On a dry riverbed one recent sunny morning, residents of Kasengela village toiled away mixing cement and sand to make concrete. The sound of their shovels resonated through the valley while other residents, working in pairs, carried rocks to the site in wooden frames.
They were building a sand dam, a structure for harvesting water from seasonal rivers. 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.
Seasonal rivers flow a few times a year here, and with little piped water and few reliable alternatives, many people here depend on them for water. Building sand dams on these rivers, where people can scoop the sand to fetch the water or use hand pumps, helps minimize water loss through evaporation and recharges groundwater. This 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. But experts also warn that finding the right sites for structures is key to making them work.
Kasengela village is in Machakos County, which, alongside other counties of Makueni and Kitui in southeastern Kenya, is classified as arid and semi-arid. For many communities here, sand dams built on seasonal rivers have grown in popularity.
That's true for Kyalika village in Makueni County, where Rhoda Peter and her welfare group have built three sand dams along a nearby river. When The Associated Press met her, she was fetching water from one of the dams to clean utensils and wash clothes.
Peter put a yellow container on the shallow well platform and walked to the pump, pulling it up and pushing it down until it was full. Nearby, a donkey stood with two containers hanging on its back.
“When I think about sand dams, I feel happy,” said Peter, a farmer. “Our shallow well does not dry. It goes all through the dry seasons.”
Before the sand dams were built, she and her children would walk many miles to fetch water in springs in the faraway Mbooni Hills. It took them three hours, and many times they’d fall because of the rocky terrain.
Many people in Kenya's dry southeastern region rely on boreholes and rivers for water, but many boreholes produce saline water and permanent rivers are few and far for most people. Earth dams are another source, but they're also few and require regular desilting.
At the site in Kasengela, Mwanzia Mutua, the leader of the group constructing the dam, said that he used to trek seven kilometers (4.3 miles) from his home to Athi River to fetch water for his household and livestock, spending an entire day on the road. Later, a borehole was constructed, shortening the distance, but it was still far. The sand dam will reduce the walk to get water to 10 minutes, he said.
“When water is far, you spend all your time looking for it and are unable to do any other work,” said the farmer. “Cattle die because the water is far.”
The sand dam in Kasengela was completed on March 14 after two and a half months of construction, and should be ready to use by December 2025, after it fills with sand.
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.
“The water situation in Makueni is dire,” said Mutula Kilonzo Junior, the county's governor. “We have a huge deficit that we are not supplying.”
Shortages of water lead to problems for agriculture and health implications as people are forced to use unclean sources, taking the time and energy of children to fetch water, affecting their education, he said.
The 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.
“Seasonal rivers run dry barely after a week of raining. So for us, we have to store their water, and this is the best way for us to do it,” said Sonnia Musyoka, county minister for environment and climate change. “With such dams, we will enable children to stay at school, and parents to concentrate on other economic activities.”
The construction of sand dams in the region is community-driven. Africa Sand Dam Foundation — which helped build the dams in Kyalika and Kasengela — 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.
“We’ve used this model for years, and we’ve seen its success,” said Andrew Musila, development director at Africa Sand Dam Foundation, at the Kasengela site. “To us, sand dams are the best solution for water provision in arid regions and the best solution for providing communities with water throughout the year."
The usefulness of the structures has gained the attention of governments of other local counties, as well as other countries. ASDF has worked with governments and nonprofits in Malawi, Zimbabwe, Mozambique, Madagascar, Eswatini, Ethiopia, Tanzania, Somalia and India to site, design and build sand dams as well as train people in the processes.
Scientists warn that proper siting of sand dams 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.
“You cannot put a sand dam anywhere,” said Keziah Ngugi, lead author of the study and a hydrologist with interest in dryland areas. “The most important thing to observe is the siting.”
And as climate change makes drought more likely, scientists say the structures 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.
“There are good things that happen when the water table is raised,” said Dorcas Benard, an environmental and biosystems engineer. She gave examples of the emergence of alternative water sources or resources like springs and boreholes. “These are very important sources, especially within the arid and semi-arid lands."
And for residents like Mutua, the builder in Kasengela, they offer hope for improved livelihoods. Spending weeks building the dam with fellow residents may be arduous work, but the reward of having reliable water near his home will be fulfilling in immeasurable ways.
“Water is life,” he said.
