 |
| Titel |
Isotopic and geochemical tools for characterizing surface water-groundwater relationships in la Bassee floodplain area (Seine River Basin, France) |
| VerfasserIn |
Laurence Gourcy, Agnès Brenot, Emmanuelle Pételet-Giraud |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250058043
|
|
|
|
|
|
| Zusammenfassung |
| The evaluation of good qualitative and quantitative status of groundwater (WFD requirement)
needs a comprehensive estimation of the short and long term trends in order to establish
adequate river basin management plans. In this context, the understanding of surface water/
groundwater interactions is required for water quantity and quality preservation.
Hydrogeochemistry permits characterizing water and dissolved element origin and flow in
both ground and surface water.
The present study proposed testing the applicability of classical and isotope geochemical
tools to characterize surface/groundwater relationship in the flooding area of the Seine
River few kms before Paris, the Bassée floodplain. In this area, hydrological fluxes
between surface and groundwater are expected to be complex due to the presence of
three interconnected aquifers, numerous wetlands, ponds, gravel-pit lakes, and
rivers.
Borrow pits were initiated in the area beginning of the 70’s and are increasing
rapidly. This mining activity does not seem to have a direct qualitative impact on the
groundwater. Agriculture occupied today 40% of the territory of the Bassée plain for
about 46% in 1976. Cereals (wheat, maize, barley, rape, sunflower) and beetroot
cropping dominating since many years, diffuse pollution is expecting in the studies
area.
We proposed the use of various tracers of the water cycle such as δ2H, δ18O, of
water-rock interactions 87Sr/86Sr, of residence time and transfer mode CFCs and SF6 and of
anthropogenic impact 3H in order to evaluate the interconnection between aquifers
and possible relationships between surface water and groundwater in a flooded
plain.
The geochemical approach proposed in this study permitted to highlight the usefulness of
Ca/Sr, water stable isotopes, 87Sr/86Sr, dissolved gases and tritium to characterize the
relationship between surface and groundwater. The combined use of different tracers
permitted the understanding of space and time variations as well as the determination of the
nature and intensity of the relationships between water bodies. In la Bassée, a clear
discrimination exists between surface and groundwater and the influence of surface water to
groundwater is decreasing when distance to the Seine River is increasing. The infiltration of
surface water is taking place mainly close to the river bed and the flooded areas and recharge
rates are quite variable.
Improving the hydrogeological knowledge may be also necessary to understand
groundwater contamination. In La Bassée, surface water infiltration has a positive impact on
groundwater quality. River water may decrease groundwater nitrate concentration by dilution
and wetlands or gravel-pit lakes have also a positive impact by dilution, plant adsorption or
denitrification processes. |
|
|
|
|
|
|