DESIGN REHABILITATION OF WONOGIRI DAM, CENTRAL JAVA

Transcription

DESIGN REHABILITATION OF WONOGIRI DAM, CENTRAL
JAVA PROVINCE – INDONESIA
Cristina Dwi Yuliningtyas, Indonesian Minisitry of Public Works
Dwi Aryani Semadhi Kubontubuh, Indonesian Minisitry of Public Works
ABSTRACT
The Wonogiri Mutipurpose Dam has been constructed at Upper Solo River basin in 1981 for flood
control, irrigation water supply and hydropower with 1,350 km2 of catchment area. The Wonogiri
reservoir has been rapidly filled with sediment transported from the catchment especially from
Keduang tributary. Bad land use of its catchment and intensive farming of annual crops using poor
practices on the highly erosive and steep-sloped uplands as well as highly populated and intensely
farmed areas are the main causes of the sedimentation of the Wonogiri reservoir. It could be said that
any countermeasure is not taken for the sedimentation problem of the Wonogiri reservoir, it would
lose because of decrease of the storage capacity in the near future. Especially, the intake structure
that feeds water to the powerhouse and downstream irrigation system has been seriously affected by
sediment deposits at and around the intake structure. The quantity of sedimentation reached 50.9% of
the dead storage on 2005 that came from Keduang River as Bengawan Solo’s tributary.
To decrease the sedimentation and keeping the dam life time, have been planed sediment storage
reservoir countermeasures such as new spillway for sand flushing at right abutment of main dam,
closure dike and overflow weir in the reservoir.
Keywords: Wonogiri, sedimentation, Bengawan Solo
1. BACKGROUND
Administratively Wonogiri Dam located in the Solo River, Danuarjo Village Wonogiri District,
Central Java Province. Located 7 km south of the Wonogiri City. Wonogiri Dam is a clay core rockfill
dam. The high is 40.00 m from the deepest fondation excavation and 830.00 m lenght. The spillway is
non-overflow with 4 gates of 30.00 m width net.
The Wonogiri Mutipurpose Dam has been constructed at Upper Solo River basin in 1981. Since
impoundment of the Wonogiri reservoir on December 29, 1980, the reservoir has been rapidly filled
with sediments. The quantity of sedimentation reached 50.9% of the dead storage on 2005 that came
from Keduang River as Bengawan Solo’s tributary.
To mitigate sediment problem in the Wonogiri reservoir, the Master Plan and the Feasibility Study on
countermeasures for sedimentation in the Wonogiri Multipurpose dam reservoir were carried out from
2004 to 2007 by JICA continued by Ika Adya Perkasa Consultant until 2009 and continued for detail
design and supporting report by Nippon Koei Co, Ltd and Yachiyo Engineering Co., Ltd until 2010.
2. PROPOSED PLAN
In the Master Plan stage, the sediment inflow from the Keduang River and other tributaries were
estimated. And the countermeasures were proposed.
a)
Urgent Plan
- Sediment storage reservoir with new gate (it is composed with the new spillway for sand
flushing at right abutment of main dam and closure dike and overflow weir)
- Watershed conservation in Keduang River basin
Design Rehabilitation of Wonogiri Dam, Central Java - Indonesia
1
- Periodic maintenance dredging at intake
b)
Mid Term Plan
- Watershed conservation in other tributaries
c)
Long-lasting Countermeasure
- Rehabilitation of watershed conservation areas
Design annual sediment balance in the Wonogiri reservoir is shown below;
Keduang River Basin
Other River Basins
1,220
1,960
Keduang River Basin
Other River Basins
1,220
1,960
Sediment Yield
Sediment Yield
Watershed
Conservation
Watershed
Conservation
Watershed
Conservation
1,960
800
1,040
