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Current page: Home > what we do > water supply > sand dams Sand Dams and Water Supply
"I love the dams more than anything, because they came out of nowhere. We have created our own springs for our own people"
Although total rainfall is fairly significant, the concentrated rainy seasons mean that most of the water is lost to the ocean. If this rainwater could be stored, it could be used during the dry season allowing farmers to spend less time collecting water and more time on increasing food production and income generating activities.
With large annual rainfalls of up to 35" (900 mm) concentrated over several weeks, harnessing the water locally is critical for the stability of the local economy and environment. The dams, built in the seasonal riverbeds, store water beneath the sand collected behind the dam. Water is extracted either from a pipe built into the wall of the dam or by scooping water from a hole dug in the sand. The terracing of the valley sides above the dam also helps to reduce soil erosion and maintain the level of the water table around the dam site. Whilst this solution cannot guarantee to protect trees or people and livestock from all climatic eventualities, we know that they significantly improve water supplies in the area.
"The dams enable trees to grow naturally through raised water tables and a changed micro-climate. The communities are able to grow crops that would not normally be able to grow."
"Hydrological surveys on these dams have shown that they significantly increase the water table both above and below the dams. What I have known to be true from seeing landscapes transformed by these dams now has a scientific foundation."
“The dams enable us to save our time, and that enables us to do much more work on our farms than before, which helps us earn money from vegetables and increased staple crops.” Rhoda Silu, Utooni development project.
Locally accessible water means that children go to school more often – crucial for the community’s future: drought or even normal dry conditions can mean no education.
Manzaa Valley, Before and After In August 2002, the impact of these small-scale conservation activities was very evident. Even without a formal tree-planting programme, there has been a vast improvement in vegetation with water being conserved in the valley throughout most of the dry season.
"You have seen the difference that it has made to the Manzaa area. It was a quarantined region in the late 1950's and now there are many trees that have just grown without any help. It has been transformed into a valley that sustains vegetable nurseries, grow fruit trees and attract water birds during droughts." Watch our film on water.
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Excellent Development has supported the building of small-scale sand dams in Africa for over 20 years. Essentially reinforced concrete walls built across dry river beds, they retain water below the sand that collects behind them – providing a clean water supply during the dry season. Our sand dams have extraordinary long-term impacts on the communities and environments we work with. 
The dams are built using local materials and local artisans at carefully selected points in the riverbeds. Local people collect all the sand, stones and water required for the construction. Up to a 150 villagers join together to construct the dam over 5-15 days. The dams can reach a height of 12-18 ft (4-7 m). These dams are the most cost effective way of retaining some of the water that would ordinarily end up in the ocean with a couple of days.
The dams improve water capacity so that tree and vegetable nurseries can be started, and the terracing of fields reduces soil erosion and increases the amount of rain water absorbed. This increases and diversifies food production for people and livestock. Farmers are able to generate income by selling surplus produce.
