SOME IMPORTANT DAMS OF THE WORLD AND PAKISTAN

There is need to construct more small dams/barrages in the country at least six in the Punjab, four in Sindh, three in NWFP and two in the provinces of Balochistan

Dr. S.M. ALAM, M.A. KHAN and R. ANSARI
Nuclear Institute of Agriculture,
Tandojam, Pakistan
Dec 11 - 17, 2000

There is a revelation about dam in the Holy Quran. It is said that "Indeed there was for Saba a sign in their homeland: two rows of garden, one on the right hand and second on the left; and it was said to them that {Eat of the provision of your Lord, and be grateful to Him; You have an excellent town and Forgiving Lord}". "But they turned away from the obedience of Allah, so We sent against them Sail Al-Arim (flood released from the dam), and We converted their two gardens into gardens producing bitter bad fruit, and tamarisks, and some few lotetrees" . (Surah 34-Saba, Ayats 15- 16).

Dam is a barrier, which is built across a water course of a normally giant river of a country to hold back firmly the mighty water, often forming a big reservoir or lake. Dams are made of timber, earth, rock, masonry, concrete or combinations of these materials. Timber is seldom used in a dam because, timbers are impermanent and their height is not reasonable. Dams made from rock, earth, masonary are all useful. Dams have been constructed from early times to provide sufficient and ready supply of water for irrigation and other numerous purposes. For centuries dam design was based upon previous experience. Remains of ancient earth fill dams still exist in India and Sri Lanka. The earliest recorded dam is believed to be a masonry structure 49 feet (15 meters) high that built across the Nile River in Egypt around 2900 BC. A rock fill dam built around 1300 BC in what is now modern Syria is the oldest dam still in use. A very important dam is the Aswan high dam, started in Egypt in 1960 near the Aswan dam built in 1902. Half of the Egypt's population are farmers, who rely entirely on irrigation. Virtually, a rainless country, Egypt depends for its existence entirely on the Nile, the second longest river in the world.

Irrigation means artificially watering the soil to initiate the growth of crops. The first large irrigation projects developed in the Eastern Hemisphere about 4000 B.C and made possible the advanced cultures of Egypt, Syria, Persia, India, Java and Ceylon. All agricultural land in Egypt is irrigated, about half in China, Japan and Pakistan, about 33 million acres in US and large parts of Europe. No country, in fact, is without its irrigation projects. Irrigation requires enormous quantities of water. For instance, one ton of sugar beets need 1000 tons of water during its period of growth; wheat 1500 tons and rice 4000 tons. At least half of it is lost by evapotranspiration. The rest is incorporated into the plants themselves (which are over 60 per cent water), and drains down into the subsoil.

One of the earliest large dams for this purpose was a marble structure, built in 1660 by a ruler in the sub-continent. Many modern dams are built for multipurposes i.e., to provide for irrigation water, water for human consumption, to aid occasional flood occurs in a country, check flow of water and to furnish power for hydroelectric plants. Many dams in the United States have constructed in Central Valley Project, Tennessee Valley Authority (TVA) Project and Mississippi Missouri River Basin Project. Among the largest are Bonneville dam, Grand Coule dam, and Hoover dam. A large dam of the Panama forms Gatun lake. Notable dams in Egypt are built on river Nile are Aswan (364 ft high an 3,280 ft long), and Sennar dams, and many important dams are built on important rivers such as the Drieper, Tigris, Euphrates, Indus, Ganges (Damodar), Yellow and Zambezi-Kariba dam (Zambia), which is 420 ft high and 1900 ft long.

Dams are categorized according to their profiles and construction materials. The principal types are earth fill, rock fill, gravel fill, solid-masonry gravity, solid masonry arch, arch gravity, structural masonry, and steel or timber. The first four types have been used from antiquity, while the others have been developed in the l9th and 20th centuries. The choices made by modern engineers regarding the materials and design that are best suited for a particular dam depend upon complicated analyses of foundation conditions, load strains, temperature and pressure changes, the chemical characteristics of local groundwater, and the probability of seism activity. Modern dams generally fall into two categories: embankment (earth fill) and masonry (concrete). Embankments are usually used to retain water across broad rivers; in part this is because such large amounts of material is needed, and earth and rock are usually more available and less expensive. The profile of an embankment dam, such as the Aswan High Dam across the Nile in Egypt, looks like a broad-based triangle. Although these dams are generally known most for their length than their height, a Dam in the Soviet Union is more than 330 meters high.

There are several different design possibilities for a masonry dam. The gravity dam utilizes the downward force for the weight of the construction materials to resist the horizontal force of the water. The base, where the force of the water is greatest, is made of concrete, its width is roughly three-fourths the height of the dam. Concrete buttress dams have materials in the wall itself through the use of support buttresses around the outside base. Extra rigidity is possible if the buttresses can be linked together, as in the multiple-arch dam, but such a structure, is only possible where no movement is anticipated in the buttress foundations. The Daniel Johnson Dam in Quebec has 14 buttresses across in crest (length) of 4,297 feet. The arch dam is built in a convex arch facing the reservoir. It has the unique advantage of reinforcement from the water pressure itself, which keeps the masonry joints closed tight. The strength of this design was tested in Italy, in 1963, when the Vaiont Dam remained basically undamaged after a huge quantity of soil and rock slided into the reservoir, causing water to surge over the top of the dam.

