According to the Guinness Book of World Records, the clearest water in the world is in our region, the Top of the South.
You’ll find it at Te Waikoropupu Springs, also known as Pupu Springs in Golden Bay.
The springs are the largest freshwater ones in NZ and the clearest in the world.
They are estimated to pump out a combined 14,000 litres of water a second, or 1,200,000m³ per day, yup that’s right! (How much is that in plain english? – 1.2billion x 1 litre milk containers a day that’s all – or for those of you Imperially inclined according to onlineconversions.com = 2,536,051,702.6 pints a day [US, liquid] )
According to Wikipedia that’s enough, or it was in an older TV documentary to provide all the water to Boston for 24 hours.
Clear, well the world record is at 63m for visibility in fresh water and this is where that record was set.
In fact so clear that, with optical instruments, scientists have said it approaches the theoretical maximum for optically pure water. If you are interested in the full terminology for “average black-body visibility” then I believe the above link will satisfy your craving.
And its world famous for diving, although that has practically ceased lately.
The clearest seawater, by comparison, is under the Antarctic ice cap, perhaps not the easiest to view even with a long range tank on your back.
Part of the reasoning for this is the unique topography of the region, for example the large cave system, part of which is Nettlebed Cave. Nettlebed Cave is NZ’s deepest cave system, 889 metres below the surface. It spans 24 kms through the Mount Arthur region of the Top of the South.
From a caving website comes this information too…
…the extreme optical purity, which is uncommon for karst water, is interpreted as a result of the long residence time between aquifer recharge and re-emergence in the springs. According to Williams (1992) the water stays underground roughly three to eight years.
And while we are on the topic of water, another famous export from the area and concerned our clear water is 26000 Vodka, with the claim that the vodka is made from 26,000 year old, ice age water – water entirely untouched by humans and contaminants and sourced from a bore in a secret location.
In related news from the Pupu Springs, check out the underwater clarity of this absolutely “spellbinding” photo here.
UPDATE Dec 2011
FURTHER RELATED READING
1] NZ Gazettes Worlds Clearest Water Site as a Regional Treasure just check out the photo in this article!
2] of what significance is a Karst Aquafier to the Springs? Check out “that photo” half way down the page for proof!)
3] three more photo’s of the springs here