Canterbury Strategic Water Study (CSWS) Stage 3

Final Report Canterbury Strategic Water Study (CSWS) Stage 3 Multi-stakeholder evaluation of water storage options PREPARED BY: Ian Whitehouse (facilitator) Andy Pearce (Chair) Grant McFadden (facilitator) On behalf of the Canterbury Mayoral Forum

SUMMARY Introduction Stage 3 of the Canterbury Strategic Water Study (CSWS) was a preliminary stakeholder assessment of a range of water storage options for Canterbury (options identified previously in Stage 2 of the CSWS). CSWS Stage 3 is part of a broader consideration of water availability and management. The report and public response to it will contribute to the comprehensive public engagement programme on Canterbury water management planned for 2008/09. The key findings of CSWS Stage 3 are that - before strategic water storage and water management decisions can be made - rigorous scientific and public consideration is required of: the impacts of land use intensification and its effects on water quality mitigation and management systems for water quality, and methods for maintaining or improving flow variability and low flows in major rivers. This summary has been prepared by the authors of the Stage 3 Report of CSWS (Ian Whitehouse [facilitator], Andy Pearce [Chair] and Grant McFadden [facilitator]) to accompany the release of the report by the Canterbury Mayoral Forum, March 2008. Background - Canterbury Strategic Water Study (CSWS) The Canterbury Strategic Water Study (CSWS) was initiated by Ministry of Agriculture and Forestry (MAF), Ministry for the Environment (MfE) and Environment Canterbury (ECan) following the severe drought of 1998. The drought raised concerns about whether Canterbury would run out of water in the future. CSWS Stage 1, published in 2002, was a sub-regional water balance evaluation of current and likely future water supply and demand (undertaken by Lincoln Environmental). Stage 1 concluded that, on an annual basis, there is enough water in Canterbury to meet likely future demand - but some catchments are water short and peak demands could not be met on a weekly basis. It also concluded that water storage should be considered as part of meeting future demands for water - primarily for irrigation - to supplement supply in times of low natural flows. CSWS Stage 2, under the auspices of the Canterbury Mayoral Forum, began in 2004, and identifies potential water storages in Canterbury and their hydrological feasibility, including the area they could irrigate and their impacts on river flows. The Aqualinc report on Stage 2 will be published in 2008. CSWS Stage 3, also undertaken for the Canterbury Mayoral Forum, began in early 2006. It involved an initial evaluation by multi-stakeholder groups of the environmental, social, cultural and economic impacts of the water storage options identified in CSWS Stage 2. The findings of CSWS Stage 3 are summarised below. CSWS Stage 3 identified two over-arching critical issues - land use intensification and its effects on water quality; and maintaining or improving, flow variability in major rivers - that need to be rigorously explored (including improved mitigation and management systems) and subjected to comprehensive public debate before Canterbury is in a position to make sustainable, long-term decisions about water storage or water management more broadly. [This public discussion will be the focus of CSWS Stage 4 a comprehensive public consultation programme to be undertaken in 2008]. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 2

CSWS Stage 3 Objective The objective of Stage 3 was to undertake a preliminary evaluation of the water storage options identified in CSWS Stage 2 against a range of environmental, community, cultural, social and economic concerns, and to assess the likely public acceptability of each option. CSWS Stage 3 Process Multi-stakeholder groups were used to first, develop a framework to evaluate water storage options for Canterbury, and secondly to use this framework to evaluate water storage options from CSWS Stage 2 (and additional options identified by the group). The multi-stakeholder evaluation groups included people with a wide range of interests in water in Canterbury irrigation, angling, farming, environmental concerns, community development, Ngai Tahu, recreation, and conservation. Participants were present in their personal capacity as knowledgeable individuals or experts not as representatives of any organisation. Irrigators and farmers made up more than half of each group. Environmentalists and conservationists made up about a fifth of each group. The CSWS Stage 3 Report reflects the full range of views of participants, not just those of the majority. CSWS Stage 3 included five workshops developing the evaluation framework, two full days of information presentations and 14 one-day evaluation workshops. The options were evaluated on a six-point scale against 22 topics covering social, economic, cultural and environmental impacts. The evaluation identified the key concerns likely to influence public acceptability of each of the water storage options. The evaluation findings were discussed, in a very limited manner, with some interest groups including local government, Fish and Game and Aoraki Conservation Board, and at a public meeting in Timaru. Extensive public consultation is planned following the release of the CSWS Stage 3 Report as part of developing a Canterbury Water Management Strategy. CWSW Stage 3 Options Evaluated The multi-stakeholder groups evaluated water storage options based on 12 major reservoirs from Hurunui to Pareora Rivers. The group s evaluations indicated that some options, including Lake Sumner, Lake Coleridge, Lake Opuha, and reservoirs in a mid Hurunui River tributary, Lees Valley, Stour River and Pareora River, were more likely to meet a range of expectations and requirements than other options considered. For the sub-region from Ashley River to Rangitata River, the group considered that an integrated system, combining several individual options, was desirable and should be investigated further. Evaluation of water storage options for the Hurunui area was completed at the end of 2006, for South Canterbury in early 2007, and for mid-central Canterbury in September 2007. The options evaluated are merely potential storage sites and related infrastructure. Significant studies and extensive public and stakeholder engagement are required to fully develop any proposal based on any of the options evaluated. The CSWS Stage 3 evaluation process identifies a range of environmental, social, economic and cultural concerns and issues that need to be addressed for each of the options. Further studies and engagement may identify other issues, all of which would have to be considered and managed for any of the options to be taken further. CSWS Stage 3 only considered options based on major reservoirs (more than 50,000,000m 3 ). Limited consideration was given to on-farm storage. The option of no more major storage was also evaluated. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 3

