Trustpower fail to do their homework on the Rakaia

Monday 7 November 2011, 8:09AM

By Fish and Game NZ



Fish & Game believe that a Trustpower scheme to take water from the Rakaia River could have a significant effect on the salmon fishery and the Rakaia mouth yet the power company have failed to properly investigate the consequences of the scheme.

The comments come following an application from Trustpower to vary the Water Conservation Order that exists on the Rakaia River to allow increased irrigation and hydro power generation.

Fish & Game Regional Manager Ross Millichamp says the scheme will dewater side braids and backwaters of the river, which they believe provide valuable habitat for juvenile salmon.

In contrast Trustpower state there will be enough habitat for juvenile salmon in the faster flowing mainstem, in spite of a lack of research findings supporting this theory.

“Trustpower have also stated in their application that they don’t know if the scheme will cause the Rakaia River mouth to close more frequently, which would affect fish migration and fishing opportunities,” said Millichamp.

“Trustpower have just not done their homework. They need to do more field work or we risk putting pressure on an already strained salmon fishery.”

Fish and Game also have a number of other concerns with the Trustpower proposal, including effects on water quality in the region and fishing at Lake Coleridge. For more details refer below to the following summary of the Fish & Game submission on Trustpower’s application to vary the Water Conservation Order. 

A summary of Fish & Game’s submission:

Water Quality Concerns

The 40,000 additional hectares that will be irrigated under the proposed scheme will have major impacts on lowland waterways through nutrient discharge from intensified land-use. Because this is considered to be outside of the scope of the WCO, TrustPower are not suggesting any mitigation measures for this. Until water quality standards and nutrient limits are set in the command area, this proposal should not be considered. Much of the run-off will end up in Lake Ellesmere and prevent any recovery of this outstanding wetland.

Concerns on the Effect on Salmon Populations and Angling

F&G are concerned at the lack of information about the likliehood of rivermouth closures once the scheme is in place. The following two statements are made in a TrustPower report of river mouth and coastal processes. The conclusion of this report offers no further comment on the issue of river mouth closures.

“Further hydrological analysis of time-series data is required to assess the likelihood of increased duration of low flow events at the river mouth.”

“It is unclear from the hydrological modelling results (Tonkin and Taylor 2010, Beca 2011)

whether the Project will increase the duration of low flows periods at the hapua, or whether the effects of changes in flow due to the Project will attenuate downstream to be negligible at the river mouth.”

Lake Coleridge will be held at a higher level for a longer period than it experiences now. It will also not drop as low as it does now. The high levels will be experienced during spring with a gradual draw down over summer to its lowest level in late summer/autumn. A recreation expert (Greenaway) hints at possible effects of a high lake on shoreline anglers and effects on boat users during low levels. Since the high lake level will be experienced during the very popular high country opening period for fishing, F&G consider it appropriate that TrustPower investigate further the effects on shoreline angling during this period. This would involve using expert shore line anglers to assess angling suitability at different lake levels and assessing the loss (or gain) as a result of the scheme. The effect should be expressed by a difference in angling days.

Experts for TrustPower predict a 4-7% reduction in juvenile salmon habitat and then go on to say that the effect of this is nil because there is plenty of available habitat in the Rakaia and it is not limiting. F&G maintain that this is still not well understood, earlier studies on the Rakaia (Davis et al, 1983) concluded that habitat is limiting in the Rakaia.

Even if we accept that the percentage of juvenile salmon habitat loss is 4-7%. Then this is an effect, in our opinion, that has to be mitigated or offset. TrustPower have not come up with any mitigation measures for this effect.

There are minor effects identified for angler and salmon lies. There is no mitigation suggested for that either as TrustPower consider that these values are also not habitat limited

General comments

TrustPower need to obtain a variation to the WCO (that Fish & Game won for in the 1980’s) for their project to proceed. We asked ECan Commissioners to set up a collaborative process before proceeding to a hearing. Unfortunately that has not occurred and parties are forced to proceed to formal, expensive hearings.

Under the ECan Act 2010 any WCO amendment has to have regard to the principles of the Canterbury Water Management Strategy. The first order priorities under the strategy are the environment, customary use, community supplies and stock water. Both hydro electricity development and irrigation are second order priorities under the CWMS. So far, TrustPower have only developed a proposal that has positive benefits for second order priorities. There are no positive benefits for the environment.


Angler submissions were vital in winning a WCO for the Rakaia and will be vital in preventing it from being undermined. Please take the time to write a simple submission about the issues that concern you directly. These are due at Environment Canterbury by 5pm on November 21. They can be sent by mail to P.O. Box 345, by email to or submitted online at .