Typology of groundwater - surface water interaction (GSI typology) - with new developments and case study supporting implementation of the EU Water Framework and Groundwater Directives

The EU Water Framework and Groundwater Directives outline an approach to water administration in which interactions between groundwater bodies, groundwater dependent terrestrial ecosystems and surface water bodies (associated aquatic ecosystems) take on a central role. To facilitate monitoring and status assessment the directives allow grouping according to typologies. A typology used for evaluating interdependency between groundwater bodies, riparian areas and streams must be based on processes controlling flow, contaminant transport and attenuation. The typology of Groundwater – Surface water Interaction (GSI typology) has been developed
as a process oriented scaled framework classifying interactions between the three hydrological components. The controlling processes are characterised using an eco-hydrological approach
based on geomorphology, hydrogeological setting and flow paths on gradually smaller scales. As part of a programme of measures to obtain good ecological status of associated coastal waters (including a Natura 2000 site) an assessment was conducted in a 50 km² catchment area in a moraine landscape by combined use of new developments of the GSI typology and a
field campaign of nitrate concentration measurements in groundwater, tributaries and streams. One purpose was to delineate sub-catchments in which nitrate concentrations in a shallow local groundwater body exceeded threshold values derived from good status objectives for the coastal ecosystems. Another purpose was to assess in which selected sub-catchments riparian area hydrology restorations or reductions in nitrate input from fields were appropriate measures
to reduce nitrate loads to streams and ultimately to the associated coastal waters.