Illustrating how aqueducts were located in the gullies they cross
On this map you can see three (3) aqueducts (the red lines placed on the green line of the route of the water race)
We can assume that in all cases the crossing is placed at the point where the loss of altitude occasioned by going up and down a gully is balanced against the high per linear metre cost of an aqueduct, the low cost of digging a race and the geological conditions.
For the whole length of the race, McLeod will have made this judgement at every stream.
If you look at the photo enlarged and at the aqueduct half way up Horse Gully Stream. Going up and down the gully involved 2600 metres of digging in easy ground, but it sacrificed just on 0.7 metres of altitude to do that. an aqueduct is smooth compared to a race (trench)dug into soil and a 400 metre aqueduct could have spanned the mouth of the Horse Gully Stream and only sacrificed perhaps 0.1 metres. The difference would have been reflected in the fact that the race thus had to go 2600 metres further up the Waitaki Valley for its intake to still be above the water level in the reservoir at Ardgowan. I hope you can get that!
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Photo taken in Papakaio, New Zealand
Misplaced? Suggest new location