The spark coming from our water

The 220-metre long machine, nicknamed Eliza Jane by local schoolchildren, broke through the ground near Loch Ness in the Highlands, marking the end of a major phase in the £140m sustainable energy project by Scottish and Southern Energy (SSE).

As the tunnel boring machine pushed through the rubble and emerged into the daylight, SSE chief executive Ian Marchant said it was a "significant" moment in a "large and complex" project.

Glendoe is the first major hydro-electric scheme in Scotland since Errochty in Perthshire opened more than 50 years ago.

It will produce up to 100MW of energy, enough to power 250,000 homes, when it becomes operational at the end of this year.

Eliza Jane has been at the heart of the project. Built in Germany, it was shipped to Tyneside before being transported to the Monadhliath mountains, to the east of Fort Augustus in Inverness-shire, in 2006.

It was taken in sections to the site and assembled before it began work in September of that year.

Since then, it has created five miles of tunnels to allow water collected in a new reservoir 600 metres from the loch to reach an underground power station near the loch's south-east corner, before being discharged into the loch itself.

For many, Glendoe is not only an example of Scotland's civil engineering tradition, but also a welcome return to hydro-electric power north of the border.

"Hydro schemes were fairly common in the 1950s," said Professor Alan Ervine, of the civil engineering department at the University of Glasgow.

"Then it was concluded that they had come to the end of the road because all the large sites had been more or less taken up. Now we are starting to go down that route once more because of the need to create renewable energy."

Plans for the hydro-electric scheme were given the go-ahead by the then Scottish Executive in July 2005. At the time, Enterprise Minister Nicol Stephen said it would make a "significant contribution" to meeting renewable energy targets.

Since then, Scotland's target for the amount of electricity from green sources has been raised from 40% by 2020 to 50%.

Glendoe will make its own contribution towards achieving that target.

With average annual rainfall in the area reaching about 2000mm, compared with under 700mm in Edinburgh, SSE says that Glendoe is ideally located to generate hydro-electric power.

Meanwhile, the 600-metre drop from the reservoir to the turbine is the highest of any hydro station in the UK, allowing it to generate more energy from every cubic metre of water than any other facility.

Although its initial installation will produce some carbon dioxide, the actual operation of the facility will not and supporters say that it will prove to be a vital piece of the renewable energy mix for Scotland's future.

Environmental campaigners have largely welcomed Glendoe's construction. Duncan McLaren, chief executive of Friends of the Earth Scotland, said: "This is a very useful scheme and is a significant contribution to moving us towards meeting our targets.

"Hydro-electric is a reasonably regular and reliable form of power but it can be, within reason, turned on and off at will. It is not like wind, when you take the power when it is running.

"It is the ability to mix things like hydro with wind, wave, tidal and solar power that means we can look forward to a largely, if not wholly, renewable power future.

"This scheme has been done sensitively and my understanding is that any environmental impact has been managed effectively. It is another signal of our ability to meet and indeed exceed the renewable energy target."

The new reservoir will be formed by the construction of a kilometre-long dam at Glen Tarff, while the actual power station will be housed in an underground cavern 250 metres below ground level.

It will contain the turbine, which will be turned by the force of the water flowing through it, and the generator, which turns that force into electricity.

According to SSE, the facility, which will be operated remotely from Perth, will be able to generate electricity at full capacity within just 30 seconds.

Supporters of hydro-electric power believe there is potential for further schemes in Scotland, arguing that it could be a cost-effective and reliable form of generating renewable energy.

Tom Douglas, a consulting engineer and former visiting professor at Strathclyde University, said that in the 1940s, some 102 possible hydro schemes were identified but only 29 were built.

"There have been various mis-statements relating to whether there is any more hydro potential in Scotland," he said. "The reality is that there is a considerable amount of further hydro power potential to be developed in the Highlands. The economics are in favour of not just a single scheme on its own, but a programme of schemes.

"I'm all in favour of a long-term programme that would bring in one or two schemes a year."

However, he said that government backing was vital for the creation of new facilities.

The Scottish Government yesterday said that it was in full support of hydro-electric power and reiterated its opposition to nuclear energy.

Scotland's Energy Minister, Jim Mather, said the focus was on renewable energy and welcomed Glendoe into the mix.

He added: "Scotland has abundant natural resources to generate clean, green power and Glendoe will make a significant contribution to fulfilling our renewable energy potential.

"We are building an energy strategy that embraces a whole mix of renewables - from biomass to wave and tidal power - as well as significant opportunities for clean fossil-fuel technologies and carbon storage. All this can be done without unnecessary and costly new nuclear power."

Engineering feats

• Forth Bridge
  One of the largest steel bridges in the world, completed in 1890 and seen as an engineering marvel.

• Caledonian Canal
  Linking Fort William to Inverness, it was designed by renowned engineer Thomas Telford.

• Tay Bridge
  After the original collapsed during a violent storm in 1879, a second was opened in 1887. Linking Dundee to Fife, it remains in use.

• Glasgow Subway
  Opened in December 1896, it is the third-oldest underground system in the world, after London and Budapest. Around 14 million passengers used it in 2007.

• Rannoch hydro-electric plant
  Originally opened in 1920, it draws water from Loch Ericht and is one of the oldest hydro-electric plants in Scotland. Reopened in 2000 after a £10m refurbishment.

• The Falkirk Wheel
  The iconic canal boat lift, created to re-establish east to west coast boat access, has proved a popular tourist attraction.

• The Clyde Arc
  Opened in 2006, the "squinty bridge" was the first new road bridge over the Clyde since 1969.

Future works:

• New Forth road bridge
  Due to replace the existing bridge, scheduled for completion in 2016, at an estimated cost of £4.2bn.

• M74 extension
  It has been called Scotland's most important infrastructure project in Scotland over the next 10 years.