CSWS Stage 3 Key Findings and Conclusions 1. Impacts of both land use intensification and larger areas of intensively-used land must be rigorously addressed with good science and understanding of mitigation and management options before any major water storage option proposal can be progressed. In the evaluations of all the water storage options (and discussion with interest groups) the risk to water quality from land intensification (particularly dairying) from increased irrigation was a major concern. 2. Current approaches to river management do not adequately protect flow variability and the water storage options proposed would lead to substantially reduced flow variability in some rivers at, or near, minimum low-flow for much of January through March. All water storage options will affect river flows through takes to storage (mainly outside the irrigation season), and by both releases from storage and run-of-river takes to meet irrigation demand during the irrigation season. 3. The CSWS Stage 3 evaluation indicates a desire for an integrated and reasonably equitable solution to Canterbury s future water that addresses water demand in mid-central Canterbury regions including south of Rangitata River, minimises the major storages required, puts water back into lowland streams, protects flow variability and low-flows in major alpine rivers, and fully and properly accounts for environmental and social impacts. 4. The South Canterbury evaluation confirmed how water short the area is unless it can access water from alpine rivers (Waitaki and Rangitata Rivers). The current Opuha scheme is unlikely to meet demand from its existing irrigators in all years. In very dry years, like 1988, the lake may not refill in autumn/winter leading to irrigation restrictions of three months or more. The evaluation has identified the key features of the major water-storage options in Canterbury and a range of environmental, social, economic, cultural, infrastructure and equity issues, tradeoffs and concerns that would have to be considered and managed for any of the options to be taken further. All options have positives and negatives. For some participants all options were acceptable, for others all options were unacceptable. CSWS Stage 3 Key Contributions Provides a preliminary assessment of the likely and important considerations that will determine the acceptability of major water-storage options in Canterbury. Highlights the need to address the impacts of both land use intensification and larger areas of intensively-used land, and concerns about flow variability and low flows in major rivers. Confirms how water-short South Canterbury is. Contributes to this year s public consultation programme on water management in Canterbury. Next Steps CSWS Stage 4 Water storage is only one of the things that need to be considered in a water strategy for Canterbury. Other issues that need to be considered include land use intensification, water quality, cultural values, tangata whenua objectives, and recreation uses. Extensive public engagement is planned on all water-related issues as part of developing a Canterbury Water Management Strategy (CSWS Stage 4). The CSWS Stage 3 Report and public response to it will contribute to this public engagement programme. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 4

1 Introduction Canterbury Strategic Water Study (CSWS) The CSWS was initiated by Ministry of Agriculture and Forestry (MAF), Ministry for the Environment (MfE) and Environment Canterbury (ECan) following the severe drought of 1998 that raised concerns about whether Canterbury would run out of water in the future. The first stage of the study, published in 2002, was a sub-regional water balance evaluation by Lincoln Environmental of current and likely future water supply and demand. This indicated that regionally, on an annual basis, there was adequate water to meet all future requirements but that this did not apply to all catchments individually, and peak demands could not be met on a weekly basis. That is, there is plenty of water in total but it s not always in the right place at the right time. The study suggested this mismatch of supply and demand could be addressed by the seasonal storage of water, by intercatchment transfers and through new ways to manage underground and surface water systems together. Storage is required to supplement supply in times of natural low flows to meet future irrigation demand. A second stage of CSWS, under the auspices of the Canterbury Mayoral Forum, began in 2004 and identifies potential water storages in Canterbury and their hydrological feasibility, including the area they could irrigate and their impacts on river flows. The Aqualinc report on CSWS Stage 2 will be released in 2008. The third stage of the study, also under the auspices of Canterbury Mayoral Forum, began in early 2006. CSWS Stage 3, reported here, evaluates the environmental, social, cultural and economic impacts of the water storage options. Evaluation of water storage options for Hurunui area was completed at the end of 2006, for South Canterbury in early 2007 and for mid-central Canterbury in September 2007. The CSWS approach, endorsed by the Canterbury Mayoral Forum from the start of the project, seeks to address all of the interests and values associated with water across the region. The first two stages of the project focused on water supply and demand, the third stage attempts to incorporate many of the wide range of interests and values associated with water. The fourth stage will extend the involvement of interests in water in Canterbury. The evaluation process reported here starts with the premise, from the CSWS Stage 1 water balance study, that major storage reservoirs should be considered as part of future water supply in Canterbury. In the mid-central Canterbury evaluation the group did discuss the likely impacts if there was no new major water storage in the area. The options evaluated are not development proposals they merely identify potential storage sites and related infrastructure. The CSWS Stage 3 evaluation of storage options is only a preliminary evaluation. Significant studies and extensive consultation are required to fully develop the proposals. The CSWS Stage 3 evaluation process identifies a range of environmental, social, economic and cultural concerns and issues that need to be addressed for each of the options. Further studies and consultation may identify other issues, all of which would have to be considered and managed for any of the options to be taken further. Neither CSWS 3 nor the evaluation groups are advocates for any particular storage option. CSWS 3 and the evaluation groups do support further work to develop an integrated Canterbury-wide approach to address future water supply and demand and to address water quality concerns from land intensification. The CSWS is a research and evaluation programme. CSWS does not have a statutory basis and is not part of a RMA process. It will not produce a water allocation plan. The technical parts of CSWS deal only with water quantity. Water quality, in-stream impacts and other aspects are included in the CSWS Stage 3 evaluation of storage options but no technical appraisal of these has been carried out for the study beyond a brief evaluation of Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 5

