STATEMENT OF REBUTTAL EVIDENCE OF Michael James THORLEY

Transcription

1 BEFORE THE BOARD OF INQUIRY IN THE MATTER of the Resource Management Act 1991 AND IN THE MATTER of the Tukituki Catchment Proposal STATEMENT OF REBUTTAL EVIDENCE OF Michael James THORLEY Sainsbury Logan & Williams Ref: Lara J Blomfield Solicitors Fax: Cnr Tennyson Street and Cathedral Lane Phone: PO Box 41 Napier

2 CONTENTS 1. INTRODUCTION Surface water depletion Statement of Evidence of Mr Ian McIndoe Surface water depletion Statement of Evidence of Mr Timothy Baker Assessment of cut off depth Seven day assessment of Direct hydraulic connection Implications of Policy TT Amended Policy TT CONCLUSION...13 EXHIBITS Exhibit MJT R1: Reproduction of Figure 17.6 Ruataniwha Plains aquifer system crosssection (from Luba, 2001: Hawkes Bay. In Rosen, M.R.; White, P.A. ed. Groundwaters of New Zealand. New Zealand Hydrological Society, Wellington. Pp ) Exhibit MJT R2: Map of Ruataniwha Plains and Tukituki River area with bore and crosssection locations Exhibit MJT R3: Cross-section A-A of bore logs in the lower Tukituki River area. Orange intervals indicate deposits of a low permeable nature. Blue intervals indicate deposits of a higher permeable nature Exhibit MJT R4: Cross-section of bore logs in the upper Waipawa River area. Orange intervals indicate deposits of a low permeable nature. Exhibit MJT R5: Cross-section of bore logs in the upper Tukituki River area. Orange intervals indicate deposits of a low permeable nature. Page 2

3 1. INTRODUCTION 1.1 My name is Michael James THORLEY. I work as a Senior Hydrogeologist at Beca Limited. 1.2 My qualifications and experience are as set out in my evidence in chief. 1.3 I reconfirm that I have read and agree to comply with the Code of Conduct for Expert Witnesses in section 5 of the Environment Court s Practice Note (2011). Purpose and scope of evidence 1.4 The purpose of this evidence in rebuttal is to address matters raised in the statements of evidence filed by submitters. 1.5 I do not repeat matters that are addressed in my evidence in chief. However, to assist the Board, where another witness has raised a significant matter that I have already addressed (and on which I have nothing further to add), I provide a cross-reference to my evidence in chief (or to my original technical report that is included in the folders provided to the Board). 1.6 I provide narrative on matters raised by other witnesses only where I consider that what they are saying may not be correct or that it should be qualified in a manner that is not already addressed in my evidence in chief, or adequately covered in the Expert Conferencing Joint Witness Statement Water Science and Hydrology (25 October 2013). 1.7 For the avoidance of doubt, any failure to cross-reference or specifically discuss any matter raised by other witnesses which is covered in my evidence in chief, does not mean I agree with that evidence of the other witnesses. My opinion remains as stated in my evidence in chief and as identified in the expert conferencing statement dated 25 October 2013, except to the extent covered or identified now in this rebuttal brief. 1.8 My evidence will address the following matters: (a) (b) Statement of evidence by Mr Ian McIndoe (Mr Apple), dated 8 October 2013 Statement of evidence by Mr Timothy Baker (Horticulture New Zealand), dated 8 October 2013 Page 3

