Swiss Alps dam building (glaciation)

Question 1

type of landscape

Answer 1

glaciated

Question 2

why is dam building taking place

Answer 2

-initially constructed in the 1960s to provide Switzerland with hydroelectric power
-key aim: optimise the water level so there is maximum availablility before heavy demand periods
-it is able to maximise profits by offsetting the cost of pumping water into the Lal des Dix in the summer against income from generating energy during winter
-energy: 1/3 of swiss energy comes from storage power stations, 1/4 from river run off schemes and less than 5% from fossil fuels

Question 3

energy

Answer 3

-the water stored behind the dam drives the turbines in 4 power stations with a capacity of 2000 Cwh annually (enough to power 400000 Swiss households)

Question 4

Grand Dixence

Answer 4

-contructed in the 1960s
-cost: 1600 million swiss francs
-stores over 400 million m>3 per year
-Lac des Dix behind the dam and 4 pumping stations send water through 100km of tunnels into the reservouir

Question 5

Grand Dixence use

Answer 5

of the water available:
-85% for electricity generation
-15% to deal with sedimentation
-capacity of 2000 Gwh annually- enough to power 400000 households

Question 6

impacts on flows of material and energy: energy

Answer 6

reduced flow in the Borgne River (a tributary of the RhOne), below the dam has resulted in higher concentrations of pollutants at Les Haudere from both agricultural and domestic sources

Question 7

impacts on flows of material and energy: sedimentation

Answer 7

-15% used for sedimentation
-build up of sediment behind the dam is caused by the loss in energy at rates of 20-40m per year
-some of the water has to be used to purge the sediment- moving it downstream
-at these times the water has high levels of turbidity and sediment concentration of up to 20000 mg/l

Question 8

how does sedimentation change the land forms?

Answer 8

-it leads to very clear water being returned to the natural river channels below the power stations -it has excess energy due to none of it being used to transport sediment–> increased channel erosion
-channel scour: when the valley/ river bed is eroded by the water released from the dam it strips vegetation and erodes the stone

Question 9

consequences of these changes to the landscape:

Answer 9

-lack of discharge means that some of the rivers below the dam virtually dry up in the summer
-there has been significant contraction in the size of the channels and the scale of contraction increases with distance downstream.
-the amount of sediment eventually flowing into Lake Geneva has halved since the construction of the dam
-there is risk of sudden and unexpected flooding when excess water has been released in the Val d’Herens