tarbela dam

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 Tarbela Dam (Urdu: ب لیرب ت ) is a dam on the Indus River in Pakistan.It is located 50 kilometers North-West of Islamabad near the Haripur District. It is the largest earth filled dam in the world and it produces much of Pakistan's hydroelectricity . T arbela Dam is part of the Indus Basin Project, which resulted from a water treaty signed in 1960 between India and Pakistan, guaranting Pakistan water supplies independent of upstream control by India. Construction began in 1968, and continued until completion in 1976. The dam has a volume of 138,600,000 cubic yards (106,000,000 m³). With a reservoir capacity of 11,098,000 acre-feet (13.69 km³), the dam is 469 feet (143 m) high and 8,997 feet (2,743 m) wide at its crest. It helps to maintain the flow of the Indus during seasonal fluctuations.  A new , smaller hydro-elect ric power project has been developed downstream known as the Ghazi Barotha Hydel Power Project. Its is solely for generating electricity and has a water channel with the highest flow in the world. While the dam has fulfilled its purpose in storing water for agricultural use in Pakistan, there have been environmental consequences to the Indus river delta. Reduction of seasonal flooding and reduced water flows to the delta have decreased mangrove stands and the abundance of some fish species. Performance of HYDEL POWER STATIONS [01/07/2007 - 30/06/2008] Tarbela Installed Capacity 3478 MW Effective Capacity (Max.) 3702 MW Effective Capacity (Min.) 1350 MW Energy Generationm 14959.18 GWH Auxiliary Consumption 69.79 GWH Maximum Load 3702 MW Plant Factor 49.1 % Availability Factor 94.67 % Tarbela Dam Tarbela Dam is one of the world’s largest earth and rock filled Dam and greatest water resources development proj ect which was

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Tarbela Dam (Urdu: دنب لیبرت ) is a dam on the Indus River in Pakistan.It is located 50 kilometers

North-West of Islamabad near the Haripur District. It is the largest earth filled dam in the world

and it produces much of Pakistan's hydroelectricity. Tarbela Dam is part of the Indus Basin

Project, which resulted from a water treaty signed in 1960 between India and Pakistan,

guaranting Pakistan water supplies independent of upstream control by India. Construction beganin 1968, and continued until completion in 1976. The dam has a volume of 138,600,000 cubic

yards (106,000,000 m³). With a reservoir capacity of 11,098,000 acre-feet (13.69 km³), the dam is

469 feet (143 m) high and 8,997 feet (2,743 m) wide at its crest. It helps to maintain the flow of 

the Indus during seasonal fluctuations.

A new, smaller hydro-electric power project has been developed downstream known as the Ghazi

Barotha Hydel Power Project. Its is solely for generating electricity and has a water channel with

the highest flow in the world.

While the dam has fulfilled its purpose in storing water for agricultural use in Pakistan, there have

been environmental consequences to the Indus river delta. Reduction of seasonal flooding andreduced water flows to the delta have decreased mangrove stands and the abundance of some

fish species.

Performance of HYDEL POWER STATIONS

[01/07/2007 - 30/06/2008]

Tarbela

Installed

Capacity3478 MW

Effective

Capacity(Max.)

3702 MW

EffectiveCapacity

(Min.)

1350 MW

Energy

Generationm14959.18 GWH

Auxiliary

Consumption69.79 GWH

MaximumLoad

3702 MW

Plant Factor 49.1 %

AvailabilityFactor

94.67 %

Tarbela Dam

Tarbela Dam is one of the world’s largest earth and rock filled Damand greatest water resources development project which was

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completed in 1976 as a component part of Indus Basin Project. TheDam is built on one of the World’s largest rivers – the Indus known

as the “Abbasin” or the father of rivers.

Emerging from the land of glaciers on the northern slopes of Kailash

ranges, some 17,000 feet (5182 meters) above sea level, the river

Indus has its source near the Lake Mansrowar in the Himalyancatchment area. It flows over 1800 miles (2900 k. metres) before itoutfalls into the Arabian sea draining an area of about 372,000

square miles (964,261 sq.kms).

