the comprehensive study on water resources development and

The Comprehensive Study on Water Resources Development and Management in Bali Province

Final Report – Main Report (II-4-30)

Buleleng

Karangase

Bangli

Klungkung

Gianyar

Badung

Denpasar

Tabanan

Jembrana

Paddy Area with Irrigation

Paddy Cropping more than twice covers 100% of paddy area.

2 Paddy Cropping does not extend to 100% of paddy area.

2 Paddy Cropping will cover all paddy area with Alternative 1 Plan.

2 Paddy Cropping will cover all paddy area with Alternative 2 Plan.

No Paddy Irrigation

Figure-II-4.19 Potential Area for Improvement of Crop Intensities 4.3 Dam Development Facility Plan

There are two multipurpose dam Projects that is Ayung Dam planned in Ayun River and Benel Dam planned in Aya Barat River in Bali Province. The Ayung dam (Buangga dam) Project was studied as one scheme in the hydroelectric power development projects by JICA. Detail design on Ayung dam with purpose of irrigation, water supply and power generation was carried out in 2002 by Indonesian Government. Benel dam project was planned for the purpose of irrigation and water supply and already took place in registration to National Development Plan (Blue Book). Review of detail design on Benel dam was carried out in 2004 by Indonesian Government.

4.3.1 Ayung Dam Development Plan

(1) General

Due to population growth, industrial developments and advanced urbanization in Southern Bali area (Badung Regency and Gianyar Regency), the water demand which target year of 2025 is projected to 6,050 l/sec in total, or 2.6 times of current demand. To fulfill the water demand of target year 2025, the development of water resources such as river water, springs and deep wells shall be required.

Judging from the remained water potential in future in Denpasar and its surrounding area, river water was recommended for the development method of water resources with comparing water sources such as springs and wells which were supposed to almost exhausted for production.

With aim at water supply for drinking water and irrigation water as well as river maintenance water, Ayung River was selected for the development river of water resources in feasible from the result of flow regime analysis. Ayung Dam project shall be situated for water resource as central water supply system. By using the differential head of water stored by reservoir of Ayung dam, electric power shall be generated.

Ayung River originated in Mt. Mangu (El. 2,020m), flows to the south direction and flows into Indian Sea going through the east of Denpasar City with it catchments area of 302 km2(based on GIS data) and river length about 62 km(based on GIS data).

The construction purpose of Ayung dam is shown as follows:

Development for Municipal Water 1,800 l/sec (155,500m3/day）



Water supply for the Irrigation Water and Unspecified River Maintenance Water Electric Power Generation (7,900 kW)

(2) Flow Characteristic and Water Use in Ayung River

There are two water level observation stations which are Sidang station and Buannga station observing for 14 yeas started from 1973 as shown in Table-II-4.21.

Table-II-4.21 Observation for Water Level Observation Stations in Ayung River

Name of Station Catchment’s

Area (km2)

Data 1970's 1980's 1990's 2000's

WL 1973-1979 1980-1986 N.A N.A Sidang 217.00 Q 1973-1979 1980-1986 N.A N.A WL 1973-1979 1980-1986 N.A N.A Buangga(Old) 178.80 Q 1973-1979 1980-1986 N.A N.A WL N.A N.A N.A 2000-2001Buangga(New) 178.80 Q N.A N.A N.A N.A

Note) WL: Water Level, Q: Discharge Based on the data arrangement of daily discharge at Buanngga stations which located near the proposed Ayung dam site, daily discharge and 15 days average discharge are shown in Figure-II-4.20. Regarding with tendency of discharge every rainy season and dry season for 14 years, discharge shows regular fluctuation, namely, with showing increase in rainy season and decrease in dry season. Minimum discharge during dry season shows from 5.0 to 7.0 m3/sec.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec1972 1973



0

5

10

15

20

Disch

arge

(m3/

s)

0

50

100

150

200

Rainf

all(m

m/d

ay)

0

5

10

15

20

Disch

arge

(m3/

s)

0

50

100

150

200

Rainf

all(m

m/d

ay)

0

5

10

15

20

Disch

arge

(m3/

s)

0

50

100

150

200

Rainf

all(m

m/d

ay)

Note) Red mark shows observed discharge.

Figure-II-4.20 Daily Discharge and 15 days Discharge at Buangga Station (1/2)







Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0

5

10

15

20

Disch

arge

(m3/

s)

0

50

100

150

200

Rain

fall(

mm

/day

)

0

5

10

15

20

Disch

arge

(m3/

s)

0

50

100

150

200

Rainf

all(m

m/d

ay)

0

5

10

15

20

Disch

arge

(m3/

s)

0

50

100

150

200

Rainf

all(m

m/d

ay)

0

5

10

15

20

25

Disch

arge

(m3/

s)

0

50

100

150

200

Rain

fall(

mm

/day

)

0

5

10

15

20

Disch

arge

(m3/

s)

0

50

100

150

200

Rain

fall(

mm

/day

)

Note) Red mark shows observed discharge.

Figure-II-4.20 Daily Discharge and 15 days Discharge at Buangga Station (2/2)

Flow regime at Buangga station is shown in Table-II-4.22, based on the analysis of discharge duration curve from 1973 to 1986 as shown in Figure-II-4.21.

