[1] It was built at the confluence of the Walawe river and the Belihul Oya, a location 400 metres (1,300 ft) above mean sea level.

[3] With the Mahaweli and Laxapana hydroelectric power projects implemented, the demand for electricity in Sri Lanka rapidly increased.

A reservoir type hydroelectric power plant was planned to be constructed across the Walawe river, which would address the shortage of electricity in the country.

[5] Sir Alexander Gibb & Partners did the design work and Balfour Beatty were the contracts to lay roads, drive a tunnel and build the power station.

[4] However, as the reservoir was being filled, a large leak occurred on the side of the right bank, about 300 metres (980 ft) downstream from the dam, causing a landslip.

The leakage of approximately 2,100 litres (460 imp gal) per second continues, but has not affected power production at the plant, which has been in full operation since its commissioning in 1992.

[9] The karstic ground has created complex geological conditions, and as a result the exact mechanism of the leak cannot be established, so remedial measures have been unsuccessful.

Although an irrigational release valve (IRV) is there in the dam to supply water to the farmlands in the downstream areas, the yield and cultivable acreage has declined since the Samanalawewa project was commissioned.

Of the water released from the Samanala Dam for agriculture in the downstream areas, two-thirds is from the leak and only one-third has to be supplied via the IRV.