This Chapter gives a brief description of hydrochemical methods with detail provided on the significant changes in chemical composition that can occur spatially, both vertically and horizontally. Hydrochemical investigation techniques and detailed modelling applications are set out in other texts and are not repeated here. Suffice to say that the collection of accurate samples for hydrochemical analysis is an important part of Investigating Groundwater and it is essential that the field worker has an understanding of the chemical laboratory requirements for sample collection otherwise inappropriate analyses will be carried out at considerable (lost) expense. Detailed field examples are given to illustrate the importance of sample selection.

Sources for salts in rainfall are described. Guidance is provided for field sampling design and collection of reliable samples for hydrochemical analysis. The collection of samples for isotope analysis occurs at the same time as samples for basic water analysis and a review of isotope occurrence and examples of field data are also provided in this Chapter. Detailed examples are provided of isotope analysis and interpretation.