Cruachan - the hill with the hole

Looking along Loch Awe from Cruachan Reservoir, Britain's biggest energy storage system.




2.5 miles (4kms)

1200ft (366m)
1hr 45min

About the walk

The Cruachan Reservoir collects rainfall from a fairly small catchment, 9 square miles (23sq km) bounded by the rocky ridge of Ben Cruachan. Even with Cruachan's 116in (2,945mm) of rain a year, only 4 megawatts of power are generated, not enough to supply Oban, to the west.

The big battery

But Cruachan is more than just a rather small power station. It's a rechargeable storage system for electrical energy, a very big electric battery. The demand for electric power varies from day to day, and even from minute to minute. There's the surge at the advertising break during your favourite soap, as a million kettles get switched on at once. Coal and oil power stations can be stoked up or cooled off, but only quite gradually. Nuclear stations run at the same rate day and night. And the greenest energy sources, wind and wave generators, give power according to the weather. So there has to be a way of taking electricity out of the National Grid when there's too much, and putting it back when it's most needed.

Cruachan power

Fortunately, an electric generator running backwards becomes a motor, and a turbine turns into a pump. At 'white-meter' (off-peak) times of day, water is pumped from Loch Awe up to Cruachan Reservoir, 1,000ft (305m) above. And at 7:15 on a weekday evening, it flows back down again. The stored energy in the battery of your car is sufficient to keep it running for about half a minute, but that's enough to start it in the morning and run the CD player when the engine's off. Full to the brim, Cruachan Reservoir, with the capacity of about half a billion car batteries, in theory holds enough potential energy to supply the UK's peak demand for 10 minutes. In fact the water can't be drawn down that fast, but at full flow Cruachan can supply 400 megawatts, enough for most of Glasgow. Time your arrival for 7:15pm, and you could see the reservoir sinking at an inch (2.5cm) per minute. The same amount of water will be flowing out into Loch Awe, just beside the visitor centre. The whole process – pumping up and then retrieving the potential energy – is not much more than 50 per cent efficient. The waste heat ends up in Loch Awe, where it benefits the fish farm opposite the visitor centre.

The secret source

The Cruachan powerhouse makes a fairly small impact on the outer world. Around 12 miles (19.3km) of pipes bring water into the reservoir, and the outgoing or incoming electricity loops across the hill on high pylons. The 1,030ft (314m) dam is only visible once you reach the corrie; the power station itself is actually buried deep in the heart of the mountain.

Walk directions

The uphill path starts past the railway station, but first walk along the road (towards Oban) to a tarred lane opposite the entrance to the power station proper (not the visitor centre, slightly further to the west). This gives a view under the railway viaduct to some of the lower waterfalls. Return and take the uphill path from the corner of the parking pull-off, signed for the station and Ben Cruachan. It passes under the railway by a low arch, then continues uphill in steep zigzags through birch, rowan and oak. There are various points to stop and admire Loch Awe, which disappears glittering in the distance. White speckled stones in the path are Cruachan granite. The path continues on steeply to the top of the wood.

Here a high ladder stile crosses a deer fence. (The generously sized dog flap beside it may be the easier way for people as well!) With the stream on your left, continue uphill on the small path to a track below the Cruachan dam. Turn left, across the 275kV Bridge, and up to the base of the dam, which measures 1,030ft (314m) wide and 150ft (46m) high. Because it's tucked back into the corrie, it can't be seen from below, but it is clearly visible from the top of Dun na Cuaiche, 12 miles (19.3km) away. The hollows between the 13 huge buttresses send back a fine echo. Steps on the left lead up below the base of the dam, then iron steps take you on to the dam's top.

From here you can look across the reservoir and up to a skyline that's slightly jagged at the back left corner, where Ben Cruachan's ridge sharpens to a rocky edge. In the other direction, your tough ascent is rewarded by a long view across Lorn. Turn right to the dam end, where a track leads down right to a junction, then right for 50yds (46m).

The former path to the right (west) of the Falls of Cruachan has been closed off at the bottom, where it crossed the railway. Just before the 275kV Bridge, turn down left on the path used for the ascent. The views along Loch Awe are even more awesome on the way down.

Additional information

Steep rugged paths, 2 ladder stiles

Wooded slopes and high corrie

Good, but steep metal ladder onto the dam top will need to be bypassed

OS Explorer 377 Loch Etive & Glen Orchy

Two pull-ins on north side of A85, below railway station. Also lay-by 0.5 miles (800m) west. Not visitor centre car park

Cruachan Visitor Centre

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About the area

Discover Argyll & Bute

This is a county that’s all about awe-inspiring landscapes and unique island cultures. Ex-Beatle Paul McCartney put the area on the map when he wrote Mull of Kintyre, recorded in 1977 with the local pipe band backing his group. Kintyre is a long, thin peninsula that points south from the mainland, sheltering the mouth of the Firth of Clyde from the open sea. It’s very nearly an island, with just a narrow isthmus connecting it with Knapdale, to the north.

Tucked away at the end of the Firth of Clyde, Bute has been the holiday playground for generations of Glaswegians and is home to some of the finest golden beaches anywhere on the west coast. It may not boast the wild mountain grandeur of some of Scotland’s other islands, but Bute is blessed with swathes of heathery moorland and a range of low, fertile hills, perfect for walking and studying the local wildlife. Such is the variety of landscapes that make up this county.

To experience the sights and sounds of the area, visit Dunoon in late August for the Cowal Highland Gathering, when more than 150 pipe bands from all over the world compete for prestigious trophies.

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