EVIDENCE OF RICHARD TREVOR de JOUX HEARING THREE ORARI SUB CHAPTER

Transcription

1 BEFORE THE CANTERBURY REGIONAL COUNCIL In the Matter of The Resource Management Act 1991 Between CANTERBURY REGIONAL COUNCIL And ORARI WATER SOCIETY INCORPORATED Submitter EVIDENCE OF RICHARD TREVOR de JOUX HEARING THREE ORARI SUB CHAPTER

2 Introduction 1. My name is Richard de Joux. I am a hydrologist and hydrogeologist with 40 years experience. I hold a Bachelor of Science degree majoring in Geology and a New Zealand Certificate of Science (Civil Engineering option). During my previous employment as a hydrologist with the South Canterbury Catchment Board I carried out many of the flow gaugings and hydrological investigations within the Orari Catchment, and prepared a report on the Water Resources of the Orari River (de Joux, 1980). 2. In 1997 I assisted the Orari River Water Users Group at an Environment Canterbury hearing for replacement resource consents, and I have also provided technical assistance for the Orari Water Society Incorporated (OWS) at the many working parties held by ECan during the Orari River Flow and Allocation Regime review. ). 3. I am presently the Managing Director of Environmental Consultancy Services Ltd, a Company specialising on surface water and groundwater resource investigations, and preparation of resource consents to take and use water. 4. Although this is a regional council plan hearing, I have complied with the code of conduct for expert witnesses contained in the Environment Court s Practice Note dated 1 November 2011 when preparing this evidence. Scope of Evidence 5. My evidence includes: 5.1. Comments on the development of the Orari River flow model prepared by Jen Ritson, including comments on the various assumptions made and agreements or disagreements during the finalising of the model; and 5.2. Comments on the Conjunctive Use Zone concept; and 5.3. Comments on the proposed minimum flows for the Orari River and its tributaries. Summary of findings 6. The Orari River model is a simplification of a complex hydrological system. There is an insufficient period of recorded flow data within the lower Orari River to confirm the accuracy of the predicted naturalised flows, therefore the reported flow statistics need to be considered with caution. 7. The model is an improvement on the model (de Joux & Scarf, 2010) used for the Pareora River flow review, and can best be used to compare various flow regimes and changes in reliability of supply for abstractors rather than being seen as a tool for predicting actual residual flows within the river. 8. I do not believe that the Conjunctive Use method is technically sound, or that the imposition of restrictions on groundwater abstractions during times of low flows will materially improve surface flows within the Orari River. However I realise that the Orari River abstractors, in combination with the Orari River Steering Committee have adopted the concept of the Page 1 of 20

3 Conjunctive Use zone as a management tool. I believe that this is a major concession from the abstractors that needs to be recognised. 9. Given the uncertainty over the effectiveness of restricting abstractions within the Conjunctive Use zone, I believe it is essential that a greater effort is placed on the accurate recording of surface flows within the Lower Orari River and that, in conjunction with accurate water metering of abstractions, a review of the effectiveness of the flow regime is undertaken before implementing the proposed increase in minimum flow 3 years from the Plan becoming operative. 10. Although the minimum flow for Ohapi Creek appears to be low in terms of MALF, it is actually within the range of NES minimum flows for other Canterbury rivers when compared to its Median flow. The Orari River 11. I have prepared maps of the Orari Catchment showing the location of the various sites that I refer to and these are attached as figures 1 to While the Orari River has been described as being unique because it has a significant groundwater/surface water interaction and little storage 1 I do not consider that the Orari is any more unique than the Pareora River (or for that matter the Ashburton River). Both of those rivers also rely on a significant surface water/groundwater interaction and both are heavily committed to abstractive uses. 13. I do however consider that the Orari River is unique in another way, in that it is most likely the youngest river, both hydrologically and geologically in New Zealand. It is well documented that the Orari River flowed southward into the Waihi and Temuka Rivers and did not have a defined channel between (approximately) SH72 and the Coast. The flood event of 1852 caused the river to form its own channel to the Coast in its present location. 14. The river bed is geologically young and very permeable, which is the reason why surface water is lost rapidly into the surrounding groundwater system. It needs to be accepted that the River will never flow continuously over its entire length even under natural conditions. A Gorge flow of at least 3800 l/s 2 is required to maintain surface flow at the SH79 (Upper Orari) Bridge under natural conditions. 15. The River ceases to flow between upstream of SH79 Bridge (between Thatchers and Flatman Roads) to downstream of SH1 Bridge (at or about Ohapi Settlement Road) for significant periods every year. The River is usually dry at SH79 Bridge from early December onwards. 16. Ritson (document titled Orari model assumptions ) shows that under usual flow conditions, approximately 6,000 l/s is lost from the Orari River between the Gorge and upstream of Ohapi Creek. Much of this loss is permanent and primarily recharges Dobies and Ohapi Creek to the south, and groundwater to the north of the River. The river can be classified as intermittently flowing rather than ephemeral in nature, and this has implications on how minimum flows should be set for such water bodies. This will be discussed in more detail by Rachel Dunningham. 1 Orari Steering Group minutes dated 23 February 2012 comments by Lee Burbery 2 Ritson model has a constant natural loss of 3950 l/s between the Gorge and SH72 Bridge Page 2 of 20

