Standardized Schoeller diagrams—A Matlab plotting tool

Abstract A complete water analysis typically contains at least 65 chemical and physical parameters. This variety of parameters complicates temporal or spatial comparisons of different water samples. Hence, special hydrogeological diagrams, such as the Schoeller diagram, were developed to facilitate the evaluation and interpretation of analytical results of multiple samples. In conventional Schoeller diagrams, the concentrations of calcium, magnesium, sodium, chloride, sulfate, and bicarbonate/carbonate are plotted as points on logarithmic scales. Points of one analysis are connected to form characteristic signatures of each sample. Occasionally, resulting parallel signatures indicate a similar water genesis. Here, we present standardized Schoeller diagrams and introduce a practical Matlab tool for this purpose. Standardization means that the different logarithmic axes are shifted towards each other so that the signature of a selected sample becomes a horizontal line. This procedure greatly facilitates comparisons of water samples to the chosen standard and increases the informative value of the diagrams. However, manual implementations of standardizations are arduous and time-consuming, as a single calculation of the relocation of each axis is necessary. In addition, the calculations must be repeated if another sample is chosen as the standard. We developed a Matlab tool that allows the fast generation of standardized Schoeller diagrams with many options and implements user-specific preferences with just one command. Probably the most useful feature is that users can choose which parameters are displayed, opening up new areas of application for Schoeller diagrams.