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

Abstract

Soil moisture is an important hydrological state variable governing water balance partitioning, agricultural productivity, and ecosystem functioning. Despite its importance, particularly in the arid and semi‑arid lands (ASALs), no comprehensive synthesis has assessed how soil moisture is observed, modeled, and applied across Kenya’s diverse hydro climatic regions, with approximately 89% of its land being ASAL. This systematic review evaluates the state of soil moisture science in Kenya by analyzing peer‑reviewed literature published between 2000 and 2026. Following the PRISMA guidelines, we screened 847 records from Web of Science, Scopus, and Google Scholar, with 63 studies meeting the inclusion criteria. Results show research activity on soil moisture has increased markedly since 2015, dominated by remote sensing approaches (54%), followed by in‑situ measurements (29%) and modeling studies (17%). Spatially, studies are concentrated in the central highlands of Kenya and the Mount Kenya region (41%), while ASAL regions, where soil moisture plays a critical role in drought risk and water security, remain underrepresented (18%). Thematically, agricultural applications predominate (52%). despite their prevalence, relatively few agricultural studies demonstrated how soil moisture information is integrated into operational decision-making or advisory systems, indicating a gap between research outputs and practical implementation, with fewer studies addressing drought monitoring (21%), ecosystem dynamics (15%), or hydrological processes in urban systems (4%). Key gaps include limited ground‑truth networks, weak integration of soil moisture into operational early warning systems, sparse coverage of pastoral and urban landscapes, and minimal attention to subsurface and vadose‑zone dynamics. We propose a research agenda emphasizing expansion of in‑situ monitoring networks, development of Kenya‑specific soil moisture products, improved coupling with climate services, and greater focus on water‑limited systems. This review provides the first national‑scale synthesis of soil moisture science in Kenya and establishes a foundation for advancing hydrological research and applications in the region.