Lower southern tributaries – mining privileges

Report No. R21/10 ISBN 978-1-99-002743-7 (print) 978-1-99-002744-4 (web)

Jen Dodson

May 2021

Lower Waitaki River southern tributaries – mining privileges

Report No. R21/10 ISBN 978-1-99-002743-7 (print) 978-1-99-002744-4 (web)

Jen Dodson

May 2021

Name Date Prepared by: Jen Dodson 27/7/20 Senior Scientist - Hydrology Reviewed by: Suz Gabites 16/10/20 Team Leader - Hydrology External review by: Mark Megaughin - Beca 10/2/21 Approved by: Fiona Shanhun 17/5/21 Chief Scientist

Report No. R21/10 ISBN 978-1-99-002743-7 (print) 978-1-99-002744-4 (web)

200 Tuam Street PO Box 345 Christchurch 8140 Phone (03) 365 3828 Fax (03) 365 3194

75 Church Street PO Box 550 Timaru 7940 Phone (03) 687 7800 Fax (03) 687 7808

Website: www.ecan.govt.nz Customer Services Phone 0800 324 636

Lower Waitaki River southern tributaries – mining privileges

Executive summary

Background: From 1874 to 1960, mining privileges to take water for gold mining purposes were granted without any minimum flow conditions in and a small part of Canterbury. When the Resource Management Act (RMA) came into force in 1991, these privileges were converted into deemed permits which were set to expire in 30 years. The deemed permits are coming up for renewal in 2021 and will for the first time be subject to minimum flow conditions in accordance with the Waitaki Catchment Water Allocation Regional Plan (WCWARP).

The problem: There are currently 23 deemed permits without minimum flow conditions in the Lower Waitaki River southern tributaries catchments including the Awakino River, Kurow River, Otiake River, and the Otekaieke River. To determine the appropriate minimum flow conditions for permit renewal under the WCWARP, we need to calculate the natural 1 in 5-year 7-day low flow, 7-day mean annual low flow [MALF (7d)], and mean flow for each river.

What we did: Our field team conducted 16 sets of concurrent gaugings at various sites along the four rivers. We naturalised these gaugings using available or estimated water usage data. We then correlated the spot gauging sites with long-term flow recorder sites, creating regression relationships between the sites. We determined the flow statistics 1 in 5-year 7-day low flow, MALF(7d), median, and mean for the recorder sites and applied the regression relationships to calculate the same flow statistics at the gauging sites. These flow statistics were then used to develop minimum flow values. We mapped the extent of dry reaches in the Kurow, Otiake and Otekaieke rivers using current and historical aerial images available on Google Earth to investigate the suitability of minimum flow locations.

What we found: There are 14 consents and 23 deemed permits to take water from the Awakino, Kurow, Otiake, and Otekaieke rivers. Flow recorder data are available at locations upstream of all water take consents from the Otekaieke and Maerewhenua (adjacent to the Otekaieke) rivers for 32 and 50 years, respectively. In addition, there are recorders on the Awakino and Kurow rivers at the downstream end of their catchments at SH83. Most of the gauging sites correlate well with the Otekaieke recorder. The Otiake River at lower gorge is the exception to this and better correlates with the Maerewhenua River.

The Kurow, Otiake, and Otekaieke rivers are all naturally dry at SH83 under both MALF(7d) and the 1 in 5-year 7-day low flow conditions. The WCWARP does not limit allocation on these individual rivers. All four rivers are currently over-allocated with respect to the Land and Water Regional Plan (LWRP) rules. Water usage is high for most of the consents compared to the rest of Canterbury. The current minimum flows on some consents on the Awakino, Otiake, and Otekaieke rivers are roughly in line with the 1 in 5-year 7-day low flow measured further up the catchment.

What does it mean? The 1 in 5-year 7-day low flow, MALF(7d) and mean flow values determined for each river can be used to inform minimum flow conditions when considering the replacement of the deemed permits. As the Kurow, Otiake, and Otekaieke rivers are all naturally dry under MALF(7d) and 1 in 5-year 7-day low flow conditions at the lower ends of the catchments, the minimum flow values should be set higher up the catchments in the flowing reaches as recommended by Policies 3-5 of the WCWARP.

How we have considered climate change: NIWA’s climate change report projects this area will see an increase in temperature along with a decrease in summer rainfall and an increase in winter rainfall. This will lead to reduced river flows, and along with impacts on environmental flows and associated habitat and biodiversity, irrigators will be placed into restriction more often.

Environment Canterbury Technical Report i Lower Waitaki River southern tributaries – mining privileges

ii Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

Table of contents

Executive summary ...... i

1 Introduction ...... 1

2 Waitaki Catchment Water Allocation Regional Plan (WCWARP) ...... 1

3 Method ...... 2 3.1 Data availability ...... 2 3.1.1 Flow recorders and gauging sites ...... 2 3.1.2 Naturalising gaugings ...... 4 3.1.3 Dry reach mapping ...... 4

4 Analysis ...... 6 4.1 Awakino River ...... 6 4.2 Kurow River ...... 10 4.3 Otiake River ...... 14 4.4 Otekaieke River ...... 17

5 Climate change ...... 22

6 Results ...... 23

7 Summary and next steps ...... 25

8 References ...... 26

Appendix 1: River gaugings ...... 27

Appendix 2: Low flow frequency analysis ...... 29

Appendix 3: Dry reach mapping using Google Earth ...... 31

Environment Canterbury Technical Report iii Lower Waitaki River southern tributaries – mining privileges

