SPA - Hydrogeology

The qualities of the very lightly mineralised waters of Spa are due to the conjunction of particularly favourable geological, geographical and climatic circumstances.

Geographically speaking, the very lightly mineralised waters emerge on the South Easter, South and South Western slopes of Spa between the crests of la Vecquée and la Porallée (575 metres at their highest point), and the hill of about 300 metres

The geological substratum in which they come together is formed of Cambrian rocks about 500 million years old.  These comprise alternating quartzites, phyllites and quartzo-phyllites.  They are heavily folded and fractured.
During the Post-Primary period (about 250 million years), these rocks were peneplaned. They are covered by more recent deposits of clay with flint from the Cretaceous period (about 100 million years) and sands from the Tertiary period (about 50 million years). The Cambrian rocks were heavily weathered and leached. On account of this, heavily demineralised rocks are to be found as deep as several dozen metres. At their peak, the fen (Fagne, derived from a word in the Walloon dialect meaning marshland situated in an elevated region) of Malchamps is to be found with its peaty deposits covering Tertiary sands. Thus, the rain and melting snow which percolate through all these layers deprived of soluble products, are naturally filtered without an increase in their saline load. The result is a pure water with a sodium content among the lowest of the very lightly mineralised waters. The Spa waters are not identical -far from it- and their remarkable properties vary with the underground genesis of the three natural mineral waters. The best-known and most widely distributed is SPA REINE, which owed its name to the memory of H.M. Queen Marie-Henriette, who had a strong partiality for it. Spa Reine spring is situated at an altitude of 440 metres and its catchment area comprises principally the Fagne de Malchamp with a maximum altitude of approximately 600 metres.