in-stream impacts by Dr John Hayes, Cawthron Institute. A strategic evaluation of water quality and land use is likely to be part of CSWS Stage 4. Water in Canterbury The alpine rivers provide nearly 90% of Canterbury s surface water with Waitaki and Rakaia Rivers providing nearly half. These rivers are also major contributors to groundwater. River recharge is estimated to provide nearly 60% of total recharge to the groundwater system between Rakaia and Waimakariri Rivers, the remainder coming from land-surface (rainfall) recharge. Canterbury uses about 60% of all water allocated nationally for consumptive use. About 80% of Canterbury s water use is for irrigation. There is about 1,000,000ha of irrigable land in Canterbury with resource consents for irrigation on about 650,000ha. There is increasing demand for water for irrigation from groundwater and run-of-river takes. Allocation has reached a stage where Environment Canterbury considers some groundwater zones to be over allocated and where new run-of-river takes are less able to provide reliable supply for irrigation. Notwithstanding this there are filed applications seeking allocations for more water from most rivers and groundwater zones. Canterbury water is in a gold rush period where irrigators are trying to secure a right to an increasingly scarce resource. Water, through irrigation, is critical to Canterbury s land-based economy. Irrigation provides opportunities for high-value crops that require reliable water supply and allows farmers to meet market expectations to deliver products in tightly-specified time periods and to increasingly exact specifications. The primary sector contributes over 60% of New Zealand s exports. In Canterbury the proportion is likely to be higher. Exports provide the foreign exchange needed to buy imported fuel, equipment and a wide range of consumer products that underpin New Zealanders standard of living and lifestyle. About 70% of all irrigated land in New Zealand is in Canterbury. Public perception is that all of the irrigated land is in dairying production or being converted to dairying. In fact, the main irrigated land uses are arable 27%, dairy pasture 34% and other pasture 36%, with the remaining 3% in horticulture and viticulture. The resource consent process makes case-by-case decisions and seems ill suited when resources are scarce, not plentiful. All of the multi-stakeholder group that were involved in developing the framework for this CSWS 3 evaluation agreed that the current salamisliced decisions could well produce a sub-optimal outcome. Certainly the consent process limits a strategic approach. The CSWS seeks to facilitate a strategic approach to meet future water demands for sustaining Canterbury s land-base prosperity without compromising environmental values or resource limits. CSWS 3 Coverage Over 20 options based on 12 storage reservoirs were evaluated. The storages evaluated range from Hurunui River in the north to Opihi River in the south. No options were evaluated north of Hurunui River as the CSWS Stage 1 study had shown that potential demand in the Waiau area could be met from Waiau River without storage. South of Opihi River, the proposed Hunter Downs scheme (using water from Waitaki River) was not evaluated as the proposal was in the resource consenting process. The evaluation only looked at major storage options of at least 50,000,000m 3. On-farm storage was not evaluated. On-farm storages of up to a million cubic metres are being established in mid Canterbury to increase reliability of supply where water is supplied intermittently (such as from Rangitata Diversion Race). By themselves, on-farm storages are unlikely to meet future water demand but may be a useful complement to major storage dams. One of the mid-central Canterbury group, who has created on-farm storage, indicated that the capital cost, per unit of water, is about eight-times more for on-farm storage than for a major storage dam. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 6

The evaluation primarily looked at storage options identified by Aqualinc, though participants did suggest some additional options and variations to those proposed by Aqualinc. The options brought to CSWS 3 were those Aqualinc considered to be the most promising of the options identified in previous studies. Aqualinc filtered out many of the storage sites previously identified for example in mid-central Canterbury Aqualinc identified 49 storage sites from previous studies (see map below) but only modelled and presented options to CSWS 3 based on three reservoir sites. Major water storage options identified by Aqualinc for mid-central Canterbury from previous studies. Only the four most promising of these (Lees Valley dam, Waianiwaniwa dam and Stour River dam) were modelled by Aqualinc and presented to CSWS 3. A Lake Coleridge option was presented to CSWS 3 by Trustpower. Options integrate run-of-river abstraction and storage All the options evaluated combine major storage with run-of-river abstraction to supply water for irrigation at a very high level of reliability. Run-of-river water is used to meet irrigation demand whenever possible (i.e. when the river is above regulated minimum low flow). Releases from storage are used to meet run-of-river shortfall (particularly in the latter half of the irrigation season and in dry seasons). Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 7

2 Evaluation Process Evaluation Framework The evaluation used a 26-topic framework covering a wide range of environmental, economic, social and cultural aspects. A copy of this framework is provided in Appendix 1. The framework was developed by a multi-stakeholder group (see Appendix 2 for a list of those involved). Many of those involved in the development of the evaluation framework were also part of the subsequent multi-stakeholder groups that carried out the evaluation of all or some of the storage options. The multi-stakeholder group involved in the development of the framework identified that it needed to be better informed about current knowledge on key issues relating to water and irrigation in Canterbury. Two day-long workshops were held in August and September 2006 with presentations from experts covering social and economic impacts of irrigation, water quality and irrigation, land-use intensification (including impacts of dairying), impacts on river birds, in-stream (fish) impacts, climate change impacts, Ngai Tahu and water, and electricity and irrigation. Multi-Stakeholder Groups The evaluation of water storage options for Canterbury was done by multi-stakeholder groups of about 15 30 people in three pieces options for Hurunui River in four one-day workshops in September to December 2006, for South Canterbury in four workshops in February to April 2007, and for mid-central Canterbury in five workshops from May to July 2007. In early September 2007 a one-day workshop of participants from all three groups and from the CSWS Mayoral Forum Steering Group explored an integrated option for midcentral Canterbury. The multi-stakeholder groups included people with a wide range of interests in water in Canterbury irrigation, angling, farming, environmental concerns, community development, Ngai Tahu, recreation, and conservation. Irrigators and farmers made up more than half of each group. Most of the participants were male. Environmentalists and conservationists made up about a fifth of each group. A core of 8 people was involved in all three groups with an additional four people involved in the evaluations for two areas. Lists of participants are provided at the end of the evaluation for each of the three areas. The multi-stakeholder groups provided a very robust evaluation of the water storage options, identifying the key features of each option and the beneficial and adverse impacts. There was generally a range of views with differences understood and respected by others in the group. The summaries presented here of the evaluations reflect the full range of views of participants, not just those of the majority. Hydrological Modelling For all options, daily irrigation demand and river flows were modelled by Aqualinc using 30 years of river and climate records (generally 1973 to 2003). Irrigated area for Hurunui District and mid Canterbury storage options was assessed using a very high reliability of water supply in the 30 years modelled there could not be more than 10 continuous days without water or a restriction on water supply. The modelling for South Canterbury used a lower reliability criteria that of the current Opuha Scheme. The modelling assumed that all new schemes would use highly-efficient spray irrigation. A description of the modelling approach and detailed results are provided in the CSWS Stage 2 report. Evaluation Process No site investigations or environmental impact assessments have been made of any of the potential water storage sites. Many of the sites have been identified in previous studies and limited technical information and cost estimates are available from these. Most of the Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 8

