Abstract
Measurements of the environmental isotopes carbon-14 and oxygen-18 and of the electrical conductivity in ground water, together with MODFLOW-88 (DOS) simulations of pumping tests, were used to achieve a detailed understanding of the functioning of an aquifer in the area of a well field. The methodology was applied in the sedimentary basin of the Cariri region, in the south of Ceará State in Brazil. Localized hydraulic connections between adjacent aquifer units could be detected, and mixing ratios for the contributions from the units involved were determined. Cone of depression simulations for a three-year drought period revealed well interference and a drastic lowering of the piezometric level, thereby explaining the hydrogeologic changes and transformations in vegetation that were observed in the area of the well field. The combined use of the modeling tools and the geochemical field observations is shown to provide more detailed insight into the conceptual model of the groundwater flow system.
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Acknowledgements
We owe thanks to the state and federal funding agencies, respectively, FUNCAP and CNPq, for financial support, and to Hydroisotop/ Germany for δ18O measurements. The local water companies CAGECE and COGERH provided logistic support. Karen Pennesi and Anthony Donegan edited the paper.
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Mendonça, L.A.R., Frischkorn, H., Santiago, M.F. et al. Isotope measurements and ground water flow modeling using MODFLOW for understanding environmental changes caused by a well field in semiarid Brazil. Environ Geol 47, 1045–1053 (2005). https://doi.org/10.1007/s00254-005-1237-y
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DOI: https://doi.org/10.1007/s00254-005-1237-y