Pupu Springs

The Te Waikoropupu Springs are a set of lakes that are fed from freshwater springs. They are unique for two reasons, the exceptional clarity of the water, and the immense amount of water that comes up every minute. There are several faults in the ground, and the water is pushed up through the faults. The Maori have imbued the area with spiritual significance.

I really didn't expect these pictures to accurately capture the turbulence of the water. Because the water is so clean and clear, it is difficult to appreciate the volume that is moving to the surface.

These waters are known for their exceptional clarity. The horizontal visibility was measured at 62 metres. Anything over 20 metres is considered 'very clear'. This was the highest clarity reported for fresh water, "close to the theoretical maximum for optically pure water." "As well as ranking among the very clearest waters in the world, these spring waters are virtually indistinguishable from pure water as regards their spectral irradiance attenuation in the ultraviolet and beam attenuation in the green region of yellow-colured organic material and remarkable blue-violet colour." Quoted text is from "Optically pure waters in Waikoropupu ('Pupu') Springs, Nelson, New Zealand", Davies-Colley and Smith, New Zealand Journal of Marine and Freshwater Research. Article located here, and here: www.rsnz.org/publish/nzjmfr/1995/65.pdf

The clarity is related to the sheer volume of water that comes up through the vents. The average discharge is about 14,000 litres per second. That's about the same as 40 bathtubs. Additionally, it is estimated that the water is filtered though the karst aquifer system over a period of 3-10 years.