Lah-Yisir river catchment project area is located between Bure and Finoteselam Towns. The general objective of the study is numerical simulation of the groundwater flow system of the Lah-Yisir river catchment to evaluate the response of the hydrogeologic system to different stresses and their resulting consequence on the system. The model has been conceptualized the boundary conditions, the aquifer thicknesses, the upper layer and bottom layers of the model by using satellite images , SRTM (DEM) using global mapper 12 Software, Field Traverses and with Geophysical and actual drilling log information. Initial prescribed hydraulic head is assigned by subtracting 20-40m from the top layer elevation and the horizontal hydraulic conductivity used for the simulation is 0.0024m/day to 7.272 m/day produced by interpolation of the pump test data. the value used for recharge package are, 0.00178 m/day in the area assumed to be fractured and to 0.00006 m/day in areas which is not fractured or clay deposits.it is calculated by using soil water balance method considering slope (physiography), land use and land cover, soil type( geologic character). In well package, there are 30 abstraction wells including shallow wells and major springs which naturally discharges varying from 86.4m3/day to 1036m3/day ( discharging in 12 hours pumping rate) in a cell. Among these, 15 wells have been used as observation point and Lah, Yisir and Silala Rivers are treated with river package. The model was calibrated with mean error -4.6, absolute mean error 7.7 meter and RMSE of 10.2 meter. The calibration was conducted by adjusting recharge, conductivity and riverbed conductance. The model is less sensitive to river bed conductance, more sensitive to recharge and moderately sensitive to hydraulic conductivity. the simulated inflow of the model is 8.3291950E+05 m 3 /day which is nearly equal to simulated outflow 8.3291556E+05m /day with difference 3.9375000m 3 /day and 0.00% of error. There are two scenarios conducted which are increased groundwater withdrawal and altered recharge. Under steady state simulation, the current withdrawal rate estimated was 3.2378340E+04m 3 /day. The Steady state withdrawal rates were increased by 20%, 75%, and 150%, to see the system response in the scenario. The increments are equivalent to withdrawing of additional 3208.6m 3 /d, 6572.16m 3 /d and 18,061.84m 3 /day respectively and the head declines insignificantly from average of 2 to 5 meter. This difference does not alter the natural recharge and observed that the impact is insignificant and it can be permissible for development of additional boreholes or more abstractions. While increasing the withdrawal rate by 150%, it changes the head by about 10 meter that causes the alteration of the natural discharges. The other scenario is decreasing of the recharge to aquifers, the simulation response of the system to 15% and 50% recharge decrements and the result is average head decrease of 11.61 to 45.78 meter drawdown that adversely affects the groundwater table which indirectly cause problem of the natural discharges and it should be come up with afforestation of non-cultivated areas and by terracing methods as a recommendation and solution.