List of Figures

Figure 3-1: Flow recorder and gauging locations for the Lower Waitaki River southern tributaries (Awakino River to Maerewhenua River) ...... 3 Figure 3-2: Example Google Earth imagery of Otekaieke on 4/7/19 showing the river flowing until upstream of SH83 ...... 5 Figure 3-3: Example Google Earth imagery of Otekaieke on 3/10/2019 for bottom part of image but 4/7/19 for top part of image showing the river flowing to the edge of the image ...... 5 Figure 3-4: Dry reaches of the lower Waitaki southern tributaries...... 6 Figure 4-1: Flow recorder, gauging, dry reaches, historical and current surface water take consent locations for the Awakino River ...... 7 Figure 4-2: Awakino River flow data at SH83 ...... 7 Figure 4-3: Awakino River usage data (1/1/10-31/1/20) ...... 8 Figure 4-4: Awakino River usage data as a percentage of the consented rate (1/1/10-31/1/20) ...... 9 Figure 4-5: Correlation of Awakino River at SH83 with Otekaieke River at upstream weir ...... 9 Figure 4-6: Comparison of recorded Awakino River flows at SH83 with flows derived by regressions ...... 10 Figure 4-7: Correlation of Awakino River East Branch at above upper intake with the recorder at SH83 ...... 10 Figure 4-8: Flow recorder, gauging, dry reaches, historical and current surface water and groundwater take consent locations for the Kurow River ...... 11 Figure 4-9: Hydrograph for the Kurow River at SH83 ...... 11 Figure 4-10: Kurow River usage data (1/1/10-31/1/20) ...... 12 Figure 4-11: Kurow River usage data as a percentage of the used consented rate (1/1/10- 31/1/20) ...... 12 Figure 4-12: Correlation of the Kurow River at Gorge with the Otekaieke River at upstream weir .... 13 Figure 4-13: Correlation of the Kurow River at Curries with the Otekaieke River at upstream weir .. 13 Figure 4-14: Correlation of the Kurow River at SH83 with the Otekaieke River at upstream weir ..... 14 Figure 4-15: Gauging, dry reaches, historical and current surface water take consent locations for the Otiake River ...... 15 Figure 4-16: Otiake River usage data (1/1/10-31/1/20) ...... 16 Figure 4-17: Otiake River usage data as a percentage of consented rate (1/1/10-31/1/20) ...... 16 Figure 4-18: Correlation of Otiake River at Lower Gorge with Maerewhenua River at Kellys Gully .. 17 Figure 4-19: Correlation of Otiake River at Mt Bell Station with the Otekaieke River at upstream weir ...... 17 Figure 4-20: Flow recorder, gauging, dry reaches, historical and current surface water and groundwater take consent locations for the Otekaieke River ...... 18 Figure 4-21: Hydrograph for Otekaieke River at upstream weir (2013-2019) ...... 18 Figure 4-22: Otekaieke River usage data (1/1/10-31/7/19) ...... 20 Figure 4-23: Otekaieke River usage data as a percentage of consented rate (1/1/10-31/7/19) ...... 20 Figure 4-24: Correlation of Otekaieke River at Eastern Road Bridge with the upstream weir ...... 21 Figure 4-25: Correlation of Otekaieke River at SH83 with the upstream weir ...... 21 Figure 5-1: Otekaieke ALFs and the IPO index ...... 22

iv Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

List of Tables

Table 2-1: Waitaki Catchment Water Allocation Regional Plan limits ...... 1 Table 3-1: Recorder and gauging locations in the investigation ...... 2 Table 4-1: Current deemed permits and post-RMA water take consents in the Awakino River ...... 8 Table 4-2: Current deemed permits in the Kurow River ...... 12 Table 4-3: Current deemed permits and post-RMA water take consents in the Otiake River ...... 15 Table 4-4: Current deemed permits and post-RMA water take consents in the Otekaieke River ... 19 Table 6-1: Regression results and calculated MALF(7d), 1 in 5-year 7-day low flow, and median values ...... 24 Table 6-2: Regression results and calculated mean values ...... 24 Table 6-3: Allocation and minimum flows with respect to MALF(7d) and 1 in 5-year 7-day low flow values ...... 25

Environment Canterbury Technical Report v Lower Waitaki River southern tributaries – mining privileges

vi Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

1 Introduction There are currently 23 consents granted in the Lower Waitaki River southern tributaries catchments that are existing mining privileges (also referred to as deemed permits). They were originally granted between 1874 and 1960 to take water without any minimum flow conditions on the rivers. The rivers with deemed permits are (from west to east): • Awakino River • Kurow River • Otiake River • Otekaieke River.

These consents are expiring and are collectively coming up for renewal in October 2021 and will for the first time have minimum flow restrictions applied. These will be in accordance with the Waitaki Catchment Water Allocation Plan (WCWARP).

The purpose of this report is to present these consents and, along with consents that have been granted later (under the Resource Management Act), show their impact on the natural flows of these four rivers by calculating naturalised flow statistics for assisting with a limit setting process.

2 Waitaki Catchment Water Allocation Regional Plan (WCWARP) The WCWARP provides environmental flow regimes which apply to the rivers of the Lower Waitaki River southern tributaries catchments: • the Awakino River is given a minimum flow but not an allocation limit (Rule 2-Table 3B xviii) • the other rivers are subject to the “All other rivers and streams” rule (Rule 2-Table 3B xxii) in the WCWARP which sets a minimum flow of the 1 in 5-year 7-day low flow at the downstream end of the catchment, but again no allocation limit (Table 2-1).

All water takes that exceed 10 m3 per day at rate greater than or equal to 0.005 m3/s require resource consent.

Table 2-1: Waitaki Catchment Water Allocation Regional Plan limits Allocation Flow sharing Minimum flow River Limit threshold (m3/s) (m3/s) (m3/s) 0.4 Oct-Apr Awakino River at SH83 None 1.0 0.5 May-Sep All other rivers and 1 in 5-year 7- None Mean flow streams day low flow

The WCWARP defines the flow-sharing threshold as any water taken, diverted, dammed or used pursuant to the flow-sharing regime in addition to the allocation limit. We take this to mean a B block with a B minimum flow of 1.0 m3/s for the Awakino and the mean flow for all other rivers and streams, with takes sharing the flow with the river on a 1:1 basis. As there is no A block limit, it is not apparent when a B block should be implemented. The supporting Section 32 report says “flow-sharing enables a proportion of the water flows and levels to be allocated to activities supporting people and communities social, economic and cultural wellbeing and health and safety”.

Environment Canterbury Technical Report 1 Lower Waitaki River southern tributaries – mining privileges

3 Method

3.1 Data availability

3.1.1 Flow recorders and gauging sites Three of the rivers have rated water level (flow) recorders installed. However, the recorders for the Awakino and Kurow rivers only have approximately one year of data. The Otekaieke River recorder has 25 years of data from 1970 to 1995; it was reinstalled in February 2013 and so has seven recent years of data. We have also included the Maerewhenua River (an adjacent catchment) in the analysis as a primary site which has had a recorder at Kelly’s Gully since 1970.

The Otekaieke and Maerewhenua flow records are not affected by consented abstractions, i.e. the flow is natural. The Awakino and Kurow records are affected by all the abstractions in their catchments as they are located at the downstream end at SH83. The Otekaieke and Maerewhenua flow records are used to generate flow statistics (7-day mean annual low flow [MALF(7d)], 1 in 5-year 7-day low flow, median, and mean). The MALF(7d) is calculated by first taking a seven-day rolling daily mean for the entire flow record. Then the minimum value per water year is taken as the 7-day annual low flow (ALF(7d)). Finally, the mean of all ALFs(7d) is then used as the MALF(7d). A minimum of at least 10 years of flow data is recommended for the final calculation of MALF(7d) to ensure a representative aggregate mean. The 1 in 5-year 7-day low flow is taken from the low flow frequency analysis of the ALFs(7d) using the Log Pearson 3 distribution to determine that flow which is likely to occur once every five years (see Appendix 2). The median and mean values are daily values from the entire record.