Table-II-4.22 Flow Regime at Buangga Station in Ayung River (m3/s)

Max. 75-day (High)

185-day (Normal)

275-day (Low)

355-day (Droughty) Min. Remarks

22.55 10.47 8.98 8.01 7.18 6.58 Data 1973-1985



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80 90 100

Percent of Time(％)

Dai

ly D

isch

arge

(m3/

s)

1973 1974 1975 1976 1977 1978 1979 1980 19811982 1983 1984 1985

Figure-II-4.21 Discharge Duration Curve at Buangga Station (1973-1985) Current state of water use for irrigation water and municipal water is shown in Table-II-4.23. There are 6 weirs for irrigation with total irrigated area 8,800 ha and 2 weirs for municipal with total 1,350 l/sec along Ayung River.

Table-II-4.23 Existing Weirs for Water Use along Ayung River Name of Facilities Purpose Remarks

1)GERANA Irrigation Area:997ha (for Badung Regency) 2)SENGENPEL Irrigation Area:47ha (for Badung Regency) 3)KEDEWATAN Irrigation Area: 3,334 ha (for Badung Regency,Denpasar City,Ginyar

Regency) 4)MAMBAL Irrigation Ares:3,628ha(for Badung Regency, Denpasar City) 5)PERAUPAN Irrigation Area:25ha(for Denpasar City) 6)IPA AYUNG Municipal Intake Rate:1,050 1/s

(for Badung Regency, Denpasar City)

7)OONGAN Irrigation Area:781ha(for Denpasar City 8)WARRIBANG Municipal Intake Rate:150 1/s (Plan 300 l/s) Total Irrigated Area:8,812 ha (Excluding GERANA 7,815 ha)

Intake Rate: 1,350 1/s (Excluding Plan WARIBANG: 1,200 l/s) The location of weirs as mentioned above Table is shown in Figure-II-4.22.



Ayung Dam

Sengempel(47ha)

Kedewatan (3,334ha)

Mambal(3,628ha)

Peraupan(40ha)

IPA Ayung I,II,III (1,050 l/sec)

Oongan(781ha)

IPA Warribang (300 l/sec)

Figure-II-4.22 Existing Weirs along Ayung River (3) Methodology for Water Resources Development in Ayung River

Basic Policy for the development of water resources depending on Ayung dam reservoir is summarized as follows:

◆ For the municipal water supply, to cope with increasing of demand targeted 2025 in Denpasar urban area, water of 1,800 l/sec shall be developed. Water supply plan was aimed at probability with 1 year for ten yeas during dry season.

◆ For the irrigation water supply, to keep up current cropping pattern in irrigated area, unspecified water shall be developed. Water supply plan was aimed at probability 1 year for 5 yeas. Cultivation area of paddy from single cropping to double cropping shall be expanded even during the drought season for the purpose of income increase.

◆ For the electric generation, by using the differential head of water stored in Ayung reservoir, electric power of 7,900 kW shall be generated for the purpose of contribution for electric demand in Bali.

◆ For the environmental maintenance water of river, by outflow discharge stored by Ayung dam, existing habitat for fauna and flora as well as natural landscape shall be conserved or improved. In the river flowing to Denpasar City, water quality shall be improved due to the water conveyance of purification water developed by dam reservoir.

(4) Calculation for Water Use Capacity

(a) Water Use Calculation Model

Water use calculation on capacity for municipal water and unspecified water such as river maintenance water and purification shall be proceeded in accordance with calculation flow as shown below:



Ayung Dam（A1） Area1= 217.0 Km2

Din Dam Inflow

Ayung Dam Reservoir

1 Dam Outflow

A2= 13.0 Km2 Remains CA （A2） Remains Discharge＝90%xDinx(A2/A1)

Irrigation（Badung:100%） ← 2 Weir Sengenpl (47 ha)

A3= 1.2 Km2 Remains CA（A3） Remains Discharge＝90%xDinx(A3/A1)

Weir Kedewatan (3,334 ha) 3 → Irrigation（Badung:72%, Gianyar:28%）


Irrigation（Badung:78%, denpasar:22%） New Irrigation supply （1 cultivation for Paddy ）

← ← 4 Weir Mambal (3,628 ha)


Irrigation（Denpasar: 100%） Vested water for drinking

New Water Supply

← ← ←

5 Weir Peraupang (25 ha) WTP（IPA Ayung：1,050 lit/s) Intake for New Water Supply


Irrigation（Denpasar: 100%） ← 6 Weir Oongang (781 ha)


River Maintenance ← 7 Weir （IPA Waribang：300 l/s +400l/s)


8 River Mouth (Ayung River)

① D isch arg e a t D am S ite

② C alcu la tion for D i k i

③ D isch arg e C a lcu la tion

④ D isch a rge B a la nce ＝ ③ - ②

P roced u res

④ ： 0

⑤ S u p p ly ⑥ S tored in R es .(=④ )

⑦ B a la n ce for D d

⑧ R eq uired C ap a city C alcu lation

Figure-II-4.23 Calculation Flow for Municipal Water and Unspecified Water

(b) Conditions for Calculation

Conditions for calculation of capacity are shown in Table-II-4.24.

