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| Titel |
Characterization and interaction of precipitation, river water and groundwater in the Vietnamese Mekong Delta - A case study in the Plain of Reeds |
| VerfasserIn |
Le Duy Nguyen, Ingo Heidbüchel, Bruno Merz, Heiko Apel |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250126587
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| Publikation (Nr.) |
 EGU/EGU2016-6329.pdf |
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| Zusammenfassung |
| An understanding of the interactions between surface water and groundwater systems in the
Vietnamese Mekong Delta (VMD) is important not only for water resources planning and
management, but also for the livelihood of the majority of the population in the delta.
Precipitation and ground water, but also river water is used as drinking water in the
communes of the Delta. Particularly the ground water is increasingly exploited, but the
important processes like river – aquifer interaction and ground water recharge rates are
largely unknown. This study thus aims at the characterization of processes between the
different water resources. For this the different water sources were sampled over longer time
periods and analysed for isotopic composition (2H, 18O). Additionally surface and ground
water levels were recorded, as well as the temperature profile at and under the river bed in
order to identify the river-ground water interaction. First results indicate that the isotopic
composition and the local meteoric water line of the precipitation is very similar to the
GNIP data for Bangkok, indicating similar isotopic sequestration and origin of the
rainfall in the region (near ocean areas of SE-Asia). The isotopic composition of
precipitation and river water exhibits a strong seasonal signal indicating the monsoonal
influence. During the monsoon season both precipitation and river water is depleted in
stable isotopes, while the dry season shows an enriched composition. This also
indicates the different composition of the river water over the seasons. During the rainy
season the portion of rain water, i.e. surface runoff stemming from the Mekong basin
but also direct rainfall contribution in the Mekong Delta is considerably larger,
as expected. The enriched composition during the dry season indicates a larger
ground water, i.e. base flow portion, but also a generally higher evaporation due to
the lower atmospheric moisture. The isotopic composition of the ground water
differs depending on the depth of the well. The deep wells (>200m depth) have a
different signature compared to the shallow wells (10-20m), and do not show seasonal
variations indicating that the deep aquifer has no connection to the shallow aquifer
and the surface water. The isotopic compositions as well as the water tables of the
shallow GW wells show a seasonal signal, which, however, differ from well to well
depending on the location of the wells. The isotopic composition of the wells differs
considerably from the river water, but is similar to the mean precipitation signal. This
indicates that the ground water recharge possible stems mainly from rainfall, not from
seepage from the river bed. The ground water data also indicate that the dynamics and
likely also the GW recharge are heterogeneous. Possible factors influencing the
interaction of surface to ground water are the distance to the river, but also the small
scale variability of physical aquifer properties. The identification of the causes of
the differences between the ground water wells will be subject to further studies. |
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