The Abbay River basinAbbay River Basin has been identified as the main socioeconomic growth corridor in EthiopiaEthiopia due to its significant water resourceWater resources capacity for agricultural and hydropower production. Sustainable water resourcesWater resourcesplanningPlanning and management require detail study of the hydrological processes of the basin. Several hydrological studies have been reported in the Abbay River basinAbbay River Basin; however, water resourcesWater resources planners are often faced with the large uncertainty in the previous hydrological studies results. Thus, this study explores the advancement in the hydrological studies in the Abbay River basin. This review covers the main hydrological studies, such as spatial and meteorological data analysis, water resourcesWater resources potential and development, application of hydrological modelsHydrological models, ungauged hydrological modellingHydrological modelling, and climate change impactClimate change impact on hydrologyHydrology. The review found that the majority of previous studies reported unreliable hydrological modellingHydrological modelling results in some of the Abbay RiverAbbay River subbasins. The sources of uncertainty for hydrologic modellingModelling in the Abbay River basinAbbay River Basin might be associated with water diversion for small-scale irrigationIrrigation, infrastructure development in the headwater catchments, the existence of artificial open reservoirs, upstream water supply abstraction, poor watershed managementWatershed management, and hydro-meteorological variables measurement errors. Moreover, the lack of reliable spatiotemporal coverage and a disparate distribution of hydrometric gauging locations results in considerable uncertainty in the Abbay River basinAbbay River Basin hydrological prediction. Thus, one of the important areas for possible research in the Abbay River basinAbbay River Basin is reducing the hydrological processes modellingModelling uncertainty. This can be achieved by utilizing emerging technologies for hydro-meteorological data observation. The application of merged satellite products and ground rain-gauge observations can enhance the reliability of hydrological modellingHydrological modelling results in the Abbay River basinAbbay River Basin. Furthermore, the majority of prior hydrological studies in the Abbay River basinAbbay River Basin have been relied on secondary hydro-meteorological data; however, primary data (field data collection) could help to better understand hydrological processes. Integrating primary and secondary hydro-meteorological data can help to obtain improved hydrological process modellingModelling results. The lack of continuous ground monitoring in high-elevation zones is one of the most significant challenges in the hydrological process modellingModelling in the Abbay River basinAbbay River Basin. The satellite meteorological products and citizen science ground-based meteorological data can provide more reliable information on the spatiotemporal variability of Abbay River basinAbbay River BasinhydrologyHydrology. In general, more reliable hydrological modellingHydrological modelling results can be achieved by citizen science-based data collection, frequent monitoring and maintenance of hydrometric gauging stations, merging satellite products and ground rain-gauge meteorological observations, and advances in the simplified representation of hydrological processes in the physical hydrological modelsHydrological models.
