Tourist gem’s sparkle even purer
The crystal clear waters of the Te Waikoropupu¯ Springs in Golden Bay have become even clearer, a study says.
Scientists say the average visual clarity of the water at the popular tourist destination is 75m, up from 63m when it was first measured in 1993.
Te Waikoropupu¯ Springs are the largest coldwater springs in the Southern Hemisphere and contain some of the clearest water measured in the world.
They are the subject of a Water Conservation Order application that seeks to preserve their exceptional clarity, with hearings scheduled to begin this week.
NIWA scientists contracted by the Tasman District Council deployed instruments for three months between October 2017 and January 2018 at the springs near Takaka to measure the clarity of the water. Pure water has a visual clarity of about 83m, and the springs were now ‘‘broadly comparable’’ to Blue Lake in Nelson Lakes National Park, which has a visual clarity of 70-80m, the study says.
Tasman Kempthorne measurements reassuring’’.
There was no evidence to indicate any decline in visual clarity in Te Waikoropupu¯ in the 25 years since the direct measurement of 63 m was made, he said.
However, campaigners say they remain concerned.
Save Our Springs co-ordinator Kevin Moran said while he was ‘‘delighted’’ at the study’s findings, he was still very concerned about the impact of intensive dairy farming on the aquifer’s health.
Moran asked why nitrate levels measured in the springs were continuing to rise.
‘‘I also wonder why the levels of nitrate measured at Te Waikoropupu¯ are 40 times that of other Takaka waterways?’’
Moran said hundreds of tons of nitrates were estimated to leach from neighbouring dairy farms into the aquifer.
It took about 10 years for most of the water from the aquifer to make its way to the surface of the springs – about the same length of time intensive farming had been mayor Richard said the new were ‘‘very occurring in the Takaka Valley.
This meant we ‘‘didn’t know yet’’ what was to come from the past 10 years as a result of intensive irrigation and the extensive use of urea fertiliser, he said.
Nelson iwi Nga¯ti Tama ki Te Waipounamu Trust and Andrew Yuill have applied for a Water Conservation Order for the springs and associated water bodies. The application includes a draft order, which applies to the springs, the aquifer, hydraulically connected groundwaters, the Takaka River and all its tributaries.
Te Waikoropupu¯ hold extremely high spiritual significance for Nga¯ti Tama, which proposes to identify and the protect outstanding values associated with the springs and recognises itself as kaitiaki (guardian) of it and the aquifer. It seeks to pre- serve the aquifer in its natural state.
A Water Conservation Order would provide the highest possible protection for the springs.
The first hearing is scheduled to be held at Takaka, starting on Tuesday.
The council said the springs’ clarity was measured using a beam transmissometer which captured 60 measurements in oneminute bursts every 10 minutes, resulting in almost one million data-points.
As the project ran over several months, it also provided a comprehensive data set to assess how visual clarity varies over different time scales, from hours to months.
‘‘Given the time taken and number of data-points gathered we can have a high level of confidence in the result,’’ Kempthorne said.
He suggested the measurements were likely to be repeated at regular intervals, perhaps every five years, to give the community reassurance that nothing was changing with the purity of the Springs water.
The recent monitoring also measured temperature, dissolved oxygen and turbidity at the Springs.
NIWA would compare the results to the council’s regular water quality sampling and that of the Friends of Golden Bay.
The clarity measurements found small daily variations corresponding to about 1-2m, with the highest visibility at midnight, and lowest around midday.
This was likely to be due to plants in the spring basin releasing light-scattering oxygen bubbles as they photosynthesise during the day.
Underwater video demonstrated that ‘‘dancing"’ white marble sands on the floor of the springs coincided with some short-term episodes of reduced visual clarity, lasting between a few hours and several days.
Visual clarity was as low as 4m for a short time in mid-January following almost 240mm of rainfall that resulted in surface waters entering the springs’ basin from the surrounding bush reserve.
Te Waikoropupu’s clarity appeared to result from extremely efficient natural filtering removing particles within the Springs aquifer before re-emergence of the water.
Te Waikoropupu Springs is one of Golden Bay’s most popular tourist attractions.