How seasonal rivers, streams and laghas could help ease water crisis

Kaki sand dam in Katalwa river.Residents queue water jerricans as early as 5:30 am in the morning at Garissa water kiosk by Kiambere-mwingi water and sanitation company (KIMWASCO) in mwingi town,Kitui county .Water is rationed in the area to serve for a long time making the residents to use water sparingly at their homes to conserve the rare commodity. [David Gichuru] Though prone to sweltering heat, biting droughts, and chronic water poverty, the arid regions of northern Kenya are rich in non-perennial waterways, commonly known as seasonal rivers. These seasonal rivers are unique in that they typically flow for relatively short periods during the rainy season. Water experts note that the quality characteristics of seasonal river water can change rapidly. Therefore, comprehensive data and information on their hydrology are essential to support agricultural development programmes, drought response, and climate mitigation efforts. Despite their lack of perenniality, these seasonal waterways-including laghas, the dry river valleys typically found in low-lying, semi-arid areas-can transform into large rivers from upstream rainfall and eventually merge with perennial rivers such as the mighty Tana or Ewaso Nyiro. Water poverty Likewise, streams located in remote, arid regions remain ecologically and environmentally significant to their surrounding ecosystems. "In their resilience, seasonal rivers have proven-and continue to prove-to be ideal habitats for many distinct species. They support a wide range of organisms and contribute substantially to ecosystem biodiversity," says Dr Mohamud Hashir Ali of Garissa University. "These species have finely adapted to the cyclical presence and absence of water," he adds. Northern Kenya is home to numerous seasonal rivers, streams, and laghas, which Dr Hashir argues could help alleviate water poverty-provided that appropriate water storage infrastructure is developed and utilised effectively. He explains that these waterways support xerophytic plant species, including yucca trees, agave, acacia, cacti, members of the pineapple family, and gymnosperms-all of which have specially adapted to survive in water-scarce environments. "A detailed study and further research into these plants-with their deep roots for water storage, small leaves, and thick cuticles-could support agricultural diversification and enhance plant development in dryland areas," he suggests. Dr Hashir further underscores the vital role of seasonal rivers, streams, and laghas in arid regions, describing them as critical water sources of immense importance. "Besides providing water, these non-perennial ecosystems and their biodiversity sustain people, livestock, and vegetation with food and essential resources," he says. "What remains is for environmental science to step in and examine both historical and future potential for the benefit of humanity, animals, and plants." Echoing this view, Josephine Mwende Nzelu from Kyuso Sub-County in Kitui notes that during floods in the seasonal River Ithui, residents grow vegetables and other food and cash crops to supplement their subsistence livelihoods. However, Nzelu laments that due to climate change and unpredictable rainfall patterns, it has become increasingly difficult to forecast when water will arrive or how much will be available. Water experts concur, observing that without thorough research and hydrological assessments, the flow characteristics of these rivers remain largely unknown-making water storage planning difficult. "Under such circumstances, seasonal rivers cannot be used for hydroelectric power generation," Nzelu notes. "Since no notable studies have been undertaken on the streamflow of seasonal rivers, laghas, and streams, there is little data to support water storage or the scheduling required for HEP production," adds Alex Kaimenyi, a water specialist based in Garissa. Kaimenyi explains that a water reservoir functions much like a battery-storing energy in the form of water when supply is high and demand is low, particularly during peak seasonal flows. He stresses that the advantage of pumped water storage is that large hydroelectric plants can start quickly and generate power on demand. Power stations situated along rivers with significant seasonal fluctuations require vast reservoirs to remain functional during dry periods. This necessitates the impounding and flooding of extensive tracts of land-a sharp contrast to rivers with well-documented streamflows, such as the River Tana. Flowing nearly 1,000 km from the snow-capped peaks of Mount Kenya and the Aberdares to the Indian Ocean at Kipini, the River Tana's streamflow is well-documented, averaging over 5,000 million cubic metres (MCM) annually, though it varies significantly both seasonally and year-to-year. Between 1944 and 1978, the average annual flow at Garissa was 6,105 MCM, ranging from just 1,789 MCM in 1949 to a record 13,342 MCM in 1978. "If such streamflow variation is attributed solely to climate change, then clearly, this is not a new phenomenon," remarks Kisumu-based environmentalist Kenneth Ogosiah. Ogosiah reaffirms that water reservoirs operate as energy banks, storing potential power during periods of high flow and releasing it for generation during peak demand. "The key advantage of pumped water storage is that it enables rapid power generation-an essential capability for modern energy systems," he explains, laughing that this is "besides the age-old adage that nothing is as changeable as the weather." Despite the opportunities, farmers in the Ithui River zone in Kitui County have largely been unable to store water from seasonal floods. "We still rely on continued farming, and some people have resorted to drilling private wells along the river to maintain their crops," says Nzelu. However, while well drilling represents a significant investment in water security, hydrologists caution that unregulated, unprofessional drilling may tap into older, deeper aquifers that contain higher concentrations of harmful dissolved substances such as arsenic and fluoride. Dr Hashir notes that despite the unpredictability of rainfall and the uncertainty surrounding streamflow volumes, most seasonal rivers in northern Kenya are rain-fed. Breadbasket Ogosiah suggests that more research is needed into these rivers precisely because they do not depend on melting glaciers, as seen in other parts of the world. He praises Kitui, Makueni, and Machakos counties for the strides they have made in harnessing seasonal rivers for productive use-but laments that the same cannot be said of northern counties such as Garissa, Wajir, Mandera, and Marsabit. "In these areas, billions of litres of water from intermittent rivers go to waste or cause destruction during floods," says Dr Hashir. He argues that while county governments have made some efforts to improve water access, they have yet to truly tap into the potential of seasonal rivers. "We have rivers such as Maalim, Togwene, Lago, Alango Arba, Maalim Shurie, and Lagh Bogol. If we could store this often-destructive water in pans and sand dams for use in agriculture and animal husbandry, we could transform northern Kenya into the breadbasket of the eastern region. Drought would no longer be injurious, and the burden of fetching water would be reduced," he explains. In Makueni County, Colleta Kanini and her daughter are already benefiting from such innovation. "Collecting water is now easier and faster than before," she says with a broad smile. "Before the African Sand Dam Foundation, a non-profit organisation, funded this project, we would walk miles under the scorching sun through dusty terrain," she recalls.

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