DAMS AND RESERVOIRS
Digley Reservoir, Holmbridge
Factors which affect the location of dams
• Areas of high rainfall so the dam is filled naturally.
• Sources of local stone, earth or concrete so that transport
costs are not too high.
• A high local water table so that water does not leak away.
• Based on impermeable rocks so that water does not leak out.
• Concrete or rock dams need firm foundations so that they can
be safely anchored.
• Rocks should dip upstream not downstream so that the dam
does not slide down the valley.
• An area which is not earthquake prone, otherwise the dam
could be damaged.
• There should be no faults or major joints so that water does
not leak out.
• Local rocks do not contain heavy mineral veins, like lead or
zinc which would pollute the water.
Draw a diagram to show the perfect
site for a dam and reservoir.
Area of high
rainfall
Dip of rocks
Quarry to
provide rock
in large
amounts
Impermeable rocks
underlying reservoir
No faults or
major joints
reservoir
dam
Strong rock
foundations for
dam supports
There are four main types of
dams:
• Embankment dams
• Arch dams
• Gravity dams
• Buttress dams
Embankment dams
Butterley dam
and reservoir,
Marsden
This dam has a by-pass
channel to prevent
overtopping of the dam by
water.
Diagram of an embankment dam.
Explain each feature of this dam.
Diagram from Geology and Environment in Britain and Ireland by Nigel Woodcock
Draw a diagram of an
embankment dam.
Add a title
water
core
Rock or
earth fill
Rock or
earth fill
Cut-off
Plan and cross
section of
Digley Dam,
1947,
Holmbridge
overflow
reservoir
road
water
Impermeable clay
Stony
earth fill
to add
weight
Earth embankment at Digley, Holmbridge
reservoir
Road on top of
dam
Earth fill
Digley Dam, Holmbridge
High water
level
Stone armour to protect dam
from erosion by waves
Rip rap is a layer of large rocks which cannot be moved by
waves. Rip rap protects the earth dam from erosion.
Overflow on Digley Dam
This maintains the reservoir level at its
maximum height and prevents it overflowing.
Back of Winscar Dam, Dunford Bridge.
This dam started to leak in 2000 and was emptied
so that it could be repaired.
It was covered by an impermeable membrane to
prevent water leaking through cracks in the
concrete.
Arch dams
Strong rock
abutments in a
narrow valley
Hoover Dam, R.
Colorado, U.S.A
Diagram of an arch dam
Explain each feature of this dam.
The dam will be very
firmly anchored to
the walls at each side
of the valley.
Draw a diagram of an arch dam.
reservoir
Dam will need firm
anchorages at both
sides.
Curved shape to
brace against
weight of water.
Add a title
Gravity dams
Gravity dams are kept in place by virtue of their weight
with braces them against the weight of water behind.
Three Gorges Dam, China
Diagram of a gravity dam
Draw a diagram of a gravity dam.
Weight to keep dam
stable
Reservoir
Made of strong rock or
concrete
Wide base for
stability
Add a title
Buttress dams
Buttress dams are similar to gravity dams, but the
buttresses at the front of the dam take the weight of
the water.
Glen Errochty, Scotland.
Diagram of a buttress dam.
Draw a diagram of a buttress dam.
Strong
rock sides
reservoir
Buttress braces
dam against the
weight of the
water
Internal fill of
impermeable material
Add a title
What type
type of
of dam
dam is
is this?
this?
What
An embankment dam
Butterley Dam, Marsden
What type of dam is this?
A buttress dam
Chief Joseph Dam, Washington State, USA
What type of dam is this?
A gravity dam
Grand Coulee Dam, Washington State, USA
What type of dam is this?
Arch Dam
Kariba Dam, River Zambezi, between Zimbabwe and Zambia
What type of dam is this?
Buttress/gravity dam
Hume Dam, River Murray, Australia
THE END