Grand Dixence Case Studies

Question 1

Where is Grande Dixence located and what is its significance?

Answer 1

Grande Dixence is situated at the head of the Val des Dix in southwest Switzerland and is the highest gravity dam in the world.

Question 2

Why was Grande Dixence initially constructed in the 1960s?

Answer 2

Grande Dixence was initially constructed in the 1960s to provide Switzerland with hydroelectric power.

Question 3

Why was the construction of Grande Dixence a lengthy process?

Answer 3

The construction of Grande Dixence was a lengthy process due to the inaccessibility of the site and severe working conditions. Construction could only take place in the summer months due to the cold temperatures in winter, which prevented the concrete from setting.

Question 4

What was the approximate cost of constructing Grande Dixence at the time?

Answer 4

The total cost of constructing Grande Dixence was approximately 1600 million Swiss Francs.

Question 5

What are the key dimensions of the Grande Dixence dam?

Answer 5

The Grande Dixence dam is 285 meters high, 200 meters wide at its base, and just 15 meters wide at the top.

Question 6

How much water does the Grande Dixence dam store annually?

Answer 6

The Grande Dixence dam stores over 400 million cubic meters of water each year.

Question 7

How is the foundation soil of the dam made watertight?

Answer 7

The foundation soil of the dam is made watertight through the presence of a deep grout curtain, which surrounds the dam and extends onto each side of the valley.

Question 8

Where were the aggregates for the Grande Dixence dam obtained from?

Answer 8

The aggregates for the Grande Dixence dam were obtained locally from deposits of moraines in adjacent valleys.

Question 9

What is the catchment area of Grande Dixence and where does the water come from?

Answer 9

Grande Dixence has a catchment area of just over 350 square kilometers, with half of the water coming from 35 glaciers that provide seasonal meltwater.

Question 10

How was the Lac des Dix created, and how is water sent to the reservoir?

Answer 10

The Lac des Dix was created behind the dam, and four pumping stations send water through 100 kilometers of tunnels into the reservoir.

Question 11

What is one of the key aims of Grande Dixence regarding water level management?

Answer 11

One of the key aims of Grande Dixence is to optimize the water level to ensure maximum availability before heavy demand periods.

Question 12

How does Grande Dixence maximize profits from water usage?

Answer 12

Grande Dixence offsets the cost of pumping water into the Lac des Dix during the summer against income generated from energy production during the winter, allowing for profit maximization.

Question 13

What is the capacity of the power stations behind the Grande Dixence dam?

Answer 13

The power stations behind the Grande Dixence dam have a combined capacity of 2000 GWh annually.

Question 14

How many Swiss households can be powered by the Grande Dixence dam?

Answer 14

The Grande Dixence dam can power 400,000 Swiss households.

Question 15

How does the Grande Dixence dam operate?

Answer 15

The Grande Dixence dam operates by storing glacial meltwater during the summer and using it to generate electricity during the high demand period of the winter.

Question 16

What percentage of Swiss electricity comes from storage power stations?

Answer 16

About one-third (33%) of Swiss electricity comes from storage power stations.

Question 17

What percentage of Swiss electricity comes from run-of-the-river schemes?

Answer 17

Another quarter (25%) of Swiss electricity comes from run-of-the-river schemes.

Question 18

What is the contribution of fossil fuels to Swiss electricity production?

Answer 18

Less than 5% of electricity production in Switzerland comes from fossil fuels.

Question 19

What is the main source of electricity production in Switzerland besides storage power stations?

Answer 19

Nuclear energy provides the majority of electricity production in Switzerland, apart from storage power stations.

Question 20

What type of energy policy does the Swiss government have?

Answer 20

The Swiss government has a strong environmentally aware energy policy.

Question 21

What has been done to minimize the environmental impact of the project?

Answer 21

The environmental impact of the project has been minimized to ensure that the area remains attractive for walkers, cyclists, and hikers.

Question 22

How are the pumping stations and power plants constructed to retain the aesthetics of the location?

Answer 22

The pumping stations and power plants are largely built underground or well concealed to retain the aesthetics of the location.

Question 23

What has been enhanced as a result of the project in terms of tourism?

Answer 23

Tourism to the locality has been enhanced, and there are now guided tours and helicopter rides available to visitors above the dam.

Question 24

What is the impact of the reduced flow in the Borgne River below the dam?

Answer 24

The reduced flow in the Borgne River, a tributary of the Rhône, has resulted in higher concentrations of pollutants at Les Haudère.

Question 25

What are the sources of the increased pollutant concentrations at Les Haudère?

Answer 25

The increased pollutant concentrations at Les Haudère are from both agricultural and domestic sources.

Question 26

hat percentage of water available at Grande Dixence is used for electricity generation?

Answer 26

85% of the water available at Grande Dixence is used mainly for electricity generation.

Question 27

What is the purpose of the remaining 15% of water at Grande Dixence?

Answer 27

The remaining 15% of water is used to deal with the problems of sedimentation.

Question 28

What are the consequences of storing water behind the dam?

Answer 28

Storing water behind the dam leads to a loss of energy and the deposition of sediment load behind the dam at rates of 20-40 cm/year.

Question 29

What are the sediment concentrations above the dam?

Answer 29

The sediment concentrations above the dam are greater than 300 mg/I.

Question 30

What are the sediment concentrations just below the dam?

Answer 30

The sediment concentrations just below the dam are between 20-50 mg/I.

Question 31

What are the sediment concentrations 3 km downstream of the dam?

Answer 31

The sediment concentrations 3 km downstream of the dam are less than 20 mg/I.

Question 32

How is the problem of sedimentation addressed?

Answer 32

To address the problem of sedimentation, some of the water in the reservoir is used to purge the sediment by flushing it out and moving it downstream.

Question 33

What are the characteristics of the water during sediment flushing?

Answer 33

During sediment flushing, the water has high levels of turbidity and sediment concentrations of up to 20,000 mg/l.

Question 34

What is the impact of trapping sediment behind the dam on the water in natural river channels?

Answer 34

The trapping of sediment behind the dam leads to very clear water being returned into the natural river channels below the power stations.

Question 35

How does the clear water in the river channels below the dam affect channel erosion?

Answer 35

The clear water in the river channels below the dam has excess energy since it is not being used to transport sediment, resulting in increased channel erosion.

Question 36

What happens to the discharge in the rivers below the dam during summer?

Answer 36

The lack of discharge in the rivers below the dam causes some of them to virtually dry up during the summer.

Question 37

What changes occur in the size of the river channels downstream of the dam?

Answer 37

There has been a significant contraction in the size of the river channels downstream of the dam, and the scale of contraction increases with distance downstream.

Question 38

How has the amount of sediment flowing into Lake Geneva changed since the construction of the dam?

Answer 38

The amount of sediment eventually flowing into Lake Geneva has halved since the construction of the dam.

Question 39

What is the risk associated with excess stored water being released in the Val d’Hérens?

Answer 39

In the Val d’Hérens, there is a risk of sudden and unexpected flooding when excess stored water has to be released.

Question 40

What are the consequences of the risk of flooding in the Val d’Hérens?

Answer 40

The risk of flooding in the Val d’Hérens has hindered both tourist use and development along the valley floor.

Question 41

How do the local residents perceive the scheme despite the risk of flooding?

Answer 41

Despite the risk of flooding, the local residents still strongly favor the scheme because they receive significant revenues from it.