Hitting a milestone in sluice technology: Victoria Dam
Found among the luscious green tea leaves of the hill country, the giant barrier that lies across the Mahaweli Ganga is located in an area of great scenic beauty, historic importance and congenial climate. It also happens to be the tallest dam of Sri Lanka. The Victoria Dam is just a 1 hour’s drive from Kandy and is found about 130 miles from the river mouth, immediately upstream of the Victoria Falls. The climate in the Victoria is broadly similar to that of Kandy, but the rainfall is less and it is considered an area which has a climate between the dry and wet zone types.
History
The need to address economic difficulties within the country in 1977 accelerated the project which had been in planning for 30 years. Designed to irrigate 901,935 acres of land and provide 600 MW of electricity, construction of the dam commenced in 1978 under the Accelerated Mahaweli Development Programme and was ceremoniously opened in April 1985 by then-President J. R. Jayewardene.
The funding, design and the technical expertise was provided by the United Kingdom. The Power Station was contracted to Costan International and the main contractor for the Dam and Tunnel was the Joint British Venture of Balfour Beatty and Edmund Nuttal. The consultant engineers on the project were Sir Alexander Gibb & Partners.
The project’s most memorable event was recorded when Her Majesty, Queen Elizabeth II visited the construction site on October 24, 1981.
Significance of the geographical area
In view of the fact that some of the decisive battles of the 15th century have been fought against the foreign invading armies in this area, it played a very significant role in the politics of the time. Palaces of Sinhalese Kings were built here, and even today many of the current inhabitants perform various rituals connected with the temple of the Sacred Tooth relic of Lord Buddha in Kandy.
Features of the dam and reservoir
Built at a deep valley just above the Victoria Falls, 300 metres below the point where the Hulu Ganga meets the Mahaweli River, the Victoria Dam is considered the crown jewel of the Mahaweli Development Project and is the only concrete dam in Sri Lanka.
The double curvature arch dam is 520 metres long with a maximum height of 122 metres, and the circular concrete- lined tunnel has a diameter of 6 metres. The gross capacity of this massive reservoir is 722,000,000 cubic metres, at a full supply level of 438 m. It is said that under the reservoir lies the old Teldeniya Town which went under water when the reservoir was filled. This ghost town rises from the waters once every few years during the driest periods of the year.
Dubbed the highest dam in Sri Lanka, the Victoria dam also has the largest Power Station in the country, since its 3 Francis turbines each have a capacity of 70 MW, generating 780 GIGA Watt hours. The 8 spillways, each with a width and height of 12.5 m and 6.5 m open automatically depending on the water level. The innovative gates which open when a predetermined water level is reached, need power only to close. The consultants who designed them were awarded “Innovative Design in Civil Engineering” by the Institution of Civil Engineers (UK). The total effective width of the spillways is 100 m, allowing a maximum discharge of 8,200 cubic m/s. Two additional low-level sluices at the base of the dam allows the purg- Design (net head)-190 meters Speed of rotation-333 revs/mm ing of accumulated silts behind the dam.
Getting there
You will find Victoria Dam about 72 aerial miles east of Colombo. From the Kandy railway station, travel 32 km on the Mahiyangana Road, passing Kundasale and Rajawella. You can take the road towards the Victoria Dam Observation Point which is 8 km from Moragahamulla Junction. Otherwise, you can take the road from Colombo to Teldeniya, which is a distance of about 84 miles. The road from Teldeniya to the site is a 4 mile long jungle track.
Food for thought
Dams impound floodwaters and release them under control or divert them for other uses, preventing the loss of life and property.
Sri Lanka has always been an innovative and clever nation. This statement was proved with the invention of the Bisokotuwa, the engineering marvel also known as the Cistern Sluice, which solved the problem of high pressures and the excessive potential energies stored in water reservoirs.
When the Victoria Dam was built, the advanced technology achieved a new milestone in the floodgate systems. The automatic opening of the stop gates when the water reaches 2/ 3rd of the reservoir’s capacity helps to control the water level without flooding the neighbouring areas.
It is widely supposed that the manual functioning of the spill gates of the other Sri Lankan dams contribute to the frequent flooding’s that we often hear of.
Maybe it is high time that we update our flood barriers and incorporate this technology to the rest of our dams so that water is discharged gradually, without risking dam failure or flooding of the surrounding settlements.
Ayeshni Wickramasinghe Generating voltage - 12.5 kV Energy production capability -
686 GWH/ year (firm) Energy production capability -
284 GWH/ year (initial) Type - Double Curvature Arch Dam Dam Crest Length - 520 m Dam Height (above foundation)
- 122 m (max.) Length - 5646 metres Diameter of tunnel - 6.2 metres
(inside concrete lining) Depth of surge chamber - 116
meters