The impact of groundwater–surface water interactions on the water balance of a mesoscale lowland river catchment in northeastern Germany

Abstract

Abstract:The glacially formed northeastern German lowlands are characterized by extensive floodplains, often interrupted by relatively steep moraine hills. The hydrological cycle of this area is governed by the tight interaction of surface water dynamics and the corresponding directly connected shallow groundwater aquifer. Runoff generation processes, as well as the extent and spatial distribution of the interaction between surface water and groundwater, are controlled by floodplain topography and by surface water dynamics.A modelling approach based on extensive experimental analyses is presented that describes the specific water balance of lowland areas, including the interactions of groundwater and surface water, as well as reflecting the important role of time-variable shallow groundwater stages for runoff generation in floodplains. In the first part, experimental investigations of floodplain hydrological characteristics lead to a qualitative understanding of the water balance processes and to the development of a conceptual model of the water balance and groundwater dynamics of the study area. Thereby model requirements which allow for an adequate simulation of the floodplain hydrology, considering also interactions between groundwater and surface water have been characterized. Based on these analyses, the Integrated Modelling of Water Balance and Nutrient Dynamics (IWAN) approach has been developed. This consists of coupling the surface runoff generation and soil water routines of the deterministic, spatially distributed hydrological model WASIM-ETH-I with the three-dimensional finite-difference-based numerical groundwater model MODFLOW and Processing MODFLOW. The model was applied successfully to a mesoscale subcatchment of the Havel River in northeast Germany. It was calibrated for two small catchments (1Ð4 and 25 km 2 ), where the importance of the interaction processes between groundwater and surface waters and the sensitivity of several controlling parameters could be quantified. Validation results are satisfying for different years for the entire 198 km 2 catchment. The model approach was further successfully tested for specific events. The experimental area is a typical example of a floodplaindominated landscape. It was demonstrated that the lateral flow processes and the interactions between groundwater and surface water have a major importance for the water balance and periodically superimposed on the vertical runoff generation.

A channel transmission losses model for different dryland rivers

“…Moreover, in (sub-)humid rivers vertical and lateral groundwater recharge can occur from winter to spring, when the surface water stages are higher than the groundwater table (see e.g. Krause and Bronstert, 2007). This recharge after drought periods or during extensive groundwater pumping may be intensified and resemble channel transmission losses of dryland rivers.…”

“…applications in Krause and Bronstert, 2007;Xie and Yuan, 2010;Engeler et al, 2011). This approach has been successfully applied to catchments and river reaches, especially in temperate and humid regions, linking distributed river and groundwater flow models.…”

Comparing model sensitivities of different landscapes using the ecohydrological SWAT model

“…Ecohydrological models have already been used successfully in lowland catchments (e.g. Schmalz et al, 2007;Habeck et al, 2005;Hattermann et al, 2006Hattermann et al, , 2008Hesse et al, 2008;Krause and Bronstert, 2007;Krause et al, 2007a, b).…”

Modelling hydrological processes in mesoscale lowland river basins with SWAT—capabilities and challenges

“…Hattermann et al (2006) incorporated a riparian zone and wetland module into SWIM to consider the effects of riparian zones and wetlands on nutrient transport into surface water of the same lowland catchment. The water balance of wetlands within flood plains of the northeastern German Havel River basin was modelled (Krause & Bronstert, 2007;Krause et al, 2007a,b) with the IWAN model (Krause & Bronstert, 2005); their simulation results proved the close interaction between river and flood plain.…”