So I've come up with the following information from my research on the drinking water in Christchurch (recall that I first was curious about it in this post):
- The water does not need filtration or chlorination. This means that there is no chlorine residual in the distribution system though, so they sample more frequently to ensure there isn't any contamination somewhere there. [Source]
- The water has a really low hardness; this explains the really soft water. Maybe I just imagined the whole "ground source makes it hard" explanation. [Source]
- Gravel and sand layers created from glaciers and rivers provide natural filtration to deep confined aquifers below. [Source]
*I wonder how deep the aquifer is, there has to be a confining layer somewhere otherwise contamination would be too easy. Gravel and sand aren't aquitards, but it could be that an advancing and retreating glacier system deposited gravels and sands and then clays and silts as the movement got slower.
So, my research thus far has led me to more questions:
What is it that makes Canadian groundwater harder? We had glaciers in Canada too, why is our water brimming with contamination that we need to chlorinate it? Are the standards different?