4 17. The cessation of abstractions of groundwater that has been derived from river losses will not cause the river to flow over its entire length. Coopers Creek 18. Figures 2 and 4 shows the location of various sites referred to in this section and plates 1 to 11 show the ephemeral nature of a large section of the creek. 19. Coopers Creek receives runoff from the southern slopes of Little Mount Peel via Kowhai and Scotsburn Streams. The present day course of the Creek is shown on maps as a continuous channel flowing approximately parallel to the Orari River course, entering the Orari River below Badham and Canal Roads. The maps give the impression that this is a continuous water course. 20. River drainage control and flood protection works within the lower Scotsburn and Kowhai Streams which were diverted into Coopers Creek in the late 1960 s and early to mid 1970 s have resulted in the upper reaches of Coopers Creek becoming grassed flood ways which only carry water following heavy rainfall events. The usual source of water for Coopers Creek is a series of three springs which arise near Silverton Road at the south eastern boundary of Mr Kerse s property. The location of these is shown in figures 2 and 4. Fed from surrounding shallow groundwater, these springs supply a relatively constant and permanent water flow into Coopers Creek. 21. Since 1 st September 2011, ECan have operated a flow recorder within the Coopers Creek Springs immediately upstream of the confluence with the Coopers Creek channel 3. For the period 1 st September 2011 to 25 th March 2013 the mean, median, and minimum flows were 206 l/s, 151 l/s and 116 l/s respectively. The flows in the Orari River at Gorge for the same period were 13,912 l/s, 7,500 l/s and 2301 l/s. Based on the long term statistics for the Orari at Gorge, the estimated longer term mean and median flows for the Coopers Creek springs are 138 l/s and 125 l/s respectively. 22. Surface flow within upper Coopers Creek is permanently lost naturally to the surrounding unconfined gravel of the Canterbury Plains. Continuous surface flow seldom occurs downstream of SH79 Bridge. During most dry periods, flow ceases below Pit Road while in drought periods, flow ceases below SH72 Bridge. Photos of Coopers Creek at various locations are appended to this evidence. 23. There is no evidence to indicate that the surface flow remains within the existing Creek channel. Depth to water readings from bores adjacent the Creek (K38/0021, K38/0023, K38/0296) indicate that groundwater levels continue to drop after surface flows within the Creek cease. 24. With the exception of times following heavy rainfall events Coopers Creek remains dry for the remainder of its channel to the Orari River. I would classify the reach of Coopers creek from SH79 Bridge to Canal Road as being ephemeral because the Creek bed is perched above the underlying aquifer. The lower part of Coopers Creek immediately below Canal Road maintains permanent flow not through contributions from Coopers Creek itself, but from groundwater recharge within Fitzgerald s Drain which enters the Coopers Creek channel at Canal Road. 25. Given the known flow pattern of Coopers Creek, it is evident that the Creek does not have the hydrological storage within its catchment to maintain permanent flow throughout its channel. Surface flows cease below SH72 in every year, regardless of any abstractions from the Creek or 3 ECan site Coopers Creek Springs at Mulligans Site number Page 3 of 20

