Continuous change of user requirements has become a constant for geo-information systems. Designing systems that can adapt to such changes requires an appropriate design methodology that supports abstraction, modularity and other mechanisms to capture the essence of the system and help controlling complexity. An important factor in the conceptual modelling of information systems is to describe structural and behavioural aspects of these systems. Traditionally, however these aspects of geo-information systems have been modelled separately, and little attention has been given to the behavioural part of such systems. Numerous techniques for the conceptual modelling of systems have emerged in the last years. We build upon these techniques, combining behavioural modelling with concepts from information modelling and formal system specifications, to define a methodology that enables the modelling of both behavioural and informational aspects of geo-information systems. The methodology aims at supporting the design process of the system, and also helps enforcing that geo-information systems are reliable, maintainable and compliant with the changing requirements.