Scottish watershed

The Scottish Mainland watershed is the drainage divide in Scotland that separates river systems that flow to the east into the North Sea from those that flow to the west into the Atlantic Ocean. At a point on the summit of Ben Lomond for example, looking west all water flows to the Firth of Clyde, and looking east all water flows into the Firth of Forth. Similarly Cumbernauld is a point on this line and arguably its Gaelic name has, for hundreds of years, reflected this fact, although there is some dispute about interpretation of the Gaelic phrase. The line joining all such points in Scotland is the Scottish Mainland watershed.

Although the concept of a geographical watershed is common, the first unequivocal reference to the Scottish watershed is to be found in Francis Groome's Ordnance Gazetteer of Scotland of 1884. H.A. Webster contributed an article to the General Survey section of Volume VI (published 1885) in which he states "The watershed or water-parting, which may be said to begin at Duncansbay [that is, Duncansby Head], follows an extremely tortuous course through Caithness and Sutherland ...". This was followed in 1895 with John Bartholomew's Survey Atlas of Scotland which shows the entire geographic feature, from the border with England to Duncansby Head.