800
Wonogiri Main Reservoir
Wonogiri Main Reservoir
Overflow Dike
Overflow Dike
800
100
Sediment Storage
Reservior
Balance : 1,920
(Sediment Deposits)
Balance : 0
1,040
800
1,960
100
Sediment Storage
Reservior
Balance : 1,000
(Sediment Deposits)
Balance : 0
Intake
Existing Spillway
Wonogiri Dam
Intake
Closure Dike
Closure Dike
Existing Spillway
Wonogiri Dam
New Spillway
New Spillway
0
0
700
Power Station
700
Power Station
140
140
Unit: 1,000 m3
Unit: 1,000 m3
Bengawan Solo River
Bengawan Solo River
840
Urgent Plan
840
Mid Term Plan
Figure 1. Design annual sediment balancing
Source: Supporting Report Volume 2 (2010)
Additional facilities as mentioned on point 1) a) are:
- New spillway with 2 gates will be constructed on the right abutmen. With widht 15.00 m (@ 7.5
m), design discharge at PMF is 1,270 m3/sec with maximum operation discharge is 400 m3/sec.
- Closure dike A from earthfill with 700.00 m counterweight lenght and 9.4 m height.
- Closure dike B from earthfill with 700.00 m counterweight lenght and 8.4 m height.
- Closure dike C from earthfill with 402.00 m counterweight lenght and 5.8 m height.
- Overflow dike with concrete fixed weir type with 298.00 m lenght and 2.0 m height.
Advantages of these countermeasure are to
a) Prevent the sediment entering into the intake
b) Make it possible to conduct sediment flushing/sluicing without reducing the water level of the main
reservoir, resulting in few effects on the water use of storage capacity of the wonogiri reservoir
c) Reduce the impact on the environment and social activities
2
Figure 2. Countermeasures Layout
Source: Proposal Document for Design Approval (2010)
3. HIDROLOGY
The hydrology conditions are:
- Hydro-meteorology: tropical climate with 29.3 oC annually mean temperature, 77.4% annually
mean humadity, kecepatan angin rata-rata tahunan 2.31 m/sec annually mean wind velocity, 5.3
mm/day annually mean evaporation.
- catchment area: 1,350 km2.
- annually rainfall: 1,990.00 mm/year calculated from 1983 ∼ 2005.
- Probable Maximum Precipitation (PMP) : 307.4 mm with Hershfield method.
- Probable Maximum Flood (PMF) : 9,710 m3/sec with LST (long and short-term runoff model)
Runoff method.
- Flood routing in reservoir.
Figure 3. Catchment Area of Wonogiri
3
4. NEW CONCEPT OF RESERVOIR OPERATION
Before going to the new operation new concept, we can see the comparation between existing and
the propose operation that is shown in the table below:
Table 1. Reservoir water lavel operation design
Original Operation
/1980
2005
1980
Control Water Level
Extra Flood Water Level　（PMF)
Low Water Level
Normal High Water Level
135.3
139.1
(m)
(m)
(m)
(m)
Ratio of Proposed Operation
to Original Operation
Proposed Operation
/2005
136.3
140.1
127.0
136.0
137.0
433
375
(MCM)
Water Use Storage
58
(MCM)
114
Dead Storage
Note: WG: Wonogiri Main Reservoir, KD: Keduang Sediment Reservoir
WG
432
58
KD
0
0
99.7%
115.1%
The new spillway should be operated as long as possible from the start of a flood for passing
sediment inflow. The release water from the new spillway is maximum 400 m3/sec. The existing
spillway gates have to be opened when the main reservoir water level reaches EL.138.2 m in order
to prevent the existing gate from being overtopped. The existing gates are opened and the new
spillway gates are closed at the same time when the main reservoir water level reaches this
elevation. The discharge is kept at no more than 400 m3/s against a flood smaller than the Standard
Highest Flood (SHF) magnitude. The existing gates are further opened when the water level of the
main reservoir reaches the maximum water level of Standard Highest Flood (SHF) or the
