grand dixence scheme, switzerland

Question 1

how much water does the dam hold?

Answer 1

400 million m3

Question 2

how large is the catchment area of the dam?

Answer 2

350km2
from 35 glaciers that give meltwater

Question 3

how many pumping stations are there?

Answer 3

4

Question 4

how many tunnels are there?

Answer 4

100km

Question 5

energy

Answer 5

powers 400,000 households
sotres glacial meltwater in the summer and generates electricity in high demand period of the winter
less than 5% of energy comes from fossil fuels

Question 6

impact on the environment

Answer 6

impact has been minimise to preserve tourist appeal
pumping stations and power plants are built underground or concealed
tourism enhanced with helicopter rides over dam
reduced flow in Borgne river has a higher concentration of pollutants from agricultural and domestic sources

Question 7

impact on glacial system

Answer 7

85% of water is used for electricity generation and the rest is used to deal with problems of sedimentation
sedimentation causes because reduced flow means a loss in energy and more deposition at the rate of 20-40cm/year
sediment concentrations above the dam is over 300mg/l and 20mg/l downstream
water in dam used to purge sediment, giving water high turbidity and high sediment concentration of 20,000 mg/l

Question 8

impacts on river channels

Answer 8

trapping sediment behind dam leads to very clear water being returned to river channels
excess energy as not being used to transport sediment = more channel erosion
lack of discharge = rivers dry up in summer
Lake Geneva has halved since construction of dam
Val d’Herens there is a risk of unexpected flooding - hindered tourism