Natural Isotopes Identify Changes in Groundwater Flows Affecting Wetland Vegetation in the Drentsche Aa Brook Valley, The Netherlands
Samer Elshehawi 1, 2  
Enno Bregman 3, 4  
Paul Schot 5  
Ab Grootjans 1, 6  
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Centre for Energy and Environmental Studies, University of Groningen, The Netherlands.
Centre for Isotope Research, University of Groningen, The Netherlands.
Physical Geography Department, University of Utrecht, The Netherlands.
Province of Drenthe, The Netherlands
Copernicus Institute of Sustainable Development, University of Utrecht, The Netherlands
Institute of Water and Wetland Research, Radboud University Nijmegen, The Netherlands
Samer Elshehawi   

Centre for Energy and Environmental Studies, University of Groningen, The Netherlands., Nijenborgh 6, 9747AG Groningen, Netherlands
Publish date: 2019-03-01
J. Ecol. Eng. 2019; 20(3):112–125
This study uses groundwater isotopes and ion composition to verify model simulations and ecohydrological studies in the Drentsche Aa nature reserve in The Netherlands, which is representative for the northwestern wetland areas in the Ice Marginal Landscape zone. At eight field sites, a total of 24 samples were analysed for their 13C, 14C, 2H, and 18O isotopes and ionic composition. The isotopes indicate that most of the fen peatlands in the area depend on the exfiltration of sub-regional groundwater flows, which confirmed the previous model simulations and ecohydrological studies. At three sites, isotopes and ionic composition indicate that the groundwater from the sub-regional system has been replaced by local infiltrated rainwater, due to nearby groundwater abstractions for drinking water, which influenced the success rates of the restoration measures. Furthermore, the evidence from chloride and 14C contents was found to indicate the presence of more saline groundwater, which are influenced by the groundwater flows near salt diapirs. Groundwater abstractions may enhance the upward flow of the saline groundwater to eventually exfiltrate at the wetlands, affecting the biodiversity of the nature reserve.