International Commission

on large dams

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TWENTY THIRD CONGRESS

ON LARGE DAMS

Brazil, june 2009

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INDUSBASIN – ROLE OF DAMS IN AGRO-BASED ECONOMY OF PAKISTAN*

Sardar Muhammad Tariq

Chairman, Pakistan Water Partnership

Pakistan

  1. Synopsis:

Pakistan since its independence in August 1947 has heavily dependent on agro-based economy. Though contribution of agricultural sector to Pakistan’s GDP has been gradually declining with the development of other economic sectors such as industries, etc. public sector largely depends on agriculture for its growth, employment and foreign exchange earnings. The IndusBasin irrigated area is the main contributor to Pakistan’s agro-based economy. This paper develves in detail about the history of basin itself and the development of water infrastructure particularly major multipurpose storage dams and their role in providing sustainable agro-based economy. The paper also deals with the major hydrological problems the IndusBasin has to face as a result of partition of the sub-continent into two independent states of India and Pakistan followed by Indus Waters Treaty of 1960. With establishment of world’s largest infrastructure in a single hydrological basin, Pakistan has to confront serious problems of water logging and salinity. This paper further describes the methods and technologies adopted in dealing with twin menace of water logging and salinity, and mega sedimentation problems created as a result of changing the course of rivers in the basin.

  1. IndusBasin

The vast Indus Plains covers an area of 207,200 square km and extends 1900 km from lower Himalayan foothills to the Arabian Sea, are underlain by sandy alluvium to depths over 305 meters in the upper reaches and upto 61 meters in the lower reaches close to the Arabian Sea. The Indus Plains constitutes a large and highly transmassive aquifer system with usable storage volume much greater than all the existing and potential storage reservoirs on the River Indus and its tributaries. Annual recharge to this ground water reservoir is estimated at 56 million cubic meter of which some 44 billion cubic meter is usable.

2.1UpperIndusBasin Catchment

The upper catchment of IndusBasin is dominated with the great Himalayan ranges which influence its weather, trap the monsoons to shed their moisture as snow and rain, and regulate the water cycle. The 400,131 square km Himalayan watershed of Indus and its tributaries includes world’s largest glaciers outside the polar region. They are the great natural storage reservoirs that feed and regulate the Indus and its tributaries. It is estimated that these glacier hold upto one trillion cubic meter of water. Storage dams built since 1960 on Indus are miniatures as compared to these natural reservoirs. In the upper reaches Indus flows, fed and regulated by snow capped mountains, numerous glaciers and extensive ice fields, first westward and then southwards cutting its way through the deepest gorges in the world – some more than 4570 meter deep.

2.2LowerMountain Catchment

In the lower mountain catchment of the Indus and its tributaries where the lower Himalayan and Siwalik ranges extend over 65,000 square km of sedimentary rock and gravel formations, part of monsoon rainfall percolates and is stored temporarily in the porous formation and is released later through springs or natural reservoir that feeds the rivers in the dry season. The aggregate capacity of this reservoir once amounted to more than 12 billion cubic meter but extensive deforestation over the years led to serious soil erosion, reduced the storage capacity and increased the hazards of floods and sedimentation inflows in the rivers and reservoirs.

2.3Lower Indus Plains

The Lower Indus Plains having alluvial river channels with aggregate length of 3540 km and width ranging from 2 km to 4 km also serve as natural reservoirs regulating the river flows. During high river storages, the channels are filled, the flood peaks are moderated and water seeps into the wide alluvial banks. When the river stage drops, the channels storage is released and the bank storage seeps out slowly as return flows. The releases from channel storage during the late summer season vary from 4 BCM to 6 BCM while those from bank storage amounting to some 4 BCM take place throughout winter season. The timing and quality of the storage releases are determined by the operations of the rivers and storage reservoirs. Effective management of the rivers to prevent deterioration is essential to maintain the gains from these natural storages on sustainable basis.

  1. Development of IndusBasin – HistoricPerspective

The IndusRiver which irrigates the IndusBasin has seven major tributaries, five on the east and two on the west in addition to numerous small rivers which also join the main Indus on the west. The integrated water resources management is not a new concept as far as IndusBasin is concerned. The upper Punjab was the first to conceive and practice it. The triple canal project was designed to integrate the three eastern rivers by constructing control works and link canals in 1905-7 and operating the link canals as an integrated system. It was a marvel of innovative engineering which heralded a new era of efficient and equitable use of water resources and made Punjab the granary of the sub continent. However the partition of the sub continent in August 1947 cut across this irrigation network whereby control structures on eastern canals fell within the territory of India and canals remained within Pakistan. Soon after the partition, India conveyed its intention of diverting the waters of eastern rivers. This would have meant strangulating the agro-based economy of a newly created Pakistanwhose 75% of GDP was solely dependent on agriculture as other sectors of the economy were non-existent.

