Some observations on the chemical classification of ground waters

Abstract Using meq/l of the seven major chemical components of water samples, six new parameters are defined for distinguishing water groups based on the geological features of the main reservoir crossed by each water sample. The chemical data and hydrogeological characteristics of the reservoirs were drawn from surveys conducted in central Italy in 1979 and 1981. Selection of the chemical parameters appears to be a useful tool for improving the definition of the hydrochemical facies during the early stages of interpreting geochemical data of water samples from the same region. The combined use of a Piper diagram and graphical representations of the six parameters leads to an improved classification of water samples in the following points. (1) Where the hydrogeological features of certain hydrogeological systems are known it is possible to draw ‘standard’ diagrams that can be used as reference diagrams for the other water samples. (2) When some water samples occupy the same position in the Piper diagram, the parameters may establish whether this group is homogeneous or made up of waters of differing hydrological histories. (3) When the chemical compositions of spring water seem to be the result of a mixing process between two or three components, the values of the parameters can be used to define the mixed waters in terms of percentage of the components.