Porqueres, in the Pla de l'Estany region, registers the highest lime concentration in Catalonia among municipalities with officially published data: 1,135 mg/l of calcium carbonate. It is followed by Santa Coloma de Queralt, in Conca de Barberà, with 857 mg/l. At the opposite extreme, Vielha has 103 mg/l, eleven times less than Porqueres.
Water hardness measures the amount of dissolved calcium and magnesium, and depends mainly on the geology of the terrain and the origin of the supply. Water that flows through calcareous terrain carries minerals; water from the thaw of granite areas carries hardly any. That is why two neighboring municipalities can have very different values if they draw from different aquifers.
“"Two municipalities separated by thirty kilometers can have a five-fold difference in the lime concentration of the water."
The Catalan map is uneven. Inland regions and plain areas tend to have high values, while the headwaters of the Pyrenean rivers show the lowest figures. Of the 153 municipalities studied, a majority are in the range that the reference scale classifies as hard or very hard water.
The data comes from the National Water Consumption Information System (SINAC), part of the Ministry of Health, which publishes official analyses of supply networks. The municipality-by-municipality compilation, with the classification and range for each town, is available in the study of water hardness in Catalonia, published under an open license for reuse, citing the source.
The practical consequences are well known: lime deposits in water heaters, washing machines, and dishwashers, reducing their lifespan and requiring more energy to heat the same amount of water. It also affects detergent consumption and skin sensation after showering. Hardness is unrelated to potability: hard water is perfectly suitable for consumption if it meets sanitary parameters.
The study was carried out by Aquaclar, a water treatment company based in Vall-Llobrega, using public records from SINAC and its own measurements in municipalities without published official data.