surcharge water level whichever is higher. Of the four gates, three are fully opened and one is kept
at 2.5 m opening in order to keep the maximum outflow being not more than 1,360 m3/s.
Existing Spillway Gates
EL.138.7m
New Spillway
Gates
New Spillway
Gates
CWL(WL.136.3m)
EL.131.0m
EL.127.0m
Main Reservoir
CWL(WL.136.3m)
EL.131.0m
EL.127.0m
Sediment Storage
Reservoir
Main Reservoir
Sediment Storage
Reservoir
WLM < CWL (=136.3m):
138.2m < WLM <SHF WL139.1m:
All spillway gates kept closed
Close New Spillway Gates and Open Existing Spillway Gates
（Priority in Storing Runoff in Wonogiri Main Reservoir）
(Qmax=400m3/s)
EL.138.7m
New Spillway
Gates
CWL1(WL.136.3m)
EL.131.0m
EL.127.0m
Main Reservoir
CWL1(WL.136.3m)
EL.131.0m
EL.127.0m
Sediment Storage
Reservoir
CWL(=136.3m)< WLM < 138.2m):
Releasing from New Spillway Gates
（Qmax=400m3/s)
New Spillway
Gates
EL.138.7m
Main Reservoir
Sediment Storage
Reservoir
SHF WL< WLM :
Three Gates Full Open and One Gate at 2.5m Opening)
Figure 4. Spillway Operation Concept
5. SEDIMENTATION
Measurement of sedimentation has been done several times since the dam was built by Gadjah
Mada University in 1985 and 1990, PBS (Bengawan Solo River Basin Development Project)
in 1986, 1987, and 1989. And the last is by PT. Mandala image Agritrans (PT. CMA) in
1993 and re-measurement in 2004 and 2005 by PBS.
4
Table 2. Reservoir capacity lost in 1980 and 1993
Reservoir
Capacity (106
m3)
Reservoir Zone
1980
Flood Control
Storage (El. 135.3 –
138.3 m)
Capacity Lost due to
Sedimentation
Value
2005
(10 m )
of Original
(%)
6
3
232
230
2
0.9
433
375
58
13.4
114
58
56
49.1
Water Use Storage
(El. 127.0 – 136.0
m)
Dead Storage
(below El. 127.0 m)
140
D.F.W.L 138.30 m
N.H.W.L 136.00 m
135
Control W.L 135.30 m
Elevation (EL.m)
2005
130
1993
L.W.L 127.00 m
125
1980
120
115
0
100
200
300
400
500
600
700
800
Storage Capacity (mil. m3)
Figure 5. Elevation-capacity curve in 1980, 1993 and 2005
6. STRUCTURE COUNTERMEASURES
6.1. NEW SPILLWAY
The spillway is used for discharging sediment and also flood control. The maximum outflow
should not be more than 400 m3/s to prevent flooding in the downstream. Sediment discharging
is more effective as the water depth is smaller or the surface gradient is steeper. Accordingly,
“400 m3/s under free flow condition” is the design requirement for the spillway. The spillway
gates are operated when the water level comes up to CWL EL. 136.3m for flood control. The
existing spillway gates will be opened and the spillway gates will be closed when the Wonogiri
main reservoir comes up to EL. 138.2 m (0.5 m below the top of the existing spillway gate). The
existing spillway discharges flood water for dam safety.
The control structure of the spillway is located at about 130 m upstream from the Wonogiri dam
axis on the right bank . It has 2 radial gates with 12.6 m height, 1,270 m3/sec capacity, 24.0 m
width, and 21.0 m length with the highest elevation is +142 m which is equal with dam crest
elevation or 1.9 m higher than PMF water level. The overflow crest is at +127.0 m.
5
6.2. CLOSURE DIKE
Closure dike consists of closure dike A of 700.0 m long, closure dike B of 700.0 m long and
closure dike C of 402.0 m long. Closure dike A with 298.0 m long overflow dike is placed at the
section between the dikes B and C. As described hereinafter, sediment deposit foundation of the
closure dike A is necessary to be stabilized by effective measures to get safety against possible
sliding failure and lateral movement to be caused by different water levels between Wonogiri
main reservoir and sediment storage reservoir and minimize settlement to be caused by weight
of the closure dike A.
