1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

Book project: Water Harvesting – Guidelines to Good Practice (Water Harvesting)

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

Africa Sand Dam Foundation (ASDF) - Kenya

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

Excellent Development Ltd. (Excellent Development Ltd.) - United Kingdom

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

Yes

2.1 Short description of the Technology

Definition of the Technology:

A sand dam is a stone masonry barrier across a seasonal sandy riverbed that traps rainwater and sand flowing down the catchment.

2.2 Detailed description of the Technology

Description:

A sand dam is typically 1 - 5 metres high and 10-50 metres across. When it rains the dam captures soil laden water behind it – the sand in the water sinks to the bottom, whilst the silt remains suspended in the water. Eventually the dams fill with sand - sometimes after only one rainfall or over 1 – 3 seasons. 25 to 40% of the volume of the sand held is actually water. A mature sand dam can store millions of litres of water – refilling after each rainfall providing a year round supply to over 1,000 people.

Purpose of the Technology: Sand dams are a simple, low cost and low maintenance, replicable rainwater harvesting technology. They provide a clean, local water supply for domestic and farming use and are suited to arid and semi-arid areas of the world. It is a solution that is scaleable and has a broader application for use as a rural and game park road crossing to replace less effective culvert bridges.

Establishment / maintenance activities and inputs: Sand dams are the lowest cost form of rainwater harvesting and its robust nature and very low operational and maintenance costs make it particularly suited to remote and poorly served regions. A typical dam using 500 bags of cement would approx be 40 metres in length with a spillway 2 metres above the bedrock. The dam is constructed using stone masonry placed in timber formwork. Such a dam costs approximately USD 11,800 (in 2012 prices). This consists of materials (cement, steel reinforcement, timber, transport) and dam permit USD 8,800 (75%), project management including technical support from skilled local artisans and dam designers USD 2150 (18%) and finance and administration costs of implementing organisation USD 850 (7%). Local people freely contribute their labour to collect rock, sand and water, terrace and protect the immediate catchment and construct the dam. If this contribution was costed and included the cost of the dam would almost double. The maintenance and repair costs of the dam provided it has been well designed and constructed is negligible. Local users are responsible for the management and repair of the dam and its abstraction system. Where a hand pump is fitted, local users fund the repair and replacement of the pump as required. The purchase and repair of petrol powered water pumps which some groups use to irrigate adjacent land is the responsibility of the members of the local group.

Natural / human environment: Because the water is stored within the sand, evaporation losses are very low, the sand filters the water and water-vector diseases such as malaria are controlled. Sand dams provide significant environmental benefits such as aquifer recharge, increased downstream flows in the dry-season, rejuvenation of river ecologies and moderation of floods. As such, it contributes to ecosystem services and climate change adaption.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

2.6 Date of implementation

If precise year is not known, indicate approximate date:

• 10-50 years ago

2.7 Introduction of the Technology

Specify how the Technology was introduced:

• through projects/ external interventions

Comments (type of project, etc.):

Sand dams are an ancient technology. Examples are found across the world's drylands although the greatest concentration is found in Kenya. They were introduced to Kenya in the 1950s from India. Dams were pioneered in Machakos and Makueni counties of Kenya by Joshua Mukusya, a visionary farmer and development worker, in 1978. He worked with a range of agencies to develop and implement the technology. In 1990, staff trained by Joshua set up SASOL to pioneer sand dams in the neighbouring county of Kitui. In 2002, Joshua teamed up with Simon Maddrell, Excellent Development's director, to establish Excellent Development Kenya, now Utooni Development Organisation (UDO) to scale up the work. Sadly, in 2011, Joshua passed away. In 2010, Excellent Development formed a strategic partnership with the Kenyan NGO, Africa Sand Dam Foundation (ASDF), to support the wider uptake beyond Kenya. Today, ASDF, SASOL and UDO are the three NGOs with the most experience of building successful sand dams, approx. 130 dams / year, although many other NGOs have adopted the technology.

3.1 Main purpose(s) of the Technology

• access to water

3.2 Current land use type(s) where the Technology is applied

Comments:

Major land use problems (compiler’s opinion): Drylands are characterised by intense and variable rainfall and a lack of vegetative cover. As a result, drylands are prone to droughts, flooding and soil erosion which result in endemic water and food scarcity.