Once water has been retained by dams, it can be utilized. Outlets called gates, allow enough water through for irrigation, water supply, or power generation; they can also control the level of water in the river bed below the dam for ecological reasons. Special gates in the form of stepped pools, locks, or fish ladders are built into many dams for the upstream and downstream passage of such migratory fish as salmon. Sluices are also used to drain the silt that accumulates behind a dam. Besides causing additional pressure on the structure, accumulated silt can eventually fill a reservoir. The most important auxiliary structure of a dam is a spillway, the lack of which greatly increases the probability of structural failure. The spillway automatically discharges any water in excess of the capacity of the dam, because of heavy rain or landslide. Spillway water is usually diverted along the side of the dam or made to shoot out from the dam in what is called a ski jump spillway. In this way the dam's foundation is not eroded.

Dams in Pakistan: Three main dams Mangla, Tarbela and Chashma (barrage) were constructed for the purpose of generating electricity and irrigating agricultural land. In addition, there are 23 barrages/head works/syphons; main irrigation canals are 45, which have extended up to 40,000 miles. Similarly, there are 90,000 water courses, which are extended up to one million miles.

Mangla Dam (on river Jhelum): Earth fill, height 380 ft above river bed, length 10300 ft. gross storage capacity 5.85 MAF, main spill way 870,000 cusecs. Lakes are 100 square miles, hydropower generation - 1000 MW capacity, completed in 1967. Tarbela Dam (on river Indus): Earth and rock fill, height 485 ft above river bed, length 9000 ft. gross storage capacity 11.3 MAF, spill way capacity 650,000 cusecs, lake area 100 square miles hydropower generation 1728 MW, completed in 1983.

The dams have been constructed for the purpose of depleting capacity of the existing water reservoirs call for at least several small dams in the country to meet the water requirements. In view of the mounting gravity of the developing situation, there is an urgency of initiating a timely move to expedite development of adequate water resources to meet the increasing need of the economy adequately, without any more loss of time. There is need to construct more small dams/barrages in the country at least six in the Punjab, four in Sindh, three in NWFP and two in the provinces of Balochistan. The names of some dams were appeared for construction in the papers. Such dams are Bhashah, Munda dam, Chotiyarion dam also in Thar (Ravee Canal), and some barrage (Sehwan) and canals in Balochistan, NWFP and Sindh. During the last 30 years, no any new dam was constructed, thus we are neglecting this dire requirement of water for the country and thus country is today suffering for this criminal neglect in the form of drought and acute water shortage throughout the country specially Sindh and Balochistan. Punjab province has plenty of sweet sub water and in case of shortage, it can meet its requirement by sinking more tubewells. But Sindh has brackish sub soil water, which cannot be used for irrigation purposes. The water shortage in Sindh province will be much more acute in the coming years and this disaster can be averted only by undertaking construction of new dams on warfooting.

The country in the next 10 years will loss water storage capacity equivalent to Mangla dam as 5 x 105 tons of sedimentation are flowing into dam every day. According to an estimate within 10 years the country's water storage capacity would deplete by over six million acre feet (MAF), which is equal to water stored in Mangla dam and this shortage will continue to increase with every passing year and the biggest sufferer will be the province of Sindh. The gigantic dams built earlier at Warsak, Mangla and Tarbela on rivers Kabul, Jhelum and the Indus, respectively, have continued emitting signals of wearing down and now they have to be supplemented with new dams to meet the needs of the times. In the meantime, the growing need of water for irrigation and other purposes has acquired alarming proportions.

Pakistan is fortunate in the soils, topography and climate, which are suitable for year round agriculture. Major agricultural areas lie within the plains formed by Indus river and its tributaries, namely Kabul, Chenab, Ravi, Jhelum and Sutlej. Indus plains are like a tunnel with number of water sources at the top, converging into single stream, which flows into the Arabian sea, near the city of Karachi. First canal were constructed some 5 to 6 centuries ago and extended under the great Moghul emperors. In earlier l9th century, there were numerous inundation canals leading from Indus and its tributaries. World's largest contiguous irrigation project was started in l9th century. After independence in 1947, many more developments in the canal systems were made. Different barrages/canals i.e., (Kotri barrage-1956, Taunsa barrage-1958 and Guddu barrage-1962), link canals (Marala-Ravi (MR), Bambanwala-Ravi-Bedian-Dipalpur (BRBD) and Balloki-Salimanki (B S) were constructed.

Turkey (780,576 square kilometers) has constructed at least 40 dams on Tigris River within last five decades for agricultural development. While, Pakistan (803,943 square kilometers), during the same period built on four dams (Mangla, Tarbella Warsak etc). If we will not construct dam, then water shortage within 10 years will rise to 6 million MAF and up to 2015 by 8-10 millions MAF. No wonder, to-day, the country is facing a serious water crisis.

