Water management plans require comprehensive knowledge of physical processes and principles controlling water resources. These mechanisms, subject to limitations, can interact in complex ways, which makes it challenging to design guidelines to achieve optimum water resources use, taking into account economic, social and environmental factors. The relationship between rivers and aquifers defines different forms of interaction between superficial water and groundwater. These processes have great relevance in inland water management and protection against pollution, as well as dependent ecosystems. Under the current legislative framework in Europe, i.e., the Water Framework Directive 2000/60/EC (WFD) and the Groundwater Directive 2006/118/EC, calculation of flow direction and exchange rates between groundwater bodies and associated surface systems are key aspects of river basin management plans. This paper examines conditioning factors of exchange processes, related basic physical principles, and criteria for establishing different conceptual models, providing a typology for systematic classification of groundwater–surface water interactions.