OCR A Level GL - 15 OCR A Level GL 2.4 GRANDE DIXENCE Case Study_ Human Activity change Glaciated Landscape system 2

Question 1

Where is the Grande Dixence Dam?

Answer 1

at the head of the Val des Dix in southwest Switzerland

Question 2

How high is the Grande Dixence Dam and why is this special?

Answer 2

1. 285 metres high 2. It is the highest gravity dam in the world

Question 3

Why was the Grande Dixence Dam built?

Answer 3

to provide hydroelectric power

Question 4

How much water can the Lac des Dix (reservoir) hold?

Answer 4

400 million m3

Question 5

How many glaciers provide seasonal meltwater to the Lac des Dix?

Answer 5

35 glaciers

Question 6

How much hydroelectric energy is produced by the Grande Dixence Dam?

Answer 6

2,000 Gwh of energy annually enough to power 400,000 households.

Question 7

What material flow was impacted during construction of the dam?

Answer 7

aggregates for the dam were extracted from local deposits of moraines

Question 8

How much did it cost to build the Grande Dixence Dam?

Answer 8

1.6 billion Swiss Francs

Question 9

What evidence is there that the Swiss government has had a long-term sustainable energy policy?

Answer 9

Switzerland produces less than 5% of all electricity production from fossil fuels

Question 10

How has the visual and sound impact of the Grande Dixence Dam been minimised?

Answer 10

The pumping stations for the dam have been built underground meaning that habitats are well concealed and undisturbed

Question 11

Who has benefitted from the pumping stations being built underground?

Answer 11

walkers, cyclists and hikers

Question 12

What is one of the long-term threats to the sustainability of the Grande Dixence Dam?

Answer 12

Climate change which is causing glaciers to melt. This may ultimately threaten the amount of meltwater in the Lac des Dix

Question 13

What energy flow problem has been created by the Grande Dixence Dam?

Answer 13

Reduced flow in the Borgne River, a tributary of the Rhône below resulted in higher concentration of pollutants at Les Haudère. These are from agricultural and domestic resources.

Question 14

What process is taking place in the Lac des Dix that reduces the capacity of the reservoir and causes damage to the Hydroelectric turbines?

Answer 14

sedimentation

Question 15

How is the dam economically sustainable?

Answer 15

It is able to maximise profits by offsetting the cost of pumping water into the Lac des Dix in the summer against income from generating energy during the winter

Question 16

How does sedimentation in the Lac Des Dix affect material flows in the reservoir?

Answer 16

the reservoir causes a lack of flow and thus a loss in energy, this leads to the deposition of sediment load behind the dam at rates of 20-40 cm/year, reducing the capacity of the reservoir and increasing the erosive power of the water downstream of the dam.

Question 17

In what way has the Grande Dixence Dam affected material flows in the river system?

Answer 17

The dam has greatly affected the sediment concentrations Above the dam, sediment concentrations are 300mg/l Immediately below the dam 20-50mg/l 3km downstream of the dam less than 20mg/l

Question 18

What is being done to mitigate against the material flow problems caused by Grande Dixence Dam in the river system?

Answer 18

Some of the water (15%) in the reservoir is used to purge the sediment - flushing it out and moving it downstream.

Question 19

What negative impacts does the purging of sediment build up in the Lac Des Dix cause for the river downstream?

Answer 19

1. high levels of turbidity, increasing erosive power of the river 2. Temporary excessive sediment concentrations in river water up to 20,000 mg/l.

Question 20

How are river channels affected by the dam?

Answer 20

The trapping of sediment behind the dam leads to clear water being returned into natural river channels which has excess energy, due to not having to transport sediment and results in increased channel erosion.

Question 21

Lack of discharge in the below-dam rivers means that

Answer 21

some virtually dry up in the summer.

Question 22

How have the material flows of the river changed due to the construction of the Grande Dixence Dam?

Answer 22

river channels have reduced in size

Question 23

How has the material flow of sediment entering Lake Geneva been impacted by the Grande Dixence Dam?

Answer 23

the amount of sediment has halved since the construction of the dam

Question 24

What potential negative impacts on energy flows are there due to the Grande Dixence Dam?

Answer 24

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

Question 25

What negative impact has the risk of flooding in the Val d’Herens valley had?

Answer 25

It has hindered development along the valley floor as businesses are afraid to risk investing significant sums of money if it could be damaged by extensive flooding.

Question 26

Give a named example of a negative social impact from the Grande Dixence Dam.

Answer 26

In December 2000 a high-pressure pipeline burst causing a landslide that destroyed a hamlet and killed 3 people.