people in the evaluation groups did not have first-hand knowledge of the proposed storage sites though there were individuals who had good knowledge of the sites. The first workshop for each of the three areas included briefing on CSWS and progress to date, an overview from John Bright and/or Andrew Dark (Aqualinc) of the storage options for the area identified as part of their CSWS Stage 2 investigation, and an evaluation by John Hayes (river ecologist, Cawthron Institute) on in-stream impacts of the proposed options. Participants identified additional options or variations on options proposed and these were modelled by Aqualinc and presented and evaluated at subsequent workshops. The evaluation of each individual option started from a technical (primarily hydrological) description by Aqualinc of the water storage and river flow changes to identify, in nontechnical terms, the key elements and concerns of the proposed options. After initial questions of clarification from participants the evaluation of the option using the framework was done by smaller groups of five to eight who reported back to all participants. Key features, positives and concerns were discussed and recorded by the facilitator. The last workshop for each of the three areas included participants reviewing how they felt about each option, the reasons for this and the relative merits of the option. This evaluation summary draws on material from the small group evaluations of each option, notes taken of group feedback and discussion on options, records of how each participant felt about each option (and the reasons for this), and group discussion of the merits and concerns about all of the options for an area. Copies of the small group evaluations using the 26-topic framework and other material are lodged at ECan with the Project Manager (Ken Taylor). A list of this material is provided in Appendix 3. Drafts of the summaries of the evaluations for each of the three areas were provided to participants for comment and suggestions. The final summaries incorporate changes in response to these. A draft of this report was sent to all participants for comment and suggestion. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 9

3 Mid-central Canterbury storage options Summary of options evaluated Irrigated area (ha) 1 Location of irrigated area 1 Lees Valley storage 141,100 2 North of Waimakariri & between Waimakariri and Rakaia Rivers 2 Waianiwaniwa storage 63,300 2 & between North of Waimakariri Waimakariri and 3 Lake Coleridge (with northern & southern storages) Not modelled 6 Rakaia Rivers North and south of Rakaia River? 4 Stour Storage 126,600 8 Rangitata Rivers & Between Rakaia and south of Rangitata R. Active storage Maximum new run-of-river take for irrigation (m 3 /s) (Mm 3 ) Waimakariri Rakaia Rangitata 656 66 3 20 4-194 35 5 20 4 - not modelled 57 7-200 - 37 9 30 1 net irrigated area, including existing irrigated areas 2 total net irrigable area north of Waimakariri River (including Loburn-Ashley) and between Waimakariri and Rakaia Rivers is 141,100ha. 3 does not include 15m 3 /s maximum take from Esk River to Lees Valley Lake. Only very rarely would substantial take to storage occur at the same time as substantial run-of-river take for irrigation. 4 if 50/50 flow sharing with Ashburton District (as per CPW/ACWT agreement) the maximum new run-of-river take from Rakaia River would be 40m 3 /s. 5 does not include 10m 3 /s maximum take to Waianiwaniwa storage. Only very rarely would substantial take to storage occur at the same time as substantial run-of-river take for irrigation. 6 irrigated area depends on what storages used and size of the run-of-river take from Waimakariri River. Likely to be able to irrigate at least 180,000ha 7 assumed that all new water is used in this option (i.e. CPW, ACWT and Barrhill-Chertsey allocations). 8 if Rangitata River take is capped at 27m 3 /s to allow 3m 3 /s of water to go south, irrigated area is 115,050ha. Total irrigable area between Rakaia and Rangitata Rivers is about 155,000ha excluding that irrigable cost-effectively from groundwater. 9 assumed that ACWT and Barrhill-Chertsey allocations are used in this option. Areas irrigated Net irrigated area (ha) North of Waimakariri Waimakariri-Rakaia Rakaia-Rangitata Total existing new existing new existing new 1 Lees Valley storage 141,100 18,000 39,100 84,000 1 - - 2 Waianiwaniwa storage 63,300-63,000 1 - - 3 Lake Coleridge (with northern & southern storages) Not - - modelled 2 4 Stour Storage 126,600 3 - - - 63,800 62,800 4 1 Split between new and existing not known most existing users are groundwater irrigators 2 irrigated area depends on what storages used and size of the run-of-river take from Waimakariri River. Likely to be able to irrigate at least 180,000ha 3 if Rangitata River take is capped at 27m 3 /s to allow 3m 3 /s of water to go south, irrigated area is 115,050ha. Total irrigable area between Rakaia and Rangitata Rivers is about 155,000ha excluding that irrigable cost-effectively from groundwater. 4 includes Barhill Chertsey area (35,600ha). Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 10

Overview map (adapted from Aqualinc) showing four options evaluated in mid-central Canterbury Ashley Gorge Lake Coleridge Head race schematic only Waianiwaniwa Valley Stour River Description and evaluation of storage options for mid-central Canterbury Lees Valley storage This is a very large storage that, with run-of-river takes, would reliably supply water to irrigate all of the irrigable area (141,100ha) north of Rakaia River including the north bank of Waimakariri River and Ashley-Loburn areas. Water would be taken from Esk River, a tributary of Waimakariri River, through a 14km tunnel to Lees Valley to provide 656,000,000m 3 active storage behind a high dam at the top end of Ashley Gorge. The floor of Lees Valley would be inundated. The height of the dam depends on decisions on operating range a 180m high dam is required if the operating range is kept small (7m), a 105m high dam would have an operating range of about 22m, or if a large operating range (72m) was acceptable the dam would be only 90m high. A small operating range provides more recreation opportunities and limits the area of seasonally-exposed lake bed. All of these options are significant dams Benmore, New Zealand s largest dam, is 110m high. The inflow from Esk River is small and initial filling of a storage lake (with a small operating range) would take about ten years. Once filled, the Esk River inflows are able to replenish active storage between irrigation seasons except in very dry years. The Group was concerned about the time required to fill the lake and options were scoped of taking water from Poulter River or pumping from the Waimakariri River at its junction with the Esk to speed initial filling. The relatively small reduction in filling time of only about 2 years was not considered sufficient, however, to offset the consenting challenges of taking water from Poulter River adjacent to or in Arthurs Pass National Park or the cost of pumping from Waimakariri River. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 11

