In this paper we present the ground water flow modelling in PVM. It requires the solution of a partial differential equation representing a 3-D diffusion process. Its numerical solution by a finite difference method leads to a very large sparse, well-structured system of linear algebraic equations. The Strongly Implicit Procedure (SIP) algorithm is chosen to solve the matrix. We also present our parallel version of SIP on PC cluster with PVM. The experiments show that our parallel SIP is very effective.