The World Bank accepted Tarbela Dam Project as a part of the

Settlement (Replacement) Plan under Indus water treaty in 1965.WAPDA was entrusted with its execution on behalf of the

Government of Pakistan. HARZA ENGINEERING COMPANYInternational who were the General Consultants of WAPDA, carried

out the review studies of the Project. In February, 1960 Tippetts –Abbett - McCarthy – Stratton of USA commonly known as TAMS

were appointed the Project Consultants, and were entrusted with thetask of investigation, preparation of detailed designs, and contract

documents for the project and also the supervision of constructionwork during its execution.

The Project – Main Features

The Project consists of a 9,000 (2,743

meters) long, 465 feet (143 meters)high (above the river bed) earth and

rock fill embankment across the entire

width of the river with two spillwayscutting through the left bank discharging

into a side valley. Its main spillway has a

discharge capacity of 650,000 cusecs(18,406 cumecs) and auxiliary spillway

850,000 cusecs (24,070 cusecs). Twoauxiliary embankment dams close the gaps in the left bank valley. A

group of 4 tunnels (each half a mile long), through the rightabutment rock have been constructed for irrigation releases and

power generation. During the construction operations, these tunnelswere used initially for river diversion. Irrigation tunnel 5 situated on

the left bank, for which NESPAK were the Project Consultants, wasput into operation in April 1976.

A power station on the right bank near the toe of the main damhouses fourteen(14), power units, 4 units, each with installed

generating capacity of 175 MW are installed on tunnel 1, 6 units(NO.5 to 10), 175 MW each on tunnel NO.2 and 4 Units ( NO.11-14)

of 432 MW each on Tunnel 3, thus making total generating capacityof Tarbela Power Station as 3478 MW.

The reservoir is 50 miles (80.5 km) long 100 square, miles (260

square kilometers) in area and has a gross storage capacity of 11.6

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MAF (17.109 million cu. Meters) with a live storage capacity of 9.7MAF (14,307 million cu. Meters). The total catchment area above

Tarbela is spread over 65,000 sq. miles (168,000 sq. kilometers)which largely brings in snowmelt supplied in addition to some

monsoon rains. Two main upstream tributaries join the Indus river,

Shyok river at an elevation of 8,000 ft. (2438 meters) above seallevel near skardu and Siran river just north of Tarbela.

Main Dam

The principal element of the project isan embankment 9,000 feet (2743

meters) long with a maximum height of 465 feet (143 meters). The total volume

of earth and rock used for the project isapproximately 200 million cubic yards

(152.8 million cu. Meters) which makes

it the largest man made structure in theworld , except for the Great ChineseWall which consumed somewhat more

material. The main embankment is a carefully designed, zonedstructure composed of impervious core, bounded on both sides by

gradually increasing sized material including coarser sands gravelscobbles and finally large sized riprap on the outer slopes. An

impervious blanket, 42 feet (12.8 meters) thick at the dam andtailing to 5 feet (1.52 meters) at the upstream end, covers 5,700

feet (1737 meters) of the alluvial foundation on the upstream side.These deposits in the valley are upto 700 feet (213 meters) deep and

in places consist of open work gravels. The dam crosses thisessentially alluvial valley and connects the last points to high ground

before the mountains give way to the plains. A 24 feet (7.32 meters)thick filter drain mattress under the embankment together withnearly vertical chimney drain provides the necessary facility to collect

the seepage.

Auxiliary Dams

The auxiliary dams resembling the

main embankment dam in designclose the gaps in the left periphery of 

reservoir. The smaller of the twoauxiliary dams, however, has a vertical

core extending down to the underlyingrock, and the larger auxiliary dam has

a short upstream blanket terminatingin a cut off to rock.

Spillways

On the left bank , two spillways

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discharges into a side channel. The total spillway capacity is1,500,000 cusecs (42,476 cumecs) which constitutes the peak

outflow resulting from routing the probable maximum flood. Theservice spillway having 44 percent of the total capacity is sufficient to

pass all but very rare floods. Its maximum discharge capacity is

650,000 cusecs (18, 406 cumecs).

The auxiliary spillway is similar in design to the service spillway. It

has nine radial gates with crest elevation of 1492 feet (455 meters)and flip bucket at elevation 1220 feet (372 meters) A longitudinal

drainage gallery along with a network of drainage pipes under the

channel and the head works has been provided to release pore waterpressure in both the spillway foundations.

