Studies into the suitability of the Coleridge area for hydro electricity generation were completed in 1906. In 1911 in response to a growing need for electricity, particularly from the city of Christchurch, construction began. The Coleridge Scheme was the first major hydro development undertaken by the New Zealand Government.

Originally commissioned in 1914 with three turbines, the station was progressively expanded with additional turbines introduced in 1917, 1922 and 1925. In 1930, the Acheron River was diverted into Lake Coleridge, increasing the catchment area to more than 800 square kilometres. In 1977, a diversion of the Wilberforce further increased the amount of water available for electricity generation, boosting the 36.5 MW station’s average annual output to 205 GWh.

Upgrades of three of the larger machines and retiring of four of the smaller less efficient machines have since resulted in the installed capacity growing to 39 MW. The energy production capability of the scheme has been boosted from 205 GWh/year to 270 GWh/year, with most of the gain being a direct result of more efficient use of the water resource.

Lake Coleridge has been identified as a good fishing habitat. Environmental monitoring includes monitoring of operational levels, inflows, lake water clarity, pH and temperature.

TrustPower takes a proactive approach to maintaining the environmental values of the Coleridge catchment by virtue of its membership of both the Lake Coleridge Habitat Enhancement Trust and Whakamatau Eel Management Trust.

Resource Consents to re-permit the existing scheme were granted in 1996 for a 35 year term.

During April 2008 the efficiency enhancement project for G8 Turbine was completed. This project involved the use of Computational Fluid Dynamic modelling to produce a high efficiency turbine wheel, and has resulted in a 12% efficiency gain. This is an excellent example of TrustPower’s commitment to enhancing efficiency and extending the life cycle of an existing plant.