6.2 Design of the Groundwater Flow Model
6.2.1 Model Grid
A finite- difference grid was designed to represent the main channels of Wadi Tanuf and the central part of Wadi Abyad. Cell sizes used in the finite difference mesh were chosen after considerations of several factors, including the model domain size, the hydraulic heterogenity, and predicted resolution required. The grid, shown in Figure (6.3), represented an area 10 km by 16 km and contains 125 rows and 89 columns. Cells in the grid, which falls outside the catchments area, were designated as “inactive “ and did not contribute to flow.
The model was oriented in a north- south direction since horizontal anisotropy was assumed to have little effect on groundwater flow in the study area. A local origin for the model and base map for the study area was selected al UTM coordinates 535 000 E and 2525 000 N.