Reservoir

The 50-miles (81 kilometers) long

reservoir created by the Project has agross storage capacity of 11.6 million

acre feet (MAF) (17,109 m.cu.meters) at the maximum lake

elevation of 1550 feet (472 meters) aresidual capacity of 1.9 MAF (2,802

m cu. Meters) at the assumed levelof maximum drawdown elevation

1300 feet (396 meters) and a netusable capacity of 9.7 MAF (14,307 m cu. Meters). The

Tarbelareservoir stores water during the summer months of June,

July and August when water either causes disaster by flooding in thesurrounding areas or goes waste into the sea. It is to be noted that

more dams can be constructed on Indus since its annual flow is

substantially more than is being stored at present. Kalabagh Dam onRiver Indus is in its advanced stages of design, while investigations

are underway for the upstream Basha Dam.

Tunnels

The four, each of half mile long,tunnels through the right (rock)

abutment initially served for thediversion of water during the final

phases of construction of the Project.

Now they are being used for Powergeneration (tunnels 1, 2, 3 andeventually 4). The discharge capacity

of each irrigation tunnel at higherreservoir elevations is approximately

90,000 cusecs (2,549 cumecs). The discharge pass through energy

dissipator structures and the water returns to the river. A fifth tunnelon the left bank designed to augment irrigation releases upto 80,000

cusecs (2,265 cumecs) at high reservoir level, has also been added

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to the project.

Power Station

According to the original plan, four

(4) power units of 175 MW generatingcapacity each were to be installed on

each of the tunnels 1, 2 and 3 located

on the right bank with the ultimateinstalled capacity of 21,00 MW. Of 

these, four (4) units on tunnel 1 werecommissioned in the year 1977. Due

to increasing prices of the fossil fuel,the Govt of Pakistan has been laying

greater emphasis on generation of cheap Hydel power. In pursuanceof this policy, WAPDA carried out studies to tap the maximum power

potential of Tarbela. As a result, it has been found possible to install

six (6) units, instead of four (4) only on tunnel NO.2. Units 5 to 8 ontunnel NO.2 were commissioned in 1982, and units 9 and 10 in 1985.Based on studies, four power units of 432 MW capacity each were

installed on tunnel NO.3. Thus the total ultimate power potential of the project enhanced from 2100 MW as originally planned to 3478

MW.

Project Implementation

On May 14, 1968, the World’s largest single contract for the

construction of civil works of the Tarbela Dam Project was signed at a

price of RS.2,965,493,217 ($ 623 Million) between the Water and

Power Development Authority and the Tarbela Dam Joint Venturewhich comprised a group of three Italian and three French heavyconstruction contractors. Later five German and two Swiss

contractors also joined the group making up a consortium of thirteenEuropean firms led by Italian firm namely Impregilo.

The construction of Tarbela Dam was carried out in three stages tomeet the diversion requirements of the river. In stage-I, the river

Indus was allowed to flow in its natural channel while work wascontinued on right bank where a 1500 feet (457 meters) long and

694 feet (212 meters) wide diversion channel was excavated and a105 feet (32 meters) high buttress dam was constructed with its top

elevation at 1, 187 feet (362 meters) The diversion channel was

capable of discharging 750,000 cusecs (21,238 cumecs).Construction under stage-I lasted 2½ years.

In stage-II, the main embankment dam and the upstream blanketwere constructed across the main valley of the river Indus while

water remained diverted through the diversion channel. By the end

of stage-II, tunnels, had been built for diversion purposes. Thestage-II construction took 3 years to complete. Under stage-III, the

work was carried out on the closure of diversion channel and

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construction of the dam in that portion while the river was made toflow through diversion tunnels. The remaining portion of upstream

blanket and the main dam at higher levels was also completed as apart of stage-III works.

Salient features/Principal data of main components of TarbelaDam and Power House Tarbela Dam

Type Earth & Rock fill  

Max. Height

(above river bed) 465 ft. (147.82 meters)Crest elevation 1565 ft. SPD (477 meters)

Length of Crest (Maindam)

9000 ft. (2743 meters)

Auxiliary Dam NO.1Length at Crest EI. 1565 ft (477 M) 2,340 feet (713 M)

Maximum Height 345 feet (105 M)

Volume including Blanket 18,000,000 cu.yds(13,752,000 cu meters)

Auxiliary Dam No.2

Length at Crest EI, 1565 ft (477 M) 960 feet (293 M)Maximum Height 220 feet (67 M)