Major land use problems (land users’ perception): “We used to fetch water from Londokwe; we could spend a night to collect water. One way was 3 to 10 km and up to 12 hours or more to go and come back [because of the time taken to queue]. If we could not make it to the river, we would send our children to fetch water. When they went fetching water that would mean they did not go to school. At times people would fight over fetching water from other people’s scoop holes. Scoop holes would be guarded in turns. The gourds [water containers] would be damaged and the water poured down. Children would not go to school [as they needed to] take care of the young ones as the parents went to fetch water. Children would fail to go to school because they were hungry – just because there was no water to cook."
Yikiuuku SHG

3.5 SLM group to which the Technology belongs

• water harvesting

3.6 SLM measures comprising the Technology

Comments:

Main measures: structural measures

3.7 Main types of land degradation addressed by the Technology

Comments:

Main type of degradation addressed: Hs: change in quantity of surface water

Secondary types of degradation addressed: Bq: quantity / biomass decline, Bs: quality and species composition /diversity decline, Ha: aridification, Hg: change in groundwater / aquifer level

Main causes of degradation: Heavy / extreme rainfall (intensity/amounts), droughts

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:

• prevent land degradation
• reduce land degradation

4.1 Technical drawing of the Technology

4.2 General information regarding the calculation of inputs and costs

other/ national currency (specify):

Kenyan Shilling

If relevant, indicate exchange rate from USD to local currency (e.g. 1 USD = 79.9 Brazilian Real): 1 USD =:

83.0

4.3 Establishment activities

	Activity	Timing (season)
1.	Collection of rock, sand and water	1-3 months before construction
2.	Construct dam	During dry season
3.	Cure dam	For 4 weeks after construction
4.	Terracing and protection of immediate catchment	1-3 months before construction

4.4 Costs and inputs needed for establishment

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Labour	Collection of rock, sand and water	Persons/day	220.0	2.5	550.0	100.0
Labour	Terracing and protection of immediate catchment	Persons/day	100.0	2.5	250.0	100.0
Labour	Construct dam	Persons/day	500.0	2.5	1250.0	90.0
Labour	Cure dam	Persons/day	50.0	2.5	125.0	100.0
Equipment	Tools	per dam	1.0	300.0	300.0
Construction material	Cement (bag = 50kg)	bags	500.0	9.15	4575.0
Construction material	Steel (12m x Y20 steel bar)	pieces	7.0	45.7	319.9
Construction material	Steel	per dam	1.0	1000.0	1000.0
Other	Skilled labour	per dam	1.0	3000.0	3000.0
Total costs for establishment of the Technology					11369.9
Total costs for establishment of the Technology in USD					136.99

Comments:

Duration of establishment phase: 6 month(s)

4.5 Maintenance/ recurrent activities

	Activity	Timing/ frequency
1.	Inspect and if necessary extend spillway or repair erosion around dam	As required / annually
2.	Maintain hand pump if fitted	As required / annually

4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)

Comments:

In 2012, in Machakos County, Kenya, the cost of materials and technical support for a dam using 250 bags of cement is USD 7,000 and USD 11,700 for a 500 bag dam. The costs in 2.6.1 are based on a 500 bag dam. The volume of a 500 bag dam is approx 140m3 of stone masonry of which 40% is mortar (sand and cement) and 60% is rock. Such a dam will typically be appropriate on rivers 30m wide and with a spillway 3 metres above the bedrock in the river bed level. Costs rise by up to 50% in more remote regions or countries. Sand dams require a lot of hard work. Community members collect the required stones, sand and water, support construction and terrace the land around the dam. If this in-kind contribution is included the costs would rise by 100%. In Kenya, with a long tradition of building sand dams, it takes from 6 to 12 weeks to plan and prepare for construction and 2 days to 2 weeks to build the dam. In other areas, with less experience and/or less community commitment, building a dam may take 6 months or more.

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Each dam is individually designed. The size, design and cost of a dam varies considerably with the size of the river and to a lesser extent, location and transport costs. Sand dams are the world’s lowest cost method of capturing rainwater in dry rural areas by a factor of 3 to 30 times compared to rain water harvesting tanks, earth dams, haffirs and rock catchments.