We set up a gauging run in early 2018 at eight other sites on the rivers. To date, 16 sets of gaugings have been carried out since January 2018. Many other historical gaugings are also available and were used in the analysis. The gauging sites are shown in Table 3-1 and Figure 3-1 along with the recorders. The gauging results and hydrographs from the permanent recorders are shown in Appendix 1. Table 3-1: Recorder and gauging locations in the investigation Site Recorder data # Date range of number available gaugings gaugings Awakino River East 1711458 No 12 29/1/2018-10/9/2019 Branch at above upper intake Awakino River at SH83 71105 7/6/1986-6/6/1988 107 23/7/1977-23/11/2020 9/11/2018-current Kurow River at gorge 1841 No 41 16/8/1971-2/3/2020 Kurow River at Curries 2367 No 53 2/6/1971-2/3/2020 Kurow River at SH83 171147 23/5/2018-28/4/2020 48 29/11/1976-29/4/2020 Otiake River at Lower 71111 No 142 24/8/1971-16/12/2020 Gorge Otiake River at Mt Bell 1711435 No 63 30/7/2015-16/12/2020 Station Otiake River at SH83 1711453 No 15 29/1/2018-2/3/2020 Otekaieke River at 71178 18/12/1970-29/6/1995 242 26/7/1984-16/12/2020 upstream weir 31/1/2013-current Otekaieke River at 171159 No 20 25/7/2003-10/9/2019 Eastern Road Bridge Otekaieke River at SH83 1711011 No 27 25/7/2003-2/3/2020 Maerewhenua River at 71106 5/3/1970-current 816 18/6/1968-10/12/2020 Kelly’s Gully

The gaugings were conducted during recessions. The hydrographs show that the recorder data fit the gaugings well. When we looked at low flows, we only used gaugings that are below the median flow in

2 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

the regression analysis in accordance with the guidance of Henderson et al. (2003). Of the recent gaugings, this ruled out between three and five of the 16 sets of gaugings, and unfortunately left the Kurow with only gaugings measuring zero flow. When we correlated sites for mean flow analysis, we used all the gaugings. Since we are fortunate enough to have a large number of concurrent gaugings, we have only used gaugings in the regressions rather than recorder data. The number of gaugings used are shown in the results section. The regressions are then used to calculate the flow statistics for the gauged sites.

Figure 3-1: Flow recorder and gauging locations for the Lower Waitaki River southern tributaries (Awakino River to Maerewhenua River)

Environment Canterbury Technical Report 3 Lower Waitaki River southern tributaries – mining privileges

3.1.2 Naturalising gaugings In order to determine the natural flows we need to naturalise the gaugings. We do this by adding back the takes to the gaugings. We know the takes that impact the gaugings from the consented allocation and the water usage data. We only naturalised flowing gaugings.

Consented allocation The consented allocation is the sum of the maximum consented surface water takes and the stream depletion component of shallow groundwater takes. There is only one active groundwater take in the area as calculated at 17/12/20 (in the Otekaieke catchment). Table 4-1 to 4-4 show the consents that have been granted as deemed permits (not shaded) along with consents granted later, post-RMA (shaded grey). Minimum flows and availability of usage data are also shown in the tables.

Historical consents Since the concurrent gaugings date back to 1973 in the case of the Kurow River, we also need to look at historical consents which have since expired and not been renewed. The locations of these are shown in Figures 4-1, 4-8, 4-15, and 4-20.

Water usage data Table 4-1 to 4-4 also list whether there is water usage data available for the Water Abstraction Point (WAP). Out of 21 WAPS, one (CB17/5025) does not have data available because it is listed as a diversion consent. Legally, water usage data does not need to be supplied for diversion consents. This particular WAP is actually a take and as such should be recoded so that it is required to be metered. There are also six inactive consents. The three other consents that do not have data available are to take <5 L/s and so do not have a legal requirement to be metered.

The earliest available water use data are from 2010 and not all consents have data available from that date. Therefore, in order to naturalise the gaugings prior to data being available, we need to estimate the usage. We estimated usage using a combination of those developed with the Naturalisation methodology/tool Version 2 (Kittridge, 2020)1 and, where these estimates are unavailable, 50% of the average rate of take during the irrigation season (October – April) for irrigation consents and 50% of the average rate of take all year round for stockwater and public water supply consents. Restrictions due to minimum flows are factored into the estimated usage data. The usage data (both actual and estimated) for 2010-2019 is shown in Figures 4-3, 4-10, 4-16, and 4-22.

3.1.3 Dry reach mapping It is known that the Kurow, Otiake, Otekaieke, and Maerewhenua all commonly go dry at certain points. The Kurow, Otiake, and Otekaieke all go dry around SH83. There does not appear to be flow resurfacing between SH83 and the Waitaki River confluences. These sites would typically be the designated minimum flow sites according to the WCWARP but since they go dry, they are not ideal. We have mapped the dry reaches in these rivers using Google Earth to determine the extent of the dry reach. The Awakino River is understood to flow the full length; this is confirmed by Google Earth imagery.

Google Earth has up to 15 images for each of the rivers. These images commence in April 2003 and are reasonably frequent from 2018 to February 2020, although not frequent enough to sufficiently determine temporal variation.

Mostly it is easy to determine if the river is flowing (Figure 3-2) but occasionally, if the satellite is directly overhead, the river reflects the light rather than showing up dark and so cannot be so easily determined. An example of this is that on 4/1/19, 0.129 m3/s was recorded on the Kurow River at SH83 yet this is not visible on Google Earth. Another issue with the chosen methodology is that Google Earth doesn’t necessarily have the whole river length in one image. In February 2020, images of the Kurow River end 3.9 km upstream of SH83 and jump to a later image where the river is flowing. Similarly, for the Otekaieke River, the 3/10/2019 image jumps to the 4/7/2019 image at roughly the same location as the river started to dry in 4/7/2019 (Figure 3-3).

1 The script estimates usage based on the known usage of nearby consents.

4 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

Start of dry reach

Figure 3-2: Example Google Earth imagery of Otekaieke on 4/7/19 (note imagery date is written mm/dd/yyyy) showing the river flowing until upstream of SH83

Flowing at edge of image

Figure 3-3: Example Google Earth imagery of Otekaieke on 3/10/2019 for bottom part of image but 4/7/19 for top part of image (note imagery date is written mm/dd/yyyy) showing the river flowing to the edge of the image

Environment Canterbury Technical Report 5 Lower Waitaki River southern tributaries – mining privileges

We have mapped the most commonly dry reaches and these are shown in Figure 3-4, and are summarised in Appendix 3.

