The River Clyde is a major river of western Scotland and the third-longest in the country at about 170 kilometres (110 mi) in length. Its river network extends to 4,244 km and drains a basin of 1,903 km2, expanding to 3,854 km2 when the Clyde estuary system with the Kelvin, White Cart, Black Cart and Leven is included. Around 1.79 million people, 33.8% of Scotland's population, live within this catchment. The river rises in the Lowther Hills and flows north-west through South Lanarkshire and Glasgow before deepening into the Firth of Clyde past the Tail of the Bank off Greenock.