Climate Change and Kenya
How do sand dams work?
1
A seasonal river is full of water and even floods
in the rainy season. But it then dries up in the
dry season.
2
Bedrock
3
During the dry season, the community dig down
to the bedrock underneath the river.
Bedrock
4
Then the community build a concrete wall using
a mixture of rubble and rocks from the river bed
and cement. An engineer from ADSE helps them
plan and build it so that it is just the right height
and location.
During the rainy season the river floods and
the water deposits heavier sand behind the
dam and carries the lighter sediment over the
top of the dam.
Lighter sediment is
carried by the river over
the dam.
Heavier sand
particles are
deposited here.
Bedrock
Bedrock
5
Over the next few years, the layer of sand builds
up behind the dam wall. The sand is watersoaked during the rainy season and retains a lot
of that water between the grains of sand during
the dry season.
6
During the dry season local people dig shallow
holes into the sand and find water. The sand
holds water and prevents it from evaporating so
quickly. Water can be used for irrigating crops,
drinking, cooking, washing and for animals to
drink.
Sand
Bedrock
Sand
Bedrock
1
Number the captions in the
right order to match the
correct picture. The first one
has been done for you.
During the next few
rainy seasons sand is
deposited next to the
dam wall.
2
The community can dig
shallow scoop holes into
the sand and find water
during the dry season.
3
The water from the sand
dam is used to irrigate
land, allowing people to
grow food.
4
A concrete wall is built
across the river using
rubble and cement.
1
5
The community dig out
the sediment from the
dry riverbed to the level
of the bedrock.
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