Figure 3-4: Dry reaches of the lower Waitaki southern tributaries

4 Analysis

4.1 Awakino River The Awakino catchment has the highest terrain in the Lower Waitaki area (Mt Kohurau 2010 m). This is likely to give more orographic rainfall and snowfall in the top of the catchment, compared with adjacent catchments (Gabites and Horrell, 2005). 28% of the catchment is above the winter snow level of 1372 m (Young, 1983). The river flows at the surface along its full length, all year round. MWD (1984) state that ‘the Awakino is different. Its summer flow is generally greater than that in the Otekaieke River although the catchment is smaller’ and ‘the few gaugings made in winter or late autumn showed less flow in the Awakino than Otekaieke’. Figure 4-1 shows the catchment with the gauging and recorder sites and the locations of the takes.

6 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

Figure 4-1: Flow recorder, gauging, dry reaches, historical and current surface water take consent locations for the Awakino River Boraman Consultants installed a recorder at SH83 for consent holders in late 2018 (Figure 4-2).

Figure 4-2: Awakino River flow data at SH83 There is a total of 0.474 m3/s water takes currently consented across seven consents (see Table 4-1). Four earlier consents were active between 1969 and 2006 but have since expired without being renewed. There are five mining right consents taking water from three WAPs (totalling 0.395 m3/s), two of which are inactive (I40/0631 and I40/0634). I40/0634 had a temporary waiver (because it was not used and therefore did not need to have a meter) in 2013. This WAP has since been confirmed as not being used thereafter. There are also two post-RMA consents under different WAPs with usage data.

Environment Canterbury Technical Report 7 Lower Waitaki River southern tributaries – mining privileges

Table 4-1: Current deemed permits and post-RMA water take consents (shaded grey) in the Awakino River

Rate Minimum River Consent WAP Consent Holder Usage data (m3/s) flow (m3/s)

Goldwyn Farming Company CRC062320 0.099 I40/0551 Limited Yes Awakino River CRC062327 Awakino Station Limited 0.099 deemed No CRC062314.1 0.085 No, inactive permits I40/0634 Awakino Station Limited CRC062331.1 0.056 No, inactive CRC062337 I40/0631 Station Limited 0.056 No, inactive Awakino River CRC203692 I40/0550 Awakino Station Limited 0.054 0.400 Yes post-RMA consents CRC180497 I40/0579 Turner-Heaton & Scott 0.025 Waitaki Yes Awakino River total consented allocation 0.474

There is therefore a total of three WAPs which all have data available from 2014 (see Figure 4-3 and as a percentage of consented rate in Figure 4-4). The estimate for I40/0551 in 2010 has been reduced from 50% of the maximum rate to 0.080 m3/s (40%) to fit with the usage of the following five years. The maximum usage for I40/0551 (blue in Figure 4-3 and Figure 4-4) was 72% of the consented rate, over 100% for I40/0550 (orange), and 93% for I40/0579 (grey). This suggests a non-compliance issue with I40/0550 in the past.

Figure 4-3: Awakino River usage data (1/1/10-31/1/20)

8 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

Figure 4-4: Awakino River usage data as a percentage of the consented rate (1/1/10-31/1/20)

There are two gauging sites on the Awakino River for which naturalised flow statistics can be produced; SH83 and East Branch.

As per Gabites and Horrell (2005), because of the impact of winter rain and snow, we removed gaugings done between May to September for the Awakino River at SH83. This leaves 15 gaugings for SH83 and 12 gaugings for the East Branch upon which to base a regression.

The correlation of the Awakino River at SH83 with the Otekaieke River at upstream weir used gaugings from 2013 onwards where there is good usage data available. Only four of the gaugings were naturalised with an assumed 50% usage for I40/0579 (unfortunately the Kittridge script did not estimate usage for I40/0579; we do not know why); all other WAPs had usage data, and so the naturalised correlations are not too much weaker (lower r2 value) than gauged regressions (Figure 4-5). There are seven higher flow gaugings included in the regression for mean flows (two of these had an assumed 50% usage for I40/0579) (Figure 4-5). The correlations are weaker if we only consider the more recent gaugings with usage data. The low flow regressions predict the flows reasonably well at low flows – a comparison of flows is shown in Figure 4-6.

Figure 4-5: Correlation of Awakino River at SH83 with Otekaieke River at upstream weir

Environment Canterbury Technical Report 9 Lower Waitaki River southern tributaries – mining privileges

Figure 4-6: Comparison of recorded Awakino River flows at SH83 with flows derived by regressions

The East Branch correlates strongly with the recorder on the Awakino at SH83 (Figure 4-7). All the gaugings at SH83 had actual usage data available to naturalise them. There were too few gauging pairs available below the median flow to undertake a robust correlation with the Otekaieke River at upstream weir. Including the high flows but removing the May to September flows left only seven gauging pairs which had a good correlation with the Otekaieke and produced a similar mean flow (within 10% difference).

Figure 4-7: Correlation of Awakino River East Branch at above upper intake with the recorder at SH83

4.2 Kurow River The Kurow gains a small amount of flow (approximately 0.050 m3/s) between the gorge and Curries Road but then large losses (up to 0.300 m3/s) naturally occur between Curries and the SH83 bridge, resulting in the river being naturally dry at SH83 under MALF(7d) and 1 in 5-year 7-day low flow conditions. Google Earth shows the river to often be dry from upstream of Settlement Road to the Waitaki River confluence (Figure 4-8). Two of the expired consents took up to 0.167 m3/s 900 m upstream of SH83 between 1969 and 2006. There is no record to say why the consents were not renewed. The recorder at SH83 shows that over the 1.5 years of record available, the river is dry for much of the time

10 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

(Figure 4-9). Because of this, many of the gaugings were dry and correlate poorly with both the Otekaieke and Maerewhenua rivers.

Figure 4-8: Flow recorder, gauging, dry reaches, historical and current surface water and groundwater take consent locations for the Kurow River

Figure 4-9: Hydrograph for the Kurow River at SH83 There is a total of 0.230 m3/s water currently consented to be taken by deemed permits across eight consents (see Table 4-2). Two further deemed permits were surrendered in 2009 and seven more recent consents were active between 1969 and 2009 (with a maximum allocation of 0.673 m3/s in 2001).

