Building a Sustainable Future: How Hydrogeologists Communicate Water Quality

Water is one of the most precious resources on this planet, and the responsibility to keep that resource usable for future generations can feel hefty. A scientist’s job involves more than just monitoring and recognizing the warning signs that water quality may be degrading. You also need to communicate that information effectively to decision makers.

The Durov diagram is quite similar to the Piper diagram as it is used to chart the chemistry of water samples and reveal relationships among sample groups. A Durov diagram demonstrates the relative concentration of 6 ion groups with two ternary plots. The ternary plot on the left represents the cations. The ternary plot on the top represents the anions. The square plot is a projection of the cation and anion ternary plots.

The Durov diagram is used to compare multiple water samples instead of just classifying one. By examining which samples are grouped closely together in the projection square you can infer which samples have similar chemical compositions and strengthen the classification of samples into facies.

This diagram is powerful when looking at multiple aquifers in a region to identify shared characteristics. By identifying those shared characteristics you can predict environmental factors such as the path of water flow, the source of contamination, or if contaminants are spreading.

An Extended Durov diagram incorporates a pH and TDS (Total dissolved solids) plot onto the original Durov plot. The pH plot is extended below the projection square and the TDS plot to the right. The Extended Durov serves the same purpose as the original, to group similar samples. With the additional parameters you can perform further geochemical analysis related to the acidity, type, and concentration of solids within a group.

A Stiff diagram is a unique way to visually represent the ionic composition of a single water sample. The values of the cations and anions for a water sample are recorded and plotted in milliequivalents per liter. The left side of the diagram shows the cation concentrations and the right side shows the anion concentrations.

The farther a point is from the center, along the X axis, the larger the ionic concentration. To create the polygonal shape the Stiff diagram is known for the individual ionic points are connected. The relative size of the plot is an indication of the total dissolved solids concentration.

It is common practice to create a stiff diagram for several samples of interest and view them all at once to make a quick visual comparison of the group. Combining a Stiff diagram with aerial imagery can be an effective presentation method if your samples are close geographically. Clearly demonstrating to decision holders where wells with higher ionic concentrations are located and why this may be a warning sign of a larger problem.