The fresh groundwater resource in Iceland is immense and mostly unharnessed (less than 1% currently used). The water has little mineral content and rarely carbonated, and is therefore in a class of its own compared to e.g. European mineral spring water. Over 95% of the Iceland population enjoys fresh groundwater (not cleaned in any way) while the rest can be mixed with groundwater, but is purified before consumption.
The untapped resource has been estimated to be on the order of 200 m³/s in the Northeast region alone.