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[[Image:Sand dam diagram.JPG|thumb|right|150px|Cross section of a sand dam]]

Regions with highly erratic rainfall often have rivers with temporary seasonal sandy bed streams. They only experience heavy water run-off for short periods of time after rain. During such periods of high flows, large quantities of sand are transported downstream. Some sand can get trapped on the upstream sides of rocks outcroppings along the stream. Such sand traps form natural water storing aquifers. The sand dam technology provides a means to reproduce this water collecting mechanism and to increase the size of existing aquifers.

==History and social context==

In Kenya, it has been used with good outcome in the Kitui, Machakos and Samburu districts. Other countries with similar dry environments such as the U.S.A, Thailand, Ethiopia and Namibia also have used it in numerous and diverse forms.