Iraq has many dams such as: Qadisiya on the Euphrates, Saddam dam on the Tigris, Hamreen dam on Diyala, Bakhma dam on upper Zab and Fathab on Tigris. In Libya, there are no permanent water courses. However, several seasonal water courses run north ward. Seventeen out of 36 planned dams have been built on the water courses. In Syria, there are many small dams, which are fulfilling many important requirements of the country. Similarly, there are more than 200 small dams in Saudi Arabia.

Pakistan is basically an agricultural country, but it has only four dams. Recurrent failure of the monsoon system has become a regular feature in Pakistan for the past five years with the result that reservoirs/dams have lowered their actual height of water. There is a dire need to find a solution to the water shortage problem, as the country's population is increasing at an alarming rate of three per cent per annum.

Water shortage in Pakistan to expansion in heat zone, inadequate contribution of announcement, below normal rainfall all over country. The water situation seems to get worst every year with reduced average rainfall.

We have limited supply of water, the best option for us is to go for recycling of sewage water, now drained it Arabian Sea. Such water can be used for agriculture purposes. Mismanagement of the distribution system, where justice comes in. There is a dire need to introduce efficiency in the water distribution system to avoid any crisis-like situation. We have vast reserves of underground water in Balochistan, Sindh and Punjab. The subsoil water can be used for drinking and agriculture purposes by purifying them. A recent report of UN Economic and Social Commission for Asia and Pacific (ESCAP), says, that shortage would be the most pressing problem in Pakistan in the coming years, largely due to mismatch between availability and extensive over use. Therefore, top priority would be given to solve the water problem of the country.

 

Some of the world' s greatest dams completed by 1990.

Name of
dams

Type

Dateof
comp-
letion

River

Country

Height
(m)

Volume
(00o cum)

Reservoir
capacity
(000 cum)

Electric Power
capacity
(megawatts)

Rogum (U)

E

1985

Vakhsh

Soviet
Union

335

71,100

13,300,000

3,600

Nurek

E

1979

Vakhsh

Soviet
 Union

300

58,000

10,500,000

2,700

Grnade Dixence

G

1962

Dixence

Switzerland

285

5,957

400,000

840

Inguri (U)

A

=

Inquri

Soviet
Union

272

3,960

2,500,000

1,325

Chicoasan

ER

1982

Grijalva

Mexico

263

14,500

1,680,000

2,400

Vaiot

A

1961

Vaiont

Italy

262

-

-

-

Sayano-
Shushen-
skaya

A

1982

Yenisey

Soviet
Union

242

9,117

31,300,000

6,400

Mica

E

1972

Columbia

Canada

240

32,111

24,669,800

1,800

Chivor

R

1976

Bata

Colombia

237

10,806

815,343

-

Mauvolsin

A

1957

Drance

Switzerland

237

2,030

180,000

-

Oroville

E

1968

Feather

U.S.

235

59,639

4,298,500

440

Chirkeys-
kaya

A

1975

Sulak

Soviet
Union

233

255.5

2,777,842

-

Tarbela

ER

1975

Indus

Pakistan

148

142,290

13,691,650

1728

Fort Peck

E

1940

Missouri

U.S.

76

96,055

23,600,000

165

Guri (U)

ERG

1985

Caroni

Venezuela

162

88,000

140,000,000

10,000

Oaha

E

1963

Missouri

U.S.

75

70,343

29,100,000

595

Mangla

E

1968

Jhelum

Pakistan

116

65,655

7,250,000

1000

Owen Falls

G

1954

Victoria

Uganda

31

-

204,800,000

120

Bratsk

E

1961

Angara

Soviet
Union

125

9,263

169,400,000

4,500

Aswan High

G

1970

Nile

Egypt

111

42,620

169,000,000

2,100

Kariba

A

1959

Zambezi

Zimbabwe-
Zambia

128

1,065

160,000,500

705

Akosombo

R

1965

Volta

Ghana

141

7,900

148,000,000

786

Itaipu (U)

GBER

1985

Parana

Brazil/
Paraguay

189

24,021

=

12,600

Grand Coulee(U)

G

1985

Columbia

U.S.

168

8,093

11,795,000

10,800

Guri (U)

ERG

1985

Caroni

Venezuela

162

88,000

140,000,000

10,000

Sayano-

A

1982

Yenisey

Soviet
 Union

242

9,117

31,300,000

6,400

Shushen-
skaya\ Krasno-
yarsk

               

G

1967

Yenisey

Soviet Union

124

4,350

73,300,000

6,090

Bratsk

E

1961

Angara

Soviet Union

40

9,563

169,270,000

4,500

Tucurut

EG

1982

Tocantins

Brazil

106

=

43,000,000

3,980

* Key: A = arch, B = buttress, E = earth fill, G = gravity, R= rock fill