4 (c) (d) (e) (f) Cut off depth below which surface water depletion is not required to be assessed Seven day assessment for direct hydraulic connection Assessment of surface water depletion and implications for existing users of Policy TT11 Further amendments to Policy TT Surface water depletion Statement of Evidence of Mr Ian McIndoe 2.1 Mr Ian McIndoe of Aqualinc for Mr Apple provided comments on surface water depletion assessments in section 7 of his statement of evidence dated 8 October The issues raised by Mr McIndoe relating to surface water depletion assessments have been discussed and agreed in paragraphs 8 to 16 of the Expert Conferencing Joint Witness Statement Water Science and Hydrology (25 October 2013). 3. Surface water depletion Statement of Evidence of Mr Timothy Baker 3.1 Mr Timothy Baker of SKM for Horticulture New Zealand has completed an initial assessment of surface water depletion and reported this in a statement of evidence dated 8 October The assessment involved collating data describing wells and their distances from surface water bodies, and making calculations of the potential surface water depletion effect. The provisions of the proposed Policy TT11 were then applied to the estimates of surface water depletion to determine the possible implications of Plan Change 6 on existing users. 3.2 Hawke s Bay Regional Council (HBRC) staff sought to work collaboratively with Horticulture New Zealand by instructing Mr Baker and I to complete a joint assessment of surface water depletion. Generally I was in agreement with the method of assessment adopted by Mr Baker, however we could not agree on which wells to include in the assessment. 3.3 Mr Baker took the approach of only including wells in the assessment that are not flagged by a comment field as flowing or non-flow artesian. This approach results in selection of wells that are very shallow (and therefore have the greatest effect on surface water depletion) and deep wells (which will have a very small or negligible effect on surface water depletion). Furthermore, this Page 4

5 approach also ignored shallower wells that may have a greater depletion effect on surface water bodies than deeper wells. 3.4 I inquired as to the origins of the flowing or non-flow artesian comment field from HBRC Groundwater Scientist Mr Simon Harper, and he was uncertain as to the source and reliability of the comment as it was no longer used by Council staff. I raised these concerns with Mr Baker and suggested this approach would produce unreliable results. I obtained the bore log (geological) interval data from Mr Harper of HBRC and loaded it into a 3D viewer to assess the presence of aquitards (layers that might limit groundwater flow) in the Lower Tukituki area that could be used as a depth cut off. Mr Harper and I assessed the data and considered a 40 m cut off to be an appropriate depth limit. However, Mr Baker considered that in the absence of a more comprehensive review of hydrogeological data, he would proceed with his selection criterion. 3.5 The issue of the cut off depth was also discussed at expert witness conferencing. All the relevant experts agreed a depth cut off was an appropriate way of selecting those wells required to complete an initial assessment of surface water depletion (paragraph 10 of Expert Conferencing Joint Witness Statement Water Science and Hydrology). All the relevant experts agreed (except Mr Baker) on a 50 m depth cut off for the entire Plan Change 6 area (paragraph 11 of Expert Conferencing Joint Witness Statement). 3.6 I present bore log (geological) data below in Section 4 that supports the agreed depth cut off of 50 m. 4. Assessment of cut off depth 4.1 Surface water depletion from groundwater pumping will be greatest in shallow wells that draw from geological deposits that are in hydraulic connection with a surface water body. As wells are drilled deeper, the vertical resistance to flow increases (that is, the soil/rock mass between the surface water body and the aquifer that can impede flow increases) and the hydraulic connection with surface water bodies decreases. This is particularly so when low permeability deposits are present between the surface body and the screened section of a well. Therefore, surface water depletion effects need not be assessed for short term management outcomes (such as that outlined in Policy TT11) for deep wells that are likely to have relatively limited hydraulic connection. Page 5

6 4.2 Dravid and Brown (1997) 1 describe a shallow aquifer (<25 m) that is predominantly recharged by the lower Tukituki River. The shallow unconfined system is perched and can be distinguished by fresher blue gravels compared with those laid down by the Ngaruroro River which form part of the Heretaunga Plains Aquifer System. Concurrent surface water flow gauging below Red Bridge suggests a loss of surface water to groundwater in the order of 1.3 m 3 /s. The lower boundary of the shallow aquifer is not precisely defined and is likely to vary across the area. The assessment of a cut off depth needs to be somewhat conservative to ensure it is not set too shallow and allows surface water depletion effects to be unduly discounted from the assessment required under Policy TT Luba (2001) 2 provides a summary of the hydrogeology of the Ruataniwha Plains and a conceptual hydrogeological cross-section. Exhibit MJT R1 shows the recent alluvial deposits of the Ruataniwha Basin described in three main units: Central Plains Unconfined Aquifer; Tukipo Aquitard; and Recent Terrace Group. These units typically overlie the Old Terrace Aquifer Group. The Central Plains Unconfined Group (Luba, 2001) extends to approximately 50 m and is the geological unit in which the hydraulic connection with the rivers will be highest. I consider that if wells are screened below this unit, they are unlikely to cause short-term or near field depletion effects on surface water bodies. 4.4 In addition to examining the conceptualisation of Dravid and Brown (1997) and Luba (2001), Mr Simon Harper of HBRC supplied me with the bore log data for the area covered by Plan Change 6 which includes the Ruataniwha Basin and lower Tukituki areas. The locations of the bore logs and cross-section locations are shown in Exhibit MJT R2. There were nearly 1000 bore records containing approximately 10,000 bore log (geological) interval entries. All of these data were imported into a 3D modelling software package Leapfrog Hydro ( 4.5 The bore log interval data had already been coded into several broad lithology facies based on the major fraction of material described by the drillers logs. There was also a field that provided a brief description of the geological materials encountered. 1 Dravid, P.N.D.; Brown, L.J. 1997: Heretaunga Plains groundwater study. Volume 1: Findings. Hawkes Bay Regional Council, Napier, 278 p. 2 Luba, 2001: Hawkes Bay. In Rosen, M.R.; White, P.A. ed. Groundwaters of New Zealand. New Zealand Hydrological Society, Wellington. Pp Page 6

