Already two decades ago groundwater and surface water were called a single resource and at the same time the extraordinary importance of the groundwater-surface water interface was identified. Nevertheless there are still tendencies in some disciplines such as hydrogeology and limnology to study both compartments as separate entities. Still, the importance and relevance of interactions between groundwater and surface water for freshwater ecosystems is often underestimated. There is a need to improve the understanding of the processes at the interface (e.g. hyporheic zone) and the impacts on adjacent compartments.

A rapidly expanding number of research projects are now investigating the implications of hyporheic exchange on the transport and transformation of nutrients and contaminants within river networks, lakes and wetlands and on controls to heat, oxygen, and organic matter budgets available to microorganisms and macroinvertebrates in streambed sediments. Research is also focusing on the response of hyporheic exchange fluxes to environmental and climatic controls at different spatial and temporal scales (e.g. river channel, alluvial aquifer, regional groundwater flow). In addition, there is a need to better understand the links between hydrological, biogeochemical, and ecological process dynamics in hyporheic zones and their implications for ecology.

We consider up- and downscaling and the development of a general conceptual framework for groundwater-surface water interfaces as among the most urgent challenges of this research. Consequently, we particularly welcome contributions that aim to close these knowledge gaps and address either scaling issues or the development of a general conceptual framework.

In addition, this session also solicits both field-based and modelling studies with a focus on:

- The development and application of novel experimental methods to investigate physical, biogeochemical and ecological conditions at the groundwater-surface water interface in both rivers and lakes;

- Investigations of the role of hyporheic processes for the retention and natural attenuation of nutrients and pollutants, particularly with respect to impacts on surface water and groundwater quality;

- Hydrological, biogeochemical and ecological modelling approaches (e.g. transient storage models, coupled groundwater-surface water models etc.);

- The relevance of groundwater-surface water interactions in metropolitan areas with their strong anthropogenic pressure on ecosystems

- Investigations of the implications of groundwater-surface water interactions for management and risk assessment frameworks with regard to the European Water Framework Directive.

SOLICITED SPEAKER:
Jennifer DRUMMOND- Centre for Advanced Studies of Blanes (CEAB-CSIC)