Table-II-4.24 Conditions for Calculation Items Contents Remarks

Duration 1972～1986 15 years Discharge Unit 5 days discharge

Intake Rate for Irrigation Unit Intake Rate per Ha × Area Rainy season: 300-4,700l/s in total Dry season : 4,200-12,000l/s in total

Depend on cropping pattern

Intake Rate for Current Drinking Water 1,350 lit/sec

Water Treatment Plant IPA AYUNG ;1,050 lit/s

IPA WARIBANG; 300 lit/s New Intake Rate for Municipal Water 1,800 lit/sec At Praupan New Intake Rate for River Maintenance Max. 400 lit/sec At Wariban



(c) Requirement Capacity Based on the Calculation Results

Calculation result for the requirement of each capacity is as shown in Table-II-4.25.

Table-II-4.25 Requirement Capacity Based on the Calculation Results Ranking Required Capacity (x 1,000m3) Year Occurred

1 15,000 1977 2(adopted) 9,000 1983

3 8,400 1985 4 5,300 1980 5 2,200 1982

On the basis of the calculation results of requirement capacity, the second capacity with 9,000,000m3 for 15 years shall be adopted in consideration of safety for water supply, reservoir scale and frequency of drought occurrence, etc.

0 .00

1 .00

2 .00

3 .00

4 .00

5 .00

6 .00

7 .00

8 .00

9 .00

10 .00

11 .00

12 .00

13 .00

14 .00

15 .00

16 .00

17 .00

18 .00

19 .00

20 .00

1 7 3 1 4 5 2 1 7 2 8 9 3 6 1 4 3 3 5 0 5 5 7 7 6 4 9 7 2 1 7 9 3 8 6 5 9 3 7 1 0 0 9

Figure-II-4.24 Calculation Result of Requirement Capacity for Ayung Dam

mil. m3



(5) Ayung Dam Reservoir Operation

A reservoir operation simulation which shows reservoir water level at Ayung reservoir, river in-flow and out-flows at weir along Ayung River in benchmark year of 1983 is shown in Figure-II-4.25 and Figure-II-4.26. According to the Figures, due to supply by outflow of Ayung dam, river discharge after reservoir operation exceed to water requirement for irrigation and municipal water at each weir.

DAM AND RESERVOIR

-10.00-9.00-8.00-7.00-6.00-5.00-4.00-3.00-2.00-1.000.00

1 2 3 4 5 6 7 8 9 10 11 12M ONT H

DIS

CH

AR

GE

(106 M

3 /S)

Res . V ol.

KEDEW ATAN 1 98 3

0.001.002.003.004.005.00

6.007.008.009.00

10.00

1 2 3 4 5 6 7 8 9 10 11 12

M ONT H

DIS

CH

AR

GE

(M3 /S

)

Q-In

W /Us e

MAMBAL 1983

0.001.00

2.003.00

4.005.006.00

7.008.00

9.0010.00

1 2 3 4 5 6 7 8 9 10 11 12

M ONTH

DIS

CH

AR

GE

(M3 /S

)

Q-In

W/Use

Figure-II-4.25 Simulation Results at Ayung Dam, Kedewatan Weir, Mambal Weir



PERAUPAN 1983

0.001.002.00

3.004.005.006.007.00

8.009.00

10.00

1 2 3 4 5 6 7 8 9 10 11 12

MONTH

DIS

CH

AR

GE

(M3 /S

)

Q-In

W/Use

OONGAN 1983

0.000.501.001.502.002.50

3.003.504.004.505.00

1 2 3 4 5 6 7 8 9 10 11 12

MONTH

DIS

CH

AR

GE

(M3 /S

)

Q-In

W/Use

IPA WARIBANG 1983

0.000.501.00

1.502.002.503.003.50

4.004.505.00

1 2 3 4 5 6 7 8 9 10 11 12

MONTH

DIS

CH

AR

GE

(M3 /S

)

Q-In

W/Use

Figure-II-4.26 Reservoir Operation Simulation Results at Puraupan Weir, Oongan Weir, Waribang Weir



(6) Requirement Capacity for Water Use of Ayung Dam

Above mentioned consideration results, requirement capacity for water use of Ayung dam shall be set up to 9,000,000 m3.

(7) Sediment

(a) Design Sediment Capacity in Bali

Based on the existing report concerning with design sediment volume of dams in Bali, Specific sediment volume per year is arranged as shown in Table-II-4.26. There are two kinds of data for Ayung dam, that is, study result of JICA Study Team in 1989 and study result of Indonesian government in 2002.

Table-II-4.26 Specific Sediment Volume for Each Dam in Bali Name of

Dams

Catchment Area

（Km2）

Design Sediment Capacity (10 x 3)

Specific Sediment Volume

(m3/km2)

Working Life

(years)

Specific Sediment Volume per year(m3/km2/year)

Remarks

Ayung(1) 217.0 8,800 40,550 50 811 Planned ,JICA 1989 Ayung(2) 218.4 5,924 27,120 65 417 Planned Indonesia (2002)Titab 69.5 1,090 15,680 100 157 Planned Telaga Tunjung 81.5 522 60 50 128 Under construction

(as of 2005) Bunel 18.3 305 16,670 30 556 Planned Palasari 42.3 1,500 35,460 50 710 In operation Grokgak 20.0 1,250 62,500 50 1,250 In operation Average - - - - 575 In operation

Sources: 1. Feasibility Study on Ayung Hydroelectric Power Development Project (1989) 2. Detail Desain Waduk ayung Di kabupaten Badung(2002) 3. Kajian dan Perubahan Desain Bendungan Telaga Tunjung(2004)

According to Table-II-4.26, design specific sediment volume per year discharge varies from 128 to 1,250. For Palasari dam and Grokgak dam, there was no data for the actual sediment accumulation since in operation.