  1. IndusBasin Waters Treaty of 1960

With stoppage of water from the three eastern rivers by India, Pakistan’s 3 million hectare of fertileland of West Punjab, the food basket of Pakistan would have gone barren. This created a serious water dispute between India and Pakistan. However, over a period of 8 years of exhaustive negotiations under the auspices of the World Bank from 1952 to 1960 the famous Indus Waters Treaty between India and Pakistan was signed in September 1960. The World Bank was also a signatory to this transboundary water allocation. Under the Treaty, India was given exclusive rights to the uses of water of three (3) eastern rivers with limited uses of waters of western rivers and Pakistan got exclusive rights on the waters of three (3) western rivers. Pakistan was given a grace period of 10 years to complete its Indus Basin Replacement Works. This Treaty though extensively lauded internationally as an example of resolving transboundary water issues between two sovereign states, created some serious hydrological shocks and challenges for Pakistan. The first challenge as stated earlier arose because the lines of partition of the Indo-Pak subcontinent separated the irrigated heart land of Punjab from the life-giving waters of the three eastern rivers.

The second challenge was that there was a serious mismatch between the location of Pakistan’s water (in the western rivers) and the major irrigated areas in the east.

  1. IndusBasin Replacement Works


To overcome major water challenges, Pakistan had to undertake major engineering works within a fixed time period of 10 years. The initial works included construction of mega rock and earth fill dam on one of the western rivers i.e. Jhelum River at Mangla, construction of inter-river link canals to transfer the waters of western rivers to eastern rivers with a number of Headworks and Barrages and later the world largest volume rock and earth fill dam i.e. Tarbela Dam was also built on River Indus, the largest river of the Indus Basin Rivers System.With additional storage water available at Tarbela, additional canals and control structures were constructed in all the four Provinces of Pakistan. With the construction of Tarbela, Mangla and Chashma Multi-purposes storage dams, storing close to 20 billion cubic meters of water and water distribution network consisting of 19 barrages, 60,000 km of main canals and1.60 million km of secondary and distributary canals, the Indus Irrigation System became the largest contiguous irrigation system in the world (Fig. 1).

Fig. 1

Schematic Diagram of IndusBasin Irrigation System

To further resolve internal contentious issues of water rights and water distribution within the country, Inter-Provincial Water Apportionment Accord was signed in 1991 among all the four Provinces which determined the 10-daily historic shares of each of 43 canal commands. To ensure equitable distribution of waters among the Provinces, Indus River System Authority known as IRSA was created under the Act of Parliament to act as a watchdog in ensuring accord implementation.

With transboundary water sharing Treaty of 1960 and Inter-Provincial Water Apportionment Accord of 1991 and 10-daily historic water share of each canal command and rotational water sharing within each canal command area, Pakistan has now well-developed water distribution system with proper check and balance mechanism in place.

