Groundwater–Surface Water Interaction: Process Understanding, Conceptualization and Modelling (Proceedings of Symposium HS1002 at IUGG2007, Perugia, July 2007). IAHS Publ. 321, 2008, 103-109.

The role of groundwater recharge and baseflow in integrated models

Jens Götzinger¹, Roland Barthel², Johanna Jagelke² & András Bárdossy²

1 Saarland Ministry of Environment, Keplerstr. 18, D- 66117 Saarbrücken, Germany

j.goetzinger@umwelt.saarland.de

2 Institute for Hydraulic Engineering, Universitaet Stuttgart, Pfaffenwaldring 61, D-70550 Stuttgart, Germany

Abstract Integrated water resources management is often concerned with problems on the river basin scale, e.g. impact assessment of climate and land-use change or the implementation of river basin management plans (i.e. the European Water Framework Directive). This requires integrated approaches of analysis and modelling. Important processes coupling the groundwater and the surface water systems (soil, unsaturated zone, surface waters) are groundwater recharge and discharge (baseflow). In this study it will be shown that these processes have been used to integrate a hydrological and a groundwater flow model. This has helped in revealing inconsistencies of process descriptions that often do not become apparent in stand-alone models if recharge and baseflow are only accounted for in the boundary conditions. Model integration provides more measurable quantities for model calibration, and provides an opportunity for an indirect check on internal state variables, the model structure, and the conceptual base of the model itself. In this study, integration shows that significant inter-basin subsurface fluxes exist in parts of the basin which contradict the delineated surface sub-basins.

Key words groundwater recharge; baseflow; model integration; MODFLOW; HBV; Neckar