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| Titel |
Understanding wetland sub-surface hydrology using geologic and isotopic signatures |
| VerfasserIn |
P. K. Sikdar, P. Sahu |
| 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 ; 13, no. 7 ; Nr. 13, no. 7 (2009-07-28), S.1313-1323 |
| Datensatznummer |
250011948
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| Publikation (Nr.) |
 copernicus.org/hess-13-1313-2009.pdf |
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| Zusammenfassung |
| This paper attempts to utilize hydrogeology and isotope composition of
groundwater to understand the present hydrological processes prevalent in a
freshwater wetland, source of wetland groundwater, surface water/groundwater
interaction and mixing of groundwater of various depth zones in the aquifer.
This study considers East Calcutta Wetlands (ECW) – a freshwater peri-urban
inland wetland ecosystem located at the lower part of the deltaic alluvial
plain of South Bengal Basin and east of Kolkata city. This wetland is well
known over the world for its resource recovery systems, developed by local
people through ages, using wastewater of the city. Geological investigations
reveal that the sub-surface geology is completely blanketed by the
Quaternary sediments comprising a succession of silty clay, sand of various
grades and sand mixed with occasional gravels and thin intercalations of
silty clay. At few places the top silty clay layer is absent due to scouring
action of past channels. In these areas sand is present throughout the
geological column and the areas are vulnerable to groundwater pollution.
Groundwater mainly flows from east to west and is being over-extracted to
the tune of 65×103 m3/day. δ18O and δD
values of shallow and deep groundwater are similar indicating resemblance
in hydrostratigraphy and climate of the recharge areas. Groundwater
originates mainly from monsoonal rain with some evaporation prior to or
during infiltration and partly from bottom of ponds, canals and infiltration
of groundwater withdrawn for irrigation. Relatively high tritium content of
the shallow groundwater indicates local recharge, while the deep groundwater
with very low tritium is recharged mainly from distant areas. At places the
deep aquifer has relatively high tritium, indicating mixing of groundwater
of shallow and deep aquifers. Metals such as copper, lead, arsenic, cadmium,
aluminium, nickel and chromium are also present in groundwater of various
depths. Therefore, aquifers of wetland and surrounding urban areas which are
heavily dependent on groundwater are vulnerable to pollution. In the area
south of ECW isotope data indicates no interaction between shallow and deep
aquifer and hence this area may be a better location to treat sewage water
than within ECW. To reduce the threat of pollution in ECW's aquifer, surface
water-groundwater interaction should be minimized by regulating tubewell
operation time, introducing treated surface water supply system and
artificial recharging of the aquifer. |
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