5 from surrounding shallow groundwater and, during such times, the Creek has permanent flow for less than 3 km of its total channel length. The Orari River Flow Model 26. A major tool used in the formulation of the proposed Orari River minimum flow regime was an Excel based computer model of the Orari River. I was requested by ECan to review that model and I provided my review on 1 June The critical assumptions within the model relate to the rate of flow loss or gain within specified reaches of the River, and the effect that stream depleting groundwater abstractions might have on the lower River flows. My main concerns regarding the model were: A failure to understand that Coopers Creek is perennially dry between SH79 Bridge and the junction of Farm Road/Canal Road, near the Lower Orari confluence. The model assumes that any groundwater abstracted in the Upper and middle reaches of Coopers Creek reduces the flow in the Lower Orari River, and that by ceasing these abstractions all of that groundwater would re-appear downstream as surface flow. This is inconsistent with section of Burbery & Ritson which states: There are no indications in the piezometric data to suggest Coopers Creek imposes any significant role in the movement of groundwater.for the most part, the groundwater table lies below the stream bed of the main channel of Coopers Creek, and the creek is dry. At these times it is physically impossible for the creek to act as a drainage pathway for shallow groundwater The calculation of stream depletion effects of all groundwater takes within the catchment, regardless of the fact that during low flows, many of these abstractions are located greater than 10km from any surface water body and will not have any significant depleting effect The method used to Naturalise the river flows by assuming that if water was not abstracted at a particular point it would be retained within the River at all downstream sites. This makes no allowance for the considerable natural losses within most reaches of the Orari River. Scarf (2003) recognised this and notes It would be incorrect to assume that were the 780 l/s abstracted by the TDC just downstream from the gorge to be retained instream that the flow at all downstream sites would be increased by the same amount. Clearly a portion of that water would be permanently lost to adjacent unconfined groundwater and springfed streams. Scarf applied a proportional correction downstream for the TDC abstraction A failure to recognise that groundwater from the Orton Plains also recharges the Lower Orari River. Section of Burbery & Ritson shows that groundwater from the Orton plains recharges the lower river. A further assumption in the systems model is that groundwater sourced from the Orton Plain, not the Orari River contributes water to the Orari sub-catchment in its lower reaches about Clandeboye. In order to model this it is assumed that flows measured in Coopers Creek at the recorder site located at the confluence with the Orari River constituted such plains water At the various Orari River flow regime review technical meetings I repeatedly raised these concerns. I note that the latest version of the model (S42A report Appendix 3) now assumes that only 70% of the abstracted water would re-appear. This seems to Page 4 of 20

6 be a very arbitrary number and is still likely to overestimate the impact of abstractions in the lower river A potential double accounting of effects by including the effects of the use of groundwater that has been permanently lost to the river into the model. If the groundwater has been permanently lost it follows that the subsequent use of the groundwater by abstractors will not affect the surface flow of the river. 27. The consequence of the above factors is that the model overstates the amount of effect that groundwater abstractions actually have on the River. This then overestimates the allocation within the catchment and leads to an overly optimistic expectation that restricting groundwater takes will ensure that there will be higher residual flows within the River. 28. After much debate and deliberation at technical meetings, it was agreed to amend the flow model to account for depletion effects at times of lower flows when much of the Orari River ceases to flow. The river was conceptually divided into three reaches as explained by Jen Ritson in a memo dated 3 rd April The revised model was based on: A permanently flowing lower section which includes the Lower Orari below Ohapi Settlement Road, and Lower Coppers Creek An intermittent middle section between Flatman Road and Ohapi Settlement Road. Stream depletion will be calculated to the nearest flowing stream point but with a new distance to the stream. When the Orari River is predicted to be running throughout its length then stream depletion rates will apply to all takes. This will be calculated using the distance to the Orari River A permanently flowing upper section upstream of Flatman Road. Upper Coopers Creek is assumed not to exist and abstractions stream depleting Coopers Creek are assumed to deplete the Orari River based on their distance to the Orari River Stream depletion was calculated using Jenkins equation. 30. With these changes, the model calibrates reasonably well upstream of Ohapi confluence. Because the proposed minimum flow is set at that site, I believe that the amended model will provide a more realistic estimation of flows at that site. 31. Regardless of my concerns about the model, it is likely that any changes in predicted flows within the River from refining the model will most likely be small, therefore rightly or wrongly the model should be accepted, not as a tool to show what the residual flows will be, but as a tool to compare what any changes in flow sharing regimes will have on the reliability of supply for consent holders. In summary: 32. The Orari River model should be accepted as being a simplification of a complex hydrological system. There is an insufficient period of recorded flow data within the lower Orari River 4 to 4 The recorder site u./s Ohapi Creek was only installed in Page 5 of 20

