Dam - view of Clyde Dam and Lake Dunstan. New Zealand. opened in 1994 New Zealand's third largest hydroelectric dam and the largest concrete gravity dam with a generation capacity of 400 MW providing 5% of the country's electricity. Its construction which flooded houses and orchards used one million cubic metres of concrete and the design makes it resistant to earthquakes. The dam wall is 100 meters high, 70 meters wide at the base, 10 meters wide at the crest and 490 meters long at the crest.supplies on Clutha River near Clyde New Zealand.