22 - 28, 2011

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates are used to manage water flow into specific regions.

Hydropower and pumped storage hydroelectricity are often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations.

Manmade dams represent some of the most incredible architectural feats in the world today. While most dams are designed to impound or retain water, others (like floodgates and levees) are often used to control water flow into certain areas.

Regardless of how they are used, no one will question the sheer power and force each dam holds. One crack or failure - one mistake in control - could easily cause a catastrophic accident with the potential to wipe out an entire city.

The following are some of the largest dams in the world as measured by their sheer volume. While they are not all necessarily in the top 10 in terms of size, they are certainly sights worth visiting.

10. SRISAILAM DAM - INDIA: Located on the Krishna River, the Srisailam Dam was constructed in the Nallamala Hills in a gorge that sits approximately 300 meters above sea level. The dam is one of the 12 largest in the country in terms of hydroelectric power production but was specifically built in order to provide irrigation for the districts of Kurnool and Cuddapah - both of which are prone to severe droughts.

9. NAGARJUNA SAGAR - INDIA: The Nagarjuna Sagar Dam can be found in the Nalgonda district of Andhra Pradesh in India. Considered as one of the largest ever built in Asia, this dam was completed in 1966 and features 26 individual crest gates. As far as construction is concerned, this dam is the tallest in the world to be made strictly from masonry and its creation resulted in the third largest manmade lake on the globe. The dam and its canals are incredibly important to the ability to irrigate nearby land.

8. VERZASCA DAM - SWITZERLAND: The Verzasca Dam, also known as the Contra dam, was built between 1960 and 1965 in Val Verzasca, Switzerland. The dam was built by Verzasca SA, a company that generates electricity on the site and will continue to do so until at least 2046. The Lago di Vogorno reservoir is artificial, created by the dam itself, and has been responsible for causing earthquakes during times when it is filled.

7. ATATURK DAM - TURKEY: Completed in 1990, the Ataturk Dam in Turkey is a rock-fill dam found on the Euphrates River. Originally named the Karababa Dam, the site was later renamed in order to honor the founder of the Turkish Republic, Mustafa Kemal Ataturk. The dam is responsible for irrigating the regions plains as well as for generating electricity.

6. MANGLA DAM - PAKISTAN: The twelfth largest dam in the world was built in 1967 and was funded in part by the World Bank. The Mangla Dam came into creation thanks to the 1960 signing of the Indus Waters Treaty in which rights to the waters contained in the Ravi, Beas, and Sutlej rivers were given to Pakistan. Before the dam was built Pakistan's irrigation system relied solely on the flow of the Indus River - most of which was completely unregulated.

5. TARBELA - PAKISTAN: Completed back in 1976, the Tarbela Dam, also known as Torabela or Pashto, is considered to be the largest dam ever constructed on Pakistan's Indus River. While it's not the largest dam in the world overall, it is the largest dam filled naturally by the earth. The dam stores water in order to not only control flooding but for use in irrigation and the production of hydroelectric energy as well.

4. FORT PECK - UNITED STATES: The Fort Peck Dam in northeast Montana is one of six dams found on the Missouri River. Construction of this dam began in 1933 as part of the New Deal put forth by President Franklin D. Roosevelt and enabled over 11,000 workers to have gainful employment during the course of construction. The dam, which is solely responsible for the formation of Fort Peck Lake, is used to control flooding and generate power.

3. ASWAN DAM - EGYPT: The Aswan Dam is actually a pair of dams - the Aswan High Dam and the Aswan Low Dam. In ancient times, it was known that the River Nile would flood each summer as the waters flowed down from East Africa. As the population along the river grew, it became necessary to find a way to control flooding in this area. Now the land is still fertile enough for farming and the people no longer have to worry about drought but the fields aren't in danger of being wiped out due to flooding, either.

2. SYNCRUDE TAILINGS - CANADA: Located near Fort McMurray in Alberta, Canada, the Syncrude Tailings Dam is approximately 540,000,000 meters in volume. The dam is currently maintained by a company known as Syncrude Canada Ltd. - a company responsible for oil extraction in the Athabasca Oil Sands. The dam serves as a barrage used to store tailings - or leftover slimes and residues - that appear as byproducts of the oil extraction operation.

1. THREE GORGES - CHINA: The Three Gorges Dam in China is projected to be the absolute largest in the world. Expected to hold over 39,300,000,000 meters in volume, the reservoir is complete but the actual dam itself will not be completed until later this year. The construction of this dam had a huge impact on life in Sandouping, resulting not only in the relocation of dozens of villages but in the scenery as well. Because of the height of the Three Gorges Dam the mountains now look a bit lower than they actually are.

