Rotary District Speaker: Tony Perryman - Sand-dam in Kenya

A sand dam is a reinforced stone masonry wall built across a seasonal sandy river. They have almost no maintenance costs and can last for upwards of 60 years (the oldest known in operation being over 100 years old). Over 2-3 Seasons, sand fills the area behind the Dam, and the local water table rises, providing potable water together with irrigation water for Crops

Water behind a sand dam raises the water table in the surrounding area which improves the soil, creating better conditions for crops and grazing. More trees can be planted which ensures that more water infiltrates the ground and less soil is washed away – creating a virtuous cycle of soil and water conservation.

During the rainy season, the sand dam fills with sediment-laden water. The heavy sand is deposited behind the dam, while the light silt is carried downstream. As much as 97 to 99% of the water flowing in the river continues downstream.

Within one to four rainy seasons, the dam fills with sand. But, up to 40 million litres of water is stored in the pores between sand particles (enough to provide over 1,000 people with year-round access to clean water). Here it can be extracted through an infiltration gallery that leads to either a water tank, tap or sealed shallow well (topped with a hand pump). 

And as the water is stored safely within the sand, it is protected from evaporation, contamination and disease transmitters, such as mosquitoes and freshwater snails.

For more information see the charity Excellent Development's web site.