An old reservoir on the course of the Brothie Burn in the centre of Clackmannanshire, Gartmorn Dam lies to the east of Sauchie and 2 miles (3 km) east northeast of Alloa. Retained by a earth embankment dam at its western end, the reservoir is a mile (1.6 km) in length, around a quarter-mile (0.5 km) wide, extends to 67 ha (165 acres) and contains a 1.8 ha / 4.5 acre wooded island.
The reservoir was built in 1713 for John Erskine, 6th Earl of Mar (1675 - 1732), as part of an ambitious scheme to provide water to power the pumps for his nearby coal mines. This scheme was unique in 18th century Britain creating what was, at the time, the largest artificial body of water in Scotland, and was a great engineering achievement. It is fed by a 2-mile / 3-km lade which draws water from the Black Devon at Forest Mill. Water from the reservoir fed a network of lades which were also to power several wool and corn mills at Keilarsbrae and Alloa into the 19th century.
After its use for industry declined, the reservoir went on to supply drinking water to Alloa and remains owned by Scottish Water, although is now leased to Clackmannanshire Council to form the centrepiece of the Gartmorn Dam Country Park. It was designated as a Site of Special Scientific Interest (SSSI) in 1971 because of importance for migratory wildfowl in the winter months and more recently for its vegetation, with transitional fen and reed beds along its shore. For a time the reservoir provided a recreational fishery, and wild brown trout, perch and pike remain.
