Environmental Earth Sciences

, Volume 63, Issue 4, pp 809–825 | Cite as

Hydrogeochemical controls on shallow alluvial groundwater under agricultural land: case study in central Portugal

  • A. I. A. S. S. Andrade
  • T. Y. Stigter
Original Article


A hydrogeochemical study employing graphical, multivariate statistical, and modeling tools was conducted in an area of alluvial deposits in the Mondego river basin, to determine the factors and processes controlling the shallow groundwater chemistry. Groundwater was collected from 29 observation wells in six sampling campaigns, between March 2001 and September 2002. Samples were analyzed for basic physicochemical parameters, major ions and some minor ions. Hierarchical cluster analysis was applied to the data set, including both the spatial and temporal monitoring data and resulted in the definition of eight distinct water types. With the aid of hydrochemical (and physicochemical) scatter plots, it was possible to identify the main processes controlling the groundwater chemistry: (1) evapotranspiration and recharge; (2) calcium and magnesium carbonate and CO2 dissolution; (3) nitrate leaching from agriculture; (4) oxidation and reduction; and (5) cation exchange. These processes are frequently common to more than one water type but unique in combination and/or extent, in space and/or time. Geochemical modeling of the water types (using PHREEQC) allowed the validation and, to a certain extent, quantification of the processes that affect the shallow groundwater evolution. These tools can provide an essential support for the assessment of groundwater vulnerability to contamination and for the elaboration of groundwater resource management strategies.


Hydrogeochemistry Shallow groundwater Alluvial sediments Agriculture Hierarchical cluster analysis PHREEQC 



The authors wish to express their thanks to the Departamento de Ciências da Terra, Instituto de Investigação da Água and Centro de Geociências da Universidade de Coimbra for the support during the progress of this study, to the farmers who allowed the installation of the observation wells on their lands, to the Escola Superior Agrária de Coimbra for the availability of the equipment for well installation, to Eng. Filipe Melo and Sr. José Borralho for the help during the installation of the wells and for many agricultural informations and finally to the Associação de Beneficiários da Obra de Fomento Hidroagrícola do Baixo Mondego and Direcção-Geral de Agricultura e Desenvolvimento Rural—Projecto Mondego for all the support in the field work and information data. The second author holds a post-doctoral research position under the Ciencia 2007 program financed by the FCT—Fundação para a Ciência e a Tecnologia.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Department of Earth Sciences, Centro de GeofísicaUniversity of CoimbraCoimbraPortugal
  2. 2.Geo-Systems Centre/CVRM, Instituto Superior TécnicoLisbonPortugal

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