Two Dimensional Numerical Groundwater Flow Modelling Of the Megech River Catchment,Ethiopia

Abstract

<title>Abstract</title> Catchment is found in the Amhara Regional State, North Gondar Administrative Zone, Gondar town and surrounding Keble River catchment. Its total area coverage is 785 km2 , and the main lithologic units of lacustrine deposits are the Middle Basalt (Aiba) and the Upper basalt (Alajie). Numerical groundwater flow modeling of the Megech River catchment, Tana Sub Basin, is conducted with the objective of simulating the groundwater flow system of the area and evaluating the response of the hydrogeological system under different stresses so that the resulting consequences for the system can be estimated. The calibrated statistics of the model area showed a mean error (ME) of 4.8, absolute mean error (AME) of 4.9, and root mean square error (RMSE) of 6.8, which are indicators of good calibration. The sensitive parameters of the model were identified during the calibration process. Therefore, the RMSE is more sensitive to hydraulic conductivity and recharge than to river conductance. The simulated water budget under steady -state conditions in the Megech River catchment was analysed. The simulated inflow of the model is 1.0703551E+06 m3/day, which is equal to the simulated outflow of 1.0703559E+06 m3/day, with a difference of -7.9617882E-01(-0.79617882) m3/day. The total withdrawal of groundwater from the Megech catchment in the well is 1.78853E+04 m3/day. A scenario analysis was conducted for decreasing recharge and increasing withdrawal rates.