Grand Dixence Scheme, Switzerland - examole of human change creating change.

What is the Grand Dixcene?

It is a hydroelectric powerdam

When was the Grand Dixcene built?

1960

Where is the Grand Dixcene?

The head of Val des dix (glacial trough) in switzerland

How much did it cost to construct:?

1600 million francs

How is the dam supplied with water?

seasonal meltwater of 35 glaciers.

How many households does the dam provide for?

400,000

What makes the dam an efficient system?

It stores meltwater from the summer, and uses it to supply energy during te winter when the demand is greater

What was done during the construction of the dam to minimise visual impact?

Power and pumping stations built underground.

What energy flow problem has been created by the dam?

Reduced flow downstream in the Borgne river - causes higher concentration of pollutants at Les Haudere, from agricultural and domestic sources.

Due to water being stored in the resevoir, what issue has been caused for the flow of water?

Sedimentation - when a loss of energy in the river causes excess deposition

How much sediment is added to the river every year?

20 to 40cm

How many power stations in the GD

4

what proportion of swiss energy comes from storage power stations?

1/3

How much water does the Grand D dam hold?

400 million m³

How much of the energy made at Grand Dixence is used for the problems of sedimentation?

15%

Why is there excessive erosion around the dam?

sediment becomes trapped above the dam, and so the middle course of the river travels super fast (high levels of turbidity) and so excess energy erodes the sides - when purging excess sediment.

How has tourism been hindered by the dam?

Flooding risks downstream as water is released from the resevoir - stopping services such as toursism as visitors can’t arrive to their destination.

What happend in 2000

A pipeline burst causing a landslide that killed three people and destroyed a hamlet.

What are the effects of the changes from the dam on glacial landforms?

As all the water is held up behind the dam, downstream rivers often dry up in the summer, river channels have shrunk. The further downstream a river is, the more contraction (shrinking) there will be.

How have the changes in the landscape affected irrigation?

Artificial irrigation channels reduced sediments, which previously stopped water infiltrating permeable rock underneath. Expensive channel lining is required.

What makes the dam a complete waste of money

climate change will mean the glacier will melt entirely, meaing there was no purpose for it and it will lie derelict and leave a scar on the landscape.

What material flow was impacted during construction of the dam?

Aggregates for dam were extracted from local deposits of moraines.

How much energy does the station produce annually

2,000 GWh.

How tall is the GD?

285m

How are material flows affected (sediment concentrations)

Above the dam, sediment is 300mg/l. Below, they are 20-50mg/l.

How big is the resevoir

400 million m3

Further change to the procceses of the river

In areas of stagnant water there will probably be more evaporation in the summer months

Changes to landforms/new landforms formed

What would’ve once been a misfit stream coming from the trough is now a manmade ribbon lake.

how did the aggregates change landforms

Sediment taken from moraines means less in the landscape.