The Wahapo Power Station, formerly known as the Okarito Forks Power Station, had its beginnings at a public meeting in June 1957. It was commissioned, using a generator set that had previously been employed at the Homer Tunnel project, in 1960.
During 1990 the scheme was redeveloped on the existing site, continuing to utilise the natural storage from Lake Wahapo. The station now has a rated output of 3.1 MW and an average annual output of 14.5 GWh.
The Wahapo Hydro Electric Scheme plays a vital role in ensuring the reliability of supply to South Westland, a challenging responsibility in an area of extreme weather patterns with a rapidly growing and highly successful mainstream and eco tourism industry.
Due to the continual degrading of the river invert downstream of the lake outlet, and spasmodic extreme flood events, access to the Lake Wahapo Weir and upstream spawning grounds can prove challenging for native fish, and salmon and trout can become trapped in weir rock work when spilling from the scheme is restricted This can occur once or twice a year, at which time Fish and Game West Coast are contracted by TrustPower to undertake recovery operations.
After many attempts to find a satisfactory route to establish upstream access for native fish, a path was agreed with the Department of Conservation. This has resulted in the establishment of a pipe-type pass, with fish rest areas, between the Zalas Creek confluence and the supply race. Discussions with Fish and Game are continuing, with a view to finding ways of preventing introduced fish species becoming stranded below the lake outlet weir, within this dynamic and often volatile catchment.
Existing Resource Consents for the scheme expire in March 2009. In this regard, wide consultation has been undertaken with interested parties, in particular the Department of Conservation, Tangata Whenua and West Coast Fish and Game. The reconsenting application was lodged with West Coast Regional Council in September 2008.