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| Titel |
A successive-steady-state approach to integrated surface-subsurface modelling for runoff generation on the field scale |
| VerfasserIn |
W. M. Appels, P. W. Bogaart, S. E. A. T. M. van der Zee |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250070580
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| Zusammenfassung |
| In groundwater dominated lowland catchments the larger part of precipitation on drained
agricultural fields recharges the groundwater or reaches surface waters through subsurface
drains. However, shallow subsoil structure deterioration due to sealing or compaction,
shallow groundwater tables and long and intense precipitation events facilitate ponding
of water at the soil surface. During a rainfall event, the ponded area on the field
expands and surface runoff reaches the field boundaries when one or more series
of ponds form continuous flow paths to the channels and ditches surrounding the
field. To understand catchment discharge characteristics it is important to quantify
the relative contributions of different flow routes in a catchment. Also, as surface
runoff is the main contributor of pesticides and one of the main contributors of
phosphorus to surface-water bodies, it plays an important role with regard to the
contamination, the eutrophication, and the implications for ecological functioning of aquatic
ecosystems.
In order to further quantify the relations between groundwater conditions, infiltration
rates, and ponding and surface runoff, we developed a computer model that incorporates the
saturated, unsaturated zones and a heterogeneous surface topography. The simplifications
underlying the model are:
The surface microtopography is static, therefore the configuration of ponds and
their spill points to other ponds can be determined before the actual model
simulation and stored in a database.
The unsaturated zone is in hydrostatic equilibrium, therefore there is a unique
relationship between the volume of water stored in a soil column and the
elevation of the groundwater table. By using the total subsubsurface storage
volume as state variable, problems usually associated with saturated-unsaturated
zone interactions are bypassed, while still allowing for correct computation of
both groundwater flow, and unsaturated zone effects on surface infiltration and
thus runoff generation.
In the saturated zone only horizontal flow occurs. Radial flow towards the ditches
is accounted for via a ditch entry resistance.
With this model it is possible to efficiently analyse, with adequate accuracy, the relations
between the various compartments. In this presentation we describe the model structure, and
present applications to both instructive hypothetical cases and real-work field-scale
applications. Issues regarding upscaling of towards catchment and regional scales are
discussed. |
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