Tungnaa was gradually eroding a chasm through the Sigalda Hill, where
a 40 metres high dam was built to create a 14 square kilometre
reservoir for the hydroelectric power plant, which has been operated
there since 1977-78. It is a 925 metres long rockfill,
coated with asphalt on the lake side. A one kilometre long
headrace channel directs the water to the three 74 metres high
pressure shafts, each generating 50 Mw. The tailrace channel is
about 550 metres long.