These dams are not only amongst the largest, but are considered some of the most functional, beautiful, and aesthetically pleasing in the world. Seeing one of the enormous dams in person will prove to be an absolutely breathtaking experience.

In Pakistan, three major dams i.e. Mangla, Tarbela and Chashma were constructed for the purpose of generating electricity, storing water and irrigating agricultural lands.

In addition, there are 23 barrages/head works/siphons; main irrigation canals are 45, which have extended up to 40,000 miles. Similarly, there are 90,000 watercourses, which are extended up to one million miles.

Mangla Dam (on river Jhelum): Earth fill, height 380 ft above riverbed, length 10,300 ft, gross storage capacity 5.85 MAP, main spillway 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 riverbed, length 9000 ft, gross storage capacity 11.3 MAP, spillway capacity 650,000 cusecs, lake area 100 square miles hydropower generation 1728 MW, completed in 1983.

At present only 11 per cent of the total water resources are stored in Pakistan, as no new water reservoirs were constructed after Tarbela, while countries like China had built 6000 water reservoirs during this period.

Since the per capita water availability is continued to drop, situation calls for a national consensus for developing small or big dams all over the country to meet the formidable challenges of water shortage.

In view of the mounting gravity of the developing situation, there is an urgency of initiating a timely action 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.

As a matter of fact, building new dams will help overcoming silting in the Mangla and Terbela dams. These dams will provide additional storage of water to meet the existing water shortages, generating a large chunk of hydropower for meeting the growing demand of agricultural, industrial, and domestic consumers through low cost option, reducing dependence on imported fuels, creating employment for persons during construction and significant numbers after commissioning.

A long debate is going on in the country over the issue. Practically, it takes about 10-15 years to build a dam. Thus, in order to properly manage the impending water and energy crisis, construction of dams should be started with immediate effect. If dams are not built immediately, it would have disastrous effect especially for the people of other provinces.

Today, Pakistan is suffering in the form of drought and acute water shortage especially in Sindh and Balochistan. The inadequate management of our water resources is one of the prime causes of our poverty.

The issue of water distribution and water management is extremely complex. Water distribution and allocation among the provinces remain a contentious issue. Punjab province has plenty of sweet sub water and in case of shortage, it can meet its requirement by sinking more tube wells.

But, Sindh has brackish subsoil 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 war footing.

Agriculture sector consumes about 75 per cent of water but the industry, commerce, and public health are also largely dependent on the availability of water. Water use for irrigation purposes in the country is quite high and inefficient, rather wasteful.

According to WAPDA's Vision 2025, there would be acute shortage of water during the next 10 years and Pakistan would become an extremely water-short country by 2012 with per capita water availability of only 1000cm. It was 5650cm in 1951 and 1400cm in 2000, which will go down further 885cm by 2025.

With such shortage of water, it is anticipated that agricultural production may face shortfall by 16 million tons by the year 2020, leading towards a grave famine-like situation, if timely action is not taken. It simply means that by 2025, we will need to have 3-4 large reservoirs, otherwise we will be short of drinking water, agrarian growth will suffer, the economy will be adversely affected, and the poor will remain poor.

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. To save and utilize the available water, construction of additional water reservoirs is essential for sustainable agriculture, the backbone of the country's economy.

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 was constructed some 5 to 6 centuries ago and extended under the great Mogul emperors.

In earlier 19th century, there were numerous inundation canals leading from Indus and its tributaries.

World's largest contiguous irrigation project was started in 19th 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 bar-rage-1962), link canals (Marala-Ravi (MR), Bambanwala-Ravi-Bedian-Dipalpur (BRBD) and Balloki-Sulimanki (BS) were constructed. If we will not construct dam, then water shortage will rise up to 8-10 millions MAF by 2015.

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 percent per annum. 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 totally drained it from Arabian Sea.

The government, public water utilities and the people should take measure to augment availability of sweet water, minimize wastage, and penalize those who pollute water by discharging untreated effluents in the rivers, canals or other waterways.

There is a dire need to introduce efficiency in the water distribution system to avoid any crisis-like situation. The subsoil water can be used for drinking and agriculture purposes by purifying the water.

From extensive investigations, it has been proved that Pakistan is rich in basic resources, but sincere and concerted efforts are needed to develop them for the service of the country.

The growing shortage of water requires intensive efforts, which should be made to preserve water and utilize available water resources if we are to become self-sufficient in food, embark upon socio-economic development, and alleviate poverty. But, unfortunately, new dams construction has fallen prey to political controversies, afflicting the development of all four provinces.