5.1 Climate

5.2 Topography

Comments and further specifications on topography:

Land forms: Sand dams only suit seasonal rivers with sufficient sandy sediment and an accessible bedrock

Altitudinal zone: Also 1,001-1,500 m a.s.l.

Slopes on average: Also moderate

5.3 Soils

If available, attach full soil description or specify the available information, e.g. soil type, soil PH/ acidity, Cation Exchange Capacity, nitrogen, salinity etc.

Soil water storage capacity: The aquifer behind the dam must consist of sandy sediments with a high porosity and drainable porosity

5.4 Water availability and quality

Comments and further specifications on water quality and quantity:

Availability of surface water: Sand dams only suit seasonal rivers

Water quality (untreated): Good drinking water because the sand filters the water. Water abstracted through an infiltration gallery has a high bacterialogical quality but water is often used for small scale irrigation and livestock watering.

5.5 Biodiversity

Comments and further specifications on biodiversity:

Sand dams rejuvenate riverine ecologies and increase local biodiversity

5.6 Characteristics of land users applying the Technology

Indicate other relevant characteristics of the land users:

Land users applying the Technology are mainly common / average land users

Difference in the involvement of women and men: The dams are built by members of registered self-help groups, typically 50 members / group and two-thirds women. The primary concerns of these groups tend to be food and water. Sand dams provide for people, livestock and crops. Water collection and farming are primarily undertaken by women in Kikamba culture and hence women have the greatest vested interest to imrpove food and water availability. Many men migrate away from the area in search of work.

Population density: 50-100 persons/km2

Annual population growth: 2% - 3%

Off-farm income specification: This varies considerably, but most self-help group members are subsistence farmers

5.7 Average area of land used by land users applying the Technology

5.8 Land ownership, land use rights, and water use rights

Land ownership:

• state

Land use rights:

• communal (organized)

Water use rights:

• communal (organized)

Comments:

Legal agreements for construction and access between the self-help group and the owners of land adjacent to the dam and registering the dam and its associated water rights by the self-help group with the Kenyan Water Resources Management Authority (WRMA) is vital to safeguarding water rights, controlling water and sand abstraction, formalising the authority of the self-help group to levy water tarriffs if appropriate and ensuring there is open access to all to water from scoop holes.

5.9 Access to services and infrastructure

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

Water availability and quality

Income and costs

Other socio-economic impacts

Socio-cultural impacts

Ecological impacts

Water cycle/ runoff

Soil

Biodiversity: vegetation, animals

Climate and disaster risk reduction

6.2 Off-site impacts the Technology has shown

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change

	Season	increase or decrease	How does the Technology cope with it?
annual temperature		increase	well

Climate-related extremes (disasters)

Meteorological disasters

	How does the Technology cope with it?
local rainstorm	well
local windstorm	well

Climatological disasters

	How does the Technology cope with it?
drought	well

Hydrological disasters

	How does the Technology cope with it?
general (river) flood	well

Other climate-related consequences

Other climate-related consequences

	How does the Technology cope with it?
reduced growing period	well

Comments:

The capacity of the spillway would be increased to control peak flood events

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?

Comments:

The very low cost of operating and maintaining sand dams means they are well suited to remote, poorly served regions. Because it is a low cost technology that requires a major community contribution and the knowledge and skills of locally trained artisans, it’s a solution particularly suited to community ownership and self-supply. This contributes to effective implementation.

6.5 Adoption of the Technology

Of all those who have adopted the Technology, how many did so spontaneously, i.e. without receiving any material incentives/ payments?

• 0-10%

Comments:

100% of land user families have adopted the Technology with external material support

Comments on acceptance with external material support: Sand dams require external material support including technical advice to correctly site, design and construct

