Dams along the Mahaweli | Sunday Observer

Dams along the Mahaweli

Victoria Dam: spill gates
Victoria Dam: spill gates

The Mahaweli River is the longest river in Sri Lanka. The river originates from the mountains belonging to the Kirigalpoththa and the Thotupola mountain ranges and pours in to the Indian Ocean near Trincomalee; a journey that spans a length of 335 kilometres.

Water from the Mahaweli is used for two main purposes; agriculture and generation of Electricity. Thus, the river is dammed at six locations to divert water for irrigation and to run power houses. More than 40% of our nation’s electricity requirement is fulfilled by these six dams, namely, Victoria, Randenigala, Rantambe, Polgolla, Kothmale and Bowatenne.

Today, I will share with you some information on two dams that are quite close to our ancestral home in Kandy.

The Polgolla Dam

The Polgolla dam is a manmade structure built across the river to increase the depth of water and to divert its flow towards the hydroelectric power station at Ukuwela. Water is transfered via a penstock to the power station situated about 5 kilometers away. Technically, a construction of this nature is known as a “Barrage”, but, most often it is erroneously referred to as a Dam. The Polgolla Barrage is 14.6 metres high and 144 metres long and consists of ten spill gates. It has a Gross Storage Capacity of 4.1 million cubic metres and a live storage capacity of 2.1 million cubic metres.

The opening of the underground tunnel or penstock is located near the Katugasthota – Madawela road just before the Uyanwatte junction. The power station at Ukuwela consists of two 20 Mega Watt hydroelectric generators that were commissioned in July 1976. Water from the power station is discharged into the Amban River which in turn flows into the Mahaweli River 140 km downstream of the Polgolla Barrage.

As you approach the dam, there are sign boards directing you to the Waterdrome. A Waterdrome or a water aerodrome is an area of open water used regularly by seaplanes or amphibious aircraft for landing and taking off. My wife used to teach at a school in the vicinity of the dam; she used to love watching the seaplanes land and take off from the lake formed by the Polgolla Barrrage.

The Polgolla Barrage can be reached from three routes. From Kandy, take the Kandy Teldeniya road, turn left to the Lewella road and proceed till you reach the river. Then turn left and proceed about a kilometre along the bank of the river till you come to the barrage. You can also take the Kandy – Madawala road and take the turn to the right at the Uyanwatte junction.

The third route is from the Kandy – Katugasthota road. Take the turn to the right before the Mahaiyawa tunnel and proceed till you come to the Uplands Junction. Take the turn to the right onto Dave Road and proceed right down till you come to the river.

The Victoria Dam

Roughly 30 kilometres downstream from Polgolla is the Victoria Dam. It happens to be the tallest dam in Sri Lanka, and feeds a 210 Mega Watt power station; the largest hydroelectric power station in the country!

Originally, the Victoria dam project was scheduled to be completed within 30 years. But, due to economic difficulties during the time, the government decided to accelerate the construction of the dam. Thus, work on the dam commenced in 1978, and was completed in April 1985.

The Victoria Dam, considered as the crown jewel of the Mahaweli Development Project is situated in a deep valley just above the Victoria Falls rapids and 300 metres below the point where the Hulu Ganga meets the Mahaveli River. The Dam was designed and constructed with expertise and funds from the British government. Her Majesty, Queen Elizabeth II visited the construction site on October 24, 1981, while Margaret Thatcher, the Prime-Minister of the United Kingdom at the time, attended the opening Ceremony in 1985.

This double curvature arch dam is 520 metres long, 122 metres high and has a width of 6 metres at the crest and is 25 metres wide at the base. There is a road way at the crest over which vehicles could travel. Water from the dam is fed to the powerhouse via a 5,646 metre long tunnel, which houses three penstocks that have a diameter of 6.2 metres each. These penstocks which have a net head of 190 metres , feed three 70 Mega Watt (12.5 Kilo Volt) turbines, capable of generating up to 780 Giga Watt hours of electrical energy annually.

The eight spill gates that automatically open when the water level reaches the spill level is a special feature of the Victoria dam. What is interesting here is that the spill gates only need power to close; an award winning design! Each spill gate has a width and height of 12.5 metres and 6.5 metres respectively. In addition, there are two low-level sluices at the base of the dam which facilitate the purging of silt accumulated behind the dam.

The Victoria Reservoir created by the dam covers a surface area of 22.7 square kilometres and has a gross storage capacity of 722,000,000 cubic metres. When the reservoir is full the water level reaches the bottom of the barrage at Pogolla. When full, the scenery surrounding the reservoir is out of this world. The Fatima Church at Padiwatte standing above the level of water, with its image reflecting on the blue water creates a wonderful picture.

The Observation Point on a hill overlooking the dam provides a comprehensive view of the dam and the surrounding area. To reach this point proceed about 32 kilometers on the Kandy- Mahiyangana road and turn right at the Moragahamula Junction and travel a further 8 kilometres. This is a popular picnic spot for visitors, especially for school children from all parts of the country. There is a museum of sorts with a model made to scale showing the full area covered by the Project supported by photographs depicting the important stages of construction of the dam.

The best time to visit the Dam is when the spill gates are open. The last time they were open was about three years ago. I was lucky to be in Kandy at that time and I was able to witness this with my own eyes. The water gushing out of the gates, cascading down and making a booming sound as it splashes is a spectacle in itself.

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