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Pupu Springs
| This is probably
GOLDEN BAY'S most famous attraction, and its story and mysteries are still
a fascinating one.
Looking down at the
Takaka Valley from the top of the Takaka Hill you will notice the flat
valley floor is separated sharply from the steep hills to the right, and
rather less sharply from the Tasman Mountains to its left. Several million
years ago earth movements caused the two hilly blocks to rise, while the
wedge-shaped area containing today's valley was lowered.
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The marble rock of
the Takaka Hill is famous for its cave system, underground rivers,
sinkholes, and associated features. Research has shown that a huge system
of flooded chambers exists in the buried marble under the valley.
Overlying the marble is a thick layer of sandstones which do not permit
the passage of water through them, and act as the 'cap rock' over the
waters within the marble. In the Waikoropupu Valley the surface river has
eroded down through this cap rock to a point where the underground water,
at great pressure, has been able to burst through and emerge as springs.
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| The water from the
main spring is a constant cold temperature of 11.7°C, clear and slightly
salty. The flow is not constant; it varies from 7 cubic metres per second
during droughts to a maximum of 21 cubic metres per second. The springs
system is the largest in New Zealand, and among the 100 largest springs in
the world (it ranks about 90th).
Where does the
water come from? Researchers from early times favoured the Takaka River,
as nothing else could supply the enormous volume. This river goes dry
during most summers at a point a little below Lindsay's Bridge, near Upper
Takaka, where the river flows hard against the Pikikiruna Fault which
separates valley from hill slopes. A section of 4.5 kilometres of the
riverbed remains dry, the water being taken underground through sinks in
the thick gravels.
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How to prove the
connection? This was done several years ago, during a dry spell. Daily,
very accurate measurements of the springs’ discharge showed a slow but
steady decline in volume. Then a large quantity of water was released from
the Cobb Dam into the Takaka River and 10 hours later the discharge rate
at the springs rose, to fall again in subsequent days. Other releases of
water gave the same upsurge in the springs flow.
The business of
seawater intrusion is fascinating. For some time it has been known that
there are three large freshwater springs in GOLDEN BAY, a few kilometres
offshore in depths of 12-14 metres. It is thought that these are part of
the marble water-system, and as fresh water flows out, some seawater is
drawn into the vents, finding its way to the main vent at Pupu.
The area is a Maori
taonga (treasure) and a waahi tapu (sacred place), please respect it.
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