Review of classification systems and new multi-scale typology of groundwater-surface water interaction

The EU Water Framework Directive outlines a new approach to water administration in which interactions between groundwater bodies, groundwater dependent terrestrial ecosystems and surface water bodies take on a central role. In this context, a review and an evaluation of earlier classification systems for groundwater, riparian areas and wetlands as well as for streams and rivers are given. A new multi-scale and process oriented typology integrating interactions between the three components of the hydrological continuum is proposed. The typology is based on geomorphologic, geological and hydrological concepts reflecting functional linkages and controlling flow processes on gradually smaller spatial scales. On a catchment scale of more than 5 km, the Landscape Type classifies the groundwater flow systems and the groundwater system based on regional geomorphology and regional hydrogeological setting, respectively. This scale characterizes the complexity of regional flow processes that control discharge patterns. On an intermediate or reach scale of 1–5 km, the Riparian Hydrogeological Type classifies the hydrogeological setting adjacent to a riparian area aquifer in greater detail. This scale characterizes physical contact between a groundwater body and a riparian area aquifer as well as stability and flux of groundwater to the riparian area aquifer. These factors are critical for maintaining diverse riparian ecosystems. Within a local scale of 10–1000 m, the Riparian Flow Path Type classifies the dominant flow path through the riparian area to the stream, based on flow path distribution through the riparian area. This scale characterizes the riparian area’s capability of maintaining high water quality of an adjacent stream. The GSI typology has been developed for the most important landscapes of Denmark and is exemplified by a moraine landscape. Finally, application possibilities are discussed.