7 confirm the accuracy of the predicted naturalised flows, therefore the reported flow statistics need to be considered with caution. 33. The model is a definite improvement on the model (de Joux & Scarf, 2010) used for the Pareora River flow review, and can best be used to compare the changes in reliability of supply under various flow regimes rather than indicating the residual flows remaining in the river. This is the best that could be done at this time based on the data available. Conjunctive Use zone 34. The minutes of a technical meeting held on 24 th January 2012 note that I expressed concern about using the conjunctive use method, and that any model would need to be modified because including all takes at their maximum rates would overestimate actual effects. Despite comments made at that meeting, the minutes concluded that the Conjunctive Use Zone concept is technically sound 35. I realise that the Orari River flow and allocation regime steering committee have adopted the Conjunctive Use zone approach, however I disagree that the Conjunctive Use zone is technically sound because: The method used to assess depletion is the Jenkins method, which requires, amongst other things, that the stream bed fully penetrates the aquifer. This requirement is to ensure that any groundwater flow between the stream and the aquifer remains horizontal. The use of a 30 metre deep cutoff for bores within the Conjunctive Use zone therefore includes many bores for which the requirements for stream depletion to occur using Jenkins method are not met Section of ECan report R00/11 (Guidelines for the Assessment of Groundwater abstraction effects on Stream Flow) refers to situations when groundwater is significantly deeper than the stream level. In such cases, the natural seepage loss is caused by a hydraulic gradient of 1 ie the flow is vertical and cannot be affected by any further lowering of the groundwater table. The guidelines refer to situations where the depth to water below the stream surface is five times the maximum depth of water in the stream, and also where the depth to groundwater is greater than twice the stream width. In both these cases, any further lowering of groundwater will not increase stream seepage. This situation occurs for most of the groundwater abstractions within the Conjunctive Use zone During normal irrigation season conditions, there is no flowing water within the Orari River between at least SH72 Bridge and Ohapi Settlement Road, therefore stream depletion from groundwater abstraction simply does not occur. 36. For the above reasons, I do not believe that the Conjunctive Use method is technically sound, or that the imposition of restrictions on groundwater abstractions during times of low flows will materially improve surface flows within the Orari River. 37. I understand that the OWS have agreed to adopt the conjunctive use approach and I believe that this concession needs to be fully appreciated and understood by all parties involved in this hearing. In order to obtain consensus within the Orari Steering Committee, the irrigators have conceded a great deal on a concept which has, as yet, not been proven to provide any environmental benefits to the River. Page 6 of 20

8 38. Given the uncertainty over the effectiveness of restricting abstractions within the Conjunctive Use zone, I believe it is essential that a greater effort is placed on the accurate recording of surface flows within the Lower Orari River and that, in conjunction with accurate water metering of abstractions, a review of the effectiveness of the flow regime is undertaken before implementing the proposed increase in minimum flow 3 years from the Plan becoming operative. The proposal is certainly not sophisticated enough to use as a basis for long term changes to abstraction and allocation regimes on the river. 39. I am advised by OWS that the Orari Steering Group have negotiated a review policy with the Department of Conservation as follows. However OWS has included a minor amendment to the policy to reflect the fact that this review is focused on the minimum flows and allocation for the columns labelled 3 years from the plan being operative. The 2040 regime has always been a vision signalling future change. A decision is required when that plan is developed based on much better data and understanding at that time, not as part of this review in 3 years time. At three years from the plan becoming operative, the flow regime set out in Table 15, columns labelled 3 years from operative (excluding the Ohapi catchment) will be reviewed, subject to the requirements below. The purpose of the review is to determine whether the predicted modelling outcomes from June 2012 have been achieved and whether the flow regime specified in Table 15 is safeguarding the aquatic ecological values of the catchment. The outcome of this flow regime review will not provide for the minimum flows identified in Table 15 to be decreased or the allocations limits identified in Table 15 to be increased. The review will include additional data collected from flow monitoring sites within the Catchment, water metering data, and any other scientific data considered relevant. The review will consider - i. the reliability of supply for irrigation currently and in the future ii. actual water use for irrigation, iii. effectiveness of the conjunctive use zone for managing surface and shallow groundwater as one, iv. adverse and/or positive effects on instream values and habitat from current and future water abstractions,. v. whether it is necessary to increase instream minimum flows and decrease allocation as per Table 15 to safeguard the aquatic ecological values of the catchment 40. I consider it is appropriate to include such a policy given the current uncertainty about how the catchment functions and whether the model currently being used provides an appropriate basis for determining on suitable allocation limits and minimum flows. Minimum flows 41. The flow statistics reported by Burbery & Ritson (ECan report R10/36) are based on flow correlations with the long term recorders. While this is a generally accepted hydrological technique, there are a number of constraints to its use. The main constraint is that the flow distribution (flow duration curve) of the primary site should be representative of the secondary site. In rivers that either lose or gain water (such as the lower Orari River), the flow pattern at the downstream site is always influenced by the inflow or outflow of groundwater and can be markedly different to that of the upstream permanently flowing site. Page 7 of 20

