The Bacho catchment, model area, is located in upper Awash River basin. The model domain hasrnan area of 4553km2.The area dominantly covered with volcanic rocks. The upper cover is a thinrnalluvial deposit at Bacho plain. Pyroclatic flows, ash, ignimbrite and basaltic rocks interlayeredrnforming the top aquifer layer. Below these units massive and welded ignimbrite comes withrnextensive and recognizable thickness with low permeability and eventually the last model domainrnlayer is a very thick scoraceous basalt that cover wide area with relatively better groundwaterrnpotential and permeability.rnA groundwater flow model was developed for the Bacho Catchment in the upper Awash basin tornanalyze the groundwater flow characteristics and determine the aquifer parameters for futurerngroundwater management and planning. This model will assist the decision makers to developrnlong term strategies to ensure environmentally responsible and economically sustainable use ofrnthis valuable natural resource.rnThe numerical model simulates groundwater flow within three hydrostratigraphic units; the toprn150m unit comprises basaltic and pyroclastic rocks; the middle is 100m thick ignimbrite which actrnas confining layer; and the third is a unit with 300m thick scoraceous basalt layers which is thernmajor aquifer in the model domain. Most water boreholes were developed in first and thirdrnhydrostratigraphic layers for domestic, industrial and irrigation purposes.rnConceptually developed model of research area was represented to numerical model by means ofrncomputer code_ processing modflow version 8.0.15. The area was discretized to three layers andrna uniform grid size of 200m by 200m active model cells. Total perimeter boundary is about 492kmrnof which 75% is no flow and about 25% is head dependent flow boundaries. The model wasrnsimulated with a steady state condition. Analytically determined aquifer parameters were encodedrnand five flow package namely, drain, head dependent boundary flow, recharge, river leakage andrnwell packages were simulated.rnConceptual model was developed from the hydrological, geological and hydrogeological historicalrndata and field observations. The conceptual model was translated in to mathematical expressionrnusing processing modflow code. The model was calibrated by trial and error method by comparingrnthe observed and measured hydraulic head and water balance.rnivrnRecharge components to the aquifers are from rainfall, inter aquifer flow from Abay basin acrossrnthe northern boundary and Awash River at upstream part. Discharge is predominantly throughrngroundwater leakage to rivers, under aquifer outflow across the southern boundary to Adaâ€™a plainrnand withdrawal by pumping. Groundwater is dominantly flow from north to south in general. Inrnthe upper layer groundwater flow is towards center of model area and dominantly towards AwashrnRiver at lower topography.rnThe model was most sensitive to recharge, horizontal hydraulic head, and river hydraulicrnconductance. It is less affected by change in vertical hydraulic conductivity and other aquiferrnparameters. The calibrated model recharge volume is estimated to be 1.07Mm3/day. In flow fromrnriver leakage is approximated 0.330Mm3/day and general head dependent inflow is aboutrn0.683Mm3/day. The final calibrated model total outflows is calculate to be 2.09Mm3/day. At finalrnmodel calibration resulted in the spatial recharge distribution ranges from 5.4x10-5m/d to1.99x10-rn4 m/d; horizontal hydraulic conductivity varies from 0.44m/d to 9.2m/d and 0.07m/d to 45m/d inrnthe top and bottom aquifer layers, respectively.rnRecharge reduction by 50% and groundwater withdrawals scenarios were formulated to examinernthe aquifer response to such stresses. Accordingly, occurrence of both stresses simultaneously willrncause surface water to lose 23.4% amount of water to sub-surface system and water level droppedrnwith an average of 20.6m in the research boundary. However, increase of recharge throughrninjection well will only rise water level by 2.65m and discharges much of the recharge water tornAwash River. Introduction of 100 productive wells at expected potential area like center of Bachornand Holeta resulted in 3.8 m overall decline of head in the model area and less drawdown at Holetarnwater wells.rnMost rivers and stream channels are losing type in the upper higher topographic locations while atrnlower Bacho flat land almost all river gains about 1.78Mm3/day of groundwater as baseflow.rnHence, river _ groundwater interaction is very recognizable flow process in catchment.