Loch Lomond is a freshwater Scottish loch that spans the Highland Boundary Fault, often considered the boundary between the Lowlands and Highlands of Scotland. Traditionally forming part of the boundary between the counties of Stirlingshire and Dunbartonshire, it is today split between the council areas of Stirling, Argyll and Bute and West Dunbartonshire. Its southern shores are about 23 kilometres (14 mi) northwest of the centre of Glasgow, Scotland's largest city. The loch forms part of Loch Lomond and The Trossachs National Park, which was established in 2002. From a limnological perspective, Loch Lomond is classified as a dimictic lake, typically undergoing two mixing periods each year. This occurs in the spring and autumn when the water column becomes uniformly mixed due to temperature-driven density changes