Sand Dams & Drylands: Small solutions; big impacts

www.excellent.org.uk

Sand Dams & Drylands:

Small solutions; big impacts.

Simon Maddrell

Founder, Excellent Development

SandDamMan@btinternet.com

www.excellent.org.uk

About Excellent Development

• Supports community-led rainwater harvesting and sustainable

agriculture in rural drylands.

• Pioneers of the application of sand dams in different contexts:

Eight countries with agricultural and pastoral communities • Kenya (Ukambani & Northern Rangelands), Tanzania, Sudan, Chad,

Zimbabwe, Mozambique, Swaziland & India.

• Enabled communities to construct 900+ dams since 2002

• Almost 1 Million people with access to clean water.

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Where do sand dams work?

Sand Dams are a drylands solution requiring:

• Sufficiently seasonal rivers

• Sufficiently sandy sediment

• Accessible bedrock

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Technical sustainability – life cost

• Along with sub-surface dams are the most cost-effective form of

rainwater harvesting in drylands (UNDP).

• Virtually zero operation and maintenance costs: • Last over 50 years

• 5% need one-off repairs

• 2% failure rate (80% of which have been repaired)

Built in Mwala District, Kenya, 1957. Drank 2013

Built 1985

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Technical sustainability – design

Breaking the rules to manage dryland seasonal river flows:

• Enabling the river to flow in the same way as before: • Central spillways.

• Dams not always straight.

• Managing river floods with multiple spillways.

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Social sustainability – community ownership

• Community registered, built and managed.

• If there is a hand pump – communities

charge for water and maintain the pump.

2 Million days invested in self-help projects since 2002

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Saving 2-10 hours per day enables communities to invest in sustainable development of their land.

Sustainable Land Management

2 Million days invested in self-help projects since 2002

Saved nearly 1 Billion hours collecting water since 2002

Social sustainability – reinvesting time

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Environmental sustainability

Virtuous Cycle of Soil & Water Conservation

Terraces

Sand Dams

Trees

Maintain water

& soil in farms

Water for people,

livestock,

vegetables

& tree nurseries

Retain more

water & soil in

farms

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Advantages of sand dams

Water protected from:

• Contamination.

• Evaporation.

• Disease vectors, such as

Bilharzia-carrying snails,

and mosquitoes.

Water yields up to

40M litres per annum

Multi-Use Water Source

Clean water for people

Saving time:

bringing clean water*

to within 30-90 mins

of people’s homes.

Nearly 1 Million People since 2002

Multi-Use Water Source

Irrigation of smallholder farms

• Demonstration farms.

• Vegetable plots.

• Tree nurseries.

• Community plots and

individual plots.

Nearly 1 Million Trees since 2002

Water for livestock & wildlife

Multi-Use Water Source

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• Primarily a sub-surface dam (6m deep & 0.9m high)

• Created an earth dam wing by scooping out the bend

Sand dam in Rajasthan, India

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• Sand dams are recharging 3 govt. tube wells in one village in

Rajasthan – doubling output and removing salinity.

• 100 smallholder farmers irrigating more land and producing

vegetables for the first time.

Recharge & salinity reduction in India

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Potential of sand dam road crossings

Potential to leverage infrastructure investments

for the benefit of water supply and agriculture

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Sand dams as rural road crossings

Sand Dam road crossing, Machakos, Kenya

Serves nine villages with est. 40M litres/annum

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Problems with culvert bridges in drylands

• Culverts unable to handle seasonal river flows

• Exacerbated by blockages from river flotsam

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Sand dam rural road crossing

Makueni County, Kenya

• Road crossing with four commercial

farms next to the dam.

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Water for year-round smallholder irrigation

Makueni County, Kenya in November 2014

• Commercial farm growing ‘out of season’

maize, vegetables, papaya etc.

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Sand dams:

Small solutions; big impacts.

Simon Maddrell

Founder, Excellent Development

SandDamMan@btinternet.com

www.excellent.org.uk

Small dams support smallholder farmers

• More than 2 billion people depend on smallholder farms,

which provide 80% of the foodΨ

• Smallholder farmers are 71% of the world’s poorest people*

75% of the world’s poor live in drylands§

• The World Bank acknowledges that small-scale dams &

smallholder farmers are an essential part of the solution to

global hunger and poverty.

Small-scale dams:

Sand dams, check dams, sub-surface dams, water-spreading weirs

* UNEP 2013 Ψ IFAD 2011 § UNCCD