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| Titel |
Paleo-modeling of coastal saltwater intrusion during the Holocene: an application to the Netherlands |
| VerfasserIn |
J. R. Delsman, K. R. M. Hu-a-ng, P. C. Vos, P. G. B. de Louw, G. H. P. Oude Essink, P. J. Stuyfzand, M. F. P. Bierkens |
| 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 ; 18, no. 10 ; Nr. 18, no. 10 (2014-10-02), S.3891-3905 |
| Datensatznummer |
250120486
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| Publikation (Nr.) |
 copernicus.org/hess-18-3891-2014.pdf |
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| Zusammenfassung |
| Coastal groundwater reserves often reflect a complex evolution of marine
transgressions and regressions, and are only rarely in equilibrium with
current boundary conditions. Understanding and managing the present-day
distribution and future development of these reserves and their hydrochemical
characteristics therefore requires insight into their complex evolution
history. In this paper, we construct a paleo-hydrogeological model, together
with groundwater age and origin calculations, to simulate, study and evaluate
the evolution of groundwater salinity in the coastal area of the Netherlands
throughout the last 8.5 kyr of the Holocene. While intended as a conceptual
tool, confidence in our model results is warranted by a good correspondence
with a hydrochemical characterization of groundwater origin. Throughout the
modeled period, coastal groundwater distribution never reached equilibrium
with contemporaneous boundary conditions. This result highlights the
importance of historically changing boundary conditions in shaping the
present-day distribution of groundwater and its chemical composition. As
such, it acts as a warning against the common use of a steady-state situation
given present-day boundary conditions to initialize groundwater transport
modeling in complex coastal aquifers or, more general, against explaining
existing groundwater composition patterns from the currently existing flow
situation. The importance of historical boundary conditions not only holds
true for the effects of the large-scale marine transgression around
5 kyr BC that thoroughly reworked groundwater composition, but also for the
more local effects of a temporary gaining river system still recognizable today. Model results further attest to the impact of
groundwater density differences on coastal groundwater flow on millennial
timescales and highlight their importance in shaping today's groundwater
salinity distribution. We found free convection to drive large-scale fingered
infiltration of seawater to depths of 200 m within decades after a marine
transgression, displacing the originally present groundwater upwards.
Subsequent infiltration of fresh meteoric water was, in contrast, hampered by
the existing density gradient. We observed discontinuous aquitards to exert a
significant control on infiltration patterns and the resulting evolution of
groundwater salinity. Finally, adding to a long-term scientific debate on the
origins of groundwater salinity in Dutch coastal aquifers, our modeling
results suggest a more significant role of pre-Holocene groundwater in the
present-day groundwater salinity distribution in the Netherlands than
previously recognized. Though conceptual, comprehensively modeling the
Holocene evolution of groundwater salinity, age and origin offered a unique
view on the complex processes shaping groundwater in coastal aquifers over
millennial timescales. |
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