Vienna's water carries genuine hardness and, more distinctively, very high magnesium alongside a high bicarbonate reading — a combination that gives the water substantial buffering capacity, well suited to a moderately dark, amber-malt-forward mash without needing much correction. That's a real, checkable fit with the style history the city is best known for, rather than a coincidence layered on afterward.
High magnesium is the number that actually stands out here
The classic reference figures for Vienna water: calcium 200 ppm, magnesium 60 ppm, sodium 8 ppm, sulfate 60 ppm, chloride 12 ppm, bicarbonate 250 ppm. That magnesium figure is genuinely unusual among the profiles on this site — most of the water sources here run well under half that, and magnesium at this level contributes its own mineral, slightly bitter-sharp character alongside whatever calcium and bicarbonate are doing. Combined with a bicarbonate reading second only to Dublin's among this site's profiles, Vienna's water carries real alkalinity, enough to comfortably buffer a mash built around Vienna malt's own moderate colour and toasty character without either fighting the mash pH or leaving it too high.
A water profile that outlasted the beer it was named for
Anton Dreher developed Vienna Lager in the 1840s using this water and the newly developed Vienna malt together, and while the beer style itself largely migrated and transformed abroad (most visibly into the lighter Mexican amber lager tradition that carries the name today), Vienna's own water chemistry hasn't gone anywhere — it's the same hard, high-alkalinity profile regardless of what style is currently most associated with the city. A homebrewer chasing the historical original rather than its modern descendant is really trying to reunite this specific water chemistry with the malt it was originally paired against.
Using this profile
These are historical reference figures rather than a live reading of Vienna's current municipal supply, so test your own water first. Building toward it means real gypsum and calcium chloride additions alongside enough bicarbonate-boosting mineral (often via chalk or baking soda, used carefully) to reach this water's genuine alkalinity; see the Vienna Lager style guideline for how this specific mineral profile connects to the malt bill it was historically brewed against.