Water from the storage lake would be released through Ashley Gorge to a headrace at the downstream end of the Ashley Gorge. This headrace links to the Waimakariri River abstraction structure and to an infrastructure of canals (or tunnels) south between Waimakariri and Rakaia Rivers. Irrigation demand would be met, in the first instance, from run-of-river takes from Waimakariri River as available within the rules of the current Waimakariri River Regional Plan. When Waimakariri River takes can not meet irrigation demand water would be taken from Rakaia River (for irrigating Selwyn area) and/or from storage. The run-of-river take would reduce flow, in the section of Waimakariri River below the Gorge Bridge to the mouth, to the minimum low flow (50m 3 /s at Gorge Bridge) for much of the summer January through end of March. There would be significant impact on flows in Ashley River. In Ashley Gorge, winter flows are reduced as water is harvested to storage, while in the irrigation season flows are substantially increased as flows of up to about 80m 3 /s are released to meet irrigation demand. In the Ashley River below the irrigation headrace flow magnitude and variability would be reduced though there is opportunity to manage releases from the storage to provide flushing flows, flow variability and increase currently-low minimum flows in the lower Ashley River. Evaluation of Lees Valley option The Group was attracted to this option as a single solution to meet all future irrigation demand north of Rakaia River. With the Lees Valley storage, the Waianiwaniwa Valley storage (see below) would not be required. The scale of the project was seen a positive on the one hand but also as presenting challenges. One person summed up this feeling with the comment too large, too hard. Funding of a $1 billion project was seen as beyond the resources of a community-based scheme and would require Government and/or external investment. The option was seen as a regional option requiring very wide support. This was seen as a challenge, though not necessarily an insurmountable one. The time to initially fill the storage was seen as a negative, adding to the investment challenge, though it was felt there may be possibilities of staging irrigation development and/or using water from the lake during the filling period. Concern about the time to fill led some to question whether there was a risk of the storage failing to refill after very dry seasons, although this had not occurred in the 30 years modelled as part of the Aqualinc investigation. Storage performance may need further investigation. As noted above, shortening the fill time by taking water from Poulter River or pumping from the Waimakariri River at its junction with the Esk, was not favoured by the Group. For some of the Group, the impact of the diversion of water from the Esk, to fill the Lees Valley storage, was not considered to be an issue for river flows through Waimakariri Gorge. Others had concerns about abstraction anywhere above the Gorge. Some commented that it was important that the Waimakariri River above the Gorge Bridge not be messed up. The Waimakariri River Regional Plan, Rule 7.5, prohibits the erection of a weir on the Waimakariri River or any of its tributaries above Woodstock i.e. the structure required to divert water from the Esk River is prohibited in the Plan. The significant scale was a concern to some of the Group because of the increased risk of nitrate leaching and other water quality issues from the large increase in intensive land use (including dairying). It was acknowledged by many of the Group that these risks may be mitigated or avoided through adoption of best land management practices though some believe this would not be sufficient to solve the problems of nitrate leaching and other water quality impacts. The Group believed the proposed new irrigation would positively impact on flows in lowland streams and on the water available for groundwater irrigators on the lower plains. Annual rainfall recharge to the groundwater system is almost doubled on irrigated land compared to non-irrigated land. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 12

The dam will be a very significant structure. There was discussion of the relative merit of a very high dam with a small operating range versus a high dam with a large operating range. The very high dam, with its smaller operating range, was seen as offering recreational opportunities close to Christchurch. It was also seen as providing more hydro-generation. On the other hand, it would be more expensive and take longer to fill. The major canal (or tunnel) infrastructure required to distribute irrigation water, particularly across the top of the Plains, will impact many landowners. It was felt that compulsory land acquisition would not be popular given the experience with the proposed Central Plains scheme. Any option, however, for new irrigation south from Waimakariri River will require a major headrace across the top of the Plains between Waimakariri and Rakaia Rivers. The Group had concerns about the impacts on the Ashley River. High flows in the Ashley Gorge would enhance opportunities for expert kayaking but would likely displace trout, juvenile salmon and native fish, be dangerous for anglers, hunters and swimmers, and change the river character at the popular picnic area and campground at the downstream end of Ashley Gorge. Flows in the lower Ashley River would also be significantly changed, affecting wildlife, fisheries and recreation, though some adverse impacts may be mitigated by release of flushing flows and by increasing low flows with releases from storage. Some of the group expressed considerable concern in regard to the impact of reduced flows and loss of flow variability ( flat-lining for much of the summer) in the lower Waimakariri River on ecological, mahinga kai and recreation values. Concern was expressed on the likely reduction in the number of days suitable for salmon angling, reduced flows for jet boating and possible changes to river mouth. Salmon anglers prefer to fish the river as flows fall after flood freshes. In this option (and the Waianiwaniwa Valley storage described below) run-of-river takes would cause after-flood flows to fall quicker, reducing the number of days of best fishing conditions. There was also concern about possible reduction of supply from the Waimakariri River to the Christchurch City aquifer system from reduced flows in the river. One of the group had concerns about the possible impacts on gravel transport in Waimakariri River and on coastal dynamics. Some in the Group commented that the Waimakariri River Management Regime needed to be revised to improve flow variability and increase the protection of low flows. Waianiwaniwa Valley storage This option is similar to the proposed Central Plains scheme (CPW) except water supply is not restricted to Selwyn area and could also be used north of Waimakariri River. Water from Waimakariri River is diverted through a canal or tunnel to a 194,000,000m 3 storage in Waianiwaniwa valley, above Glentunnel, at the top of the Plains between Waimakariri and Rakaia Rivers. The lake is dammed by a 50m high, 2km long dam and inundates about 12km 2 of farmland. Irrigation demand would be met, in the first instance, from run-of-river takes from Waimakariri River as available within the rules of the current Waimakariri River Regional Plan. When this can not meet irrigation demand water would be taken from Rakaia River (for irrigating Selwyn area) and/or from storage. The run-of-river take would reduce flow in the Waimakariri River below the Gorge Bridge to the mouth to the minimum low flow (50m 3 /s at Gorge Bridge) for much of the summer January through end of March, though not quite as often as with the Lees Valley option (above). Evaluation of Waianiwaniwa Valley option The Central Plains irrigation scheme has been extensively discussed in the media and views strongly expressed in letters to newspapers. Views are somewhat polarised on the attractiveness, or otherwise, of the option. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 13

