Numerical Modeling of the Groundwater Flow in the Area Around Atbara Town, River Nile State, Sudan

Abstract

This paper emphasized on the numerical modeling of ground water as it is vulnerable resources to many environmental risks and is essential to sustainable development. The main geological units in the study area are Pre-Cambrian Basement Complex, Upper Cretaceous sedimentary formation, Oligocene Hudi Chert and Quaternary superficial deposit. The threedimensional groundwater flow model was performed to evaluate the groundwater potentiality and assess the effect of groundwater withdrawal to the regional water level and flow direction in the Atbara basin of Sudan. The model was calibrated using 3D Finite difference visual MODFLOW. The model calibration criteria such as absolute residual mean, root mean square error and mass balance error of water into and out of the system were adjusted to suitable values. Hence, model calibration seemed to be more acceptable with average of 0.756 m and average absolute residual mean of 0.633 m and average normalized root mean square of 2.45%. The contour maps of the simulated heads produced by visual MODFLOW show fair similarity with the contour map drawn using initial heads which confirm the reliability of visual MODFLOW application and acceptable model calibration for the problem. Therefore, numerical simulation indicated that, a sharp drop of hydraulic head can be observed at the center of the model area, east of Atbara River, generated cone of depression and a continuous decline of head with respect to the time as a result of heavy groundwater abstraction. The southwest part of the area between Atbara River and River Nile represents relatively high permeability zone and the model confirmed it to be the most productive region in the area and can be used for storing additional groundwater. Observation wells elaborate the reasonable match between the observed and calculated heads through the entire simulation period.