Advantages and disadvantages

hydroelectric power, irrigation and drinking water purpose.The advantages of such dams are:1. Flood control during heavy rain and water accumulating season. Without the dams flooding may result in the downstream of the river mostly in the plains.2. During heavy rainy season water just goes to the sea without benefiting anyone. Dams prevent it and the water is used later beneficially.3. Power can be produced without any pollution. Really a clean energy.4. Controlled irrigation can be done which will allow the farmer to sow and harvest in time without depending on rain so much.5. Neighboring cities gets good water throughout the year.6. employment for the power station people and agriculturist etc.

Disadvantages: When Dams are built government does not really take care of the villagers in that area, which will be affected by the construction. Many villages will be gone under the dam.If proper care is not taken the silt from the flowing rivers get accumulated in the dams and the capacity of the dams gets reduced in course of time.

Environmental impact. Construction activities can harm the environment by causing noise and pollution.Huge mass of water collected in one place may cause some weight disturbance to the earth which is not proven but there is a theory going around.

sukker barrage

Dams and Barrages

DamsA dam is a barrier that impounds water or underground streams. Dams have played a key role worldwide in development. Dams are built to supply water, control floods, irrigate agricultural lands and provide for navigation. They have also been built to generate electric power.

Picture: Tarbela Dam

Benefits of Dams:1. Power generation:Hydroelectric power is a major source of electricity in the world. Many countries are making dams on rivers for power generation purposes.

2. Water supply:The water requirement of many urban areas of the world is fulfilled from dams.

3. Stabilize water flow / irrigation:Dams are often used to control and stabilize water flow, often for agricultural purposes and irrigation.

4. Flood prevention:Excessive precipitation in an area results in floods, which causes huge loss to life and property in the low lying areas of a river where the flood water flows. Dams and reservoirs are effective and can be used to maintain water levels in a river. The flooding downstream of water can be temporarily stored in a dam and released later when it is required.

5. Land reclamation:Dams (often called dykes or levees in this context) are used to prevent ingress of water to an area that would otherwise be submerged, allowing its reclamation for human use.

6. Recreation and aquatic beauty:Dams play an important place for recreational purposes. People may have come to enjoy the reservoir for recreational and aesthetic reasons. Often the reservoir will be placid and surrounded by greenery, and convey to visitors a natural sense of rest and relaxation.

7. Navigation:Natural river conditions, like currents, changing river levels, and snowfall, create major obstacles and problems for local inland navigation. Dams can effectively be used for controlling the levels of water in a river where inland navigation is carried.

Disadvantages of Dams1. Seepage and evaporation2. Groundwater table effects3. Sedimentation behind dams4. Erosion downstream by sediment-starved waters5. Clogging of rivers by side-canyon floods

BarragesA barrage dam is a special kind of dam which consists of a line of large gates that can be opened or closed to control the amount of water passing the dam. The gates are set between flanking piers which are responsible for supporting the water load. They are often used to control and stabilize water flow for irrigation systems.

Picture: Chashma Barrage

Difference between dam and barrageBoth the dam and barrage are barriers constructed across a river or natural water course for diverting water into a canal mainly for purposes of irrigation, water supply etc. or into a channel or a tunnel for generation of power.

In case of a barrage, its entire length across the river i.e. between the banks is provided with gates having their bottom sill near the river bed level. Thus, the storage behind the barrage is solely created by the height of the gates.

The dam on the other hand has spillway gates almost near its top level and the storage behind the dam is mainly due to the height of concrete structure and partially due to the gate height. In both the cases, however, the number and size of gates is adequate to pass the design flood during monsoons.

Tarbela dam

Taunsa barrage near multan

Jinnah barrage

Guddu barrage

chasma

kotri barrage

Pakistan major DamsA dam is very essential in every field. Dam is very barrier built across a water course to hold back or control the water flow. Dams divert the flow of river water into a pipeline, canal, or channel. Others raise the level of inland waterways to make them navigable by ships and barges. Many dams harness the energy of falling water to generate electric power. Dams also hold water for drinking and crop irrigation, and provide flood control.

Tarbela Dam

The world's largest earth-filled dam on one of the world's most important rivers - the Indus - is 103 km from Rawalpindi. The dam was completed in 1976 at a cost of Rs.18.5 billion. Over 15,000 Pakistani and 800 foreign workers and engineers worked during its construction. It is the biggest hydel power station in Pakistan having a capacity of generating 3,478 MW of electricity. Its reservoir is 97 km long with a depth of 137 meters while total area of the lake is 260 sq.km. Permits are required for visiting the Dam. Please contact Public Relations Officer (PRO), Water and Power Development Authority (WAPDA), Tarbela (Tel: 051-568941-2). A No-Objection Certificate (NOC) from the Ministry of Interior (Shaheed-e-Millat Sectt.), Islamabad is also required for foreign visitors.

Mangla Dam

World's third largest earth-filled dam is only 115 km south-east of Rawalpindi. One has to turn left from Dina Town and the dam on river Jhelum is about 14 km to the east. The dam is 3,353 meters long and 116 meters high above the river bed. It is designed to store 5.88 MAF water and also used for power generation. In the centre of the dam there is a Gakkhar Fort from where one can have a panoramic view of the lake. For permit to visit the dam, please contact PRO, WAPDA, Mangla. A NOC from the Ministry of Interior is required for foreigners only.

Warsak Dam

The gignatic multi-purpose Warsak Dam is situated 30 kms north-west of Peshawar in the heart of tribal territory. It has a total generating capacity of 240,000 kw and will eventually serve to irrigate 110,000 acres of land.

Small dams

Ghazi Barotha dam Gomal dam

Hub dam

Khanpur dam