Concerns expressed about the CPW option were echoed in the Group s discussion of the Waianiwaniwa Valley option. Some of these concerns are the same as those for the Lees Valley option (above) the increased risk of adverse water quality impacts from the increased area of intensive land use, and the impacts of the reduced flows in the lower Waimakariri River. In addition, concerns were raised on the impacts of damming Waianiwaniwa Valley including those on the significant population of Canterbury mudfish, a nationally endangered species. The Group thought the recreation gains from the storage lake would be small. The Group recognised that this option, like the other options evaluated, would increase land use options and lead to an increase in the area under higher-value crops (e.g. seed crops and vegetables) and other high-value land use (e.g. dairying). This would provide significant economic benefit at the farm, district and regional scale and, in turn, retain and probably enhance health, education and other social infrastructure though not necessarily in the irrigated area. There was comment, however, that this option (unlike Lees Valley storage) would not fully meet the irrigation demand north of Rakaia River. It was felt that this option was more immediately do-able than the Lees Valley option (because of scale) and should not be dismissed just because it would not be required if Lees Valley option was built. The conservation and landscape issues for the Waianiwaniwa options were thought to be less than those for the Stour River option (see below). Lake Coleridge option Trustpower provided limited information on an option they are currently scoping that would supply water from Lake Coleridge to a major storage to the north (e.g. Waianiwaniwa Valley storage) and south to RDR and Barrhill-Chertsey distribution systems. Information from Trustpower was provided on a confidential and privileged basis. Trustpower will release information on this option once scoping studies are completed. Trustpower consider that operating requirements and lake-level constraints mean that while Lake Coleridge can be used to improve short-term reliability of water supply for irrigation it can not provide the storage required to improve reliability in dry years. Additional major storage is required to provide a high level of reliability of water supply in all years. The option described by Trustpower increases hydro-generation capacity and the area able to be reliably irrigated in mid-central Canterbury. The option does not require changes to the current conditions for Trustpower s abstractions from Wilberforce and Harper Rivers, nor to rules restricting fluctuations in Lake Coleridge. In the irrigation season, flows in the Rakaia River through the Gorge would be reduced. Flows below the Gorge would comply with the Rakaia Water Conservation Order. Evaluation of Lake Coleridge option The Group had less information on this option than for other options, in particular no information on irrigable area and no detailed modelling of the impact on river flows. Acknowledging information limitations, many in the Group thought this option had merit, combining additional hydro-generation with improved reliability of water supply (and probably an increase in irrigated area) while retaining flows in Rakaia River below the Gorge. The reduction in summer flows through Rakaia Gorge appear to be relatively small but were a concern to the Group and it was acknowledged that Trustpower had focused scoping investigations on possible impacts in this reach. Some in the Group noted that the reduction in flow in the Gorge would mean less water for fishing and that this might possibly change the fishing experience to that associated with a smaller river. It was noted that the flow reduction would be unlikely to adversely impact jet boating in the Gorge. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 14

The use of a siphon to take water south across Rakaia River was seen as attractive by the Group enabling a connection to the RDR without requiring pumping. This was seen as a significant positive for the Barhill Chertsey irrigation scheme. It was noted that reliability of supply would also be increased for the Barhill Chertsey scheme. New takes of water above Rakaia Gorge are not permitted under the Rakaia Water Conservation Order (WCO). The Group discussed the proposed diversion of water from Lake Coleridge in relation to the WCO. The Group felt there would be considerable opposition to Trustpower s proposed option because it does not comply with the WCO. Some commented that while the impacts to the WCO rules would appear to be minimal, the potential to set a precedent by reviewing (and changing) a WCO would be a very major hurdle for this option. It was noted that water from Coleridge could provide opportunities to improve flows in the lower Ashburton River (and possibly Selwyn River) and that this may be welcomed by some parties who do not appear to consider the possibility of reviewing the WCO. The Group believes it is important that the option must not compromise the values of the Rakaia WCO. The Group considered that any review of Rakaia WCO must not be an excuse for an all-out assault on the WCO. For some in the Group, a WCO had the same standing and importance as a National Park. Fish and Game is opposed to any changes to the WCO. One of the Group, who is employed by Fish and Game, took no further part in the evaluation when it became apparent that the Group was discussing a water storage option that requires a challenge to the Rakaia WCO. He stated he did not believe that a public process should be used to undermine a river plan which has been determined via a thorough legal process in the light of robust scientific evidence. The Group recognised the importance of the Rakaia River in providing water to midcentral Canterbury it is a big, alpine-fed river able to provide water north and south to irrigate a large area. The Trustpower option was seen as increasing irrigation from the Rakaia River while at the same time increasing electricity generation. That Lake Coleridge was already a managed natural storage was seen as a positive (in comparison to creating a new reservoir) as was the ability to supply water north (to Selwyn District) and south (to Ashburton District). It was recognised, however, that Lake Coleridge was not a stand-alone option but would require other storage (for dry-year reliability). The Group considered that the use of Lake Coleridge water was likely to be a critical part of an integrated option for mid-central Canterbury. Stour River storage This option takes about 6m 3 /s of water from upper South Ashburton River (about 3km above Buick s Bridge) to fill a 200 million cubic metre storage behind a 80m high dam in a natural gorge in the Stour River. About 6km 2 of land, much or all under Department of Conservation management, is flooded behind the dam. There may be hydro-generation potential although the lake would have an operating range of about 70m. In one very dry period modelled the storage lake took three years to fill. The canal from the take in the upper Ashburton River to the storage lake would be sited to avoid sensitive wetlands in the vicinity of Maori Lakes. This option utilises run-of-river takes from Rakaia and Rangitata River and the existing Rangitata Diversion Race (RDR) infrastructure. Irrigation demand would be met, in the first instance, from run-of-river takes from Rakaia and Rangitata River as available within the rules of the national water conservation orders on these rivers. When this can not meet irrigation demand water would be taken from the Stour storage. About 126,600ha of land between Rakaia and Rangitata Rivers can be reliably irrigated in this option including existing areas irrigated from RDR and the Ashburton Lyndhurst schemes. This is over 90% of the area (below RDR) irrigable by surface water in Ashburton District. If 3m 3 /s water from the Rangitata River is taken south (rather than to the Ashburton District), the area reliably irrigated in this option between Rakaia and Rangitata Rivers is reduced to 115,050ha. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 15