9 42. The National Environmental Standard (NES) for minimum flows suggests a flow of 90% of MALF for rivers with median flow less than 5000 l/s and 80% MALF for rivers with median flow greater than 5000 l/s. I note that there has been no further progress with the NES which is on-hold pending consideration of further advice from the Land and Water Forum. At this time the NES has no status under the RMA and has not been gazetted. 43. Table 1 provides flow statistics for some South Canterbury Rivers, compares the ratio of MALF to Median flows, and then shows the NES minimum flow as a percentage of the median flow. Mean Median MALF MALF/Median NES min %Median Ohapi correlated with Waihi % % Ohapi recorder % Orari Gorge % % Orari u/s Ohapi % % Sth Ashburton Mt Somers % % Nth Ashburton Gorge % % Pareora upper Gorge % % Pareora Huts % % Waihao McCulloughs % % Otaio Colliers % % Orari River minimum flow upstream of Ohapi 44. The application of the NES minimum flow for the Orari upstream of Ohapi Creek is not appropriate because the NES method does not account for rivers that are frequently dry upstream (or downstream) of the minimum flow site. The proposal to retain the existing minimum flow of 200 l/s between December to April for a period of 3 years will ensure there is no reduction in existing residual flow over that period. In fact the proposal will improve the existing residual flows because the minimum flows increase to 400 l/s (August-October) and to 900 l/s (May to July). The increase in minimum flow to 500 l/s after 3 years, in combination with flow sharing starting at higher flows will provide even greater protection for residual flows. Coopers Creek minimum flow 45. Until recently, two resource consents for the abstraction of groundwater in upper Coopers Creek were required to cease taking when the flow in Coopers Creek at SH72 Bridge fell to 50 l/s. Given the fact that if the flow at SH72 Bridge is at or below 50 l/s then the Creek will be dry at SH79 Bridge. The benefit of having a minimum flow based at SH72 Bridge is therefore questionable. 46. Table 15 uses a minimum flow site upstream of Ohapi Creek for the imposition of flow restrictions. With the exception of Ohapi Creek and Rhodes Stream abstractions (referred to later in this evidence) all abstractions are treated in the same manner and all have the same degree of equity when restrictions are required. This regime also includes Petries and Lower Coopers creek 47. With the availability of more reliable flow and water use data in the future, it will be possible to review the adequacy and effectiveness of the proposed flow sharing regime. Such a review may show that some abstractions (such as upper Coopers Creek) may better be controlled by a Page 8 of 20

