.493
573
587.3
320
1963
1,070.8
493.5
183.4
Dam &
Waterway
HP
ROBINSON FALLS P/S
KUALA TERLA P/S
HABU P/S
TELOM TUNNEL
SULTAN YUSSUF P/S
KAMPUNG RAJA P/S
SULTAN ABU BAKAR DAM
Figure1 Layout Plan of the Cameron Highlands Hydroelectric Scheme
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The Ringlet Reservoir is a man-made lake created upstream of the concrete dam on Sg. Bertam. It
impounds the waters of Sg. Bertam and its tributaries and those of Sg. Telom, Sg. Plau’ur, Sg. Kodol and
Sg. Kial which have been diverted from the Telom catchment through the Telom Tunnel into the Bertam
catchment. The designed gross storage of the reservoir is about 6.7 million cubic meters, of which, 4.7
million cubic meters is usable storage. Water from the Ringlet Reservoir is channeled through a tunnel to
the Sultan Yussuf (Jor) Power Station and then is discharged through a tailrace tunnel into the Jor
Reservoir of the Batang Padang Hydroelectric Scheme.
The Ringlet Reservoir, which has an estimated dead storage of 2.0 million cubic meters, would have a
useful life of approximately 80 years.
2. Features of the Project Area
2.1 Catchment Characteristics
The Cameron Highlands catchment is situated on the Main Range of the Peninsular Malaysia. The
average elevation of the catchment area is approximately 1,180 m with the highest peak, Gunung
Brinchang at approximately 2,032 m above sea level and many of the other peaks are over 1,524 m.
The Cameron Highlands catchment that contributes water to the Ringlet Reservoir includes several
sub-catchments and has an area of 183 km2. The main rivers of the Cameron Highlands catchment,
namely the Sg. Telom and Sg. Bertam drain eastwards into the Sg. Pahang and subsequently into the
South China Sea in the eastern coast of the Peninsular Malaysia.
Table 3 Detailed Breakdown of the Cameron Highlands’ Catchment Area
Area
Total
Major Catchment
Sub-Catchment
[km2]
[km2]
Plau’ur
9.6
Kial
22.7
Telom
110
Kodol
1.3
Telom
76.4
Bertam
Bertam
73
73
2.2 Land Use Changes
The construction of the Cameron Highlands/Batang Padang Hydroelectric Scheme in the sixties has
provided in addition to the power generation facilities, some reasonable good access into the interior of
the Cameron Highlands area. It may have therefore helped to encourage land development and other
economic activities growth in the area during and post construction periods. Forest in the Cameron
Highlands area is progressively being cleared to make ways for agricultural and construction activities.
Table 4 Land Use Changes in Bertam Catchment
Bertam Catchment
Vegetation/
[km2]
Land Use
1950’s
1980’s
Forest
46.5
45.1
Tea/Orchards
15.2
10.4
Vegetable/Flower
5.1
7.0
Urban
4.1
Open/Grassland/Scrub Forest
5.8
6.0
3
1990’s
43.5
6.6
8.1
4.2
10.2
Table 5 Land Use Changes in Telom Catchment
Vegetation/
Land Use
Forest
Tea/Orchards
Vegetable/Flower
Urban
Open/Grassland/Scrub Forest
Telom Catchment
[km2]
1950’s
99.1
6.3
5.0
-
1980’s
90.3
6.2
10.7
0.5
2.7
1990’s
74.1
6.2
23.2
1.1
5.8
3. Major Impacts
Extensive deforestation and indiscriminate earth bulldozing in the Cameron Highlands area for
agricultural and housing development has resulted in widespread soil erosion over the land surface. The
extent of soil erosion occurring in the area particularly that of Cameron Highlands Scheme catchment is
increasing, the impact of natural vegetation destruction on the environment and the stations’
generation/operation is a major cause for concern. It leads to sedimentation of the streams and the Ringlet
Reservoir from which water is drawn to the power station. Excessive sediment particles drawn into the
power station will cause damage and shorten the useful life of the mechanical parts of the generating
plant, whereas excessive sediment deposited in the Ringlet Reservoir will affect its storage as well as
useful life of the reservoir.