(8) Design Sediment Capacity for Ayung Dam

With reference to design sediment capacity for Ayung dam, based on the detail design of Ayung dam in 2002 as shown in Table-II-4.27, specific sediment volume per year was set up as 417m3/km2/year. As compared Ayung dam with another dam in Bali, this value is classified as average.

Design sediment capacity for 50 working life is calculated as shown in below:

417 m3/km2/year × 218.4 km2 × 50 years = 4,553,640 m3 = 4,600,000 m3

In consideration of the relationship between possible dam height and reservoir volume, design sediment capacity for Ayung dam shall be secured by dividing into capacity with 1,000,000m3 stored in reservoir and capacity with 3,600,000 m3 stored or controlled by check dams constructed at upstream in Ayung River and Siap River.

Table-II-4.27 Design Sediment Capacity for Ayung Dam and Check Dams Method of

Secure Sediment Capacity

for Facility Planned Location of Facility

Reservoir 1,000,000 Ayung Dam Reservoir

2 Check Dams 3,600,000 Near upstream edge of reservoir located in Ayung River and Siap River

(9) Storage Capacity Distribution

Due to above mentioned study results storage capacity distribution is shown in Table-II-4.28. Normal water level and low water level were fixed from accumulated capacity of each purpose by using reservoir capacity curve as shown in Figure-II-4.27, are also shown in Table-II-4.28.



Table-II-4.28 Design Capacity Distribution for Ayung Dam Purpose Capacity(m3) Water level Remaarks Effective Capacity 1) Municipal 2) Irrigation 3)River Maintenance

9,000,000

Normal Water Level EL 366.0 m (Capacity of 10,000,000 m3)

Drinking:1,800 l/s Irrigation:：7,720ha Cultivated Area Expansion:1,000 ha

Sediment Capacity 1,000,000 Low Water Level EL 325.0 m

For 10 years

Total 10,000,000 -

250

300

350

400

450

0 5000 10000 15000 20000 25000 30000 35000 40000

Storage-capacity（103m3）

Elev

atio

n（EL

.m）

EL366m

10000 103m3

Elevation W atere surface areaHi Ai Vi =(Ai+Ai-1)*(Hi-Hi-1)/2 ∑Vi

(Elm) (m2) (m3) (103 m3)1 290 6,949 02 300 15,652 113,005 1133 310 28,852 222,520 3364 320 48,589 387,205 7235 330 81,006 647,975 1,3716 340 137,643 1,093,245 2,4647 350 229,470 1,835,565 4,3008 360 386,546 3,080,080 7,3809 370 565,700 4,761,230 12,141

10 380 772,953 6,693,265 18,83411 390 930,870 8,519,115 27,35312 400 1,116,508 10,236,890 37,590

Storage-capacityi

Normal Water Level: EL 366.0 m (Accumulated Capacity 10,000,000 m3)Low Water Level : EL 325.0 m (Accumulated Capacity 1,000,000m3)

Figure-II-4.27 Reservoir Capacity Curve for Ayung Dam (10) Existing Geological Survey

The Ayung dam (Buangga dam) was studied feasibility as one scheme in the hydroelectric power development projects by Jica in 1989, when core-drilling, seismic refraction prospecting and laboratory tests were carried out. In the study, two alternative dam sites, the upstream site for a concrete gravity dam of 40 m in height and the downstream site for a rock fill dam of 100 m in height were compared. Additional geological investigation including core-drilling, electric resistance prospecting and laboratory tests were executed at the downstream site by PKSA in 2003, and a concrete gravity dam of 100 m in height was designed. Quantities of the existing survey carried out in Buangga dam (Ayung dam) are listed in Table-II-4.29.



Table-II-4.29 Existing Geological Survey Survey Item Quantities Executing Body Remarks

Feasibility study on Ayung Hydroelectric Power Development Project (1989) Mapping 20 ha, 1:1000 in scale PLN upstream & downstream site Core drilling 4 holes, total 362 m PLN upstream & downstream site Seismic refraction prospecting 6 lines, total 2310 m JICA upstream & downstream site Laboratory test upstream & downstream site Detail Design Ayung Multipurpose Dam, Payangan & Buangga - Bali (2003) Core drilling 5 holes, total 480 m PKSA downstream site Electric resistance prospecting 20 points PKSA downstream site Test pit 4 pits PKSA downstream site Trench cut 4 points PKSA downstream site Laboratory test PKSA downstream site

(11) Selection of Dam Site

(a) Alternatives for Planned Dam Site

Three alternative dam sites of more than 10 M m3 in storage capacity were proposed on the Ayung River from the confluence of the Ayung River and Pungsa River to its approximately 3 km downstream in the preliminary study based on 1:25,000 scale topographic maps. The three sites, A, B and C in sequence from the upstream, were compared through the follow-up site investigations (See Figure-II-4.28).

(b) Selection of Dam Site for Ayung Dam

C site is excluded due to its unsuitable social environmental impact, since the right bank of the C site was extensively developed for new hotel buildings. Although no significant differences between A site and B site in topographic feature and economical efficiency, the plan of A site can minimize impacts of commercial rafting and has advantages of available topographic maps and geological data. A Chinese cemetery located on the left bank of A site is avoidable by the layout design of the proposed dam. Consequently A site has been selected as the optimum site. The summary of the comparison is presented in Figure-II-4.28.

