The Dillmans/Duffers/Kumara Power Generation Scheme had its beginnings in 1927, with power being generated for the first time in 1928.

The scheme today consists of the Duffers Powerhouse, fed by races that in turn feed Kawhaka Creek, downstream artificial lake storage that in turn feeds the Dillmans Powerhouse, and the Kumara Powerhouse fed by a race from Dillmans.

With heads of 13-metres at Duffers, 46-metres at Dillmans and 78-metres at Kumara, and capacities of 500 kW, 3.5 MW and 6.5 MW respectively, the scheme has an average annual output of 47.9 GWh. The scheme remains of critical importance to security of supply within the region, especially when Transpower is undertaking maintenance on one or the other of the two existing circuits to the region. 

The Dillmans Scheme supports a recreational fishery in the Kawhaka Catchment and in the Kapitea Reservoir, which is also used for power boating because of it’s predominantly wind free nature. The reservoir also acts as a buffer against flood events in the lowercatchment, while the Wainihinihi Race System supports Whio or Blue Duck breeding pairs.

Overall the scheme has been responsible for the development of excellent roading to provide public access for a wide range of recreational pursuits including fishing, shooting, canoeing, tramping and fossicking. Because the Kawhaka intake acts as an impediment to the upstream migration of some native species, a purpose built native fish pass has been installed and commissioned to mitigate this effect. Potential impacts of the occasional draining of the Kawhaka race for maintenance purposes are minimised by close consultation with Fish and Game West Coast, and efforts to carry out this maintenance, whenever possible, outside the spawning season.

The West Coast Regional Council granted Resource Consents for a period of 35 years during March 2001. In keeping with compliance conditions required by the new consents the residual flow at the Kawhaka Creek has been increased.