There is a little trend towards spontaneous adoption of the Technology

Comments on adoption trend: There is some evidence of spontaneous adoption amongst development agencies working in regions suited to sand dams.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
“I will be able to rent a plot of land near to the sand dam and grow vegetables (tomatoes, peppers, and French beans). My animals will also be healthy because they will always be able to drink here, even during the droughts.” Mauwa Maingi, self-help group member, aged 87, 2010
Mbatha Mbuli, 83. "My family collects water from a near-by well, about ½ Km away, but the water is very salty. It takes one hour to collect water, and needs 6 trips to fetch enough to last the day. There is a pipeline nearby but we must pay 2 shillings per 20 litres. I planted 9 different crops last year, but only 2 survived. I wanted to work with Excellent on this project because I had heard that the projects you support help communities like us to build sand dams, grow trees and create seed banks. I would like to grow trees like Neem in the future and a sand dam here will really help with that. Excellent shares in the interests of the community and they listen to the community and take direction from us"
Stephen Hussey, Dabane Trust, 2011 “Dabane has made its name by getting water out of sand rivers – Our next step is to ensure we don’t over abstract – the answer to that, especially upstream, is sand dams. Without a doubt.”
Milka Mutunga, Kilili Catchment SHG, Kenya 2009-10 "The distance that I used to travel in order to fetch water has been reduced..now I am able to plant more vegetables close to my home. I have learnt how to dig terraces which have helped in increasing the yields that I harvest from my farm..If this is not development then I do not know what development means"
Kimanthi Ngovi, Yikiuuku SHG “The sand dams have done an incredible work for us – water availability at a shorter distance has helped me in saving time for other activities. When water was a long way away I had to get time to collect water in one day and dig terraces on the other day. Today I can fetch water and dig terraces on the same day.”

Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Sand dams provide a safe, reliable, year round, local supply of water for people, crops and livestock in water scarce environments How can they be sustained / enhanced? The very low cost of operating and maintaining sand dams means they are well suited to remote, poorly served regions. Community ownership is critical to their effective management.
Sand dams save farmers hours every day that they can invest in improving their farms to grow more food and create the potential for farmers to irrigate trees and crops, water livestock and generate an income How can they be sustained / enhanced? Don’t build a sand dam in isolation. An independent evaluation in 2010 of 2 sand dam programmes found the long term impacts on poverty, food security and incomes were greatest when sand dams were integrated within a wider community development programme aimed at improving food production, livestock management and land management practice.
Because it is a low cost technology that requires a major community contribution and the knowledge and skills of locally trained artisans, it’s a solution particularly suited to community ownership and self-supply. This contributes to effective implementation. How can they be sustained / enhanced? Don’t short cut community ownership. Communities better understand and are able to implement solutions to their problems if they are central to the planning of the solution. Genuine community commitment and ownership from initial planning to on-going management is vital to realise the intended benefits and full potential created by a dam. Legal registration and agreements to safeguard community access and water rights help this.
Sand dams provide significant environmental benefits such as aquifer recharge, increased downstream flows in the dry-season, rejuvenation of river ecologies and moderation of floods. As such, it contributes to eco-system services and climate change adaption. How can they be sustained / enhanced? Support terracing, tree planting and conservation farming in the wider catchment. This conserves soil and water on farms, increases aquifer recharge and base flows into the dam and reduces the amount of silt in the sand dam aquiver. Research and disseminate evidence of these benefits and the value of these eco-system services
The technology is scaleable and has a broader application for use as a rural and game park road crossing to replace less effective culvert bridges. How can they be sustained / enhanced? In order to upscale this solution, there is a need for greater awareness and advocacy of the technology and its benefits amongst these groups. Nothing generates interest in sand dams more than exposure to successful examples

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view	How can they be overcome?
Although sand dams are technically replicable, their application in new contexts requires careful understanding and consideration.	Excellent Development has developed a framework tool to help agencies identify the political, economic, social, technical, legal and environmental factors that should be taken account of when introducing sand dams to a new context.
Sand dams require the technical knowledge and skills of local artisans in order to correctly site, design and construct them	The technical barriers to adoption are low: The technical skills required have and can be developed locally. Learning exchanges between implementing organisations and developing technical manuals and resources aids this learning
This is a drylands solution. Sand dams can only be built on seasonal rivers with sufficient sandy sediment and where the bedrock or impermeable layer is accessible in the river bed.	Increase awareness of the criteria that determine the technical suitability of a site. Use simple field tests, such as sediment seiving and probing, to assess potential sites and to map the potenial application of sand dams.

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

Be buffered website including Managing the Water Buffer for Development and Climate Change Adaptation. Groundwater recharge, retention, reuse and rainwater storage. Steenbergen F. van and A. Tuinhof. (2009) which includes sand dams

Available from where? Costs?

www.bebuffered.com/3rbook