4. Northland Region
4.1 Catchment #194: Wairoa (Northland)
This catchment is the sixth largest in the North Island and has:
- an existing hydro-electric power station (Wairua Falls),
- no controlled lake storage.
Table 4: Hydropower Opportunities in the Wairoa (Northland) Catchment with High to Medium Confidence of Proceeding in the Next 20 Years.| Name | MW | Average Energy Production (GWh p.a.) | Public Reference |
| Purua Rapids | 3 | 13 | T&T 1978 |
4.1.1 Purua Rapids (16/2)
The Purua Rapids are located about 15km north-west of Whangarei. In the vicinity of the outfall of the Hikurangi Swamp the Wairua River drops over a series of rapids and low falls between the Purua Bridge and the Wairua Bridge on the Road. The greatest drop occurs 5km downstream from Purua Bridge, being a waterfall some 8.5m in height. The 20.5m³/s mean flow of the Wairua River, relatively large for Northland from a catchment of 567km² suggests hydroelectric potential of an order proportionate to that developed at the one existing hydroelectric power station in Northland, at Wairua Falls.
The hydroelectric potential of the site could most readily be developed by construction of a concrete barrage-type control structure on the rock sill at the top of the waterfall, diverting water by means of a short canal and penstock to a power station below the falls. A 3MW generator would give approximately 13GWh p.a. (50% plant factor5).
4.2 Other Opportunities in this Region
4.2.1 Prohibited
There are no known prohibited opportunities.
4.2.2 Undefined
#19 Wairoa Catchment
Mangakahia - 5MW
Manganui (18/1) - 9MW6
Whatoro (18/2) - 4.2MW6
The general shortage of water supply in Northland may result in storage reservoirs being built for community or irrigation requirements. These may also provide an opportunity for electricity generation.
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