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| Titel |
Linking soil moisture balance and source-responsive models to estimate diffuse and preferential components of groundwater recharge |
| VerfasserIn |
M. O. Cuthbert, R. Mackay, J. R. Nimmo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 3 ; Nr. 17, no. 3 (2013-03-07), S.1003-1019 |
| Datensatznummer |
250018819
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| Publikation (Nr.) |
 copernicus.org/hess-17-1003-2013.pdf |
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| Zusammenfassung |
| Results are presented of a detailed study into the vadose zone and shallow
water table hydrodynamics of a field site in Shropshire, UK. A conceptual
model is presented and tested using a range of numerical models, including a
modified soil moisture balance model (SMBM) for estimating groundwater
recharge in the presence of both diffuse and preferential flow components.
Tensiometry reveals that the loamy sand topsoil wets up via preferential
flow and subsequent redistribution of moisture into the soil matrix.
Recharge does not occur until near-positive pressures are achieved at the
top of the sandy glaciofluvial outwash material that underlies the topsoil,
about 1 m above the water table. Once this occurs, very rapid water table
rises follow. This threshold behaviour is attributed to the vertical
discontinuity in preferential flow pathways due to seasonal ploughing of the
topsoil and to a lower permeability plough/iron pan restricting matrix flow
between the topsoil and the lower outwash deposits. Although the wetting
process in the topsoil is complex, a SMBM is shown to be effective in
predicting the initiation of preferential flow from the base of the topsoil
into the lower outwash horizon. The rapidity of the response at the water
table and a water table rise during the summer period while flow gradients
in the unsaturated profile were upward suggest that preferential flow is
also occurring within the outwash deposits below the topsoil. A variation of
the source-responsive model proposed by Nimmo (2010) is shown to reproduce
the observed water table dynamics well in the lower outwash horizon when
linked to a SMBM that quantifies the potential recharge from the topsoil.
The results reveal new insights into preferential flow processes in
cultivated soils and provide a useful and practical approach to accounting
for preferential flow in studies of groundwater recharge estimation. |
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