Stiff Diagrams are a common and powerful tool for the representation of surface water / groundwater main ions. Anion and cation concentrations are represented on equivalent weight (meq/l), and usually cations are represented at the left side and anions at the right side. Traditionally, this diagram is useful for the comparison of the main water chemical components by examination of a series of diagrams, however it was not easy to compare the diagrams with the position of the observacion point.

To enhance the chemical analysis on regional scale this tutorial has coupled the Stiff Diagrams with their position on a QGIS project. The diagramas are generated from a spreadsheet with Python on a Jupyter Notebook and stored a vector file (.svg), then the images files are referenced on a style file (.sld) and uploaded to QGIS3.

Complex geochemical simulations are entirely possible to be performed with Phreeqc coupled with Aquifer App and Python. Brines can be simulated at different concentrations to obtain relations that are input of other variable density flow models. In this case we have model one brine, sodium bicarbonate, with the REACTION keyword with moles values that range from 0.5 to 12 moles. Values of mass, volume, concentration, and density were processed in Python from the dataframes generated from Aquifer App.

We define evaporation as the process of removing water from the chemical system in Phreeqc and this can be achieved with the REACTION keyword and a negative reaction coefficient. We have developed an applied case of water evaporation from precipitation water and the mix of the resulting water to restore the original volume. The whole Phreeqc setup, simulation and result analysis process has been in Aquifer App.

An example that demonstrates the Phreeqc and Aquifer App capabilities to model ion exchange. This example uses the cation ion exchange approach where only the EXCHANGE keyword is used because EXCHANGE_MASTER_SPECIES and EXCHANGE_SPECIES are included in phreeqc.dat database. The model output is parsed as charts and tables and the solution composition and description are calculated and compared before and after the exchange.