Sand Dams & Drylands: Small solutions; big impacts. Simon - - PowerPoint PPT Presentation

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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

• f 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

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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