Environment Canterbury Technical Report 11 Lower Waitaki River southern tributaries – mining privileges

Table 4-2: Current deemed permits in the Kurow River

Minimum Rate River Consent WAP Consent Holder flow Usage data (m3/s) (m3/s) CRC062354 Goldwyn Farming 0.017 No, inactive CRC062346 Company Limited 0.006 CRC136473 Irving 0.028 Kurow River CRC140602 0.016 I40/0626 No deemed permits CRC140594 0.028 Yes CRC140587 Westmere Farm Limited 0.056 CRC153793 0.028 CRC140608 0.051 Kurow River total consented allocation 0.230

All eight current deemed permits use the same WAP which has usage data from the end of 2015, although two permits are inactive (Figure 4-10). The maximum usage from the WAP is 91% of the total used consented rate (Figure 4-11). The correlations used gaugings from 2018 onwards since concurrent gaugings for the gorge and Curries sites are not available earlier and only dry gaugings are recorded at SH83 prior to 2018. Usage data for naturalising the flows are therefore available.

Figure 4-10: Kurow River usage data (1/1/10-31/1/20)

Figure 4-11: Kurow River usage data as a percentage of the used consented rate (1/1/10-31/1/20)

12 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

There are two gauging sites on the Kurow River for which naturalised flow statistics can be produced; Gorge and Curries.

The Kurow River is unaffected by abstractions at both the gorge and at Curries and flows at both sites correlate well with the Otekaieke River at upstream weir (Figure 4-12 and Figure 4-13). Therefore, gauged flows are reflective of natural flows. Including the higher flows for the mean flow regressions incorporates an additional two and three gaugings respectively (Figure 4-12 and Figure 4-13). The gauged flow at the SH83 recorder on the Kurow River also correlates with the Otekaieke River when higher flows are included but not when considering flows less than median flow (0.072 m3/s) because many of the gaugings are dry during these times (Figure 4-14). This relationship is therefore not suitable for determining low flow statistics.

Figure 4-12: Correlation of the Kurow River at Gorge with the Otekaieke River at upstream weir

Figure 4-13: Correlation of the Kurow River at Curries with the Otekaieke River at upstream weir

Environment Canterbury Technical Report 13 Lower Waitaki River southern tributaries – mining privileges

Figure 4-14: Correlation of the Kurow River at SH83 with the Otekaieke River at upstream weir

4.3 Otiake River The Otiake River is most commonly dry from the hill upstream of SH83 to the Waitaki River confluence, and at its driest, is dry from the exit to the lower gorge (Figure 4-15). We have no recorder on the Otiake River but have gaugings at the gorge, Mt Bell Station, and at SH83.

The Otiake River has a total of 0.300 m3/s currently consented (see Table 4-3) across 11 consents. There are nine deemed permits (totalling 0.260 m3/s) taking water from three WAPs and two further consents each with their own WAP, one of which is inactive. A further five post-RMA consents were active between 1969 and 2007 (with the allocation being >0.582 m3/s between 1969 and 2001 - one consent had an unspecified rate).

14 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

Figure 4-15: Gauging, dry reaches, historical and current surface water take consent locations for the Otiake River

Table 4-3: Current deemed permits and post-RMA water take consents (shaded grey) in the Otiake River

Rate Minimum Usage River Consent WAP Consent Holder (m3/s) flow (m3/s) data CRC062366 Grants Rd Lot Owners 0.062 CRC120578 0.006 I40/0637 Cricklewood Water Limited CRC136404 0.002 Otiake River CRC141651 Parker 0.043 deemed CRC180573 0.015 No Yes Cricklewood Station Limited permits CRC180333 I40/0638 0.042 CRC147490 Parker 0.027 CRC062375 Parker 0.021 I40/0639 CRC180335 Cricklewood Station Limited 0.042 Residual Otiake River CRC180571 I40/0612 Cricklewood Station Limited 0.017 0.050 Lone Yes post-RMA Ck consents CB17/50 CRC157858 Dennison 0.023 0.191 No, inactive 19 Otiake River total consented allocation 0.300

Water usage data for I40/0639 was combined with data for I40/6038 in the database (see Figure 4-16). Water usage data shows that for all four WAPs, the usage exceeded the consented rates at times. The

Environment Canterbury Technical Report 15 Lower Waitaki River southern tributaries – mining privileges

maximum exceedance for the combined I40/0638 and I40/0639 was 107%, 115% for I40/0637, and 366% for I40/0612 (see Figure 4-17).

Figure 4-16: Otiake River usage data (1/1/10-31/1/20)

Figure 4-17: Otiake River usage data as a percentage of consented rate (1/1/10-31/1/20)

There are two gauging sites on the Otiake River for which naturalised flow statistics can be produced; Lower Gorge and Mt Bell Station.

The lower gorge correlates with the Maerewhenua River at Kellys Gully (Figure 4-18). The lower gorge is affected by one take that has been consented since 1969. The low flow correlation for the lower gorge used nine gaugings from the 1970s (with the usage script (Kittridge, M., 2020) estimating zero usage), five from 2004 (with usage estimated by the script) and then 11 gaugings from 2018 onwards with actual usage data. The full range correlation used 14 gaugings from the 1970s (with the usage script estimating zero usage), five from 2004 (with usage estimated by the script), and then 15 gaugings from 2018 onwards with actual usage data. The strength of the correlations decreases if we only consider the recent gaugings.

16 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

Figure 4-18: Correlation of Otiake River at Lower Gorge with Maerewhenua River at Kellys Gully

The Mt Bell site is affected by all four WAPs. The correlations for Mt Bell (Figure 4-19) with the Otekaieke River used gaugings from 2017 (with actual usage data) since they provide stronger correlations than including earlier gaugings which rely on usage estimates.

Figure 4-19: Correlation of Otiake River at Mt Bell Station with the Otekaieke River at upstream weir Only one flowing gauging has been measured at SH83 (0.192 m3/s on 19/1/19). Since the gaugings are also dry in winter, it is likely that the MALF(7d) and 1 in 5-year 7-day low flow are naturally zero.

4.4 Otekaieke River Google Earth shows the Otekaieke River drying from Eastern Road bridge at its most severe and often drying from adjacent to Doctors Creek Road to the Waitaki River confluence (Figure 4-20).

There is a recorder upstream of the weir (71178) that has been in place since February 2013 (Figure 4-21). However, this site was also active between 1984 and 1995 and two recorders were previously installed and maintained by NIWA: Otekaieke at Stockbridge (71102) and Otekaieke at Gorge (71167).

Environment Canterbury Technical Report 17 Lower Waitaki River southern tributaries – mining privileges

These three sites are located very close together with no extra inflows or abstractions between sites, so flows are comparable and able to be added together to create a long-term record.

