The Clutha River / Mata-Au is the second longest river in New Zealand and the longest in the South Island. It flows south-southeast 338 kilometres (210 mi) through Central and South Otago from Lake Wanaka in the Southern Alps to the Pacific Ocean, 75 kilometres (47 mi) south west of Dunedin. It is the highest volume river in New Zealand, and the swiftest, with a catchment of 21,960 square kilometres (8,480 sq mi), discharging a mean flow of 614 cubic metres per second (21,700 cu ft/s). The Clutha River is known for its scenery, gold-rush history, and swift turquoise waters. A river conservation group, the Clutha Mata-Au River Parkway Group, is working to establish a regional river parkway, with a trail, along the entire river corridor.