The study aims to get better understanding of the groundwater flow system of the Hormat-rnGolina basin using numerical groundwater flow modeling under steady-state condition. Thernbasin comprises inter-mountain valley (Kobo Valley) which is the most fertile irrigable land.rnThe basin is part of the western escarpment of Afar Rift and measures about 811 km2.rnThe study was ambitious in the sense that the modeling was conducted with limited datarnparticularly for the highland volcanic part of the basin. Two aquifer units: the fractured basaltrnand the valley fill sediments aquifer were identified in the basin. The fractured basalt aquiferrnforms the highland part and underlies the alluvial sediments aquifer. The two-aquifer systemsrnwere assumed to be hydraulically connected. Deep groundwater circulation was assumed forrnthe highland volcanic aquifer, because of the absence of shallow groundwater features such asrnsprings and base flow of the rivers.rnThe groundwater flow system in the two aquifers of the basin was modeled using PMWINrnPro (Chiang et al., 1998) as pre-and post processor for MODFLOW (McDonald andrnHarbaugh, 1988). The model was run for steady-state conditions in unconfined aquifer. Therngrid cell size of the model was taken 250 x 250m and 500m x 500m for the valley part and thernhighland volcanic aquifer respectively. Model area and the layer top elevation were delineatedrnby the ASTER DEM processing and use of topographic maps. The hydraulic conductivityrnvalues were determined from pumping test data analysis and literature review for the alluvialrnsediment aquifer and the fractured volcanic aquifer respectively. Recharge was estimatedrnfrom water balance method.rnThe model was calibrated using observed hydraulic heads from 37 wells. The model wasrncalibrated to the root mean square error (RMSE) of about 6m and it was sensitive to rechargernand hydraulic conductivity. The model simulated water budget showed that the basin receivesrna total recharge of (in-flow) 48mmy-1 and discharge it to the river for steady state condition.rnSimilarly, the model generated total in-flow for the highland volcanic aquifer and the alluvialrnsediments aquifers were 54mmy-1 and 52mmy-1 respectively. The model result showed thatrnthe valley fill sediment receives more in-flow from horizontal flux (40mmy-1) than otherrnrecharge sources. In this study, the model was calibrated but not verified. Thus, the modelrnresults obtained should not be interpreted as a perfect simulation rather as system response forrnreasonable model input parameters.