Groundwater models are used to predict the groundwater flow processes using mathematicalrnequations based on certain simplifying assumptions. Numerical modeling method is used torninvestigate the possibility of groundwater transfer (interbasin groundwater flow) betweenrnUpper Awash River basin and Upper Rift Valley Lakes basin. Within the study thernhydrogeology is investigated from previous studies, a conceptual groundwater model isrnproduced and the numerical model is developed from this. The model conceptualization isrndone by idealizing the study area into three models related to the surface water divide and thernmain perennial Rivers and lakes. For these three basins the boundary conditions are identifiedrnand incorporated into the models. The boundaries are Upper Awash River, Meki River, ZiwayrnLake, and Koka Lake in addition to bottom and top surface of the aquifer in concern. Thernmodels are three dimensional steady state by finite element method. All the study basins arerndiscretized according to finite element method into equal element dimensions. The elementsrnare three dimensional. The finite element model used in the study was TAGSAC. Thernmodeling process was towards estimating the hydraulic head in the model basins of the studyrnarea by a means of finding the hydraulic conductivity of different geological classificationsrnand estimating surface recharge in terms of some percentage of the rainfall of the study area.rnFinally the models are calibrated with the measured hydraulic head for each model basins.rnThe models results show that the groundwater divide and the surface water divide are notrncoincident. There is a clear hydraulic head difference which can make groundwater to flowrnfrom Upper Rift Valley Lakes basin towards Upper Awash basin in the middle of the studyrnarea, along Ziway- Koka Lake and from Upper Awash to Rift Valley Lakes basin at west andrneast part of it.rnKey Words: Upper Awash River basin, Upper Rift Valley Lakes basin, Interbasin flow,rnGroundwater flow Modeling, Hydraulic head, TAGSAK