10 minimum flow in the Orari at Gorge, however that may raise concerns about equity of restrictions. Ohapi Creek minimum flow 48. Table 1 shows that while the NES minimum flows for hill country fed rivers are usually between 25% and 42% of their median flows, the NES for the groundwater sourced Ohapi Creek would be 65% of its median flow 49. Ohapi Creek is largely influenced by groundwater inflow, the flow pattern is less variable than the Orari River and the MALF is a significantly higher portion of the median flow (72%) than the hill fed rivers. 50. The proposal is to leave the Ohapi Creek minimum flow regime at the present 570 l/s / 730 l/s flows. If the minimum flow was set to a comparable percentage of median flow for the other rivers shown (ie around the 35% value) it would be 685 l/s, which is similar to the existing minimum flows for Ohapi Creek. 51. So while the minimum flow for Ohapi appears to be low in terms of MALF, it is actually within the usual range of flows when compared to the Median flow. Rhodes Stream 52. Rhodes Stream receives its recharge from groundwater arising upstream of Clandeboye. It flows into the old Orari Lagoon via a drain which, although connected to the Orari River at its mouth, is located downstream of the flow recorder on the Orari River upstream of Ohapi Creek. For that reason, it is not practical to impose restrictions on Rhodes Stream abstractions based on flows upstream of Ohapi Creek. 53. There is presently no available hydrological data on which to base a minimum flow for Rhodes Stream. The S42A report also acknowledges this fact and recommends that the existing minimum flow is retained until sufficient information becomes available to review that flow, and I believe that this is a sensible approach. References Burbery, L; Ritson, J: 2010: Integrated study of surface water and shallow groundwater resources of the Orari catchment. ECan Report R10/36. ISBN March 2010 de Joux, R T; 2011: Review of Orari River Synthetic Flow Model report. de Joux R.; Scarf F. 2010: Review of the hydrology, water allocation and management of the Pareora catchment water resources. ECS Client Report No. ECS09021, January de Joux, R T; 1980: The Water Resources of the Orari River. South Canterbury Catchment Board Publication No. 24. October Page 9 of 20

11 Pattle Delamore Partners Ltd & Environment Canterbury; 2000: Guidelines for the Assessment of Groundwater Abstraction Effects on Stream Flow. ECan Report R00/11. ISBN June 2000 Ritson, J; 2012: Orari model assumptions doc Document prepared and circulated to the Orari River technical group 4 th April Scarf, F; 2003: Low flows of the main stem and tributaries of the Orari and Temuka Rivers and Ohapi Stream. ECan report U03/38. May 2003 Page 10 of 20

12 Figure 1 : Orari River catchment (Source: Ritson 2012) Red lines denote normal extent of naturally dry river bed Page 11 of 20

13 Figure 2: Orari River Location of sites Gorge Recorder Scotsburn/Kowhai Coopers Ck Springs ECan site Flatman Road Dry from here to Ohapi Settlement Road SH79 Bridge Coopers Ck SH72 Coopers Ck SH79 Coopers Ck Belfield Rd SH1 Bridge Page 12 of 20

14 Figure 3 : Orari River - Location of sites SH1 to coast SH1 Bridge Coopers Ck perennially dry SH79 to Canal Road. Ohapi Settlement Road Permanent flow from here to the coast Fitzgeralds Drain Discharges into dry Coopers Ck at Canal Road Canal Road Lower Coopers Ck Petries Creek Orari u/s Ohapi Rhodes Stream Ohapi Creek Page 13 of 20

15 Figure 4 : Coopers Creek Springs Coopers Creek bed (Scotsburn/Kowhai Streams) Silverton Road Combined flow from springs is measured by ECan at site Coopers Creek at Mulligan s prior to entering Scotsburn/Kowhai Stream bed Page 14 of 20

16 Plate 1: Coopers Creek Springs at Mulligan s (ECan site Page 15 of 20

17 Plate 2 : Upper Coopers Creek Scotsburn/Kowhai Stream bed upstream of Spring confluence Plate 3 : Coopers Creek immediately downstream of spring confluence Page 16 of 20

18 Plate 4 : Coopers Creek at SH72 (previous minimum flow site) Plate 5 : Coopers Creek at Orari-Belfield Road Page 17 of 20

19 Plate 6 : Coopers Creek SH1 Bridge Plate 7 : Coopers Creek Burnham Road Page 18 of 20

20 Plate 8 : Coopers Creek Farm Road near Badham Road Plate 9 : Fitzgerald Drain Badham Road Page 19 of 20

21 Plate 10 : Fitzgerald Drain Canal Road entry to Coopers Creek bed Plate 11: Coopers Creek bed, Canal Road above Fitzgerald Drain confluence. Page 20 of 20