Groundwater resource assessment methods in the Ethiopian Rift Valley Basin: a systematic review

Water resources, particularly groundwater underpin the socio-economic development and ecological integrity of hydrogeologically complex regions such as the Ethiopian Rift Valley Basin (ERVB), where groundwater resources exhibit significant spatial variability due to active faulting, volcanic processes and heterogeneous geological condition. This systematic review synthesises groundwater assessment methods applied in the ERVB, drawing on 80 peer-reviewed primary studies published between 2016 and 2025 and adhering to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 reporting guidelines. The synthesis characterises methodological trends, evaluates tool performance, critically appraises study quality and identifies evidence-based priorities for advancing hydrogeological research. Original articles were identified from Scopus, Web of Science, GeoRef and Google Scholar. The review reveals methodological evolution, including a marked increase in publications since 2022 and a broad shift towards integrated, simulation-based assessment frameworks. Hydrological modelling (26.25%) and integrated geospatial techniques (20.0%) are the dominant methodological categories used to characterise and quantify groundwater resource dynamics. Persistent data scarcity and limited long-term monitoring networks are the critical constraints on model calibration, uncertainty assessment and predictive reliability. Thus, the reliability of future groundwater studies depends on bridging the gap between advanced simulation tools and the persistent field-based data scarcity. Specifically, it supports SDG 6 (Clean Water and Sanitation) by improving regional groundwater monitoring and protection; SDG 2 (Zero Hunger) by enabling precise assessments for effective irrigation planning; and SDG 13 (Climate Action) by identifying tools to mitigate climate impacts and enhance local resilience.