Canterbury Strategic Water Study (CSWS) - A Summary

Evaluating storage options . . .• Group of 15 - 28 including individuals from Fish & Game,

local farmers, Community Development, Ngai Tahu, a Resource Management consultant, farmers from across Canterbury, environmentalists, Irrigation New Zealand and Water Rights Trust, Forest & Bird, and others with an interest in water.

• People present in personal capacity, not as representatives• Group identifies additional options to those from Stage 2.• Evaluate each option against 22 topics covering social,

economic, cultural & environmental impacts on 6-point scale.

• Evaluation in three bites:– Hurunui – South Canterbury – Rangitata River – Ashley River

• Based on Aqualinc identifying hydrologically-feasible storages that increase irrigable area and improve reliability

• Only considered options based on major reservoirs (>50,000,000m3) (almost all in-channel)

• Many options considered,

& rejected, by Aqualinc

All options integrate run-of-river takes with storage:

– Run-of-river water used to meet irrigation demand whenever possible;

– Releases from storage used to meet run-of-river shortfall (particularly in late summer & dry seasons).

Overall . . .

• All options have positive and negatives.

• For some Group participants, all options are acceptable

• For some, all options are unacceptable

• Overarching concerns about

irrigation leading to

land use intensification

which means adverse

impacts on water quality

CSWS Evaluation groups• Farmers & irrigators in majority• Range of other interests (environment,

conservation, angling, kayaking, community development . .)

• Few women, Maori, or people from small towns• Limited number of people had on-the-ground

knowledge of proposed sites

CSWS Stage 3 was not• A process with statutory standing

• A technical evaluation of water quality or other environmental impacts

• Based on site visits

Evaluation of Hurunui options

• Range of options based on South Branch dam, Lake Sumner and a dam on a mid-Hurunui tributary (e.g. Mandamus).

• Group’s thinking changed through the process with the option of managing Lake Sumner within historical range becoming more attractive as concerns increased about a high dam on South Branch with loss of salmon fishery and other adverse impacts

• A combination of managing Lake Sumner with some other “back-up” storage (but not South Branch dam) may allow much of the land to be irrigated

• Aqualinc modeling results need to be revised given proposed Hurunui River Regime Plan

Comments from interest group discussions on Hurunui options

• Big dams not favoured, particularly on main tributaries. On-farm storage offered as an alternative.

• Irrigation seen as intensive dairying and leading to N & P pollution & bad bugs. Skeptical (at best) that best practice would solve issue.

• How can this be a strategic study if one of the options – NO DAMS – is not being considered? Some strong opposition to dams on rivers, more irrigation & dairying.

• Irrigation seen as only benefiting farmers at a cost to the environment with society (not the farmers) bearing the consequences of land-use practices.

• Hurunui District mayor & councilors recognise the need to have a strategy for water and development as part of their long term plan.

• National Conservation order application for Hurunui River lodged.

How the group felt about the options . .

South Branch(current rules)

Strongly positive Strongly negativeNeutral

L. Sumner (with “natural” lake variation)

South Branch & L. Sumner

L. Sumner & South Branch

Evaluation scale

South Branch (Mosley rules)

L. Sumner(without var.)

L. Sumner & Mandamus(with “natural” var.)

L. Sumner & Mandamus(without var.)

Raised Sumner

South Canterbury options

• Using only water from within area:– Raised Opuha dam;– Opuha dam + Opihi dam (near Fairlie)– Pareora dam

• With Tekapo water:– Opuha + Opihi dam (two operating ranges)– Opuha + Tengawai dam– Opuha + off-channel storage– Opuha only

South Canterbury evaluation• Very water-short area. Storage options constrained by

water availability (Opuha, Opihi, Tengawai, Pareora)• Opuha scheme is unlikely to be able to meet demand of

its existing irrigators in all years. In very dry times, like in 1988, lake may not refill in winter/autumn & irrigation restrictions of 3 months or more

• Tekapo water required but significant challenges: – Meridian consent; – cultural (water mixing); – environmental; – use of water for electricity generation

versus use for irrigation. • Prefer option based on use of

Tekapo water with current Opuha• Pareora stand alone option but

more hydrology needed

Raised Opuha

Opuha + Opihi

Opuha + Opihi 20m range 5m range

Opuha + Tengawai

Opuha only

Pareora

How the group felt about the options . .

