Water Harvesting Through Sand Dams
Sand dams are reinforced concrete walls built across seasonal river beds to hold underground water in aquifers in the sand that collects behind them. They may be one meter (3′ 3″) to four (13′ 1 ½”) metres high and up to 90 metres (98 yards) across. Each sand dam may hold up to 10 million litres or 2.64 million US gallons of water.
After construction, water is collected either from a pipe built into the dam wall, or a take-off well, or by digging holes in the sand behind the dam. Each dam will supply a clean supply of water for people, animals, tree nurseries, and irrigated vegetables. A sand dam may indirectly benefit up to thousands of people, as the use of the stored water is never restricted to the people who built the sand dam.
Sand dams are ideal to harvest water in remote rural communities because they can be built by the community, are low cost, low tech, require minimal maintenance, save water from evaporation and provide quality water even in drought conditions.
If a community group wants a sand dam, they provide the labor, sand, water and stones, terracing and on-going maintenance. UDO contributes technical advice and materials. An experienced artisan supervises the construction.
A registered Self Help Group in a semi-arid community must submit documents to the UDO office attaching copies of their certificates and list of members. It may be hand delivered, given to a UDO field officer, mailed, or scanned and emailed. The Self Help Group should be registered by their country’s Ministry of Culture and Gender or Department of Social Services. The Self Help Group should be committed in working towards food security, water security, income generation and improving health to its members.[learn_more caption=”How do people get water from the sand?”] Water is collected from the sand dam by a pipe near the bottom of the sand dam wall downstream; an off-side well upstream; a water tank built into the dam wall on the upstream; or scoop holes upstream. Most often, several of these methods of extracting water from sand are used at the site.[/learn_more] [learn_more caption=”Where are sand dams appropriate?”] Sand dams are most appropriate in semi-arid and arid areas that experience short, heavy, erratic downpours. These areas typically have seasonal (ephemeral) rivers with sand beds. Places along a seasonal river bed may have a place where the local people dig scoop holes for water, indicating an aquifer and rock bed where a sand dam may be built. Sand dams are generally built in remote rural areas without supportive infrastructure and where government is unlikely to provide water and sanitation needs of the people. People in these areas know that their survival depends on their own efforts. They are also familiar with getting water from sand, as their families have been doing this for generations. Many of them walk miles every day to their ‘hole’ and may spend hours in a queue waiting for their turn to draw water. . Areas where there are community self help groups that work together on tasks of mutual assistance are ideal for sand dam building. Sand dams are low cost and low tech, but someone needs to own them and take care of them and use the water for maximum benefit to all. An active community group that already has an agenda for self and community benefit is a good potential partner in sand dam building.[/learn_more]
The contents of this page were written by UDO’s long-term volunteers Jacob (PhD) and Alvera (EdD) Stern, and is published in Educational Concerns for Hunger Organization’s (ECHO’s) book, Agricultural Options of the Poor.