There were incidences of water qualities and aquatic lives in the Ringlet Reservoir being badly affected
in the past when excessive sediment/silt content and high chemical content (e.g. pesticides and
fertilizers) resulted in dying of fish and wide spread of water hyacinth. Cases of landslide have also been
reported which have led to the destruction of properties and crops as well as loss of lives.
A number of studies were conducted in the past to examine the effects of development in the hydro
scheme catchment on the hydro power station. The studies (Choy, 1987, 1989, and 1991) have shown
that the operation and maintenance as well as energy generation of the hydro stations of the Cameron
Highlands Scheme are affected by the land development. The severity of sedimentation has led to a study
which reported that the carrying capacity of the Telom Tunnel had been reduced to 40% (WLPU, 1986).
Further studies of the land use impact (Choy & Hamzah, 2001, and Choy 2002) and a review of
some previous studies recently done, give the following findings:
• Average annual temperature for urbanized area in the catchment has increased slightly in
recent years.
• There is an increase in the annual mean runoff for the catchment subsequent to the land use
changes (Figure 2 and Figure 3).
4
2500.0
Annual runoff (mm)
Runoff = 0.7226(Rainfall) - 90.07
Period: 1984 to 1998 (R = 0.87)
2000.0
1500.0
Runoff = 0.6495(Rainfall) - 13.641
Period: 1964 to 1983 (R = 0.85)
1000.0
1000.0
1500.0
2000.0
2500.0
3000.0
3500.0
Annual total rainfall (mm)
rainfall-runoff 1964-1983
rainfall-runoff 1984-1998
線形
線形
Linear (rainfall-runoff 1984-1998)
Linear (rainfall-runoff 1964-1983)
Figure 2 Rainfall-Runoff Correlation for Upper Bertam (at two different periods)
Annual runoff (mm)
2500.0
2000.0
Runoff = 0.8537(Rainfall) - 339.91
Period: 1987 to 1998 (R = 0.77)
Runoff = 0.7495(Rainfall) - 167.06
Period: 1964 to 1980 (R = 0.90)
1500.0
Runoff = 0.4608(Rainfall) + 280.34
Period: 1981 to 1986 (R = 0.90)
1000.0
1000.0
1500.0
2000.0
2500.0
3000.0
Annual total rainfall (mm)
rainfall-runoff 1964-1980
rainfall-runoff 1981-1986
rainfall-runoff 1987-1998
Linear (rainfall-runoff 1964-1980)
Linear (rainfall-runoff 1981-1986)
Linear (rainfall-runoff 1987-1998)
Figure 3 Rainfall-Runoff Correlation for Sg. Telom (at 3 different periods)
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• Water utilization for generation decreases due to increased infiltration losses in dry days and
spilling losses in wet days because of intake closing or increases in peak flow (Figure-4 and
Figure-5).
Cum. Annual Energy Output (GWh)
Cum. Annual Energy Output (GWh)
250
200
Slope, Sr4 = 0.1574
1992
150
Slope, Sr3 = 0.1348
1982
100
Slope, Sr2 = 0.1565
1972
50
Slope, Sr1 = 0.1802
0
0
200
400
600
800
1000
1200
1400
3
Cum.
Annual
Runoff(Million
(MillionmM3)
Cum.
Annual
Runoff
)
Figure 4 Double Mass Curve (Annual Runoff vs. Annual Energy Output)
of Robinson Falls Power Station (1964 to 1998)
1200
Cum. Annual Energy Output (GWh)
Cum. Annual Energy Output (GWh)
1000
Slope, Sh4 = 0.158
800
Slope, Sh3 = 0.1238
1986
600
Slope, Sh2 = 0.1707
400
1970
200
Slope, Sh1 = 0.1863
0
0
1000
2000
3000
4000
5000
6000
7000
3
Cum.Annual
Annual
Runoff(Million
(MillionmM3)
Cum.
Runoff
)
Figure 5 Double Mass Curve (Annual Runoff vs. Annual Energy Output)
of Habu Power Station (1964 to 1998)
6
• The suspended sediment load in the Sg. Telom and Sg. Bertam River have increased by
twentyfold and seventeenfold respectively since 1960’s (Figure 6 and Figure 7).