A site

B site

C site

A site

B site

C site

Ayung River, forming

120 hi h V h

A building on the right

b k f C it

0 0.5 1 km

N

Figure-II-4.28 Location Map of Alternative Dam Sites


Final Report – Main Report(II-4-42)

Tabl

e-II

-4.3

0 Su

mm

ary

of P

lann

ed A

ltern

ativ

e D

am S

ite E

valu

atio

n

Not

e: E

valu

atio

n F:

fair,

P: p

oor o

r not

reco

mm

ende

d, U

: uns

uita

ble

Alte

rnat

ive

Dam

Si

te

A S

ite

B S

ite

C S

ite

Sc

hem

atic

Pro

file

of d

am a

xis

Dam

Des

ign

Stor

age

Cap

acity

10,0

00,0

00 m

3 Ef

fect

ive

Stor

age

Cap

acity

9,0

00,0

00 m

3 Se

dim

ent C

apac

ity

1,0

00,0

00 m

3 N

orm

al W

ater

Lev

el

36

6.00

m

Dam

Top

Lev

el

37

1.00

m

Foun

datio

n Le

vel

30

5.00

m

Dam

Hei

ght

66

m (o

n th

e pl

ug o

f 30

m h

igh)

Stor

age

Cap

acity

10,0

00,0

00 m

3 Ef

fect

ive

Stor

age

Cap

acity

9,0

00,0

00 m

3 Se

dim

ent C

apac

ity

1,0

00,0

00 m

3 N

orm

al W

ater

Lev

el

34

1.00

m

Dam

Top

Lev

el

34

6.00

m

Foun

datio

n Le

vel

27

9.00

m

Dam

Hei

ght

67

m (o

n th

e pl

ug o

f 30

m h

igh)

Stor

age

Cap

acity

10,0

00,0

00 m

3 Ef

fect

ive

Stor

age

Cap

acity

9,0

00,0

00 m

3 Se

dim

ent C

apac

ity

1,0

00,0

00 m

3 N

orm

al W

ater

Lev

el

31

0.00

m

Dam

Top

Lev

el

31

5.00

m

Foun

datio

n Le

vel

26

3.00

m

Dam

Hei

ght

52

m (o

n th

e pl

ug o

f 30

m h

igh)

Topo

logy

/Geo

logy

EL. 3

90 m

~ <

20°,

EL. 3

40-3

90 m

30

-40°

EL

. 280

m-3

40 m

50-

60°,

Riv

erbe

d 2

0 m

wid

e B

edro

ck: W

elde

d tu

ff: C

H~C

M c

lass

Tu

ff br

ecci

a: C

L~C

M c

lass

R

iver

bed:

sand

and

gra

vel w

ithin

5 m

thic

k A

bur

ied

valle

y of

old

Ayu

ng R

iver

is a

ssum

ed.

F

EL. 3

90 m

~ <

20°,

EL. 3

00-3

90 m

30

-40°

EL

. 270

m-3

00 m

50-

60°,

Riv

erbe

d 20

m w

ide

Bed

rock

: Wel

ded

tuff:

CH

~CM

cla

ss

Tuff

brec

cia:

CL~

CM

cla

ss

Riv

erbe

d: sa

nd a

nd g

rave

l with

in 5

m th

ick

A b

urie

d va

lley

of o

ld A

yung

Riv

er is

ass

umed

.

F

EL. 3

50 m

~ <

20°,

EL. 3

00-3

50 m

30-

40° (

right

ba

nk:

EL.3

20 m

~ 20

-30°

), EL

. 25

0 m

-300

m

45-5

0°, R

iver

bed

20 m

wid

e B

edro

ck: W

elde

d tu

ff: C

H~C

M c

lass

Tu

ff br

ecci

a: C

L~C

M c

lass

R

iver

bed:

sand

and

gra

vel w

ithin

5 m

thic

k A

bur

ied

valle

y of

old

Ayu

ng R

iver

is a

ssum

ed.

F

Soci

al A

spec

ts

No

resi

denc

e in

pro

pose

d re

serv

oir a

rea

Com

mer

cial

rafti

ng

Chi

nese

Cem

eter

y on

the

left

bank

F~ P

No

resi

denc

e in

pro

pose

d re

serv

oir a

rea

A s

tart

poin

t o

f com

mer

cial

rafti

ng a

nd s

ome

faci

litie

s

F~ P B

uild

ings

of h

otel

on

the

left

bank

C

omm

erci

al ra

fting

U

Avai

labl

e Su

rvey

D

ata

Topo

grap

hic

map

(1:

5,00

0), 5

dril

ling

hole

s（48

0 m）

, 1 se

ism

ic li

ne (5

00 m

) and

labo

rato

ry te

sts e

tc.

FN

one

P N

one

P

Con

clus

ion

F F~

P U

Riv

er d

epos

it Vo

lcan

ic a

sh

Tuff

Bre

ccia

W

elde

d tu

ff O

ld ri

ver d

epos

itTu

ff br

ecci

a Ex

istin

g bo

reho

le

400m

300m

200m

EL.3

71m

EL.3

66m

?