7 4.6 The coded lithology proved useful for evaluating the presence of aquitards in the lower Tukituki River area. A cross-section through the lower Tukituki is shown in Exhibit MJT R3. The model shows several clay/silt dominated deposits within 50 m (depth) of the land surface which are likely to act as aquitards, noticeably lessening the hydraulic connection between the surface water body and the aquifer system. 4.7 Exhibit MJT R4 and Exhibit MJT R5 show cross-sections along the Waipawa River and the upper Tukituki River respectively. In this area, the lithological coding did not provide useful results, mainly because many of the intervals are described as gravel even though they may be clay bound and act as an aquitard. Therefore, I grouped the data as low permeability deposits, if there were descriptors such as clay, silt, peat and ash recorded. This indicates a more variable distribution of materials than the lower Tukituki area, which is to be expected, and suggest multiple low permeability deposits within 50 m (depth from) of ground surface which will act to lessen the hydraulic connection with surface water bodies. 4.8 Based on the above, I consider a cut off depth of 50 m to be appropriate and sufficiently conservative to ensure potential surface water depletion effects are captured in Policy TT11. If a well is taking groundwater from depths shallower than 50 m, an initial yet more detailed assessment would be required to identify whether surface water depletion is likely to be an issue and requires further assessment under Policy TT All the relevant experts apart from Mr Baker agreed to a 50 m depth cut off. I have included the cut off depth in an updated assessment of surface water depletion outlined in Section 6 and included it in an amended form of Policy TT11 in Section Seven day assessment of Direct hydraulic connection 5.1 Many submitters raised concerns about the implications of take restrictions during minimum flows and the effectiveness of these measures on returning flow to the rivers. The relevant experts agreed that it would be more appropriate to reduce the period used for the assessment of the Direct category of hydraulic connection from 150 days to 7 days (paragraph 16, Expert Conferencing Joint Witness Statement Water Science and Hydrology). Page 7

8 5.2 Reducing the assessment period to 7 days, reduces the number of takes likely to be classified as Direct but does not significantly alter the surface water allocation due to surface water depletion from groundwater pumping. Classifying Direct hydraulic connection over 7 days is also more in keeping with the short term management approach of full take restrictions during minimum flow periods and is likely to show greater benefits to the surface water body during times of restriction. This change to Policy TT11 was agreed by all of the relevant experts. 5.3 I have used the 7 day assessment criterion in an updated assessment of surface water depletion outlined in Section 6 and included it in an amended form of Policy TT11 below in Section Implications of Policy TT I have updated Mr Baker s assessment (dated 8 October 2013) to account for the more recent amendments to Policy TT11 and I have extended it to include the entire area of Plan Change 6. A summary of the updated assessment of surface water depletion from groundwater takes using the amended criteria currently proposed in Policy TT11 (included in Section 7) is set out in Table 1. The calculations are based on the Jenkins 3 method, and use a Transmissivity of 2000 m 2 /day and Storage Coefficient of 0.1. I consider the assessment to be conservative mainly because of the model I have used, and irrigation return water is not included. 3 Jenkins, C.T. 1968: Techniques for computing rate and volume of stream depletion by wells. Ground Water, 6(2), p Page 8