100.0
Discharge (m3/sec)
Discharge ( Cumecs )
SEDIMENT DISCHARGE = 0.0097 (DISCHARGE)3.8197
Period: Before 1964, (R = 0.91)
10.0
SEDIMENT DISCHARGE = 0.2718 (DISCHARGE)3.6193
Period: Aug 1990 to Aug 2000, (R = 0.90)
1.0
SEDIMENT DISCHARGE = 0.1119 (DISCHARGE)3.5868
Period: Aug 1987 to Jul 1990, (R = 0.83)
0.1
0.1
1.0
10.0
100.0
1000.0
10000.0
Suspended Sediment Discharge ( Tonnes / Day )
Suspended Sediment Discharge (tons/day)
Figure 6 Sediment Rating Curve – Sg. Telom at 49 M.S.
(before 1964 and from August 1987 to now)
100.0
Discharge (m3/sec)
Discharge ( Cumecs )
SEDIMENT DISCHARGE = 0.8295 (DISCHARGE)3.9635
Period: 1955, (R = 0.98)
SEDIMENT DISCHARGE = 1.7079 (DISCHARGE)4.1649
Period: Nov 1986 to Jan 1990, (R = 0.80)
10.0
1.0
SEDIMENT DISCHARGE = 6.0076 (DISCHARGE)2.9612
Period: Feb 1990 to Aug 2000, (R = 0.89)
0.1
0.1
1.0
10.0
100.0
1000.0
Suspended Sediment Discharge ( Tonnes / Day )
Suspended Sediment Discharge (tons/day)
Figure 7 Sediment Rating Curve – Sg. Bertam at Robinson Falls
(before 1955 and from November 1986 to now)
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10000.0
Since its operation in 1963, the Ringlet Reservoir has lost nearly 53% of its gross storage to
sedimentation, which is presently estimated as reaching a volume of about 3.5 – 4.0 million cubic meters.
Figure 8 shows the storage capacity curve of the Ringlet Reservoir. The currently estimated sediment
deposition rate in the Ringlet Reservoir is in the range between 350,000 to 400,000 cubic meters per year.
Figure 9 shows the decline in trap efficiency over time for the Ringlet Reservoir calculated using the
Brune’s method on an annual basis, which shows the current trapping efficiency of the reservoir to be
about 56 % as shown in Figure 9.
7.00E+06
6.00E+06
5.00E+06
4.00E+06
3.00E+06
2.00E+06
1.00E+06
0.00E+00
1040.0
-1.00E+06
1045.0
1050.0
1055.0
1060.0
1065.0
1070.0
ELEVATION (m)
1963
Approx. (1963)
多項式
2000
Approx. (2000)
多項式
Figure 8 Ringlet Reservoir – Reservoir Capacity Curve (1963 vs. 2000)
(Choy & Hamzah, 2000)
100
90
80
70
Trap Efficiency
(%)
STORAGE CAPACITY (m3)
8.00E+06
60
50
40
30
20
10
0
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
2015
Operation Period
Figure 9 Ringlet Reservoir – Trap Efficiency vs. Operation Period
8
2020
1075.0
Most of the incoming sediment is therefore unlikely to be deposited in the Ringlet Reservoir and will be
carried down to the Sultan Yussuf Power Station and discharged into the Jor Reservoir. Presently, 45.2%
of the 3.9 million cubic meters gross storage of Jor Reservoir is filled with sediment.
A study in 1999/2000 (SNC-Lavalin, 2000) indicates that the sediment deposition in the Ringlet
Reservoir has not affected the safety of the dam. However, the substantial reduction in the live storage of
the reservoir would largely reduce the capability of the Sultan Yussuf Power Station to generate peaking
power for the load requirement of the National Grid and would also reduce the capability of the reservoir
to regulate incoming high flow. The former will make the Sultan Yussuf Power Station to be no different
from other run-of-river stations and will result in financial loss; the latter will pose a risk of the dam
being without flood control capacity, hence leading to frequent spillage and flooding of the downstream
Bertam Valley during monsoon.