Figure 4-20: Flow recorder, gauging, dry reaches, historical and current surface water and groundwater take consent locations for the Otekaieke River

Figure 4-21: Hydrograph for Otekaieke River at upstream weir (2013-2019) There are currently nine consents to take a total of 0.483 m3/s from the Otekaieke River (see Table 4-4). This comprises one deemed permit (0.283 m3/s), just downstream of the recorder, and eight post-RMA consents. The post-RMA consents each have their own WAP except for I40/0548 which serves both CRC073249.2 (a take from a pond) and CRC951084.4 (a take from a spring which feeds the same pond). These two consents are non-concurrent. Neither CRC0733249.2 nor CRC950552.1 are included

18 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

in the allocation since they take from the pond. CRC950551.1 fills the pond and an allocation of 0.079 m3/s has been included (the sum of CRC073249.2 and CRC951084.4) even though the consent wording is ‘to divert up to the total flow of the Otekaieke River’. The take from the spring is included in the allocation. CRC950551.1 does not have usage data and so the usage for CRC0733249.2 and CRC950552.1 have been used as a proxy for the take from the river. Table 4-4: Current deemed permits and post-RMA water take consents (shaded grey) in the Otekaieke River

Rate Minimum Usage River Consent WAP Consent Holder (m3/s) flow (m3/s) data Otekaieke River Otekaieke Community water CRC062363.1 I41/0056 0.283 No Yes deemed company permits CRC022209 I41/0050 Metherell Farm Limited 0.012 No Yes CRC084382 I41/0047 Council 0.003 No No CRC000971 I40/0575 Bayley 0.019 No Yes CRC185420 I40/0604 VPS Properties Limited 0.034 No Yes Otekaieke No, CRC950551.1 CB17/5025 0.079* River post- Pond water diversion RMA level consents CRC950552.1 I40/0549 MFS Ventures Limited 0.034} from Yes CRC073249.2** 0.045}pond 0.200 Yes I40/0548 CRC951084.4** 0.045 No Yes CRC171896 CB17/5022 0.005 0.200 No Warnbro Enterprises Limited CRC062308 I40/0155 0.002*** 0.200 No Otekaieke River total consented allocation 0.483 *Whilst CRC950551.1 has an allocation of 0.079 m3/s in Accela because of the takes from the pond (which are not in the allocation), the consent wording is ‘to divert up to the total flow of the Otekaieke River’. I40/0548 serves both CRC073249.2 a take from the pond and CRC951084.4 a take from a spring which feeds the pond. ** non-concurrent *** Stream depleting groundwater take with daily rate of 0.0023 m3/s and a stream depletion of 90%.

There are two expired consents that were active between 1985 and 2012. One of these (CRC001655) was surrendered due to lack of water, believing that “Stony Creek is over-allocated” (C12C/25268). At the time of application of the consents, the applicants realised that there was insufficient water (a flow of 0.005-0.010 m3/s in summer) and they would have to share the resource. There has only been usage data available since 2017 which shows that I40/0575 takes less water than is consented (0.019 m3/s) (Figure 4-22). There is one consented shallow groundwater take (<0.005 m3/s) with a high degree of hydraulic connection. The smaller takes (<0.005 m3/s) do not have usage data. The maximum usage for I41/0056 is 92% of the consented rate, for I40/0575 it is 68% and the other WAPs with usage data all use over 100% of their consented rate (Figure 4-23). CRC204515 has just been granted (14/12/20) which replaces both CRC073249.2 and CRC951084.4 with a maximum rate of 0.045 m3/s being taken from WAP I40/0548, as well as up to 0.091 m3/s which is authorised under CRC062363.1, all with a minimum flow of 0.200 m3/s at the recorder.

Environment Canterbury Technical Report 19 Lower Waitaki River southern tributaries – mining privileges

Figure 4-22: Otekaieke River usage data (1/1/10-31/7/19)

Figure 4-23: Otekaieke River usage data as a percentage of consented rate (1/1/10-31/7/19)

There are two gauging sites on the Otekaieke River for which naturalised flow statistics can be produced; Eastern Road Bridge and SH83.

Using gaugings from 2003 onwards (seven low flow gaugings plus one high flow gauging in 2003-2004 and eight low flow gaugings plus four high flow gaugings in 2018-2019), we found good relationships between the gaugings at the recorder site and naturalised flows at Eastern Road Bridge (Figure 4-24). The usage is estimated in 2003 and 2004 but the usage for I41/0056 (the take at the weir downstream of the recorder, the largest take) was gauged on all but one gauging run in 2003. Since three small takes (<5 L/s) have no usage data, their usage has been estimated.

The lowest site, at the SH83 Bridge, had no historical measurements. On every visit during the 2003/2004 field survey this site was dry, but of the 15 recent gaugings (since 2012), twelve were flowing (however, seven of these were when the flows at the recorder were greater than median flow). It appears that the river was dry more in 2003-2004 than 2018-2019 when there were similar and higher flows at the recorder (Figure 4-25). The recorder was not in place during the 2003-2004 gauging run to be able to compare longer term flows and we cannot find a groundwater level recorder in the area with data for both time periods. We hypothesise that the groundwater levels were lower in 2003-2004, resulting in a drier riverbed at SH83. Flowing gaugings at SH83 from 2018-2019 (12 low flows plus four high flows)

20 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

were naturalised with the abstraction data, and correlate well with the recorder when considering the full range of flows (Figure 4-25) but do show that the river is naturally dry under MALF(7d) and 1 in 5-year 7-day low flow conditions.

Figure 4-24: Correlation of Otekaieke River at Eastern Road Bridge with the upstream weir

Figure 4-25: Correlation of Otekaieke River at SH83 with the upstream weir

Environment Canterbury Technical Report 21 Lower Waitaki River southern tributaries – mining privileges

5 Climate change Climate change projections for the Canterbury Region are provided in Macara et al., (2020). These projections are superimposed on three global circulations that affect the natural variability of weather: • El Niño-Southern Oscillation (ENSO) is the most dominant mode of inter-annual climate variability - it impacts New Zealand primarily through changing wind, temperature and rainfall patterns. El Niño events typically cause stronger south-westerly winds and drier than normal conditions in the north and east of New Zealand, and La Niña causes more north-easterly airflow, with generally drier conditions in the west and south of the . • The Interdecadal Pacific Oscillation (IPO) affects New Zealand through drier conditions in the east and wetter conditions in the west during the positive phase with the opposite in the negative phase. • The Southern Annular Mode (SAM) affects New Zealand through higher temperatures and settled weather during the positive phase and lower temperatures and unsettled weather during the negative phase.

According to Macara et al. (2020) the area of the southern tributaries of the Lower Waitaki River sees little change in rainfall through ENSO phases.

The IPO can modify New Zealand’s connection to ENSO, and it also positively reinforces the impacts of El Niño (during IPO+ phases) and La Niña (during IPO- phases) (Macara et al., 2020).

