The dam that nurtures Uda Walawe – By MAHIL WIJESINGHE
Source : sundayobserver
The sprawling Uda Walawe reservoir of Embilipitiya is one of the largest irrigation schemes in the South-Central area of the island.
The Walawe basin nestling in parts of the Ratnapura, Hambantota and Moneragala districts is adorned with many tourist attractions. Among them, the most popular attractions are the Uda Walawe reservoir and its adjoining Udawalawe National Park. Having crossed over this reservoir embankment on many occasions during my visits to Southern and Eastern destinations, I take a peek into this magnificent work of irrigation engineers of years gone by.
It was a great moment in the history of the irrigation sector in then Ceylon in the latter part of 1950, when former Prime Minister, the late Sir John Kotelawala inaugurated work on the Walawe Ganga reservoir scheme, the second multi-purpose project undertaken in Ceylon after the country gained independence.
Walawe Ganga
The 138-kilometre long Walawe Ganga is one of Sri Lanka’s largest rivers. It enters the sea on the Southern coast near the Godawaya estuary in Ambalantota, 20 kilometres West of Hambantota. It is watered by the rains that fall on Horton Plains, which in turn feeds the beautiful stream that flows beside the Belihuloya Rest House.
The famous Haputale Gap and the Pass are also in the hinterland of its watershed as are all the hills, valleys and tanks that you see as you climb the Haputale Pass from the catchment area of the Walawe Ganga. What you see from this Pass are the lands, partly jungle and tea, paddy and chena cultivations.
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All the rain that falls in the area finds its way to the Walawe Ganga and then to the sea at Ambalantota. In a year, 1,150,000 acre-feet of water flow into the sea and with it much of our top soil. The leaders at the time thought if this water can be used to irrigate lands and generate hydro-electric power, it could produce much power to light houses and work the machinery of factories.
The site selected by the Irrigation Department engineers was in a village called Embilipitiya, on the road from Pelmadulla to Ambalantota.
Today, Embilipitiya has blossomed into a bustling town, where the sprawling lands are filled with rice fields, industries and multitudes of farming communities.
At this point, the river that has its rise at Belihuloya, Horton Plains and Haputale Pass, enters the plain through a narrow valley, which offers many advantages for the construction of a dam.
Since the river receives an unfailing annual supply of water, the Irrigation Department engineers have decided to hold the water here and irrigate the lands below for growing paddy and other crops such as sugarcane and chilli. At the same time, engineers planned to generate 6,000 KW of electric power for distribution in the surrounding countryside.
Embankment
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The engineering enterprise was no small task. At the Embilipitiya project site, the river was dammed by an earth embankment 100 ft. high at the river section and 17,000 ft. long.
The earth embankment was so huge that it carried a road atop wide enough to take two lanes of traffic and sufficient room for parking. A dam of about three kilometres impounds the water of the Walawe Ganga and the reservoir covers 3,413 hectares.
The earth embankment was not safe unless there was a means of directing the floods or surplus water over it. For the purpose, the engineers have erected a concrete dam in the central section of the earth dam. This concrete structure is 1,000 ft. long and 120 ft. high.
To pass the flood water there were nine radial gates, each 40 ft. long and 30 ft. high, which can be raised and lowered from a bridge on the top of the concrete structure. When these gates open, as much as 260,000 cubic feet of water per second can be passed from the reservoir to the river below.
On the right bank of the river and the right-hand end of the concrete dam is the power house, which converts energy in the flowing water into hydro-electric power.
This water, after passing the turbines, is channelled to the ‘Yoda Ela’ (literally big canal) to take the water far out to irrigate the land commanded by the ‘Yoda Ela’. Some of the water from the turbines is passed back into the Walawe Ganga to be picked up at the Liyangastota anicut, which was constructed nearly a century ago to feed the channel system under this scheme.
However, in 1986, downstream of Belihuloya near Pabahinna, another reservoir was built damming the Walawe Ganga under the Accelerated Mahaweli Development Scheme known as the Samanalawewa Reservoir to generate hydro-electric power.
The Uda Walawe reservoir, its catchment area and the vast virgin forest land have to be preserved and conserved in the veritable name of nature for posterity.
Its vast imprisoned waters have to be preserved for its prime environment. The area has also to accommodate elephants that were displaced by irrigation development under the Uda Walawe reservoir.
With all those splendid hopes of conserving the reservoir and its catchment area, the Uda Walawe National Park was gazetted on June 30, 1972.
Today, it is a paradise for wildlife and the best spot to observe Asian elephants in the wild at any time of the year.
