sand dams & drylands: small solutions; big impacts

www.excellent.org.uk

Sand Dams & Drylands:

Small solutions; big impacts.

Simon Maddrell

Founder, Excellent Development

[email protected]


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.


Where do sand dams work?

Sand Dams are a drylands solution requiring:

• Sufficiently seasonal rivers

• Sufficiently sandy sediment

• Accessible bedrock


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


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.


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

7

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


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


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


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



• 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


• 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


Potential of sand dam road crossings

Potential to leverage infrastructure investments

for the benefit of water supply and agriculture


Sand dams as rural road crossings

Sand Dam road crossing, Machakos, Kenya

Serves nine villages with est. 40M litres/annum


Problems with culvert bridges in drylands

• Culverts unable to handle seasonal river flows

• Exacerbated by blockages from river flotsam


Sand dam rural road crossing

Makueni County, Kenya

• Road crossing with four commercial

farms next to the dam.


Water for year-round smallholder irrigation

Makueni County, Kenya in November 2014

• Commercial farm growing ‘out of season’

maize, vegetables, papaya etc.


Sand dams:

Small solutions; big impacts.

Simon Maddrell

Founder, Excellent Development

[email protected]


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

sand dams & drylands: small solutions; big impacts

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