『Summary
Water balance and groundwater dynamics of a floodplain catchment
in the Northeast German lowlands are investigated with consideration
of the variable interactions between the riparian groundwater
and surface water. Based on experimental and numerical investigations,
evidence is given for temporally and spatially variable exchange
fluxes between groundwater and surface water, which have significant
impact on the riparian water balance and groundwater recharge.
A coupled soil water balance - groundwater model is used for
the quantification of exchange fluxes across the groundwater-surface
water interface and the groundwater recharge for nested catchments
in a typical floodplain representative for the Central European
lowland catchments.
Simulation results indicate substantial exchange fluxes between
groundwater and the river, which are subjected to intensive spatial
and temporal variability. The intensities and also the directions
of exchange fluxes in particular stream reaches are characterised
by transient alterations. Groundwater-surface water interactions
are found to control the groundwater recharge dynamics in the
floodplain and outweigh the influence of vertical percolation
and root water uptake. Although groundwater contributions from
this river stretch represent only 1% of the annual total discharge
within the river its impact is much higher during low flow conditions
in summer when ca. 30% of the river runoff which is generated
in the catchment is originated by groundwater discharge from the
riparian zone along this river stretch.
The results of this study show that groundwater-surface water
interactions within the investigated riparian floodplain are far
too complex for the traditional classification concept distinguishing
between loosing and gaining sections. The temporally variable
impact of groundwater-surface water interactions furthermore highlights
the necessity to consider seasonal effects when assessing the
significance floodplain processes and functions.
Keywords: Riparian zone; Groundwater-surface water interactions;
Floodplain; Water balance』
Introduction
Materials and methods
Study area
Nested discharge observations
Process oriented modelling approach
Underlying concepts
Relevant process descriptions
Model setup
Calibration and validation of the model
Results and discussion
Nested observations of discharge dynamics
Simulation of riparian water balance at the Lower and Central
Havel River
Simulation of exchange fluxes between floodplain and lowland
river
Temporal variability of exchange fluxes
Spatial pattern of exchange fluxes
Mean monthly exchange rates
Simulation of groundwater recharge in floodplain
Impact of groundwater-surface water exchange fluxes on the total
floodplain water balance and groundwater recharge
Importance of riparian groundwater contributions for the river
discharge
Conclusion
Acknowledgments
References