During the summer of 2017-18 (i.e. December 2017 – February 2018), the SAM was positive for 86 days, and negative for just four days (Macara et al., 2020). This was associated with New Zealand’s hottest summer on record, as well as New Zealand’s hottest month on record (January 2018) (Macara et al., 2020). Omarama, the closest record available, recorded the second hottest month on record.

These circulations will continue to cause variability within an expected increase in global temperature which will generally result in drier summer conditions. At times, natural variability will add to the human- induced trends, while at others it may offset part of the anthropogenic effect (Macara et al., 2020).

We looked at annual low flows (ALFs) for the Maerewhenua and Otekaieke in relation to ENSO and IPO but saw no identifiable pattern for the Maerewhenua. The Otekaieke appears to have lower ALFs during negative IPO which is contrary to projected wetter conditions in the east (Figure 5-1).

Figure 5-1: Otekaieke ALFs (yellow dots) and the IPO index

Macara’s report details the impacts of two of the four scenarios of future greenhouse gas concentrations (called Representative Concentration Pathways (RCPs) by the Intergovernmental Panel on Climate

22 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

Change (IPCC)) by mid-century (2040) and late century (2090) on temperature, rainfall and flows in Canterbury. RCP 4.5 is a mid-range scenario where greenhouse gases stabilise by 2100. RCP 8.5 is a ‘business as usual’ scenario where greenhouse gas concentrations continue to rise at the current rate. The strongest effects are therefore felt under RCP 8.5 by late century.

As with the rest of Canterbury, the Lower Waitaki River southern tributaries area will see increases in annual mean temperature (by up to 3˚C under RCP 8.5 by 2090). The annual mean maximum temperature increases by the same amount for the two RCPs by mid-century, but the increase is larger under RCP 8.5, with warming of 3-5˚C projected by 2090. The annual mean minimum temperature is projected to increase by up to 2˚C by 2090 under RCP 8.5.

There is little change projected in the annual rainfall by 2040, but by 2090 it is projected to increase by up to 5% under RCP 4.5, and by 5-10% under RCP 8.5. The area of the Lower Waitaki tributaries traditionally has most of its rainfall in the spring and summer. By late century under RCP 8.5 there is projected to be up to a 10% decrease in summer rainfall and an increase over the rest of the year, with up to 35% more rainfall in winter.

The number of snow days is projected to decrease. This may impact on the flows in the Awakino River by increasing winter flows and decreasing late spring flows.

The area is traditionally dry (with 200-250 dry days2 a year). Under climate change, the number of dry days is projected to increase by up to 5 days by mid-century under both scenarios and by up to 10 days under RCP 8.5 by late century. The number of dry days is likely to increase in summer and decrease in winter.

There is a projected increase in potential evaporation deficit (PED)3 of 75-150 mm. Higher PED values indicate drier soils and are used as a measure of drought potential.

The decrease in summer and autumn rainfall along with the increase in temperature result in the MALF(7d) being projected to decrease by up to 20% by 2040 and up to 50% by 2090. These reduced flows will affect environmental flows and associated habitat and biodiversity and will mean that irrigators will be placed into restriction more often.

6 Results Water usage in the Lower Waitaki River southern tributaries appears to be significantly higher than elsewhere in Canterbury (with many takes consistently taking >100% of their consented rate compared to an average of 65% in the Opihi catchment and 29% in the Temuka catchment in 2014-15, Dodson and Steel, 2018).

Only the Awakino River flows at the downstream end of its catchment, whereas the other three rivers are dry most of the year. Most of the sites correlate well with the Otekaieke recorder at upstream weir. The Otiake River at the lower gorge is the exception to this and correlates with the Maerewhenua River, see Tables 6-1 and 6-2.

2 A dry day considered here is when <1mm of rainfall is recorded over a 24-hour period. 3 Potential evapotranspiration deficit is the difference between potential evapotranspiration (PET) and rainfall.

Environment Canterbury Technical Report 23 Lower Waitaki River southern tributaries – mining privileges

Table 6-1: Regression results and calculated MALF(7d), 1 in 5-year 7-day low flow, and median values

Naturalised Naturalised Site Affected by Naturalised Site Name Regression Equation N r2 MALF(7d) median Number water takes 7Q5 (m3/s) (m3/s) (m3/s) Awakino River 71105 SH 83 (Boraman rec) y = 0.9689*Otekaieke + 0.222 15 0.64 All takes 0.442 0.397 0.877 1711458 East Branch Above Upper Intake y = 0.3242*Awakino - 0.0069 12 0.70 No 0.136 0.122 0.277 Kurow River 1841 Gorge y = 0.3789*Otekaieke + 0.0837 10 0.72 No 0.170 0.152 0.340 2367 Curries y = 0.4173*Otekaieke + 0.1024 10 0.72 No 0.197 0.178 0.384 171147 SH 83 (rec) only 1 year of record All takes 0 0 Otiake River 71111 Lower Gorge y = 0.1755*Maerewhenua + 0.1329 25 0.49 1 take 0.237 0.210 0.420 1711435 Mt Bell Station y = 0.3643*Otekaieke + 0.0005 30 0.59 All takes 0.083 0.066 0.247 1711453 SH 83 only 1 flowing gauging All takes 0 0 Otekaieke River 71178 Upstream Weir (rec) 32 years of record No 0.227 0.181 0.676 171159 Eastern Road Bridge y = 1.0722*Otekaieke - 0.022 15 0.85 5 takes 0.222 0.172 0.703 1711011 SH 83 y = 1.2986*Otekaieke - 0.4871 6 0.64 All takes 0 0 0.391 Maerewhenua River 71106 Kellys Gully (rec) 50 years of record No 0.591 0.439 1.635

Table 6-2: Regression results and calculated mean values Site Naturalised Site Name Regression Equation N r2 Number mean (m3/s) Awakino River 71105 SH 83 (Boraman rec) y = 0.7413*Otekaieke + 0.3117 22 0.64 1.135 1711458 East Branch Above Upper Intake y = 0.3697*Awakino - 0.0331 13 0.87 0.387 Kurow River 1841 Gorge y = 0.3712*Otekaieke + 0.0868 12 0.84 0.499 2367 Curries y = 0.4338*Otekaieke + 0.092 13 0.83 0.574 171147 SH 83 (rec) y = 0.5466*Otekaieke - 0.2158 9 0.85 0.391 Otiake River 71111 Lower Gorge y = 0.2069*Maerewhenua + 0.1085 35 0.72 0.692 1711435 Mt Bell Station y = 0.4713*Otekaieke - 0.0469 40 0.78 0.477 1711453 SH 83 only 1 flowing gauging Otekaieke River 71178 Upstream Weir (rec) 32 years of record 1.111 171159 Eastern Road Bridge y = 0.8577*Otekaieke + 0.0731 20 0.86 1.026 1711011 SH 83 y = 1.2484*Otekaieke - 0.4223 12 0.89 0.965 Maerewhenua River 71106 Kellys Gully (rec) 50 years of record 2.822

The Kurow, Otiake, and Otekaieke rivers are all dry at SH83 under MALF(7d) conditions. This poses a problem for determining minimum flows at the lower end of the catchments as the WCWARP recommends. They are also dry in winter when there is little to no water abstraction and during periods of higher flows, but generally flow well throughout the year in the upper catchments.

