Niue is a large upraised coral atoll about 64km in circumference, with an area of 260 sq km. It lies in the South Pacific Ocean 560km SE of Samoa, 380km E of Tonga and 2400km NE of New Zealand. Using Google Earth is a good way to see the location of Niue, and you can zoom in right down to the enclosure around the bore at the cache site.
Niue is internally self-governing in free association with New Zealand.
It is on the route of yachts that are island hopping across the Pacific, and is serviced by weekly flights from New Zealand.
Most of the island’s coastline rises steeply to a terrace at 20m above sea level, then rises again to an undulating central plateau at around 60m asl. The capital, Alofi, and villages on the western side have been established on the lower terrace, while those on the northern and eastern coasts are on the upper terrace.
Below sea level the island consists of more than 500m of limestone underlain by a caldera-shaped volcanic structure.
There is no public transport on the island, but bicycles, motor cycles and cars are available for hire.
A third of the rain that falls on Niue percolates through the coral/limestone rock to form a fresh water lens under the island, sitting on the saline groundwater below. The size of this has been estimated at around 30 million cubic metres, or 3 months worth of recharge from rainfall.
Water is lost from the lens at the coast from seepage, and from springs in chasms and coastal caves. At low tide this flow can be observed at Matapa Chasm. Total outflow has been estimated at 4000 litres per second.
Early domestic water supplies were via rainwater collected from roofs, in some cases a village supply with a reservoir beneath a large roof. The present reticulated system comes from reservoirs supplied by 16 of the 25 bores drilled down to the fresh water lens. Total extraction from all the bores averages 26 litres per second.
For permission to claim this cache: Go to the Kapihi bore (N119B), in dry weather you can drive right to it. The land at the bore is privately owned, and there is no need to enter the fenced enclosure. Do not interfere with the pump, as this bore supplies water to the village of Mutalau. Please do not leave any rubbish here, or remove anything from the site.
Note the altitude at the site from your GPS (or just use the information above), then assuming that the lens is only a few metres thick at this bore, how far below the ground surface will the water level be?
0-10 metres,
10-20 metres,
20-30 metres,
40-50 metres,
50-60 metres, or
60-70 metres.
Email us the answer to the question, and explain briefly why bore water is used for the reticulated supply rather than any alternative source. If your GPS gave you an altitude reading, then include that also. You can log your find immediately, we will only reply to your answer if there is a problem.
(Technical information is from the South Pacific Applied Geoscience Commission (SOPAC) Technical Report 372, Niue Coastal Water Quality and Groundwater Resources Assessment)