This station is on the Waikato River, on the road from Rotorua to Te Kuiti, continuing on to Waitomo.

 
 
Here's the website for this particular station. It's  very well done - lots of good information on the station.
 
Here's an aerial of the station,

Image source

 
 

Diagramme of what's in the image above.

Image source

 
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The Waikato River, downstream of the dam.
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Lake Whakamaru, upstream of the dam.
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I wonder if they trotted her out to bang a champagne bottle on a pipe.

 
 
 
 
Hydro constitutes approximately 60% of NZ electricity generation.