The process whereby hydrogeologists interpret the available information to produce a justifiable set of simplifying assumptions to describe a groundwater system is called conceptual modelling. Although this process is inherent in all hydrogeological assessments and can therefore be regarded as synonymous with hydrogeological practice there are no standard specifications for it. A framework for conceptual modelling has been designed to both assist in the planning and process of the work and to provide an audit trail to facilitate independent scrutiny. The application of this framework is illustrated by two case histories, one of a small-scale investigation for a proposed cemetery and the other of an investigation of the migration of [...]