May 19, 2011

Trustpower take aim at Rakaia River Water Conservation order

Public meetings.
Monday 30th May
7.00 pm Methven  Heritage Centre
Tuesday 31st May 
1.00 pm  Darfield Recreation Centre
7.00 pm  Rolleston School Hall, Tennyson St , Rolleston
Wednesday 1st June
1.00 pm  Rakaia Community Centre
7.00 pm  Ashburton Masonic Lodge


Please attend and encourage others to tell what you think of their plans to unwind the Rakaia WCO and encourage more dairying.


   Trustpower takes aim at Rakaia River Water Conservation order


New Zealand’s first Water Conservation Order (WCO) was applied to the Rakaia River in 1988.  Achieving it took many years and it was contested by Federated Farmers as far as the Court of Appeal.

The WCO recognises the river’s outstanding natural characteristic in the form of a braided river; outstanding wildlife habitat above and below the Rakaia Gorge, outstanding fisheries, and outstanding recreational, angling and jet boating features.

TrustPower Ltd wants to amend the flow regime in the Rakaia WCO so that it can use the storage capacity in Lake Coleridge/ Whakamatau for irrigation as well as hydro generation.  The company says its scheme would irrigate another 40-50,000 ha. on the Rakaia’s north bank and up to an additional 30,000 ha. on the south bank.

TrustPower’s proposed  three stage “Coleridge project” involves:

  1. pumping up to 5 cumecs of water consented for Barrhill Chertsey Irrigation Ltd via TrustPower’s Highbank Pumping Station (already constructed) for irrigation on the south bank.
  2. abstracting up to 16 cumecs at Highbank, constructing a siphon under the river to transfer water from south to north, and amending the WCO to allow “banking” of water in Lake Coleridge/Whakamatau so that it can be used later during the irrigation season without applying the 1 to 1 flow sharing regime.

“Banked” or “compliant” water = water entering Lake Coleridge while flows (at Rakaia Gorge) exceed the existing WCO monthly minimum flows plus the river’s portion of the 1:1 flow share (70 cumecs) plus any existing takes not utilising the scheme.

  1. constructing a new gravity fed canal and diverting lake water directly into the canal for irrigation and hydro generation.

Hydrological work for TrustPower estimates the scheme would more than double the average number of days each year when the Rakaia’s daily mean flow is less than the minimum flow provided for in the WCO (i.e. from 23.7 to 57.1 days ). This would be most obvious from May to August.[1]  The scheme would reduce the mean annual seven-day low flow during summer months (December-March) from 114 cumecs to 104 cumecs. 

The company says the scheme would not change the consented operating levels for Lake Coleridge/Whakamatau. Changing the way the Coleridge hydro scheme is operated, however, would reduce the amount of water released from the tail race by 13.1 cumecs[2]  reducing river flows and change the timing of releases.[3]

Fish and Game, Forest and Bird and DoC are currently reviewing reports by TrustPower’s consultants to assess the scheme’s potential impacts.

The Rakaia WCO sets out a series of requirements for minimum flows in order to protect fisheries and recreation requirements. These include:

  • minimum flows which vary by month ranging between 91 and 139 cumecs;
  • 1 to 1 flow sharing (above minimum flows) so that for every cumec abstracted an an additional cumec must be left in the river; and
  • capping the allocation for abstraction below the gorge at 70 cumecs subject to minimum flows being met.

The Rakaia River is already heavily allocated.  Central Plains Water and Ashburton Community Water Trust got consent to abstract up to 40 cumecs in 2010. Prior to this, 28 cumecs has been allocated to Glenroy, Barrhill Chertsey Irrigation Ltd and Lower Rakaia Diversion for abstraction downstream of the Rakaia Gorge.  Some of the consented schemes are not yet operational so we have yet to see their full impact on the river.


TrustPower is seeking to uncouple any discussion of changes to the WCO and Rakaia flows from any consideration of the effects of land use intensification.

None of its consultants’ reports (available on CD by emailing examine the potential impacts on water quality in aquifers, streams and the lower river from irrigating an additional 70-80,000 ha. between the Rangitata and Rakaia rivers.   These impacts include increased nitrate levels in groundwater and further deterioration in the health of lowland streams.

Environment Canterbury Commissioners need to clarify that the regional council will not allow such a convenient severing of water take and land use/ water quality issues. As part of any application to amend the WCO, the Commissioners must require TrustPower to assess adequately the water quality impacts of the increase in irrigated area.


TrustPower plans to apply to amend the Rakaia WCO in mid July. The application will be considered under the Environment Canterbury ((Temporary Commissioners and Improved Water Management) Act 2010.  The Act substantially weakened the WCO provisions for Canterbury rivers by replacing the protection purpose of WCOs in Part 9 RMA with multiple use decision making criteria. 

MAF briefing papers obtained by Forest and Bird under the Official Information Act last year highlighted that one of the intentions of the ECan Act was to expedite the Coleridge irrigation scheme.

 TrustPower chairperson Dr Bruce Harker commented in March 2011: 

“We think Coleridge is on track. We are already making progress in Canterbury. We have invested tens of millions to put pumps in at Highbank that will supply Barrhill Chertsey and their irrigation flows. It’s using infrastructure that is there and avoiding the need for Barrhill Chertsey to build their own pipes. There are already pipes up the hill, so we’re just using them properly. That sort of thing generates win-win and creates wealth for the country. There will be trade-offs. We know that if we do less winter generation at Coleridge we can manage the lake to have good levels going into summer and that can add quite a bit to reliability of irrigation when there are low flows in the Rakaia River. So we think Coleridge has a role to play in increasing the reliability.

“I think Canterbury irrigation is the low-hanging fruit for New Zealand in terms of a boost to agri-wealth. We probably have a view that soft commodities are going to do okay for the next 20 to 30 years if not forever. And that’s simply on the basis of increasing populations, soil and water resources being limited and rising wealth in Asian markets. That’s very, very good for New Zealand and our soft commodities. If we’re going to turn that into a standard of living we’ve got to use what nature has given us. Again, I think the way ahead is really getting the process going and working through it and getting communities as a whole comfortable on all the agricultural practices.

(Dr Bruce Harker, Head of Infratil’s energy group and chairman of TrustPower.   Infratil Update Newsletter, March 2011.)





[1] Jowett Consulting (Febnruary 20110) “Instream habitat and the effects of flow changes in the Rakaia River” Draft for Consultation Purposes at p 32.

[2] During normal operation of the Coleridge hydro scheme up to 39 cumecs is drawn from Lake Coleridge for power generation and released back into the river. During 2010 the scheme discharged 30-34 m3/s during the summer and winter, and an average of 15 m3/s during autumn. Beca Infrastructure Ltd (18 February 2011) “Lake Coleridge Project- Rakaia River Hydrology and Geomorphology Overview”. Draft for Consultation Purposes