  1. Role of Multipurpose Dams in the Modern Economy of Pakistan
  • With the construction of multipurpose storage dams and extensive water conveyance and distribution network, the desert literally bloomed with irrigated agriculture providing the platform for the development of the modern economy of Pakistan.
  • The three multipurpose reservoir store some 20 billion cubic meter of water and numerous control and diversion structures regulate close to 130 billion cubic meter of irrigation water annually to some 18 million hectares of agricultural land increasing the cropping intensity from 80% to 150%. The Storage dams help to great extent in reducing the gap between water availability and crop water requirement thus enhancing crop productivity manifolds.
  • The engineering structures and reservoirs cumulatively provide 800 km of navigation routes to over 200,000 people living along and in close vicinity of the reservoirs and canals.
  • The water economy provided valuable base for development of other economic sectors with the availability of cheap and renewable hydropower, more than 3,000 ago-based industries have been established all over the country and there has been a gradual shift over the last 30 yearscontribution of irrigated agriculture from 75% to the GDP has reduced to present 24% with the growth of industries and other modern economies. Inspite of all this irrigated agriculture still plays a vital role in the overall economy and employs 46% of labour force, provides90% of food grains and earns 60% of the foreign exchange for the country.
  • The water structures and storage dams provide largest inland water bodies for fish culture and meet the dietary requirement of millions of people living in the central and northern parts of Pakistan in addition to providing livelihood to thousands of fishermen families. Some 50 priced varieties of fish are cultured in the reservoirs in addition to hundreds of fresh water species.
  • Pakistan is one of the most arid countries of the world with average rainfall of 240 mm per year. 75% of this rainfall is available in 90 days of the summer. The storage reservoirs helped Pakistan to integrate wet season with the dry season and over 10 billion cubic meter of water is now transferred through storage reservoirs from wet season to dry season which boosted the agricultural production in addition to meeting the water requirement of other sectors such as industries, environment, water supplies and sanitation etc.With storage reservoir, the canal diversion increased from 80 BCM to 130 BCM annually.
  • Inland reservoirs and water bodies provide safe heaven to millions of migratory birds. The regulations of water round the year through storage reservoirs minimizes the salt-water intrusion in the coastal areas in addition to recharging the ground water which now contributes 40% of water requirements of all sub sectors. The ground water reservoir spreads over some 194,000 square km mostly recharged by storage reservoirs and canals network.
  • During construction of massive water structures and mega multipurpose storage dams, a unique opportunity was provided to the indigenous labour force and close to some 50,000 unskilled labourer were trained in various trades by American and European Contractors and an unmatched force of skilled labourers consisting of construction supervisors, surveyors, dozer/dumper/crane/grader operators, welders, etc was produced. This trained labour force produced in sixties and seventies coincided with the development of petro-based economy of Middle East and Gulf States and immediately got opportunity for lucrative employment in these countries. This labour force was then remitting foreign exchange to the tune of US$ 4 billion per annum, the largest foreign exchange earnings for the country. The cumulative remittances by this trained Pakistani labour force over a period of 10 years surpasses the amount spent on the construction of Indus Basin Replacement Works including mega storage dams required under the Indus Waters Treaty of 1960.
  • The Indus Basin Rivers deposit close to 300 million tons of sediments annually in the storage reservoirs. During annual draw-down, the deposited silt is excavated by the locals and sold to farmers as a replacement soil on their agricultural land, a commercial activity which has become very payable during the recent years and provides handsome earnings to the local population.
  1. Management Challenges of Development Works

The heroic era of water engineering in Pakistan resulted in mega management challenges. The natural flow regime was drastically altered; rivers which has previously meandered over wide plains were now confined within narrow channels; sediments (amounting to some 300 million tons) which previously nourished the delta were trapped; and vast quantities of water were disgorged into desert, substantial parts of which were of oceanic origin and highly saline. The extensive irrigation network and large amount of seepages resulted in billions of cubic meters of water getting stored in the naturally deep aquifers. In many areas, water tables reached the level of the land, giving rise to the twin menace of water logging and salinity. However, with good thinking and application of water science and economics, the solution apart from lining of canals and putting less water on the land, the enhanced use of ground water offered the best solutions. This resulted in increasing evapotranspiration, drawing down the ground water table and leaching much of the salts down and out of root zones. The good thinking and good planning were classic “public good”. The good luck driver of this revolution was the modest but transforming tubewell and diesel engine for the simple reason that this decentralized “on demand” source of water closely matching crop water requirement enabled them to greatly increase their yields and farm incomes. In the public sector the introduction of tile and surface drains measuring 16,000 kmhave also played major role in lowering the water table and taking away drainable surpluses.

Similarly the sediment flow into the reservoir is another serious problem gradually reducing the storage lives of dams. With young geological formations, steep slopes and large flows, the Indus and its tributaries bring in some 300 million tons of sediments annually, Indus being the fifth largest sediment carrying river in the world.Whereas catchment management for the Jhelum river has positively reduced the sediments in Mangla Reservoir, Similar efforts have not been very successful for the catchment of Tarbela Dam on IndusRiver. To address Tarbela sedimentation issue comprehensive model studies have been carried out with little success. It is now decided to construct additional storages on Indus to prolong the life of Tarbela reservoir.

The climate change is further going to add new dimension to these challenges. It is a far drawn conclusion that to successfully combat the impacts of climate change storage reservoirs with proper management are going to play extremely important role in mitigating the negative impact on water resources of the country in meeting its multi-sectoral demands in addition to effectively controlling the floods and droughts.

References:

[1]Tariq S.M. Water Management in Pakistan.

[2]Tariq S.M.Environmental Impacts of Tarbela Dam.

[3]KirmaniS.S.Water Sector Investment Plan – Policy and Management Issues.

[4]Brisco John, QamarUsman.Pakistan’s Water Economy Running Dry, The World Bank.

[5]Duder J.N., Mufti J.I.,Tariq S.M.Mangla and Tarbela Dams and Reservoirs – An Environmental Overview.