Kenya: Sand dams built on seasonal rivers providing clean water for local communities

Rhoda Peter is collecting water for her family. It's a daily task, but one that has become much easier since this sand dam was constructed.

The structure harvests waters from seasonal rivers that flow during rainy reason but which dry out later in the year. It means she has a ready supply of the vital resource without the long journey she had to make in the past.

"I used to leave home with my children and walk to Mbooni Hills to fetch water from the springs. On the way, there were rocks that would hurt our feet and we would stumble. We would spend three hours a day getting water,” she says.

Peter and her welfare group have built three sand dams along a river near their home in Kyalika village.The county Makueni, along with Machakos and Kitui counties, is classified as arid and semi-arid.

Only 5% of Makueni’s nearly 245,000 households had access to clean piped water by 2022.The county produces about 30,000 cubic meters per day against a demand of 60,000 cubic meters.

Seasonal rivers flow a few times a year here, and with little piped water and few reliable alternatives, many people depend on them for water. So sand dams have grown in popularity.

The barrier, typically made of concrete, impedes water flow and coarse grains of sand settle behind it, creating an artificial aquifer that fills up during rainy seasons. Villagers from Machakos county are building one on a dry riverbed.

Africa Sand Dam Foundation is one nonprofit supporting communities in Makueni, Machakos and Kitui to build sand dams.

Residents approach the nonprofit with a request to build a dam and provide sand, rocks and other locally available material, plus labor.

Meanwhile, the nonprofit, through partners, provides hardware material such as cement and skilled expertise. After construction, the community manages the sand dam.

Since it started in 2010, the nonprofit has constructed 680 sand dams in the three counties.

"When you do a sand dam, anything below one meter of sand doesn't evaporate. So communities are able to access water within the sand dams during the driest month of the year, compared to open pans where it would dry or drilling of boreholes where the water salinity level increases as the year dries up," explains Andrew Musila, development director at Africa Sand Dam Foundation.

Access to water is increasingly important as human-caused climate change is leading to prolonged seasons of drought, scientists say, and the simple sand dam solution has gained traction across dry regions of Kenya and some other parts of Africa looking for reliable water sources.

As climate change makes drought more likely, scientists say sand dams minimize water loss through evaporation because they store water within sand, and that helps with water supply during dry seasons.

Additionally, they say the structures rejuvenate surrounding vegetation and recharge groundwater, raising the water table.

Makueni county government has been building sand dams with partner organizations and residents, and by 2022, it had built 71, according to county government data.

"It's an interesting and beautiful phenomenon. It has two components. One, it protects the environment and stores the water for a long period of time and then gives not only just water, but clean water. Because part of our objective is to have clean water for access – both for human consumption and for those who want to also use it for their cattle," says Mutula Kilonzo, governor of Makueni County.

But experts also warn that finding the right sites for structures is key to making them work.

A study carried out in Kitui county found that about half of 116 sand dams surveyed were not functional because they were built in locations with unfavorable factors for enabling sand dams to supply water.

Factors to consider, the study says, include the rainfall amount, the percentage of clay in the soil and the presence of visible rock formations.