Lakemaker: A general object-oriented software tool for modelling the eutrophication process in lakes. A proposition for an integrated modelling tool and simulation environment is presented. The aim of this tool is to help modelling the eutrophication processes in shallow lakes. The system architecture is divided into three main modules plus one that handles the communication between them and the user. The modules are: the Domain Base, which involves a structural description of all components and processes that make components interact; the Model Base, which contains the equations related to the components (dynamic models) and to the processes (static models); and the Database into which input and output data are stored and can be accessed. The program was implemented on a personal computer with MS-DOSĀ® operating system.