Volume 2,000,000 cu. Yds(1,528,000 cu.meters)

Tunnels at Right BankNumber 4

Length 2400 feet each (732 M)

Diameter (u/s gate shafts) 45 feet (13.72 M)Diameter (u/s of gate shafts) 36 feet (10.97 M)

Tunnel at Left BankLength 2760 feet (841 M)

Diameter (13.26 M)

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Reservoir

Length 60 miles (97 km)

Max. depth 450 ft. (137 m)

Area 60000 acres (100 square miles)Max. conservation 1550 ft. SPDA (472.45 meters)

Min Operation level 1300 ft SPD (396.25 meters)Design Gross Storage 11.3 MAF  

Existing Gross storage 9.00 MAF  

Design live storage 9.68 MAF

Existing live storage

At 1365 ft SPD 7.3 MAF

Surface Area 100 sq miles (259 sq km)

Spillways

Service Spillways

Capacity 650,000 cusecs (18,405 cumecs)No. of Gates 7 (Seven)  

Size of Gate50 ft. Wide & 61ft. high

(15.24x18.60 meters)

 

Auxiliary Spillways

Capacity 850,000 cusecs (24,070 cumecs)

No. of Gates 9 (Nine)  

Size of Gates50 ft. wide & 61

ft. high(15.24x18.60 meters)

 

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Power House  

UNITS 1~4 5~6 7~8 9~10 11~14Turbine

(Francis-

Vertical)

 

Output (BHP) 239000 239000 239000 239000 596000Rated Head

(Ft. of Water)378 378 378 378 385

MakeHitachiJapan

D.E.W.Canada

D.E.W.Canada

D.B.S.Canada

D.B.S.

EscherWyss

Canada

Generators(Umbrella

Type)

 

Output (MVA)205.882

15%184.210

15%184.210

15%184.210

15%480

Output (MVA) overload overload overload overload 432Output (P.F) 175 175 175 175 0.90

Output (K.V) 0.85 0.95 0.95 0.95 18.0Rated Speed 13.8 13.8 13.8 13.8 90.9  136.400 136.400 136.400 136.400  

MakeHitachi

Japan

C.G.E.

Canada

C.G.E.

Canada

Hitachi

Japan

Siemens-ABB

Germany 

Transformers

(SinglePhase)

 

Capability(MVA/Phase)

79 71 71 71 160

Voltage Ratio(KV)

13.2/220 13.2/500 13.2/500 13.2/500 25.0/500

Make

Jeumont-

SchneiderFrance

ASEA

CanadaHitachi

Japan

HitachJapan

Jeumont-

SchneiderFrance

Ansaldo

ComponentiItaly

Project Benefits

In addition to fulfilling primary purpose of the Dam i.e. supplyingwater for Irrigation, Tarbela Power Station has generated 341.139

Billion KWh of cheap hydel energy since commissioning. A recordannual generation of 16.463 Billion KWh was recorded during

1998~99. Annual generation during 2007~08 was 14.959 BillionKWh while the Station shared peak load of 3702 MW during the year

which was 23.057% of total WAPDA System Peak.

WB agrees on Tarbela Dam fix

Source: SAMAAIslamabad : Pakistan | 2 months ago

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1 0 Views: 24Staff Report ISLAMABAD: The World Bank has ensured funds for the expansion of the Tarbela Dam,which it considered feasible and appropriate for the country. The dam is located about 50 km northwest of Islamabad and was completed in 1974 to store water from the Indus River for irrigation and flood controland to generate hydro-electric power. WAPDA will receive 980MW more electricity with the expansion of 

