The following is
adapted from TrustPower’s online website.
In New Zealand,
TrustPower owns 36 small to medium size Hydro Generating Stations and a
large Wind Farm. They produce electricity exclusively from renewable
sources and their power stations produce enough electricity for around
220,000 households. As an electricity generator, TrustPower operates a
business that is reliant on natural and physical resources to provide the
energy needs of communities and businesses throughout New Zealand.
As a business,
TrustPower must perform to a level that can attract and retain investment.
At the same time, it must be equally aware of society’s environmental
performance expectations, and the need to deliver energy at a reasonable
cost to consumers and minimal cost to the environment.
TrustPower is very
conscious of the environmental expectations of its stakeholders, including
communities that live in that environment, and investors. It is also well
aware of the bigger picture, and the need to operate in a sustainable
The following is
adapted from RDRML’s online website.
The Rangitata Diversion Race was a dream in the
minds of the pioneering farmers in Mid Canterbury when the 750,000 acre
plain was first farmed in the mid-19th Century. Regarded as the largest
area of nearly flat land in New Zealand, all development was closely linked
to water problems – water races to supply stock on light soils and water
courses to drain heavy swamp lands.
Despite high expectations of development, it
took the massive unemployment of the 1930s depression to provide the
catalyst for the work to start in what would become the RDR. Work began on
the scheme on April 2nd 1937 and was completed in November 1944. Race water
first generated electric power at Highbank power station on June 8th 1945.
Expected to cost £1.5 million pounds, the scheme costs grew to £2 million
The RDR takes water from the Rangitata River,
restricted by resource consents. This water is then directed across the
Canterbury plains by the RDR canals and a series of syphons.
On the way, draw offs are made by three major irrigation schemes,
Mayfield-Hinds (MHIS), Valetta (VALIS), and Ashburton-Lyndhurst (ALIS). As
the RDR passes by the South Ashburton River more water is taken, again
limited by resource consent. Figure 2-1 shows the key features of the RDR
scheme as it currently stands.
Figure 2‑1: Schematic of key features in the RDR
1945 there have been a number of amendments to refine the efficiency of the
RDR. Montalto, the second hydroelectric power station was built in 1981 and
started producing electricity a year later. The Sandtrap
was designed and built at a similar time to remove much of the suspended
sediment from the water by reducing the velocity of the flow. The sediment
causes wear and tear on the hydro electric turbines and can cause gastric
problems for sheep and lambs when washed out onto paddocks. Conversely the
sediment is a good bonding agent that can help to plug microscopic holes in
the race lining.
One of TrustPowers many assets is the Highbank power scheme,
comprised of the Montalto and Highbank Hydro generation power stations. In
winter, when electricity demand increases, and the demand for irrigation
water reduces, most of the available water is used for power generation
purposes. Surplus water is used for generation during irrigation
season and outside of this all water is available for generation.
from the Highbank Scheme is dependent upon irrigation requirements which
take priority in the irrigation season. The scheme is guaranteed water for
four months of the year, but typically generates for six to eight months,
increasing to eleven to twelve months in particularly wet years.