The development and application of a digital computer model of the ground water reservoir of the island of Anholt is described.

The model is based on a finite difference, two-dimensional approach. It was successfully used to investigate if the ground water at a planned well field might be polluted by sewage from nearby cesspools. Although the model is an approximation of the real aquifer conditions, the authors found the model very useful and suggest that modelling techniques be more widely used in ground water resource investigations.