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| Titel |
A combined field and modeling study of groundwater flow in a tidal marsh |
| VerfasserIn |
Y. Q. Xia, H. L. Li |
| 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 ; 16, no. 3 ; Nr. 16, no. 3 (2012-03-07), S.741-759 |
| Datensatznummer |
250013208
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| Publikation (Nr.) |
 copernicus.org/hess-16-741-2012.pdf |
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| Zusammenfassung |
| Bald mud beaches were found among the mangrove marshes in Dongzhaigang
National Nature Reserve, Hainan, China. To investigate the possible reasons
for this phenomenon, the intertidal zones of a mangrove transect and a bald
beach transect with similar topography and tidal actions were selected for
comparison study. Along both transects, observed water table variations were
significant in the high and low intertidal zones and negligible in the
middle intertidal zones. Despite the same tidal actions and above-mentioned
similarities, observed groundwater salinity was significantly smaller along
the mangrove transect (average 23.0 ppt) than along the bald beach transect
(average 28.5 ppt). These observations invite one hypothesis: the hydraulic
structure of tidal marsh and freshwater availability may be the main
hydrogeological factors critical to mangrove development. Two-dimensional
numerical simulations corroborated the speculation and gave results in line
with the observed water table. The two transects investigated were found to
have a mud-sand two-layered structure: a surface zone of low-permeability
mud and an underlying high-permeability zone that outcrops at the high and
low tide lines. The freshwater recharge from inland is considerable along
the mangrove transect but negligible along the bald beach transect. The
high-permeability zone may provide opportunity for the plants in the
mangrove marsh to uptake freshwater and oxygen through their roots extending
downward into the high-permeability zone, which may help limit the buildup
of salt in the root zone caused by evapotranspiration and enhance salt
removal, which may further increase the production of marsh grasses and
influence their spatial distribution. The bald beach is most probably due to
the lack of enough freshwater for generating a brackish beach soil condition
essential to mangrove growth. It is also indicated that seawater infiltrated
the high-permeability zone through its outcrop near the high intertidal
zone, and discharged from the tidal river bank in the vicinity of the low
tide line. These processes thereby formed a tide-induced
seawater-groundwater circulation, which likely provided considerable
contribution to the total submarine groundwater discharge (SGD). Finally,
implications and uncertainties behind this study were summarized for future
examinations. |
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