River Tay River Tay The River Tay () is the longest river in Scotland and the seventh-longest in the United Kingdom. The Tay originates in western Scotland on the slopes of Ben Lui (), then flows easterly across the Highlands, through Loch Dochart, Loch Iubhair and Loch Tay, then continues east through Strathtay (see Strath), in the centre of Scotland, then southeasterly through Perth, where it becomes tidal, to its mouth at the Firth of Tay, south of Dundee. It is the largest river in the UK by measured discharge. Its catchment is approximately , the Tweed's is and the Spey's is
River Tay the Lyon. A flow of was recorded on 17 January 1993, when the river rose above its usual level at Perth, and caused extensive flooding in the city. Were it not for the hydro-electric schemes upstream which impounded runoff, the peak would have been considerably higher. The highest flood recorded at Perth occurred in 1814, when the river rose above its usual level, partly caused by a blockage of ice under Smeaton's Bridge. Other severe flood events occurred in 1210 and 1648 when bridges over the Tay at Perth were destroyed. During the winters of 2009–10 and 2010–11, the Tay