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Irrigation Initiatives

More than ever, TrustPower is involved in bringing irrigation opportunities to reality. Highlights over the last year include the Highbank pumps, and our application to vary the Rakaia Water Conservation Order reaching the hearing stage.

Irrigation will be a major part of our future: we are ideally placed to take advantage of the synergies with generation. Around the country, we have identified key opportunities to apply our expertise to add value and a multi-use dimension to a number of existing and proposed irrigation schemes. After all, while energy and agriculture are very different, both sectors seek the efficient and sustainable use of resources, and both want to see local communities flourish.


Delivering up to 90,000Ha of irrigation.

TrustPower’s introduction to joint generation and irrigation initiatives was in 1999, with the acquisition of the Highbank and Montalto power stations. These stations are on the 66km Rangitata Diversion Race (RDR) that also supplies irrigation water for up to 90,000Ha of mid-Canterbury land. We own 20% of Rangitata Diversion Race Management Limited (RDRML) and are represented on the company’s board. RDRML is a water supply company, and conveys diverted takes from the Rangitata and Ashburton rivers, to generator, irrigator and stock water shareholders (TrustPower Limited, Ashburton District Council, Ashburton Lyndhurst, Valetta and Mayfield Hinds Irrigation).

Water is supplied for irrigation between 9 September and 10 May, and for generation the remainder of the year. The combined annual energy output of the 28MW Highbank and 1.9MW Montalto power station is approximately 100GWh. The largely winter-based supply of water for generation aligns well with electricity demand.


New infrastructure pumps extra value from existing asset.

Our long association with joint generation and irrigation initiatives continues with the commissioning of the Highbank pump station in late 2010. The pump installation utilises the existing Highbank power station penstock infrastructure, which would otherwise be unused during summer. As a result, water is pumped from the Rakaia River to the Rangitata Diversion Race, for distribution to farmer shareholders within the Barrhill Chertsey Irrigation Company (BCIC) command area.

The pump station was commissioned with five single stage centrifugal pumps. Due to increasing demand, a sixth pump will be installed in winter 2012. The initiative is a great demonstration of how collaboration between irrigation and generation interests can forge new efficiency improvements.


Two power stations deliver enduring benefit.

Paerau/Patearoa is a fine example of a joint generation and irrigation scheme that delivers ongoing benefit. This was the last of the large community irrigation schemes, constructed by the Ministry of Works and Development, and commissioned in 1984. TrustPower acquired the generation component in 1999: the two stations have a combined installed capacity of 12.25MW.

The irrigation component is owned by the Maniototo Irrigation Company (MIC), which has a command area of around 9,300Ha. TrustPower and MIC share costs for maintaining jointly-owned assets. Water swaps between the two companies help to make the most efficient use of the resource.


Proposed canal to deliver much-needed irrigation to the Canterbury region.

One of our most exciting opportunities for the future is associated with our existing Coleridge scheme. The proposal is to take water from the lake and through a new canal, for use in generation and ultimately irrigation. In 2011 we applied for a variation to the Rakaia Water Conservation Order, which currently controls water use associated with the Rakaia River.

Hearings began in March 2012 with an independent panel of three Commissioners, appointed by Environment Canterbury (ECAN). We presented evidence as the applicant. It is anticipated the Hearings Panel will make recommendations to the ECAN Commissioners later in the year. In turn, the ECAN Commissioners can make recommendations to the Minister for the Environment. Assuming all criteria are met, the variation will pass into law.

Should the variation application be successful, Coleridge will become a key asset for delivering water to the Canterbury region. This will enable significant progress towards achieving the Canterbury Water Management Strategy.


We have recently entered into an arrangement with Opuha Water Company, owner of the joint generation and irrigation assets supplied from Canterbury’s Lake Opuha, to operate and maintain the Opuha Power Station. The arrangement includes the requirement to undertake environmental and civil safety management of the scheme, as well as dispatch of the energy produced to market.

We will continue to search for opportunities to apply existing capability across the sector – with the aim of increasing overall value.