The scale of the stakes is hard to overstate. Kenya’s drylands receive less than 700 millimetres of rain per year, yet they support about 36 percent of the national population and 70 percent of the livestock herd. Agriculture contributes roughly a third of the country’s GDP and employs more than 70 percent of the rural workforce, and it is overwhelmingly rainfed, making it exquisitely sensitive to the water held in the top metres of soil. Recurrent droughts, including the devastating episodes of 2010 to 2011 and 2022, have affected more than four million Kenyans, triggering crop failures, livestock losses and humanitarian crises. Against that backdrop, the review’s central finding is uncomfortable: the regions where soil moisture is most limiting for livelihoods account for only 18 percent of the published research.

The review, conducted following PRISMA 2020 guidelines, reveals a research landscape that has grown rapidly but unevenly. Only eight studies appeared in the first decade of the review period, but publication output accelerated sharply after 2015, coinciding with the launch of NASA’s Soil Moisture Active Passive (SMAP) satellite and the wider availability of free satellite products. Between 2020 and 2024 alone, 25 studies were published, 40 percent of the entire national corpus. Remote sensing dominates the methodological mix, featuring in 54 percent of studies, followed by in-situ measurements at 29 percent and modelling at 17 percent. The most commonly used satellite products were SMAP, the European Space Agency’s Climate Change Initiative merged dataset, SMOS and ASCAT scatterometer data, with Sentinel-1 synthetic aperture radar emerging more recently for field-scale retrieval.

Geographically, the science is strikingly lopsided. Forty-one percent of studies were concentrated in the central highlands and Mount Kenya region, including Nyeri, Kirinyaga, Embu, Meru and Tharaka-Nithi counties, an area favoured by agricultural research stations, universities and proximity to Nairobi. Western Kenya and the Lake Victoria basin accounted for 24 percent, and the Rift Valley for 17 percent. By contrast, the northern and northeastern arid counties, which comprise most of the national land area, were covered by just 11 studies, and several counties, including Wajir, Mandera, Tana River and Lamu, had no dedicated soil moisture research at all. The authors attribute this dryland deficit to historical concentration of research infrastructure, the logistical challenges of fieldwork in remote areas, and the technical difficulty of microwave retrievals in sparsely vegetated terrain.

Thematically, agriculture dominates, with 52 percent of studies addressing soil moisture in farming contexts. Eleven studies quantified the link between soil moisture and crop yields, skewed heavily toward maize, while eight examined irrigation scheduling for smallholder systems and six demonstrated that conservation tillage, mulching and cover crops significantly improve moisture retention. Drought monitoring was the second-largest theme at 21 percent, and ecosystem studies, including work in the montane water tower forests of Mount Kenya, the Aberdares and the Cherangani Hills, made up 15 percent. Urban hydrology was almost invisible: only three studies, or 4 percent, touched on soil moisture in urban or peri-urban settings, and none addressed urban flooding directly, despite repeated devastating floods in the Nairobi River basin and a national urban population projected to exceed 50 percent by 2050.

Beneath the thematic gaps lies a deeper methodological problem: validation. Only 9 of the 34 remote sensing studies, about 26 percent, compared satellite estimates against in-situ measurements, and most of those relied on short-term field campaigns rather than permanent monitoring networks. Just three studies achieved validation with more than six months of continuous ground data. Where validation was reported, root mean square errors ranged from 0.04 to 0.12 cubic metres per cubic metre and correlations from 0.45 to 0.82, with performance generally better in agricultural areas than in rangelands. The review identifies a structural mismatch here: the satellite products most widely adopted in Kenya are precisely those lacking long-duration ground networks for rigorous validation, since East Africa has no equivalent of the United States’ SCAN network or Europe’s International Soil Moisture Network.

Depth is another blind spot. Surface soil moisture, in the top 10 centimetres, was addressed by 81 percent of studies, reflecting the sensitivity of most microwave sensors, while root-zone moisture appeared in only 37 percent and deep profile measurements in a mere 8 percent. That bias matters because crops draw water from throughout the soil profile, and water stress depends on integrated root-zone moisture rather than surface conditions alone. Temporal coverage was similarly constrained: 40 percent of studies lasted a year or less, and sustained in-situ monitoring exceeding one year was reported in only four studies. The review’s quality assessment found that 59 percent of studies inadequately described uncertainty and 44 percent provided insufficient validation of satellite products.

Perhaps the most consequential finding is what the authors call the implementation gap. Despite a growing literature on soil moisture-based drought indices, only one of the 13 drought-focused studies described integration with an operational early warning system. Kenya’s National Drought Management Authority, whose bulletins drive food-security decisions, still relies primarily on rainfall data and vegetation indices, with soil moisture playing a minimal role. The gap reflects institutional unfamiliarity, the coarse 25 to 50 kilometre resolution of passive microwave products relative to county-level decision-making, limited technical capacity within operational agencies, and the absence of sustained validation demonstrating added value. The result is a persistent divide between what the research community produces and what decision-makers actually use.

The review closes with a six-point research agenda aimed at closing these gaps over the next decade. Its priorities include establishing sustained in-situ monitoring networks across Kenya’s major agroecological zones, with multi-depth measurements integrated into existing Kenya Meteorological Department, KALRO and TAHMO infrastructure; expanding research into underserved northeastern counties; building an urban hydrology research programme for Nairobi and secondary cities; co-producing drought triggers with operational agencies; developing Kenya-specific, high-resolution soil moisture products; and addressing depth and temporal limitations through approaches such as cosmic-ray neutron sensing, data assimilation and machine-learning downscaling. Emerging opportunities, including Sentinel-1 radar retrieval at 10 to 20 metre resolution and anticipatory action frameworks piloted by humanitarian organisations, could give soil moisture data a direct role in pre-emptive drought response.

For a variable recognised by the Global Climate Observing System as essential for weather forecasting, drought monitoring and flood prediction, soil moisture in Kenya remains scientifically underexploited precisely where it could save the most livelihoods. This first national synthesis makes the pattern unmistakable: research has followed infrastructure and rainfall rather than risk. Redirecting attention to the drylands, the cities and the root zone, and building the ground-truth networks to support it, would transform soil moisture from an academic variable into an operational pillar of Kenya’s climate resilience strategy.

Subject of Research: A systematic review of soil moisture monitoring, modelling and hydrological applications in Kenya

Article Title: Soil moisture research in Kenya based on a systematic review of monitoring modelling and hydrological applications

Article References: Kipkemoi, I., Rotich, B., & Kipkulei, H. (2026). Soil moisture research in Kenya based on a systematic review of monitoring modelling and hydrological applications. Discover Soil, 3(1), Article 155. https://doi.org/10.1007/s44378-026-00304-y

Image Credits: AI Generated

DOI: 10.1007/s44378-026-00304-y

Keywords: soil moisture, Kenya, remote sensing, drought monitoring, drylands, hydrology, SMAP, systematic review, agriculture, early warning systems, validation, urban flooding