Megget Reservoir is a man-made water body in Ettrick Forest, in the Scottish Borders. The 259 hectares (640 acres) reservoir is held back by the largest earth dam in Scotland. The reservoir collects water from the Tweedsmuir Hills, which is then conveyed 28 miles (45 km) via pipelines to Edinburgh. The pipelines are routed through the Manor Valley and the Meldon Hills, to Gladhouse Reservoir and Glencorse Reservoir in the Pentland Hills. The outflow from the reservoir is the Megget Water, which flows into St.