the dam. The WB officials were told by Pakistan that one billion dollars would be needed for the changeswhich would take three years. The WB announced $40 million for the work earlier on. Tarbela Dam is oneof the world’s largest earth and rock filled dams and was completed in 1976 as a component part of theIndus Basin Project. The World Bank accepted the Tarbela Dam Project as a part of the Settlement(Replacement) Plan under the Indus water treaty in 1965. WAPDA was entrusted with its execution on behalf of the Government of Pakistan. HARZA ENGINEERING COMPANY International who were thegeneral consultants for WAPDA, carried out the review studies of the project. In February, 1960 Tippetts,Abbett, McCarthy & Stratton of US commonly known as TAMS were appointed project consultants, andwere entrusted with the task of investigation, preparation of detailed designs, and contract documents for the project and also the supervision of construction work during its execution. 'WAR WITH INDIA OVER WATER' Meanwhile, Federal Minister for Environment Hameedullah Jan Afridi warned Saturday that itwas possible for Pakistan to go to war with India over water in the future. At a seminar in Lahore, Afridisaid that the country was facing a loss of Rs 100 billion annually due to impure drinking water. And threetrillion rupees were needed annually to make the environment clean. He alleged that one dictator hadentered into damaging agreements with India, which had endangered all of Pakistan’s water reservoirs. If these problems are not resolved, the two countries could fight over them. SAMAA CAPTION: A generalview of a newly inaugurated 450-megawatt hydropower project located at Baglihar Dam on the Chenabriver which flows from Indian Kashmir into Pakistan, is seen at Chanderkote, about 145 km (90 miles)north of Jammu October 10, 2008.

Tarbela Dam

Consequent to the Indus Basin Water Treaty, concluded between India and Pakistan, two major water reservoirs were planned to be constructed in Pakistan to store water mainly for irrigation (tomake up for the shortfall of water due to water sharing formula agreed vide the treaty); one of 

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these was o be built on River Jhelm at Mangla and the other on River Indus near the small townof Tarbela. Construction for the dam began in 1968, and continued until completion in 1976. Thedam has a volume of 138,600,000 cubic yards (106,000,000 m³). With a reservoir capacity of 11,098,000 acre-feet (13.69 km³), the dam is 469 feet (143 m) high and 8,997 feet (2,743 m) wideat its crest and stands 147 meters above the Indus riverbed.. It helps to maintain the flow of theIndus during seasonal fluctuations. The dam cost in 1976 was Rs.18.5 billion. Its reservoir is 97

km long with a depth of 137 meters while total area of the lake is 260 square kilometers. From theinitial storage capacity of 11.62 MAF in 1974, it has now reduced to 5.51 MAF in 2005 (i.e. 47% of initial capacity) due to silting.

Tarbela is considered as the largest earth-filled dam on one of the world's most important rivers -

the Indus. The dam was completed in 1976 at a cost of Rs.18.5 billion. It is the biggest hydelpower station in Pakistan having a capacity of generating 3,478 MW of electricity. It providesnearly 30 percent of all the irrigation water available in dry season, 2100 MW of hydropower wasto be initially generated as a by-product. By the year 1992, the generating capacity was raised to3428 MW, with the 3rd extension comprising four more units of 432 MW capacity each. ReadMore ...

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Discharge of water from the Tarbela power generation tunnels

As with the construction of large dams, while the problem of storing water has been achieved for agricultural use in Pakistan, there have been environmental consequences to the Indus river delta. Reduction of seasonal flooding and reduced water flows to the delta have decreasedmangrove stands and the abundance of some fish species.

The dam has been plagued with problems ever since 1974 when the reservoir impoundmentbegan. Two of the four tunnels being used to control the rate of filling were damaged and forcedto close. Within a week, one of the two remaining active tunnels also collapsed, bringing down

nearly half a million cubic metres of concrete and rock. The reservoir had to be emptiedimmediately to avoid a disaster. Engineers then discovered around 70 "sinkholes" in the reservoir bed, which they tried covering between 1975 and 1978 by dumping thousands of tonnes of earthby the barge load. One sinkhole that appeared in 1984 was still there in 1991 and could affect thepermeability of the dam. Downstream of the dam, a huge 50 metre-deep, 300 metre-wide plungepool formed in 1976 when the main spillway began operating. During the following year’s floods,the rocks at the base of the spillway eroded, threatening the safety of the huge concrete spillway.The auxiliary spillway had similar problems and the contractors had to undertake a three-year "rock stabilisation programme".

The rescue works on the Tarbela dam boosted the cost from an estimated $800 million in 1968 to$1.5 billion by 1986. Only continual monitoring, remedial work and maintenance have stopped thedam from releasing a tidal wave into the densely populated Peshawar Valley below. By 1999 the

Tarbela reservoir had succumbed to 32% of silting. The sedimentation still continues, graduallyreducing the life of the dam - thus the need to build more dams for storage of water and meet theincreasing demands of electricity

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TARBELA

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