Site Records

OS Grid Ref: NH 22393 10846 (access tunnel portal)
Date opened: 1959
Date closed : Operational

The Garry-Moriston scheme was constructed during the 'peak' years of the Hydro Boards construction schemes, the early-mid '50s (started 1949, the final station (Livishe) not being commissioned until 1963). The design of the scheme was relatively advanced by the Hydro Board standards of the time - whilst many schemes were still using surface power stations and steel surface penstocks for the high pressure system, Garry-Moriston was built with only one surface power station (Quoich) - three were completely underground, and one partially so. All the high-pressure systems were built underground, with high-pressure shafts and penstock tunnels.

Ceannacroc is a medium-head (295ft) development of the 'traditional' kind (dam, low-pressure tunnel, surge shaft, high-pressure shaft/tunnel, power station, short tailrace). It is noteworthy for being the first major underground power station built in the UK. Storage is provided at Lochs Loyne and Clunie, which have both been enlarged by dams, the water from Loch Loyne being led, via a small power station, through a tunnel to Loch Clunie. A tunnel supplies Ceannacroc from Loch Clunie, the tailrace from Ceannacroc discharges into the River Moriston, which is dammed again a few miles downstream, and the water utilised in the lower stage development at Glenmoriston.

The bed of Loch Clunie is gently-sloping, so rather than the 'conventional' intake tower, water is led to the tunnel entrance through a submerged 'cutting' on the bed of the loch. The gates and screens are housed in two separate shafts a little distance away, one either side of the main A82 trunk road. From there the water is taken to the main Ceannacroc tunnel, 14,000ft long, of 12' equivalent diameter in a horseshoe section, to the surge chamber. From there the water falls down a vertical high-pressure shaft, from the base of the shaft a short length of high-pressure tunnel leads to Ceannacroc power station, which is constructed underground. After passing through the turbines at Ceannacroc, a 1,700ft tailrace tunnel discharges the water into the River Moriston. A side-stream intake along the route of the low-pressure tunnel captures the flow of the Allt nam Peathrain, and an extensive system of aqueducts and intakes captures the flow of the River Doe & tributaries.

The following map should make the general layout of the scheme clear:

Illustration: Ceannacroc Map
Illustration by: Scanned by Mike Ross, from 'Water Power', June 1959

There are 105 images of Ceannacroc in the Records, and 8 webpages. They may all be accessed via the map at the bottom of this page, which is a clickable image map. Each area selected will open in a new window. Drilldown to high-resolution imagery available throughout - clicking on any image will bring up the full-resolution original in a new window. Be warned, most of these are large (2400 x 1800, as much as 700-800kb).

A short video sequence touring the machine hall exists, as does another covering the adit, LP tunnel, and surge shaft, but they are not yet online.

Photo: Ceannacroc access tunnel portal
Photo by: Mike Ross

The map below is an imagemap, and allows you to navigate the Ceannacroc pages. You can click on any of the red text on the map, or the legend on the lower right, and the web page for the corresponding feature will open in a new window

Illustration: Ceannacroc Area Map
Illustration by: Canmap, additional legend Mike Ross