Hydrochart is a free, browser-based Stiff diagram maker. It plots each water sample as a Stiff polygon — cations on the left, anions on the right, width scaled to concentration — so a whole set of bores can be compared by shape and size. Everything runs locally; your data never leaves your device.
Make a Stiff diagram in three steps
Load your data
Open the plotter and drop in a CSV or Excel file of major-ion concentrations, or paste a table. Column headers are matched automatically.
Get the diagram
Hydrochart draws a Stiff polygon for every sample, consistently scaled so shapes are directly comparable across your dataset.
Export it
Download the finished diagram as vector SVG or PNG — sharp at any size, ready for a report, thesis or paper.
What a Stiff diagram shows
A Stiff diagram plots the major cations (Na+K, Ca, Mg) down the left axis and the major anions (Cl, HCO₃, SO₄) down the right, then joins the points into a polygon. The shape encodes the water's chemical character and the overall width tracks total ionic concentration, so freshening, mixing or saline intrusion shows up as a change in the fingerprint. Because each sample is a compact shape, Stiff diagrams work beautifully as symbols placed on a map.
What data do I need?
Supply your major ions in mg/L and Hydrochart converts to milliequivalents and does the rest:
| Group | Ions |
|---|---|
| Cations | Calcium (Ca), Magnesium (Mg), Sodium (Na), Potassium (K) |
| Anions | Bicarbonate (HCO₃) and Carbonate (CO₃), Sulfate (SO₄), Chloride (Cl) |
| Optional | TDS, pH and EC — used for labelling and QA, estimated when absent |
Not sure of the layout? Download the CSV template and paste your values into it.
Why use Hydrochart
- Genuinely free. Create and view unlimited Stiff diagrams with no account. Free exports carry a small watermark; Pro (USD $29/year) removes it and adds CSV export.
- Nothing is uploaded. The whole tool runs client-side in your browser, so confidential monitoring data stays on your machine.
- Publication-ready output. Vector SVG and PNG export, with drag-to-place sample labels and leader lines for clean figures.
- One dataset, every diagram. The same file also plots Piper, Stiff, Schoeller, Chadha, Durov and Gibbs — no re-entry.
- Built-in quality control. Every analysis gets a cation–anion charge-balance error, flagged when it exceeds ±5%.
New to Stiff diagrams?
If you want the theory before you plot, read the companion guide: the Stiff diagram explained. It covers what the plot shows and how to interpret where your samples fall.