Art. XLIV.—Note on an Artesian Well at Aramoho.
[Read before the Wellington Philosophical Society, 6th August, 1901.]
About three miles above Wanganui, on the Wanganui River bank, a 4 in. bore has been made by Mr. John Walker, jun., in search of water. There is, of course, much speculation as to where the water comes from. It is struck under a layer of papa (280 ft. thick), and water was struck at bottom of this layer, at 540 ft. below the surface, in a layer of sand intermixed with pumice sand. The surface here may be 30 ft. to 40 ft. above the sea. Perhaps the water gets under the main papa stratum where it has been pierced by the volcanic heights about Ruapehu and Tongariro and follows down under the papa formation to where found. I found the temperature of the water coming out of the pipe at the surface to be 70½° Fahr., while the adjoining river-water was 42° at 6 ft. under the surface. The temperature in the shade at the time was 45°.
A few years ago a 2 in. bore was put down at the same
place and water was got at the same depth, and this has continued to supply houses in the neighbourhood successfully.
The new bore is 11 ft. off the old bore, and does not seem to affect it. This bore is about 1 chain off the river-bank on the right bank of the river.
Before this a trial bore, 14 chains down the river and 4 chains off the bank, was put down by Mr. Walker to 610 ft., but no successful water-supply was got, and no solid papa stratum was reported there.
The following notes were given to me by Mr. Walker:—
From surface to 60 ft., sand and pumice.
60 ft. to 66 ft., sand.
66 ft. to 105 ft., clay.
105 ft. to 117 ft., sand (wood at 110 ft.).
117 ft. to 127 ft., shingle.
127 ft. to 130 ft., sand.
130 ft. to 138 ft., shingle.
138 ft. to 144 ft., coarse grit.
144 ft. to 183 ft., sand.
183 ft. to 183½ ft., hard seam (taking five hours to bore).
183½ ft. to 185 ft., fine sand.
185 ft. to 239 ft., papa.
239 ft. to 260 ft., sand.
260 ft. to 540 ft., papa.
At 540 ft. water came up strongly, after boring through a hard seam. The water was got in sand intermixed with fine pumice, into which the rods were put down to 553 ft. The bore is piped with 313¼ ft. of 4 in. pipe, the top of last length being 15 in. below the surface (the rest of the bore has no pipe). A strong volume of water was got, with a good pressure.