Case Study: Orrin Falls Hydro Scheme

Meryl Marshall

The Orrin Falls (MHG62164) in Easter Ross are, or at least were, a series of attractive waterfalls with a total height drop of 15m in a gorge of the River Orrin. The first record of a hydro-scheme here is in 1898 when the landowner John Stirling “had estate workmen build a turbine house at the Orrin Falls and one further up river resulting in electric light [in Fairburn House] in 1898” (Fairburn Estate pdf). The scheme seems to have gone through several phases before being abandoned, possibly in 1961 when the Orrin Dam was built further up the river as part of the Conon Valley Hydro scheme and resulting in water being ducted through to Loch Achonachie and the River Conon. Nevertheless the Orrin Falls hydro-scheme was revived several years ago and is now in operation providing electricity for the estate (Charlotte Hingston, pers comm).

Orrin Falls dam looking west, remains of the original dam can be seen in the foreground. ©Meryl Marshall
The original dam for the hydro electric scheme at Orrin Falls was constructed c1898 it was replaced at a later date by a second one. Contributed by Meryl Marshall

The physical structures of the hydro electric scheme are on the south bank of the gorge and include:

The dam is c. 50m in length and crosses the river obliquely from northwest to southeast. It is constructed of concrete and has a thickness of 0.5m being 3.5m height at its highest. At the north end of the dam there is a fish ladder where an overspill leads onto a sloping ramp 1.5m to 2m in width.

The lade is a concrete ‘box’ channel roughly 50m in length; it is c.2m deep and 1.5m in width. There are three wooden sluices, two at the west end and one at the east end, two metal grids for catching floating debris (the one positioned diagonally is controlled by an overhead hoist) and two overspills.

The generator house is underground and at a much lower level to the lade. It is probably a recent structure on the site of an original one. It is constructed of dressed stone and is roughly 11m x 5m x 12m high.

The remains of an earlier dam are seen to the east/downstream side of the present dam. Although ruined and with water flowing over, it appears to be of similar construction to the later dam, but is only 1m in height.

A rock cut channel on the north bank is possibly an early fish ladder; it is at a higher level than is necessary today but perhaps functioned when the river was at its original level. It is roughly 20m in length, 1m in width and 1m deep.

The abutments of a bridge are situated in the middle part of the gorge above a waterfall. The bridge, probably ornamental and possibly pre-dating the hydro-scheme, is in two sections, at a slight angle to one another. The remains of the three supports or abutments can be identified (Marshall 2016).

This is a good example of a relatively early estate hydro-scheme which is of significant size and in reasonable order.

Further Information

John Stirling and the Fairburn Estate