There would be significant impacts on South Ashburton River. In the reach of about 16km from below the diversion to the Stour storage and above the Stour River, flows would be reduced to low levels for most of the time and the few remaining flood peaks significantly reduced as water is harvested to storage. Below the Stour River junction the flows in the river are also significantly altered through the combined effects of releases to meet irrigation demand and harvesting of water to storage. This leads to significant changes to the current pattern of flows. In the irrigation season high flows are common but of short duration, falling as fast as they rise (unlike natural floods), while at other times flows are often at or near the low-flow minimum. Below the irrigation take for the RDR, flows are also significantly altered with reduced variability, few freshes and long periods of low flows. As modelled the river would be at the low-flow minimum for about 30% of the time. The Group, however, believe there is opportunity, as noted below, to improve flows in the lower Ashburton River with this option. Flows in the Stour River below the dam are also significantly altered with releases from storage of up to 35m 3 /s, equivalent to the 100-year flood flow. Evaluation of Stour River storage This option utilises existing RDR infrastructure and this was seen as a positive. It was also noted that the Stour River option appears to be the best (only?) major storage option going for Ashburton District. The Group was concerned about the impacts on the Ashburton River and believed the adverse impacts would need to be minimised more than they had been in the modelled option presented. The Group believed a reservoir in the Stour Valley should provide opportunity to improve the flows in the lower Ashburton River including increasing low flows by 5m 3 /s to ensure the river mouth remains open through late summer. They believed some of the water for this could be contributed from the current stock-water system. Concern was expressed on the impact of the diversion canal and storage-reservoir on the wetlands, iconic lakes (such as Lake Emma) and landscape of the Stour River valley, though one person expressed the view that the ecological negatives were overstated in the Group s discussion of this option. The Stour River storage would be in an area that Forest and Bird is proposing for World Heritage Area status and the Natural Heritage Advisory Group, Department of Conservation, has recommended the area as a high priority for immediate World Heritage listing. A detailed assessment would be required of the ecological and landscape impacts in the vicinity of the proposed storage reservoir and for the Ashburton River. The proposed reservoir was not seen as adding significant recreation benefit because of its very large operating range. Concern was expressed on the impact on river birds. A section of the upper Ashburton River is important for some threatened and endangered bird species. The loss of most flood flows and a major reduction in variability would likely worsen habitat and major mitigation measures would need to be considered. It was recognised that there would be issues to be worked through between existing users (supplied from RDR) and new users. Existing RDR users may be reluctant to contribute as they already have a reliable water supply, as would the groundwater users who would benefit from increased land-surface recharge. As for other options there was concern about the risks to groundwater and surface water quality from the additional area of intensive land use, though some of the group believe these may be managed through best practice land management. Also, as for other options, the Group believed the proposed new irrigation would positively impact on flows in lowland streams and on the water available for groundwater irrigators on the lower plains. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 16

The desirability of getting more water south of Ashburton River (currently constrained because of the gradient of the RDR) and ultimately south of Rangitata River was identified as a key goal that this option could help achieve. Some consider that the Stour River storage could be part of a bigger picture that included use of Lake Coleridge water and the use of some water to improve flows in the lower Ashburton River (analogous to the use of Lake Opuha releases to improve flows in Opihi River in South Canterbury). Others were strongly of the opinion that this was not an option given the impact on the Stour valley, the small iconic lakes and the upper Ashburton River. Evaluation of impact of no new water storage The Group discussed the likely impacts, adverse and beneficial, if there was no new (major) water storage in mid-central Canterbury. Water is seen as Canterbury s natural competitive advantage. The Group acknowledged that water for irrigation was an increasingly scarce resource. If major storage options did not progress it was predicted that competition for water would markedly increase and that water would become a traded commodity in mid-central Canterbury. Some commented that they believed the water resource was already over-committed and that the addition of water storage would only delay the realisation that there was no more water available for irrigation. One person noted that it was not water abstraction by conservationists that had got us to the current situation and implied that irrigators needed to be facing up to the reality that water was no longer there for the taking. It was acknowledged that there were some gains to be had through more efficient water use but that these gains were not considered to be as substantial as some may claim. There was opportunity in some areas for on-farm storage to improve reliability of supply (particularly from RDR) to enable more land to be irrigated, although the additional area would be relatively small. The Group noted that if there was no new (major) water storage in mid-central Canterbury: Irrigation development would likely stop, and probably contract; Farmers would increasingly struggle to meet market expectations to deliver products in tightly-specified time periods and to increasingly exact specifications; Opportunities for high-value crops that require reliable water supply would be fewer; Rural economy would decline with flow-on impacts on rural towns (e.g. Ashburton) and Christchurch, and on health, education and other social infrastructure; The opportunities for win-win gains for fisheries and irrigation from storage, such as those from Opuha Dam, would significantly diminish. The halt to the irrigation development would stop the increase in land intensification, reducing the concerns about the risk of water quality issues associated with this increase. It was noted, however, that there are environmental risks associated with dryland farming and particularly with irrigated farming with unreliable water supply. If there is insufficient water to grow a crop to harvest either because of unreliable irrigation or lack of rain not only is the crop wasted (with loss of farm income) but unused fertiliser remains in the soil and can be leached into groundwater or streams in autumn or winter rains. In addition, during fallow or long dry periods in non-irrigated situations, nitrogen in the soil is converted (nitrification) to a soluble form (nitrate) which can be leached from the soil in autumn or winter rains. The relative magnitude of these leaching risks was discussed but no agreement reached. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 17

How people felt about the options At the last meeting the participants individually recorded how they felt about each option on a seven point scale from very positive to very negative, and why. The distribution of scores provides some indication of the relative attractiveness of different options to the group (see below). The diagrams indicate that more of the group were positive about the Lees Valley and Lake Coleridge options and that all were negative towards the option of no storage. Lees Valley Lake Coleridge No storage Waianiwaniwa Valley Stour Valley Strongly positive Neutral Strongly negative Compilation of how individual participants felt about each option on a seven-point scale from strongly positive (green or left bars) to strongly negative (red or right bars). Overall evaluation The Group found positives in all the options particularly the economic development and related social and rural community benefits. They also found negatives in all the options. The evaluation identified that all of the options (Lees Valley, Waianiwaniwa Valley, Lake Coleridge and Stour River) had significant concerns and adverse impacts that would need to be addressed. For some of the Group concerns about the impacts of land intensification and/or river impacts meant all the options evaluated were unacceptable. For others, all options were acceptable. Notwithstanding the concerns, not progressing with water storage was not seen as an option by the Group. Some considered that the way forward was on-farm and/or mediumsize storages within farmland (i.e. outside river valleys). It was felt that these smaller (offchannel) storages would be more readily accepted by the wider public because there would be fewer non-farming objections. Some felt that smaller storage (off-farm but not mega-dam) were not discussed enough. Many on the Group, and the Aqualinc technical advisors, however, believe that only major storage reservoirs (50,000,000m 3 or more) are economically viable. Many on the Group believe that future water demand in mid-central Canterbury can only be met with the addition of major storage reservoirs and an accompanying increase in runof-river abstraction but acknowledge that this should not be at a cost to the environment particularly to in-stream values and water quality although the concerns were not restricted to these. Some of the Group were strongly of the view that water quality issues must be given the same level of scrutiny as those of water quantity and that these concerns need to be addressed before any options are progressed. At least one of the group commented that the evaluation outcome was influenced by the composition of the group mostly male farmers and irrigators. This summary does reflect the full range of views expressed not just those of the majority. It was also noted that the evaluation outcome was influenced by only a few of the group being familiar with the environmental, recreation, cultural, landscape, social and other values of the land and rivers that would be most affected by each option. One person felt that there may not have Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 18