Riv

er d

epos

it Vo

lcan

ic a

sh

Tuff

Bre

ccia

W

elde

d tu

ff O

ld ri

ver d

epos

itTu

ff br

ecci

a

Volc

anic

bre

ccia

400m

300m

200m

EL.3

46m

EL.3

41m

200m40

0m

300m

Riv

er d

epos

it

Tuff

Bre

ccia

W

elde

d tu

ff O

ld ri

ver d

epos

it Tu

ff br

ecci

a

Bui

ldin

g (u

nder

con

stru

ctio

n)

Volc

anic

ash

?

EL.3

15m

EL.3

10m



(12) Topographic and Geological Outlines

(a) Topography

The Ayung River, forming a deep valley at the project area, runs southward. The Pungsa River flows into the Ayung River at approximately 400 m upstream of the proposed dam site. The riverbed with 20 m in width is at an elevation of approximately 280 m at the proposed dam site and rises up to the tableland gently dipping southward of approximately 420 m in elevation. The inclinations of the both banks of 280-340 m, 340-390 m and 390-420 m in elevation are 50-60 degrees, 30-40 degrees and 20 degrees respectively.

Proposed

Figure-II-4.29 Proposed of Dam Site

(b) Geology

According to the previous study, the basement of the site is tuff breccia with gravel, volcanic breccia and volcanic sandstone. The welded tuff flowed and deposited along the present river course. The welded tuff is well cemented and forms 10-20 high cliffs along the river. On the both banks of the river the welded tuff is overlain by thick layers of pumiceous tuff and volcanic ash. Pumiceous tuff and volcanic ash are moderately soft and easily eroded and small gullies are formed on the relatively gentle slopes of 340-390 m in elevation at the proposed dam site. Talus deposits, less than 2 m in thickness, are composed of sandy clay including some pumiceous fragments. River deposits, less than 5 m in thickness, are composed mainly of sand including some pebbles.



Figure-II- 4.30 Geological Map of Ayung Dam Reservoir Area (Source: JICA Study Team)

The following development process inferred from the review of the previous study.

The stratigraphy of the Ayung dam site is shown in Table-II-4.31

River deposit Volcanic ash Tuff Breccia Welded tuff Old river depositTuff breccia

River

d iVolcanic ash Tuff Breccia Welded tuff Old river depositTuff breccia

River deposit Volcanic ash Tuff Breccia Welded tuff Old river depositTuff breccia

Weathered zone 1. Pleistocene (~approx. 20,000 years ago) Old river valley was underlain by tuff breccia (including lahar deposit and tuff facies). Surface of the tuff breccia was weathered and softened.

2. Approx. 20,000 years ago Welded tuff and pumiceous tuff breccia covered the old valley.

3. Recent event Volcanic ash covered the surface, and the plateau composed of welded tuff and pumiceous tuff breccia was deeply dissected by the recent river valley.



Tabl

e-II

-4.3

1 St

ratig

raph

y of

Pro

pose

d Ay

ung

Dam

Site

C

hara

cter

istic

s*

Sche

mat

ic P

rofil

e G

eolo

gy

hard

ness

V

p (k

m/s

)N

va

lue

Γt

(t/m

3 )σ c

(t/m

2 ) Es

(t/

m2 )

k (c

m/s

)

Thi

ck-

Nes

s (m

) R

iver

dep

osit:

G

rey,

sand

and

gra

vel

Loos

e

<5

Talu

s dep

osit:

Li

ght b

row

n so

ft gr

avel

s, sa

nd a

nd

clay

.

Loos

e

<2

Volc

anic

ash

:

Bro

wn

loam

, an

d lig

ht-b

row

n pu

mic

e

Very

So

ft,

rela

tivel

y co

mpa

ct a

nd

stab

le

0.3~

0.5

5~10

1.4

3 3

1~

2

Pum

iceo

us tu

ff b

recc

ia:

gr

ey

to

light

gr

ey,

incl

udin

g pu

mic

es,

ande

site

, vo

lcan

ic

detri

tus

and

volc

anic

bom

b, a

nd

sand

y tu

ff m

atrix

Soft

－m

oder

atel

y ha

rd

0.7~

0.8,

50<

1.5~

2

2,

30+/

-

Wel

ded

tuff

:

Gre

y to

pur

plis

h gr

ey,

incl

udin

g w

elde

d pu

mic

e fr

agm

ents

(0.

5 cm

th

ick,

2-

3 cm

lo

ng),

Verti

cally

va

riabl

e fa

cies

and

har

dnes

s. Lo

w

cem

ente

d w

elde

d tu

ff,

Hig

h-ce

men

ted

wel

ded

tuff,

Lap

pli

tuff

of

sand

y tu

ff m

atrix

, an

d an

dest

ic f

acie

s (a

t so

me

plac

es)

occu

r in

desc

enda

nt o

rder

.

Har

d－

mod

erat

ely

hard

1.4~

1.6

3.2~

3.5

1.

8 2.

0 50

~80 10

0~12

0

8 20

30

+/-

Old

riv

er d

epos

it:

Gre

y, c

laye

y(?)

san

d w

ith c

obbl

es

of a

ndes

ite

(Loo

se?)

20

Tuff

br

ecci

a:

Yello

w b

row

n to

blu

ish-

grey

col

or,

the

brec

cias

co

nsis

ts

mai

nly

of

angu

lar

to s

ubro

unde

d fr

agm

ents

of

2 to

10

cm d

ia.

