ABSTRACT

Groundwater flow systems concerning fractured rock masses are generally inhomogeneous, irregularly anisotropic, and particularized by mixed boundary conditions. The numerical simulation of their hydraulic heads’ spatial and temporal variation by a single polynomial approximant may bear unacceptable errors. Only two iterative techniques, known as Jacobi and Gauss-Seidel methods, will be considered. Before applying finite difference algorithms, it is essential to keep in mind that, as any system is a small part of a larger one, its boundary conditions must replicate the flow regime connecting both to preserve mass input-output balance. Wrong assumptions may produce a reliable pattern of the equipotentials but leading to incorrect predictions of hydraulic gradients and flow rates. In practice, if time predictions are really needed, a simple time-dependent model may approximately answer current questions for a restricted time-span. Additionally, top and base boundary conditions require two more finite difference algorithms. For real three dimensional simulation, the problem is still more complicated.