4. Mitigation Measures
Since the early seventies, mitigation measures (Choy & Fuad Omar, 1990; Choy & Fauzan, 1997) have
been carried out periodically at various locations of the Cameron Highlands Scheme to minimize the
impact of sedimentation on the operation and maintenance of the five hydro stations. These measures
include:
• Manual removal of sediment accumulating behind the intake weirs of Kampung Raja,
•
•
•
•
Kuala Terla and Habu.
Construction of a small timber silt retention weir on Sg. Ringlet in the late seventies and a
concrete silt retention weir downstream of the Habu Power Station in the early nineties.
Pumping and excavation of sediment accumulating at upstream of the Telom Intake and
Robinson Falls Intake and in the Ringlet and Habu Silt Retention Ponds.
Desilting of the Telom Tunnel in the seventies and again in the early nineties.
Construction of a new desander (settling basin) in front of the original Telom Intake
structure to improve the sediment self-scouring efficiency (Photo 1).
Photo 1 Desander in front of the Telom Intake
5. Results of Mitigation Measures
As a result of the above mitigation measures, the inflow and accumulation of sediment in the Ringlet
Reservoir has been checked and reduced by a significant amount as shown in the following Figure 10.
9
MEASURED DEPOSITED SEDIMENT (m3)
7.0E+06
6.0E+06
5.0E+06
4.0E+06
3.0E+06
2.0E+06
1.0E+06
0.0E+00
1960
1970
1980
1990
2000
2010
2020
PERIOD MEASURED
Figure 10 Ringlet Reservoir – Sediment Deposition Rate
• If there is no action at all to check the sediment inflow, the reservoir will theoretically lose its
entire storage before or by the end of the year 2000 due to sedimentation.
• The desilting works carried out during the period between mid-seventies and early nineties
appears to have prevented more than 1.5 million cubic meter of sediment from entering and
accumulating in the Ringlet Reservoir.
• The completion of the new Telom Desander and the Habu Silt Retention Weir and subsequent
desilting works has apparently prevented at least another further 1.5 million cubic meter of
sediment from accumulating in the Ringlet Reservoir during the last few years.
• There is an improvement in energy production per unit of river discharge (kWh/m3).
6. Reasons for Success
The desilting works, new Telom Desander and Habu Silt Retention Weir completed in the period
between the seventies and early nineties has produced positive and fruitful results of reducing the inflow
of sediment into the Ringlet Reservoir.
However, the following should be taken into account:
• The mitigating measures are only able to lessen but not stop the sediment accumulation in the
Ringlet Reservoir.
• Nearly 53% of the storage capacity of the Ringlet Reservoir has already been filled with
sediment.
• There is a plan to expand the development area in the Cameron Highlands area in the future.
• It is prudent to take early action on the following:
10
To construct another silt retention weir on Sg. Ringlet at the Ringlet end of the Ringlet
Reservoir so as to further reduce the sediment inflow into the reservoir.
To examine the feasibility of desilting the reservoir so as to regain portion of the lost
storage capacity due to sedimentation.
To implement a watershed management plan and to impose the requirements for soil
conservation practices in all future development.
7. Further Information
7.1 References
1) Fook Kun, CHOY, Fauzan HAMZAH: Cameron Highlands Hydroelectric Scheme-Performance of
the Ringlet Reservoir, ICOLD, Florence, Italy, 1997.
2) Fook Kun, CHOY, Fauzan HAMZAH: Cameron Highlands Hydroelectric Scheme- Landuse
Changes – Impacts and Issues, Hydropower 01, Bergen, Norway, 2001.
3) Fook Kun, CHOY: Cameron Highlands Hydroelectric Scheme- Landuse Impacts On Performance
and development. International Symposium On Reservoir Management In Tropical and Sub-Tropical
Regions, Iguassu, Brazil 2002.
7.2 Inquiries
TNB Hidro Sdn. Bhd.
Tel: +60-5-243-5822
Fax: +60-5-243-5823
E-mail: [email protected]
This case history of hydropower good practice is published for educational and informational purposes only and may
not be used for any other purpose. Duplication for commercial purposes is prohibited. The author(s) of this
publication make no express or implied warranties concerning this case history, including no warranty of accuracy or
fitness for a particular purpose.
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New Energy Foundation, Japan, 2006
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