Mod

erat

ely

soft

40<

Sour

ce: J

ICA

198

9 Fe

asib

ility

stud

y on

Ayu

ng H

ydro

elec

tric

Pow

er D

evel

opm

ent P

roje

ct.

The

abo

ve e

ngin

eerin

g pr

oper

ties w

ill b

e re

vise

d in

the

cour

se o

f the

stud

y (P

hase

3 st

udy)

.

EL.30

0m

EL.40

0m

EL.35

0m

EL.25

0m

Volcanic ash

Pumiceous

Tuff breccia

(D~CL class)

Pumiceous Tuff

breccia (CL~CM

class)

Tuff breccia

(CL~D class)

Welded

tuff

(CM~CH class)

Probable

Ol

d river

deposits

River depositTalus

deposit

Buried

valley

Volc

anic

ash

(D)

Pum

iceo

us tu

ff br

ecci

a（C

L）

Wel

ded

tuff

(CM

)

Wel

ded

tuff

(CH

)



(c) Geological Engineering Specifications

Rock Condition

The bedrocks of the proposed dam site are composed of welded tuff classified into CH-CM class and tuff breccia classified into CL-CM class on the basis of a criteria developed by CRIEP (Tanaka, 1964) (See Figure-II-4.31). Expected shear strength of each rock class is as follows: CH class：τ0＝160 tf/m2 CM class：τ0＝ 80 tf/m2 CL class：τ0＝ 40 tf/m2

These engineering properties were estimated based on limited data of laboratory tests and naked observations of surface geological conditions. The above rock classification and engineering properties will be revised in the course of the geological investigation. In-situ rock tests will be necessary to determine engineering properties in the detailed design study.

Dam Top Level EL 370 m

Expected

Excavation line

Figure-II-4.31 Geological Profile of Proposed Dam Axis

Permeability

According to previous study, permeability coefficient of the bedrocks shows the order of 10-5 to 10-4

cm/s. Permeability of the dam site and ground water condition will be studied in the Phase 3 study. The Siap River, a main turbidity of the Ayung River, flows together at approximately 400 m upstream of the proposed dam site. The reservoir area forms a V-shaped and relatively straight valley extending N-S. Leakage risk of the reservoir and potential of landslides will be studied in Feasibility Study phase.

(13) Construction Materials

In the previous study (JICA1989), two alternative quarry sites, Bt. Payang site and Baturiti site, were proposed within 20 km from the proposed dam site (See Figure-II-4.32). Two core drillings were carried out in each quarry site. Bt. Payang site and Baturiti site were environmentally unsuitable for exploitation of construction material resources based on field investigations in this phase, since either site was located in vicinity of residences and religious facilities.

River deposits of the Ayung River are insufficient in quantity for the material resources. Although usable sound rocks forming 20 m high cliffs occur along the riverbed, the exploitation for the quarry of reservoir area is economically handicapped, since 70-80 m thick soil covering the rocks has to be removed and considerable low-quality portions were contained in the sound rocks.

Dam Top Level EL 370m



Procurement of the rock materials for the rock fill type dam of 100 m high is difficult in economical and environmental aspects. At the present moment, Karangasum site and Semarapuna site, which are located in approximately 60 km and 40 km from the dam site respectively, are economically considerable for material resources. A concrete gravity type dam is recommendable for the Ayung dam site in aspect of construction material procurement, since its required construction materials will be almost one to ten of required for rock fill type of same height and the transportation cost will be reduced.

(14) Comparison of Dam Type

Concrete gravity dam is applied by the following reasons.

Dam height can be reduced to below than 70 m by applying artificial foundation method. CH class foundation, which is dominant in the dam site, is suitable for concrete dam less than 70 m heights.

Concrete gravity dam is more efficient water storage than that of rock-fill dam, and easy to install spillway and decelerating works.

For the above reason, dam height of rock-fill dam becomes higher than concrete gravity dam to keep same storage capacity. Therefore, concrete gravity dam is less required land.

Concrete gravity dam is easy to acquire materials Concrete dam is superior to rock-fill dam in the financial aspect as shown in Table-II-4.32.

Comparison between concrete gravity dam and zoned rock-fill dam is shown in Table-II-4.32. Typical sections of concrete gravity dam, typical longitudinal section of zoned rock-fill dam and typical cross section of artificial foundation are shown in Figure-II-4.33 to Figure-II-4.35, respectively.

Table-II-4.32 Comparison between Concrete Gravity Dam and Zoned Rock-fill Dam Dam Type Concrete Gravity Dam Zoned Rock-fill Dam

Specifications

Dam height 66.0m Non overflow section elevation EL.371.0mCrest elevation EL.371.0mFoundation elevation EL.305.0mCrest length 235.0m Crest width 5.00m Dam volume 296,000m3 Min. water level EL.325.0mFull reservoir water level EL.366.0mSurcharge water level EL.366.0mDesign flood water level EL.369.0mReservoir area 0.49km2

Dam height 67.0m Non overflow section elevation EL.372.0mCrest elevation EL.372.0mFoundation elevation EL.305.0mCrest length 235.0m Crest width 10.00m Dam volume 1,500,000m3

Min. water level EL.325.0mFull reservoir water level EL.366.0mSurcharge water level EL.366.0mDesign flood water level EL.369.0mReservoir area 0.49km2

Cost JPY 10.6 billion (100%) JPY 12.6 billion (119%) (1) Construction of concrete dam is available according to the topographical and geological

condition of the site. (2) Concrete dam is easy to layout facilities such as spillway and decelerating works. (3) Scale of dam can be reduced by concrete dam. (4) Concrete dam is easy to acquire materials (5) For above reasons, concrete dam is superior to rock-fill dam in economical and

technical aspects.

