Aniwhenua Power Station

The Aniwhenua power station is a hydroelectric power facility in Bay of Plenty in New Zealand located on the Rangitaiki River upstream of the Matahina Power Station. Water is drawn from behind a dam above the Aniwhenua Falls and diverted through a canal and a headpond to the power station before being discharged back into the river. The power station is named after the falls which are adjacent to the power station.

In the late 19th century and early 20th century, numerous small local power generation stations were built by both private and local authorities. From the 1920s onward as the state electricity system expanded and the national grid was developed, development of small local power stations declined as the centralisation of electricity supply under state control increased. The 1973–74 oil shock, nation-wide electricity shortages during the winters of 1973 and 1974, a renewed policy emphasis on regional development by central government, and increased uncertainty as to future wholesale electricity price trends lead to the New Zealand government to re-evaluate its policy regarding local hydro development. As a result, in 1977 the government announced that they would subsidize local power station schemes of less than 50 MW by providing grants to cover the investigation and design work, cheap loans to finance construction as well as loans from the NZED to cover operating losses in the early years of approved schemes. The government established the Committee on Local Authority Hydro Development (CLAHD) to evaluate applications for grants or loans from supply authorities. Taking up this opportunity the Bay of Plenty Electric Power Board which had begun operations in 1928 and engaged consultants to investigate a local hydro scheme in mid-1973. Preparation of a feasibility report was authorised in December 1973, with the report being completed in September 1974. The study determined that a power station on the Rangitaiki River at its confluence with the Pokairoa Stream, midway between Murupara and Whakatane. The scheme was technically feasible and financially viable. The main identified environmental impacts were significantly reduced flows over the Aniwhenua Falls, inundation of productive farm land and the displacement of one family, as well as the long term accumulation of sediment in the lake that the project would create. The issue of the reduced flow was managed by the imposing of a minimum residual flow over the falls. The estimated cost was NZ$12.5 million.

Following the obtaining of water rights, government consent and other necessary approval, construction and equipment supply contracts were let in the second half of 1977. The civil works which commenced by the end of 1977 constructed by Downer and Company which involved the excavation of one million tons of material and the placing of 270,000 cubic metres of fill, 20,000 cubic metres of concrete and 884 tonnes of reinforcing steel.

Aniwhenua began generating on 3 October 1980. The 1982 annual report for the board showed that the total cost of the station to 31 March 1982 was $27,767,203 of which $24,628,809 was financed by government loan. The book value of the scheme as at 31 March 1992 was $21,109,000. By the 1985/86 financial year, the scheme was breaking even financially and was able to trade its way into long-run profit without any write-offs of debt. Over the period from 1989 to 1992 as its trading activities were making a loss the profits from Aniwhenua kept the power board in the black.

Power station data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).