9 Table 1: Summary of surface water depletion and potential implication for users across the Tukituki River Catchment Surface Water Allocation Zone Policy TT11 Total (L/s) (Moderate, High, Direct) Low (L/s) Moderate (L/s) High (L/s) Direct (L/s) Total (L/s) Total Kahahakuri 174 Makaretu 8 Tukipo 84 Surface Water Allocation Zone Policy TT11 Total (count) Low (count) Moderate (count) High (count) Direct (count) Total (count) Total Table 1 identifies a total potential surface water depletion effect of 1446 L/s. Half of this is estimated to occur in Surface Allocation Zone 3 (Upper Tukituki River). The assessment shows that the groundwater takes classified as High and Direct are potentially depleting 856 L/s and 541 L/s respectively, and if they were placed on restriction as currently proposed by Policy TT11 (Section 7), up to ~1 m 3 /sec of surface depletion from groundwater pumping could potentially be mitigated in surface water bodies during minimum flow periods. That seems significant considering the proposed minimum flows of between 3.5 m 3 /sec and 5.2 m 3 /sec at Red Bridge. 6.3 There are 235 wells included in the assessment of surface water depletion. Table 1 also shows the current amended Policy TT11 may affect 109 existing groundwater takes (wells) in the assessment through partial or full restrictions. 26 wells have been provisionally classified as direct or 11% of the total number of wells; 83 have been provisionally classified as high (approximately 35% of the total number of wells) and would potentially be partially restricted, that is, Page 9

10 able to take only half of their consented daily rate of take during minimum flow periods. 6.4 All of the consent holders will have the opportunity to conduct further investigations into the hydraulic connection status or to deepen their wells in order to access groundwater that is less hydraulically connected with surface water bodies. 7. Amended Policy TT Policy TT11 has been amended to take account of expert witness conferencing and I provide the amended and currently proposed version of Policy TT11 below. The main amendments include adding the 50 m depth cut off to Policy TT11 1(a), changing the Direct period from 150 days to 7 days in Table and adding a footnote for the calculation of the pumping rate over 7 days, and adding reference in Policy TT11 1(b) for an acceptable method of calculating surface water depletion, the Hunt (2008) method. 7.2 The updated surface water depletion estimates (from Table 1 in section 6) have now been used to update Table in Policy TT8. Previously, both surface water takes and those takes deemed to be depleting surface water under the current 400 m rule were included under the column Allocation Limits (L/sec). This table has now been updated to include a separate column for surface water depletion from groundwater takes titled Surface water depletion limit from groundwater takes (L/sec) and populated with the values from the surface water depletion assessment that I have described above. The updated Table is provided in the rebuttal evidence of Mr Paul Barrett. Page 10

11 POL TT11 MANAGING GROUNDWATER TAKES HYDRAULICALLY CONNECTED TO SURFACE POL TT11 MANAGING GROUNDWATER TAKES HYDRAULICALLY CONNECTED TO SURFACE WATER BODIES 1. To generally manage assess the effects of groundwater takes on surface water bodies, including wetlands, in the following manner: (a) For wells screened shallower than 50 m below ground level, an initial assessment can be based on a review of well locations, water levels and well lithology records, and the use of an appropriate scientific model using existing or known transmissivity and storativity values to determine whether surface water depletion is likely to be a concern and estimate the potential surface water depletion effects. Wells screened deeper than 50 m are excluded from this Policy; (b) An appropriate scientific method must be used by consent applicants to assess the depletion effect of the groundwater take on nearby surface water In the event that reliable data are not available to make the initial assessment, the applicant will be required to undertake an independent assessment of stream depletion effects using an appropriate scientific method e.g.: using Guidelines for the Assessment of Groundwater Abstraction Effects on Stream Flow prepared by Environment Canterbury (Techniques for evaluating stream depletion effects, Supplement to the guidelines for the assessment of groundwater abstraction effects on stream flow (2000), Report No. R09/53, ISBN ). An acceptable method is the Hunt (2008) 36 method, documented in Hunt (2012) 36A (with the Q_13 function). 2. To generally manage the effects of groundwater takes on surface water bodies, including wetlands, in the following manner: (c)(a) Subject to (a), The potential adverse effects of groundwater takes on surface water depletion shall be managed in accordance with Table 5.9.7; (d)(b) Groundwater takes that are classified as Direct, High or Medium in Table shall be included within the surface water allocation limits described in POL TT8 and POL TT9; (e)(c) Groundwater takes that are classified as High Direct in Table shall be subject to the minimum flow limits in POL TT7 and POL TT9, provided that the predicted reduction in stream depletion that will arise from ceasing the groundwater take will occur within 10 days; (d) Groundwater takes that are classified as High in Table shall be subject to the minimum flow limits in POL TT7 and POL TT9, provided that any predicted reduction in stream depletion that would arise from ceasing the groundwater take would occur within 10 days, except that irrigation takes shall be able to continue to take up to 50% of the daily volume as specified in their consent conditions for the period when flows are at or below the minimum flow. 36 Hunt, B. (2008). Stream depletion for streams and aquifers with finite widths. ASCE Journal of Hydrologic Engineering, Vol. 13, No. 2, A Hunt, B (2012): Groundwater analysis using function.xls. Prepared by Civil Engineering Department, University of Canterbury Page 11

