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d18O and d2H Isotope Ratio Analysis as a Contribution to the Clarification of Groundwater Dynamic in the Czech-German Borderland

Diana Burghardt1, Patricia Baumann1, Johannes Stock1, Linda Michel1, Thomas Krause1, Hans Jürgen Hahn2, Dirk Matzke2, Anna Katharina Böhm3
1 Institut für Grundwasserwirtschaft, TU Dresden
2 Institut für Grundwasserökologie
3 Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie

O 13.2 in Czech-German exchange on environmental-, soil- and hydro(geo)logical issues

30.05.2014, 11:20-11:40, H18, NW II

 

From 2011 until 2014, the German subproject of the EU-object 3 project ‘GRACE’ (Groundwater Absence in Cretaceous Sandstone Aquifers) is processed at the Saxon State Office for the Environment, Agriculture and Geology. The main objectives of the project are the clarification of groundwater- surface water interactions as well as falling groundwater levels, which have been observed in parts of the Saxon Bohemian Switzerland and the Zittau Mountains since many years.

The Saxon Bohemian Switzerland is characterized by forest and a unique landscape of sandstone rocks, which is designated as a national park in large parts. From a total of four groundwater storeys, the second and third (Turonian aquifers of 38-70 m and 110-140 m thickness) as well as the fourth (a Cenomanian aquifer of 23-65 m thickness) have relevance for water management (GEOS, 2007). In the predominantly forested Zittau Mountains, only the first groundwater storey (a turon aquifer of 125 – 340 m thickness) is used for drinking water supply (GEOS, 1998).

Within the German GRACE subproject, a one-year study of d18O and d2H isotope ratio development in the groundwater from selected springs and groundwater monitoring wells as well as the local precipitation was performed  in order to estimate the percentages of precipitation (groundwater recharge) in each spring and groundwater sample as well as their recharge altitudes.

In a first step, annual mean isotope ratios were derived from analyzed isotope signatures by identifying ‘outliers’ (Fig.1). Thereby, the corrected annual mean values could be used for the calculation of a local isotope altitude effect and as input signals (‘ground¬water recharge’) for a two-component mixing calculation. For each investigation area, the groundwater sample with the lightest isotope ratio was used as second input signal (‘deep groundwater’).

As a result of the study, the percentage of precipitation (groundwater recharge) was 50 to 70% and less than 20% for the spring and groundwater samples of the Saxon Bohemian Switzerland and Zittau Mountains, respectively. The local isotope precipitation effect for both areas was -0,29 ‰ d18O and  -2,2 ‰ d2H per 100 m. 

In summary it can be stated that the ground-water of the investigated springs and groundwater monitoring wells was characterized by long residence times, in particular in the Zittau Mountains.

Abb.1: Ermittung von d18O Jahresmittelwerten  für Sächsich-Böhmische Schweiz und Zittauer Gebirge
Abb.1: Ermittung von d18O Jahresmittelwerten für Sächsich-Böhmische Schweiz und Zittauer Gebirge



 

 

GEOS (1998): Übersichtsbegutachtung des Grundwasserdargebotes und dessen Nutzung im Zittauer Gebirge unter Berücksichtigung der Grundwassernutzungen auf tschech­ischem Gebiet. Auftrag des LfULG

GEOS (2007): Zustandsüberwachung Grenz­grundwasser/ Operatives Messnetz. Gut­achten im Auftrag des RP Dresden.



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Letzte Änderung 12.02.2014