Opuha + off-channel storage (Stoneleigh Rd)

With water from TekapoUsing local water only

Strongly positive Strongly negativeNeutralEvaluation scale

Mid-central Canterbury evaluation• Options – Lees Valley, Wainiwaniwa Valley,

Lake Coleridge water, Stour Valley• For some of Group all options OK, for others

none are acceptable;• Participants see storage as critical

– Some believe major storage is only option (economically)

– Others think smaller storages require more consideration

• Integrated option worth considering

Lees Valley• BIG is a positive & a negative:

– Supplies all irrigable area north of Rakaia• Big economic benefit • Big environmental risks

– Single solution (no CPW)– $1 billion +– Huge dam

• Long time for initial filling• Significant impacts on

Waimakariri and Ashley Rivers

Waininaniwa Valley

• Option evaluated similar to CPW except water not restricted to Selwyn area (could use water north as well)

• Evaluation echoed concerns and advantages expressed in media and letters to newspapers

• More immediately “do-able” than Lees Valley

Lake Coleridge

• Trustpower provided limited information, on a confidential basis, on an option they are scoping

• Diverts water from Lake Coleridge for new power generation & water to north & south (siphon) for irrigation

• Non-compliance with Rakaia WCO a major hurdle even though– Operates within consent conditions for Harper,

Wilberforce and Coleridge lake levels– Likely little impact on Rakaia flows below Gorge

• Requires other storage – Coleridge storage able to improve short-term reliability of supply but not dry-year reliability

Stour Valley• Water diverted from South Ashburton to reservoir in

Stour Valley• Rakaia and Rangitata River takes• Utilises RDR & BCI infrastructure (with changes to get

water south of Ashburton River)• Concerns about impacts on wetlands, iconic lakes &

landscape in/near Stour valley (area recommended for World Heritage status)

• Adverse impacts on Ashburton River flows (though may be able to improve flows in lower river)

“No major storage” option

• Group had an initial discussion of the impacts if there was no new (major) water storage in mid-central Canterbury:– Irrigation development would stop, probably contract– Farmers increasingly struggle to meet market

expectations (time- and product-specific)– Rural economy decline (with flow on impact on rural

towns & Christchurch) and impact on social infrastructure

– Loss of opportunities to use releases from storage to improve river ecosystems (as done in Opuha)

– Reduced environmental impacts/risks (stop land intensification & reduce new run-of-river takes) but extent debated

How people felt about the options

Lees Valley Lake Coleridge

Waianiwaniwa Valley

No storage

Stour Valley

Strongly positive

Strongly negative

Neutral

An integrated option

• At the last meeting of the mid-central Group, an integrated option was proposed to:– provide new irrigation– improve low flows and flow variability in most

rivers– only require one new storage reservoir– supply water south of Rangitata, if possible

• Aqualinc has modelled initial results

An integrated option

For the area from Ashley River to Rangitata River an option that:– provides water for significant new

irrigation– improves low flows and flow

variability in most rivers – only requires one new storage

reservoir– supplies water south of

Rangitata, if possible

X

XXRDR

Esk R

Lees VlyX

X run-of river takes

L Coleridge

Rak

aia

R Waimakariri R

Reservoirs/lakes

Ashley Gorge

Head race – schematic only

141,000ha irrigable area

RDR + BCI

Increased flows in lowland streams

CRUNCH issuesCHALLENGES to be worked through

X

X X Lake filling time

Water quality

concerns

Meeting water demand

Where to . ..

• Are we close?

• Could we work together to find innovative solutions for Canterbury’s future prosperity that use water wisely for primary production with environmental gains . . . .