In the Konso region of Ethiopia, WaterAid is helping the local community to construct a sand dam on the Arrayo River in Lehaite kebele, 17 km outside the town of Karat.

Unlike a conventional dam that stores water above the surface, a sand dam is a subsurface structure. The dam in constructed underneath the riverbed and traps and stores water between the pores of the riverbed’s sand.

The benefits of this are great since the water does not evaporate from storage as it would in a conventional dam. Additionally, the sand acts as a natural filtration system making this subsurface water safe to drink.

This type of dam is especially useful in seasonal rivers (rivers that only flow during the rainy season). Seasonal rivers appear to be dry when in fact the riverbed’s sand contains water.

A sand dam’s components are subsurface dam walls (two in this case) and PVC (plastic) slotted pipes that are buried beneath the sand at a level equivalent to the bottom of the dam wall. The slots are covered with gravel before being buried in the riverbed’s sand to prevent clogging.

Water trickles down through the riverbed sand and gravel, into slotted pipes, where it is captured and piped to a storage reservoir tank. From the storage tank it can be piped to various water points.

The water will not need any treatment because of the natural filtration that it went through and will be safer than the local groundwater (which contains high levels of fluoride).

The new sand dam will provide the community with a sustainable source of safe water, meaning they will no longer have to collect water from unsafe sources such as open ponds shared with animals. Safe water supplies are important in keeping people safe from deadly diarrheal diseases such as typhoid and cholera. Globally, 4,000 children die every day from preventable water-related diseases.

Having access to safe water close to home also frees women and children from hours of water collection each day, meaning they have more time for income generation, school and family life.

The project aims to bring access to safe water and sanitation to the whole community as well as improving hygiene practices in the area. In addition to the construction of the sand dam, WaterAid is helping local people to build low-cost latrines and handwashing facilities.

Find out more about the Konso sand dam project in the April 2010 issue of National Geographic Magazine.

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