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Dams generate hopes and fears

Switzerland’s highest dam: the Grande Dixence in canton Valais Keystone

Concerns about both climate change and safe energy supply in the post-Fukushima world have given a new impulse to one of Switzerland’s specialities: hydroelectricity.

About 900 experts in dams from all over the world converged on Lucerne this week for the annual symposium of the International Commission on Large Dams (Icold) to exchange experiences and to see how the Swiss do things.

Switzerland has a long history of dam building: the oldest dam still in use is the Wenigerweiher in the eastern canton of St Gallen, built in 1822, and today the country has the greatest density of dams in the world. The golden age of dam building was in the 1960s and 70s, and the experience acquired has since been put to use elsewhere: dam engineering is a Swiss “export item,” according to Walter Steinmann, head of the Federal Energy Office.

With the Swiss government’s recent decision to phase out nuclear power, hydroelectricity – which already covers about 60 per cent of Switzerland’s energy needs – is an obvious alternative source.

“In the last ten years we have had small hydropower projects, and now we think that in the future we will also have larger projects for new hydropower stations,” Steinmann told If current plans for four or five large pumping stations are implemented, Switzerland can become “the battery for electricity production in Europe,” he said.

New opportunities, new challenges

It is not only newly-sparked fears about nuclear power that are prompting a rethink about hydroelectricity. Climate change is having a dramatic impact on Switzerland’s mountains, and as the glaciers melt, new lakes are being formed. These are being seen as both an opportunity and a danger.

If they are dammed and integrated into the current hydroelectric system, they will obviously increase Switzerland’s power production – an unexpected bonus, as Christoph Darbellay, the president of the centre-right Christian Democrat party told the Sonntagszeitung newspaper this week: “Hydropower has much greater potential than formerly thought.”

But these lakes will themselves be at risk because of climate change. Rock slides are likely to increase as temperatures rise, not least because the permafrost which holds surfaces together is melting. These could provoke tsunami-like waves: the dams must be high enough to prevent the water spilling over.

Another major concern that has arisen in the last 20 years is the increasing amount of sediment that is getting into reservoirs as a result of erosion, Professor Anton Schleiss, chairman of the Swiss Committee on Dams, told

On the one hand this threatens to block the outflow from the reservoirs, while on the other the abrasive nature of some of these sediments seriously damages the turbines, as if they are being continuously rubbed with sandpaper, Schleiss explained.

This has happened even at Switzerland’s second biggest dam, Mauvoisin, in the southern canton of Valais, where the tunnels through which the water flows out have already had to be raised.


Schleiss assured that the foundations of Swiss dams are so firm that they will be as long-lasting as the Egyptian pyramids. Indeed, he likes to describe them as “useful pyramids”. They will in the end fill with sediment, but they will remain standing.

One of Switzerland’s selling points is its safety expertise. Dams are continuously monitored, and experts make on-site visits every week for visual checks. An annual report on each dam is sent to the Energy Office, and every five years a super-check is made.

The regulations on earthquake-proofing have recently been stepped up, and where necessary, dams are being adapted.

“It’s not like building houses, where the architects must just be reasonably competent. The Swiss Committee on Dams has to be at the forefront of knowledge,” said Schleiss. “The engineers can’t say they ‘didn’t know’.”

On Wednesday Switzerland signed a letter of understanding with China, under which it will share its safety expertise.

Social responsibility

Not everyone is happy when dams are built in their neighbourhood. Very often construction entails the resettlement of local people.

“Switzerland knows that everyone concerned has to be involved if you are to get acceptation,” said Schliess. “You have to negotiate with the population at an early stage.”

Swiss experience here too is valued by the Chinese, as Jia Jinsheng, Chairman of the International Commission on Large Dams, told

“These days social issues are the big issues, mainly because so many people are affected,” he said. “We want to understand what developed countries did, to find the best way to go forward.”

Imo Ekpo of the Nigerian ministry of water resources, and vice-president of Icold, agreed that the guidelines and procedures being discussed in Lucerne were useful in his country too.

“We have to reach out to people to convince them,” he told 

Learning from others

While Switzerland has built up a body of knowledge over the years, it also has things to learn from other countries.

Japan has experience to pass on about dams and earthquakes, while China has had to deal with the problem of sedimentation which is now worrying the Swiss.

Surprisingly enough, there is the issue of CO2 emissions from reservoirs: almost unknown in Switzerland, where they tend to be built in the high mountains, it can be a serious problem where the building of a dam leads to large areas of vegetation being flooded.

And while the Swiss have experience of the behaviour of concrete in a cold climate, they can learn from others about what it does in a hot one.

Given that many Swiss engineering firms work largely abroad, these are all things they need to know. And the learning process never ends.

“Every dam is a new prototype,” said Schliess.

Using hydropower is a long tradition in Switzerland, from both reservoirs and run-of-river stations (which exploit the flow of rivers.)

It has the highest density of dams in the world: about 5 per 1000 km2.

Hydropower currrently supplies about 56% of the country’s energy.

Most of the larger dams in the mountains were built to store water captured in summer in order to produce power in winter when demand is greatest.

Switzerland’s biggest dam is the Grande Dixence in canton Valais, built in 1961. It is 285 m high, and the volume of its reservoir is 401 million m3.

Reservoir power stations are concentrated in the south, in the cantons of Valais, Ticino and Graubünden.

Safety standards are very high, with continuous monitoring.

However some problems have emerged. Some older concrete dams are starting to deform because of the reaction of the concrete with water, which was not known about when they were built. One has had to be rebuilt, in two others structural interventions have been made.

Road and rail tunnels constructed near dams can also cause damage. In particular, three dams close by the Gotthard base railway tunnel, now under construction, are being closely monitored.

The International Commission on Large Dams (Icold) is an international non-governmental organisation concerned with the safe engineering of dams.

It was established in 1928 and has national committees from 92 countries, with about 10,000 individual members.

Its members are mainly engineers, geologists and other scientists, consulting firms, universities and laboratories and construction companies.

ICOLD enables engineers to exchange knowledge and experience about dam construction.

Its original aim was to encourage advances in the planning, design, construction, operation, and maintenance of large dams.

It is now also concerned with cost studies, harnessing international rivers, informing the general public and the financing of dams.

Since the late 1960s focus has shifted to safety, monitoring of performance, analysis of older dams, effects of ageing and environmental impact.

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SWI - a branch of Swiss Broadcasting Corporation SRG SSR