ONLY SUMMARY IS IN ENGLISH; REST OF THE REPORT IS IN DUTCH ELNAG is a special purpose analog computer especially built for the simulation of unsteady flow in unconfined aquifers (e.g. seadikes). The analog model consists of a resistance-capacitance electrical network (5000 grid-points) which allows the permeability and the storage capacity of an aquifer to be varied. The position of the free surface in an unconfined aquifer can be varied automatically. The primary aim of the report is to give information to the users of the special purpose analog computer ELNAG. After a brief introduction the mathematical formulation of different groundwater problems is given in chapter 2. Digital and analog models to solve two dimensional problems are considered in this chapter with emphasis placed on electrical analog models. The results of ELNAG are compared with results of a digital finite difference model. The approximations in both types of models, which are very similar, and the arrangement of the boundary conditions in the models are discussed in chapter 3. In chapter 4 a short description (with some pictures) of the technical equipment of ELNAG is given. Information on the solution of practical problems by means of ELNAG is given in chapter 5 and 6. For three different problems the results obtained from ELNAG are compared with solutions based on an analytic approach, respectively a finite difference model and an electrical conductive-sheet analog model. The method of implementing of some practical problems in the model will be subject of further research.