Overall Evaluation

○ ×



Figu

re-I

I-4.

32 L

ocat

ion

Map

of A

ltern

ativ

e C

onst

ruct

ion

Mat

eria

l Sou

rces

prop

osed

Ayun

g D

am si

te

Bt.P

ayun

g B

atur

iti

Kar

anga

sem

site

Sem

ara p

ura

site

(Und

a R

iver

)

Alte

rnat

ive

Bor

row

are

a K

aran

gase

m

site

Se

mar

apur

a si

te

Bt.

Payu

ng

site

B

atur

iti si

te

Type

of e

xtra

ctio

nFa

n de

posi

t Fa

n de

posi

t R

ock

quar

ryR

ock

quar

ry

Mat

eria

l Sa

nd a

nd

grav

el

Sand

and

gr

avel

C

ongl

omer

ate,

dol

erite

an

desi

te

Tran

spor

tatio

n di

stan

ce (k

m)

36

60+

7 16

Estim

ated

O

btai

nabl

e qu

ality

(106 m

3 ) in

defin

ite

inde

finite

42

1.

7

Site

con

ditio

n fa

ir fa

ir re

side

nce,

te

mpl

es

resi

denc

es,

tem

ples

C

oncl

usio

n fa

ir fa

ir un

suita

ble

unsu

itabl

e

Prop

osed

Ayu

ng D

am S

ite



Figure-II-4.33 Typical Sections of Concrete Gravity Dam

Figure-II-4.34 Typical Cross Section of Zoned Rock-fill Dam



Figure-II-4.35 Typical Cross Section of Artificial Foundation (15) Preliminary Power Generation Plan

Based on the dam specifications such as normal water level, location of pipeline and electric power plant, river water level, power generation plan by Ayung dam was studied as shown in following condition:

Intake water level was set up as 365m in elevation Tail water level was set up as 283m in elevation by taking into account with riverbed elevation,

river width, basement level of power plan. Turbine discharge for power generation was set up as 13 m3/sec based on the 2 times from the

average minimum discharge 6.5 m3/s by taking into consideration of efficiency of hydraulic turbine and generator.

Specifications for power generation are shown in Table-II-4.33

Table-II-4.33 Specifications for Power Generation of Ayung Dan Items Specifications Explanations

Generation Method Dependent for Outflow No capacity for power genaration Intake water level EL 366 m Normal water level Tail water level EL 285 m Setting up from river bed level Total head (Max.) 81.0 m =Intake-Tail = EL366m-285m = 81 m Effective head (Max.) 72.9 m =Total head×0.9=72.9m Total head (regular) 60.0 m =(NWL+LWL)-intake= EL345m –285m = 60 m Effective head(regural) 54.0 m =Total×0.9=54.0m Max. discharge 13.0 m3/s Min. discharge 6.5 m3/s

Max. Power 7.6 Mw P= 9.8 ×Head × Discharge × Efficiency(0.82)= 9.8× 72.9m × 13.0 × 0.82 = 7,615 Kw

Regular power 1.9 Mw = 9.8 ×Head × Discharge × E(0.50)= 9.8× 60.0m × 6.5 × 0.50 = 1,910 Kw

Electric Energy (Year) 41,610 Mwh =(Max.+Regular)/2 ×24 × 365 =(7.6+1.9)/2× 8,760 = 41, 610 MWh

(16) Drawings

Drawings of Ayung dam are shown in Figure-II-4.36–Figure-II-4.39.

Artificial PlugDam Basement



EXISTING ROAD

BUANGGA

APPROACH ROAD

APPROACH ROAD

DAM

MELINGGIH

EXISTING ROAD

DAM OVERALL PLAN DRAWINGSCALE 1:10000

RESERVOIR

Figure-II-4.36 Plan of Reservoir of Ayung Dam



S p illw ay

S p il lw ay B a sin

E le c tric P ow e r P la n

B

B

A

A

A x is o f D a m

C o n du it

R oa d w ay o f D am

D ive rs ion o f R ive r

A -A S EC T IO NSca le 1 :15 0

S T A N D A R D S E C T IO N O F S T IL LIN G W O R K

A -A S E C TIO NSc ale 1 :30 0

D IVE R T IO N S EC T IO N

D A M P LA N S C A LE 1 :1 00

U p S tre a m C offre rda m

Figure-II-4.37 Plan of Ayung Dam

Figure-II-4.38 Typical Section of Ayung Dam



DOWNSTREAM VIEW

SPILLWAY

STILLING BASIN

ARTIFICIAL POUNDATION CONCRETE

DAM FOUNDATION LEVEL

UPSTREAM VIEW

NWL

DAM FOUNDATION LEVEL

ARTIFICIAL POUNDATION CONCRETE

SCALE 1:1500

Figure-II-4.39 Upstream and Downstream Section of Ayung Dam

the comprehensive study on water resources development and

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