South Otago lies in the south east of the South Island of New Zealand. As the name suggests, it forms the southernmost part of the geographical region of Otago. The exact definition of the area designated as South Otago is imprecise, as the area is defined not in geopolitical or administrative terms, but rather by the area's topographical features and the similarity of its communities. Overall, it encompasses some 8,000 km² (3,100 sq mi) and has a population of approximately 20,000, but these figures vary according to the various definitions of South Otago's boundaries. The area is often seen as roughly congruous with the Clutha District, which has its administrative centre at Balclutha. However, most of the Taieri catchment, from Taieri Mouth and Henley to Mosgiel and Middlemarch, with the coastal areas around Brighton, has been part of the City of Dunedin since 1989. The southwestern part of Clutha District, around the townships of Tapanui and Clinton, are regarded as part of a separate area, West Otago. Geography South Otago is dominated by three main topographic features: forests, hill country, and floodplains. To the south is the rough bush country of the Catlins, with its forests and rugged coastline. To the north of that the land is mainly rolling hill country, dissected by the floodplains of several large rivers. With the exception of the flat, fertile floodplains, South Otago is quite sparsely populated because of relatively cold winters, geographical isolation and lack of a decent port. A former port, Port Molyneux, located near the mouth of the Clutha River was abandoned in the early 20th century after rail transportation made freighting produce by rail to and from Dunedin more economically attractive. There are a number of rivers flowing through South Otago, the largest being the Clutha / Matau-Au, the country's second longest river, which flows from Lake Wānaka in Central Otago for 340 kilometres, through Balclutha (Scots Gaelic for "Town on the banks of the Clyde") and there splits in two around the large delta island of Inch Clutha before reaching the Pacific Ocean. A significant west-flowing tributary is the Tuapeka River, starting point of the 1860s Central Otago Gold Rush near Lawrence. Also of note is the Taieri, the country's fourth longest river, which winds through rough hill country before forming the Taieri Plains to the north-east of Milton then cutting through coastal hills to reach the ocean at