Tuesday, February 9, 2010

Mangla Dam: The 12th Largest Dam in The World - - Serves as a Backbone of Pakistan's Irrigation System; While Producing Hydelpower

General Information:

The Mangla Dam, located in Mirpur District, is the 12th largest dam in the world. It was built during 1961 to 1967 with financial support from the World Bank. The project was designed and supervised by Binnie & Partners of London, and it was built by Mangla Dam Contractors, a consortium of eight U.S. construction firms, sponsored by Guy F. Atkinson Company of South San Francisco. Mangla Dam Contractors employed Pakistanis, Americans, British, Canadians, Germans, and Irish.

Historic Background:

As part of the Indus Waters Treaty signed in 1960, India gained rights to the waters of the Ravi, Sutlej and Beas rivers, while Pakistan, in addition to waters of the above three rivers within Pakistan and some monetary compensation, received the rights to develop the Jhelum, Chenab and Indus river basins through construction of the Indus Basin Project. Until 1967, the entire irrigation system of Pakistan was fully dependent on unregulated flows of the Indus and its major tributaries. The agricultural yield was very low for a number of reasons, the most important being a lack of water during critical growing periods. This problem stemmed from the seasonal variations in the river flow due to monsoons and the absence of storage reservoirs to conserve the vast amounts of surplus water during those periods of high river discharge.

The Mangla Dam was the first development project undertaken to reduce this shortcoming and strengthen the irrigation system. The dam was damaged due to an Indian Air Force raid during the Indo-Pakistani War of 1971. As a consequence, the hydro project was temporarily out of service.

The Mangla Dam project:

The Mangla Dam is the twelfth: largest dam in the world. It was constructed in 1967 across the Jhelum River, about 67 miles (100 km) south-east of the Pakistani capital, Islamabad in Mirpur district of Azad Kashmir, Pakistan. The main structures of the dam include 4 embankment dams, 2 spillways, 5 power-cum-irrigation tunnels and a 1,000 MW power station.

The main dam is 10,300 feet (3140 m) long and 454 feet (138 m) high (above core trench) with a reservoir of 97.7 square miles (253 km²). Since its first impounding in 1967, sedimentation has occurred to the extent of 1.13 million acre feet (1.39 km³), and the present gross storage capacity has declined to 4.75 million acre feet (5.86 km³) from the actual design of 5.88 million acre feet (7.25 km³). The live capacity has declined to 4.58 million acre feet (5.65 km³) from 5.34 million acre feet (6.59 km³). This implies a reduction of 19.22% in the capacity of the dam.

The power station of Mangla dam consists of 10 units each having capacity of 100 MW.

In order to remedy the storage capacity decreases, the Pakistani government has decided to raise the dam by 40 feet (12 m), to 494 feet (151 m) high. This will increase the reservoir capacity by 18% and provide an additional 644 MWH of power, but will displace 40,000 people currently living near the reservoir.

The project was designed primarily to increase the amount of water that could be used for irrigation from the flow of the Jhelum and its tributaries. Its secondary function was to generate electrical power from the irrigation releases at the artificial head of the reservoir. The project was not designed as a flood controls structure, although some benefit in this respect also arises from its use for irrigation and water supply. The Government of Pakistan had agreed to pay royalties to the Government of AJK(Azad Jammu and Kashmir) for the use of the water and electricity generated by the dam. Over 280 villages and the towns of Mirpur and Dadyal were submerged and over 110,000 people were displaced from the area as a result of the dam being built. Some of those affected by the dam were given work permits for Britain by the Government of Pakistan, and as a result, in many cities in the UK the majority of the 'Pakistani' community actually originated from the Dadyal Mirpur area of Disputed region Jammu Kashmir.

Mangla Dam is approx 67 miles (100 km) south-east of the Pakistani capital, Islamabad while Tarbela Dam is 60 miles (100 km) northwest.

Mangla Dam Raising Project (MDRP):
Government of Pakistan started a strategic project called "Mangla Dam Raising Project (MDRP)". With the completion of Mangla Dam Raising Project worth Rs62.5billion, annual water availability for irrigation purposes would increase by 2.88 MAF, while the annual energy output is expected to increase about 12per cent of the present energy production from Mangla.
Since the construction of Tarbela Dam, the MDRP is the first mega project launched in this sector.

During a briefing to the visiting journalists at Mangla Dam, General Manager Project North WAPDA Brig Mushtaq Ahmed explained that a provision for raising the dam was kept in the original design of Mangla Dam. He added it would be raised by 30 feet (9.1 m) to enhance power generation and stem floods.

As for the existing capacity of water storage in the country, heavy sediment inflows were reducing capacity of all the three major storages, Tarbela, Mangla and Chashma.

An estimate depicts that by the year 2010 these three storages will lose about 33per cent (6 MAF) of their original capacity, which implies the loss of one mega storage project.

Statistics on Storages
The statistics show the existing storages could store only 11per cent of the total available surface water while there is potential for saving 65 MAF whereas on average about 35 MAF water escapes annually into sea.

The MDRP is one of WAPDA’s projects to meet water storage challenges. The Mangla Dam’s original storage capacity was 5.88 MAF in 1967 but by 2002 it lost 1.16 MAF (20%). According to the projected figures, by 2010 it would lose another 7per cent of the capacity.

The MDRP includes rising of the dam and main spillway without making any alterations or additions in the power generation units.

The Spillway:

The main spillway of the dam was unique in nature and went through a successful test in 1992 with maximum water flow of one million cusecs.

American engineer who designed this spillway was given special award by the American government. MDRP Perspective:

The engineering plan of the MDRP was completed in February 2004 and contract was awarded to a joint venture of one Chinese and five Pakistani contractors.

The China International Water and electric Corporation (CWE) is leading this Mangla Joint Venture (MJV) while five Pakistani contractors include DESCON Ltd, Sardar M Ashraf D Baluch Ltd, Interconstruct Ltd, Gammon Pakistan Ltd and Sachal Engineering Works Ltd.

The construction work started on June 20, 2004 and is scheduled to end in 39 months by September 2005. Moreover, 21 per cent of the total workforce comprises local people and this percentage is expected to rise in future.

Compensation and Resettlement:

Out of the total project cost of Rs 62.5b, Rs 36 billion will be spent on compensation and resettlement works. Land for the New City near Mirpur and four small towns on the reservoir periphery have already been earmarked and a contract for the construction of primary and secondary roads at the cost of Rs 1,026.5 million has been awarded.

The affectees will get plots of five marla to one kanal on payment of cost of land while five marla plots will be given free of cost to refugee settlers on the land of WAPDA and Government of Azad Jammu and Kashmir.

The resettlement package includes the construction of a bridge on river Jhelum at Dhangali, establishment of a Vocational Training Institute (VTI) in New City, Vocational Training Schools in four new town, strengthening of four existing Dastkari schools for females and vocational training from outside sources.

The land compensation will be given at market price plus 15per cent compulsory acquisition charges and owners will be allowed to cultivate their land during recession.

Housing Units:

As for the housing units, the affectees will get replacement cost of house, which will be in addition to 10per cent amount for the same purpose while the owners will also be allowed to carry salvage material (malba) of their houses.

The MDRP also carries compensation for the old affectees of the Mangla Dam. They include 7,707 families and each family will receive Rs 200,000.

The AJK government will get net hydel profit @0.l5/kWh while five additional Grid Stations as per 2002-2007 plan will also be constructed at Chatter Pari. Moreover, the AJK will have hydropower projects up to 300 MW capacity.

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