12 Table 5.9.7: Management of Surface Water Depletion Effects Classification of Magnitude of surface water depletion effect surface water depletion effect Direct The surface water depletion effect is assessed as: (a) 90% or greater of the average groundwater pumping rate 37 after days of pumping; and (b) greater than 2 L/s. High Medium The surface water depletion effect is assessed as: (c) 50% 60% or greater and less than 90% of the average groundwater pumping rate 37B after days of pumping; and (d) greater than 1 2 L/s. The surface water depletion effect is assessed as: (a) 20% or greater and less than 50% 60% of the average groundwater pumping rate 37B after days of pumping; and (b) greater than 1 2 L/s. Management approach The calculated loss of surface water is included in the surface water allocation regime, and specific minimum flow restrictions are imposed on the groundwater take, subject to the proviso in POL TT11(2)(c). The calculated loss of surface water is included in the surface water allocation regime, and specific minimum flow rate of take / volume restrictions are imposed on the groundwater take, subject to the proviso in POL TT11(1)(d) in accordance with POL TT11(2)(d). The calculated loss of surface water is included in the surface water allocation regime, but no specific minimum flow or rate of take restrictions are imposed on the groundwater take. Low The surface water depletion effect is assessed as: (a) less than 20% of the average groundwater pumping rate 37B after days of pumping; or (b) 1 2 L/s or less. The calculated loss of surface water is not included in the surface water allocation regime, and no specific minimum flow or rate of take restrictions are imposed on the groundwater take. 37 The average groundwater pumping rate is based on the lesser of the daily rate assuming pumping occurs for 24 hours per day or the 7 day volume averaged over 7 days assuming pumping occurs for 24 hours per day B The average groundwater pumping rate is based on the seasonal or annual volume averaged over 150 days or full year whichever is applicable assuming pumping occurs for 24 hours per day. Page 12

13 8. CONCLUSION 8.1 Having reviewed the evidence of the witnesses listed in paragraph 1.8 I wish to amend the opinions and conclusions expressed in my evidence in chief as follows: (a) I now recommend that Policy TT11 be amended as set out in paragraph 7.1 and pages 11 and 12 of this rebuttal evidence; and Michael Thorley 8 November 2013 Page 13

14 EXHIBITS Exhibit MJT R1: Reproduction of Figure 17.6 Ruataniwha Plains aquifer system cross-section (from Luba, 2001: Hawkes Bay. In Rosen, M.R.; White, P.A. ed. Groundwaters of New Zealand. New Zealand Hydrological Society, Wellington. Pp ) A A B B C C Exhibit MJT R2: Map of Ruataniwha Plains and Tukituki River area with bore and cross-section locations Page 14

15 A A Exhibit MJT R3: Cross-section A-A of bore logs in the lower Tukituki River area. Orange intervals indicate deposits of a low permeable nature. Blue intervals indicate deposits of a higher permeable nature B B Exhibit MJT R4: Cross-section of bore logs in the upper Waipawa River area. Orange intervals indicate deposits of a low permeable nature. Page 15

16 C C Exhibit MJT R5: Cross-section of bore logs in the upper Tukituki River area. Orange intervals indicate deposits of a low permeable nature. Page 16