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Dillmans Power Scheme

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Duffers/Dillmans/Kumara Hydroelectric Power Scheme is key to ensuring reliable electricity supply to the West Coast of the South Island of New Zealand. The scheme first generated power in 1928. Today, three powerhouses produce a combined average annual output of over 47 GWh. The scheme supports many recreational pursuits; there is a recreational fishery in Kawhaka River catchment and Kapitea Reservoir.

At a Glance

LOCATION: Kawhaka Creek

Commissioned 1928

Max Capacity 10 MW

Annual output 47.9 GWh

After its commissioning in 1928, the original Duffers/Dillmans Scheme operated until the new Dillmans Scheme came on line in 1978. Today’s Scheme collects water from three intakes in the Big Wainihinihi catchment and three in the Arahura Wainihinihi catchment, with the collective inflows ending up in the Kawhaka catchment. 

An intake in the Kawhaka creek then diverts up to 12 cumecs into the Kawhaka race, for use by the new Duffers Power Station. Water discharges into Loopline Lake, sometimes called Kumara Reservoir, and in turn, into Kapitea Lake. An intake on the short dam of this lake feeds up to 10 cumecs through the Dillmans Power House into a 1.8 kilometre canal, then through the Kumara Power House, before discharging into the Taramakau River. 

The ‘head’, or height difference, is 13 metres (m) at Duffers; 46m at Dillmans; and 78m at Kumara. This elevation fall supports generation capacities of 600 kW (Duffers), 3.5 MW (Dillmans) and 6.5 MW (Kumara), and a total average annual output of 47.9 GWh. 

Environment and recreation 

There’s a recreational fishery in the Kawhaka Creek catchment and in the Kapitea Reservoir. The reservoir is sheltered, so is ideal for power boating; also buffering against floods in the lower catchment. The Wainihinihi Power Boat Race supports Whio (blue duck) breeding pairs. 

The Scheme has led to the development of excellent roading that gives public access for a wide range of recreational pursuits including fishing, shooting, kayaking, tramping and rock fossicking. 

A native fish pass has been installed at the Kawhaka intake. We occasionally drain the Kawhaka race for maintenance; we minimise potential impacts through close consultation with West Coast Fish and Game, and by doing maintenance outside spawning season whenever possible. 

West Coast Regional Council granted new Resource Consents in 2001. Compliance conditions included increasing residual flow at Kawhaka Creek, which we did.

Lake Kapitea Service Spillway
Lake Kapitea Service Spillway

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