Ring maps applied to hydrogeological and environmental studies

The use of Geographical Information Systems (GIS) has grown exponentially over recent years. This has made the production and use of maps one of the most widespread and effective ways to visualise, synthesise and communicate spatial information. The choice of the most appropriate visualisation method is fundamental especially when dealing with the representation, interpretation and communication of large heterogeneous datasets. The use of maps is widespread in hydrogeology, however, common methods of data visualisation only allow a small number of variables to be shown at any one time. Hydrochemical analysis of aquifer systems generally involves assessing several variables, including major ions, physicochemical parameters and possible contaminant concentrations. This information is appropriately contextualised only if it is related to the geographical and hydrogeological setting. Hydrochemical and environmental data are normally shown numerically in tables and graphs. This approach is suitable for organising and synthesising information but can be difficult to read and also do not provide a geographical context to the data. The choice of representing data with tables and graphs is generally motivated by lack of more advanced visualisation techniques which are effective, easy to apply and functional for the geovisualisation of extensive multivariate datasets. Ring maps have been used in this study as a tool for representing the hydrogeological setting, the groundwater chemistry and the distribution of representative contaminants that is commonly available to professionals with a technical/scientific background and that commonly operate as hydrogeologists or land quality experts for the characterisation and remediation of contaminated sites. These types of maps have already been effectively used for the representation of epidemiological data and time series datasets. They require the use of a base map at the centre of the image which is then surrounded by a series of concentric rings, each showing a different variable. The technique simultaneously and clearly shows over 12 numerical variables, the geographical position and the main hydrogeological properties of the aquifers in one single graphical representation.