lake in central South Island, New Zealand, occupying 65 square miles (169 square km) of a valley dammed by a terminal moraine (glacial debris). The lake, 1,640 feet (500 m) above sea level, receives the Tasman and Hooker rivers, which draw some of their waters from melting glaciers east of the Southern Alps; its total drainage basin is 523 square miles (1,355 square km). Pukaki is 5 miles (8 km) wide and 9.5 miles (15 km) long. It drains southward by the Pukaki River; a dam at the outlet, near the town of Lake Pukaki, regulates the lake's surface elevation as it releases water to power hydroelectric stations on the Waitaki River. Pukaki is a Maori term meaning “bunched-up water.”