ABSTRACT The study area is found in Amhara Regional State, South Gondar Administrative Zone in the Ribb River catchment and its total area coverage is 2014 km2. This research is conducted with the objective of simulating the groundwater flow system of the area and to evaluate the response of the hydrogeological system under different stresses so that the resulting consequence on the system can be estimated. Fluvio-Lacustrine deposit, Guna Phonolite, Guna Basalt, Guna tuff and upper Basalt are the main lithologic units in the study area. Input parameters are hydraulic conductivity, recharge, and groundwater withdrawals from existing wells have been. Based on geologic and hydrogeological information of the study area, the simulation is made using MODFLOW-2000 as one layer confined-unconfined aquifer system with varying transmissivity data. The model has spatially variable recharge and hydraulic conductivity under well-defined boundary condition with a model grid design of 116 rows and 148 columns. The model calibration consists of matching the 40 observation points’ simulated and observed heads to have a permissible residual head of ±10m. The model calibrated statistics showed mean error (ME), absolute mean error (AME) and root mean square error value of (RMS), of 0.053, 3.7 and 5.1, respectively, which indicate good calibration. The sensitive parameters of the model were identified during calibration process. Based on the result of sensitivity analysis, the model is very sensitive to recharge followed by horizontal hydraulic conductivity. The model is least sensitive to stream conductance. The simulated inflow of the model is 6.1667619E+05 m3/day which is equal to simulated outflow 6.1667694E+05 m3/day with difference -7.8869629E-01m3/day. Scenario analysis conducted for decreasing recharge and increasing of withdrawals rate in four and three steeps, respectively. The total amounts of groundwater withdrawal in scenario one xi (150%), two (200%) and three (250%) are 3.7284449E+04m3/day, 4.9712602E+04m3/day and 6.2140750E+04m3/day, respectively. The average declines of water levels in all scenarios in the model area are 1.3m, 2m and 3.3m, respectively. During recharge decreasing scenarios of 75%, 50%, and 25% from the calibrated value, the average declines of water levels are 31m, 23m, 12.5m in the whole model area from 40 observation wells. Model results showed increases abstraction and decreased recharge due to climatic change will create groundwater level decline, which will have adverse effect or reduce surface waters systems. Increased well withdrawal by 150% resulted in the reductions of evapotranspiration, out flow to constant head, base flow (out flow) by -26%,-17%,-1.80% respectively but the river leakage increased by 14%.Increasing well discharge by 200% resulted in the reductions of stream base flow -3.1%, evapotranspiration by -37% ,out flow to constant head by -26% and the leakage from the river to the aquifer increased by 28.8%.Similarly, increasing withdrawal by 250% resulted in reduction of groundwater base flow to the river by-4.40%, evapotranspiration by -48% and out flow to constant head by -26% but the aquifer gain from the river leakage by 43.70%.