Most part of the closure dike A of 700.0 m long is on the sediment deposit accumulated after the
reservoir impounding in 1980. The depth of the deposit is about 20 m at the deepest part.
Figure 6. Foundation Profile and Typical Section of Closure Dike
A 700.0 m long and closure dike B is connected with closure dike A. This dike axis is designed
on the consecutive ridge which separates Wonogori main reservoir and sediment storage
reservoir. Since the foundation of the dike is composed of comparatively hard and impervious
soil layers, the dike will be constructed with excavated materials from new spillway site or
proposed borrow pit. Before commencement of the dike embankment, top soil layer should be
removed to get well contact between the foundation soils and embankment materials.
A 402.0 m long closure dike have topographic and geologic conditions almost same as the
closure dike B.
6
6.3. OVERFLOW DIKE
The overflow dike is located between Closure Dike B and Closure Dike C . The overflow dike
is constructed to divert the water from the sediment storage reservoir to the Wonogiri main
reservoir for water storage. For wet season period, excess water above NHWL in the main
reservoir flows over the overflow dike toward the sediment storage reservoir. The water is used
for the sediment discharging operation in the sediment storage reservoir.
The overflow dike consists of overflow main body, apron, cut-off wall, retaining wall, scouring
protection and connection channel with a gate. The total length of the overflow dike is 298m.
The crest is at NHWL 137.0 m for the 250.0 m long. At each end side, a 24.0 m long transition
section with a slope of 1:10 from +137.0 m to +139.4 m is provided to connect the overflow
dike to the closing dike for having access for future maintenance.
There are 2 design flood for this structure, they are 1,260 m3/s for inflow into the sediment
storage reservoir only and 730 m3/s for inflow into the main reservoir only.`
PLATE NO. 120
50,000
41,772
14,000
103,774
31.416
31,416
R = 80.0 m
47,124
Plunge
Pool
EL.100.000
135
140
.500
EL.
145
er
117
ion
Stat
al
min e
Ter ctur
Stru
2.2
Pow
1:
No.
15
.000
150
2
165
142
10
1:
No.
ge
Sur k
Tan
.000
EL.
136
Acces to
Dam
160
1:
3.1
SPILL
WAY
EL.
155
X
st
Cre
21
11.7 38
20.0 23.1
= 50.1
n Cof
{Y=
fer
Dam
Mai
10
170
1
No.
.000
175
EL.
200
142
X
41
20.1 25
19.9 91.9 No.0
= 49.9
e
Gat ft
sha
5
{Y=
4
205
No.5
20
20 5
19 0
19 5
18 0
5
Acces to intake
180
185
Intake
No.10
Berm
Fore
bay
EL.128.000
EL.142.000
190
195
0
50
250
GOVERNMENT OF THE REPUBLIC OF INDONESIA
MINISTRY OF PUBLIC WORKS
DIRECTORATE GENERAL OF WATER RESOURCES
BALAI BESAR WILAYAH SUNGAI BENGAWAN SOLO
SNVT PELAKSANA PENGELOLAAN SUMBER DAYA AIR BENGAWAN SOLO
PENGENDALIAN BANJIR DAN PERBAIKAN SUNGAI II
500M
SCALE
Figure 7. Layout of the countermeasures
7. CONCLUSION
The conclusions of this paper are:
a) Effectiveness of these structure countermeasures is still unknown because its still on
construction stage.
b) There are some points that have to be rechecked based on Indonesia’s dam safety standards
such as loading conditions and PMP value.
c) Overview of the Emergency Action Plan have not been done.
7

DESIGN REHABILITATION OF WONOGIRI DAM, CENTRAL JAVA

Transcription

Similar documents

ContourGlobal acquires Fibrominn litter

Farmington River Watershed Reservoir Map

fabbriche di careggine, the ghost village buried

GWD1000W GWD1000BLS Water Dispenser

GWD860W-4 GWD860BLS-4 Water Dispenser

ross barnett reservoir hunting areas

GWD9500BLS GWD9500WS Water Dispensers

Building with Nature

GWD5440BLS GWD5440W Water Dispenser

WAC Bennett and Peace Canyon Dam Safety Projects