been real depths of thought go into evaluation of environmental, social and cultural impacts. They believe that environment, ecology and other issues not directly related to farming were not given the time they deserve. Exploring an integrated option At the end of the mid-central Canterbury evaluation, the Group recognised that an integrated approach was required that combined some of the storage options in ways that delivered water for new irrigation, maintained flows in the alpine rivers and enhanced flows in other rivers. A description of an integrated option and its evaluation are provided at the end of this report. Group membership mid-central Canterbury evaluation Andy Pearce Chairman Graeme Sutton Irrigation New Zealand Gerry Clemens Waimakariri Irrigation Ross Millichamp Fish and Game Anna Heslop Rural communicator Murray Lane Water Rights Trust Ian Morton (or Michael Oliver) Rangitata South, Orari farmer Kelvin Coe Federated Farmers, Selwyn District Councillor Te Marino Lenihan Ngai Tuahuriri Claire Mulcock Resource Mgt Consultant Bruce Allan, Environmentalist, farmer Ken Hughey Lincoln University Mervyn Gray Retired farmer, fisherman Ian Mackenzie Ashburton Community Trust, Eiffelton Irrigation Scheme John van Polanen Ashburton Lyndhurst Community Development, Selwyn District Ann Jarman Ian Morton Will Nixon Ashburton Lyndhurst Frank Scarf Hydrologist Bruce Ashburton Trading Bob McPherson Society Engelbrecht, Matthew Hall Salmon Anglers Tony Howey Rangitata South, Orari farmer Farm advisor, Ashburton Opuha Irrigation Company Barrhill Irrigation John Wright, Scheme Edith Smith Forest & Bird Michael Morrow Groundwater irrigator Hugh Canard kayaker Don Church, Ashburton Water Trust Peter Howden Environmentalist, farmer David Keely Mayfield Hinds Irrigation Many of the Group were unable to attend all five meetings. Ross Millichamp withdrew from the evaluation process at the start of the fourth workshop, when it became apparent the Lake Coleridge option would require a change to the Rakaia Water Conservation Order. Ross did attend the meeting on an integrated option for mid-central Canterbury (see Section 7). John Donkers, Central Plains Water, was present for the presentation by Aqualinc of the Lees Valley option. Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 19

4 South Canterbury options Summary of options evaluated Irrigated area (ha) 1 Reliability 2 Active storage (Mm 3 ) Average (peak) seasonal volume from Tekapo (Mm 3 ) 1 Opuha dam (current) 16,000 28 (92%) 83-2 Raised Opuha dam (6m) 18,800 23 (93%) 133-3 Opuha (current) + Opihi dam 33,000 22 (93%) 240-4 Tekapo water (5m 3 /s) with current Opuha + Opihi dam (20m operating range) 5 Tekapo water (7.5m 3 /s) with current Opuha + Opihi dam (5m operating range) 6 Tekapo water (9m 3 /s) with current Opuha + Tengawai dam 7 Tekapo water (10m 3 /s) with current Opuha dam 8 Off-channel storage (Stoneleigh Rd, South Opuha) with current Opuha dam + Tekapo water 33,000 14 (96%) 179 48 (130) 33,000 14 (96%) 121 65 (172) 33,000 19 (95%) 98 82 (208) 33,000 15 (96%) 83 94 (227) 33,000 Not modelled 163 (80 + 83) Not modelled 9 Pareora dam 6,250 2 (99%) 54-1 2 potential irrigable area in the Opihi, Opuha and Tengawai Rivers is 41,000ha Number of periods of ten or more consecutive days on irrigation restrictions. Percentage figure in brackets is the proportion of time supply equals or exceeds irrigation demand) Context The area is water short. Climate change may exacerbate this. There is about 41,000ha (net) irrigable land that could be supplied from Opuha, Opihi and Tengawai Rivers. The Opuha dam, commissioned in 1999, currently provides water to irrigate about 14,500ha. Existing irrigators are happy with the reliability of supply to date. Modelling indicates that irrigation supply would be severely restricted in very dry years such as occurred in 1988 with limited winter inflows and high irrigation demand. At such times irrigation restrictions may be in place for more than 90 consecutive days. In the 30-year period from 1972, water supply would have been less than irrigation demand for about 8% of the time. The reliability of the existing Opuha scheme was used as the benchmark for new storage options in South Canterbury. This benchmark is significantly lower than the reliability criteria used when modelling mid-central Canterbury and Hurunui District storage options. The Opuha and Opihi are regionally important trout (particularly) and salmon fisheries. Algal proliferation has been an issue below the Opuha dam and is being controlled by flushing flows. The Opuha dam has benefited fisheries and the lake is a valued recreation resource. The study by Simon Harris, Geoff Butcher and Willie Smith in 2006 showed that the Opuha irrigation scheme has had significant economic impacts on farm and to the district, and positive social changes. Total revenue per hectare for farms supplied by the Opuha scheme was 2.4 times that of comparable dryland farms. Cash surplus as a proportion of total revenue was similar for irrigated and dryland farms but the dollar value of the surplus on the irrigated farms was substantially higher. For the whole scheme the increase in total farm revenues was $40,000,000 per year with a cash farm surplus increase of $12,000,000 per year over a comparable non-irrigated area. Irrigated farms generated Final Report CSWS 3 evaluation of water storage options Hurunui River to Opihi River 20