The allocation and minimum flows are compared to the MALF(7d) and 1 in 5-year 7-day low flow values in Table 6-3 with the guideline values for allocation (from the LWRP since the WCWARP does not limit

24 Environment Canterbury Technical Report Lower Waitaki River southern tributaries – mining privileges

allocation) and the minimum flow (from the WCWARP). Since the MALF(7d) and 1 in 5-year 7-day low flow at the downstream end of the catchment are 0 m3/s for the Kurow, Otiake, and Otekaieke rivers, it is likely we will need to set minimum flow values for these rivers further up in the catchment as recommended by Policies 3-5 of the WCWARP. We have therefore provided the highest MALF(7d) and 1 in 5-year 7-day low flow in the catchments. The allocation for all four catchments is over 100% of MALF(7d), far in excess of the LWRP guidelines for 20% of MALF(7d) to be allocated. The current minimum flow affecting one consent in the Awakino River (0.400 m3/s) is close to the 1 in 5-year 7-day low flow (0.397 m3/s). The minimum flow for the Otiake for consent CRC157858 is 0.191 m3/s at the lower gorge. This was calculated in 2016 when the consent was granted. The recent gaugings have changed the regression and thus the calculated 1 in 5-year 7-day low flow is higher. Conversely, when CRC062308 was granted in the Otekaieke River, the 1 in 5-year 7-day low flow was considered to be 0.200 m3/s and the minimum flow is thus higher than what we consider the 1 in 5-year 7-day low flow to be, based on 14 more years of data (0.181 m3/s). Table 6-3: Allocation and minimum flows with respect to MALF(7d) and 1 in 5-year 7-day low flow values River Allocation MALF(7d) Percentage LWRP Minimum WCWARP (m3/s) (m3/s) of guideline flow guideline MALF(7d) allocation (m3/s) minimum flow (1 (m3/s) in 5-year 7-day low flow) (m3/s) Awakino 0.474 0.455 104% 0.081 0.400 0.397 Kurow 0.230 0.197* 117% 0.039 - 0.178 Otiake 0.300 0.253* 119% 0.051 0.191 0.210 Otekaieke 0.435 0.227* 192% 0.045 0.200 0.181 * since the MALF(7d) and 1 in 5-year 7-day low flow at the downstream end of the catchment are 0 m3/s, we have provided the highest MALF(7d) and 1 in 5-year 7-day low flow in the catchment.

7 Summary and next steps There are many consents and deemed permits that take water from the Awakino, Kurow, Otiake, Otekaieke rivers. We have long-term (> 30 years) flow records from locations upstream of these water takes on the Otekaieke and Maerewhenua4 rivers. These recorders give us a valuable insight into the natural flow regime of these rivers. We also have flow records for the Awakino and Kurow rivers at the downstream end of their catchments. Environment Canterbury has conducted many gaugings along these rivers over the last three years. The gaugings have helped to identify relationships between gauged sites and recorders. Using these relationships, we have calculated statistics such as MALF(7d), 1 in 5-year 7-day low flow and mean flow which are used to set minimum flow conditions.

The Kurow, Otiake and Otekaieke rivers go dry at the downstream end of the catchments and therefore minimum flows and allocations will need to be based on the low flow statistics further up the catchments. The WCWARP does not cap the allocation for these individual rivers. The statistics show that all four catchments are over-allocated with respect to the LWRP guidelines. The current minimum flow in the Awakino River is similar to the WCWARP guideline values. The current minimum flows in the Otiake and Otekaieke rivers are similar to the WCWARP guideline values should they be taken at the highest flowing upstream reaches (Otiake River at lower gorge and Otekaieke River at upstream weir). It may be necessary to install a recorder in the Otiake River for a minimum flow site since the correlation is not strong.

Takes that have been classified as diversions but are in fact takes (since there is no return of water to the river) should be reclassified so that they are included in metering requirements. This applies to CRC950551.1 in the Otekaieke River. This same consent has the wording that it can ‘divert up to the total flow in the Otekaieke River’. This wording should be changed in the renewal consent to cap the abstraction and leave a residual flow in the river.

4 The Maerewhenua River is adjacent to the Otekaieke River and was included in the analysis as a primary site with which to correlate flows.

Environment Canterbury Technical Report 25 Lower Waitaki River southern tributaries – mining privileges

With respect to climate change, summer and autumn rainfall are projected to decrease, and along with the increase in temperature result in the MALF(7d) being projected to decrease by up to 20% by 2040 and up to 50% by 2090. These reduced flows will affect environmental flows and associated habitat and biodiversity and will mean that irrigators will be placed into restriction more often.

8 References CRC001655, Full surrender of resource consent, Metherell Farm Ltd. C12C/25268 Dodson, J., and Steel, K., 2018. Current state of surface water hydrology in the greater Opihi catchment. Environment Canterbury Technical Report No. R18/80. ISBN 978-1-98-852018-6. Environment Canterbury. Canterbury Land and Water Regional Plan. Revised 16 Sep 2019. Gabites, S., and Horrell, G., 2005. Seven day mean annual low flow mapping of the tributaries of the Waitaki River. Environment Canterbury Technical Report No. R05/16. ISBN 1-86937-570-X. Google Earth Accessed 2 September 2020. Henderson, R., Ibbitt, R., McKerchar, A., 2003. Reliability of linear regression for estimation of mean annual flow: a Monte Carlo approach. Journal of Hydrology (NZ) 42(1): 75-95. Kittridge, M., 2020. Naturalisation methodology/tool version 2. Environment Canterbury Technical Memorandum. C20C/171736. Macara, G., Woolley, J-M., Pearce, P., Wadhwa, S., Zammit, C., Sood, A., Stephens, S., 2020. Climate change projections for the Canterbury Region. NIWA Client Report No. 2019339WN MWD, 1984. Lower Waitaki Catchment Hydrology Report. Prepared by Ministry for Works and Development, Power Directorate, Wellington, Nov 1984. RMA Resource Management Act 1991. Revised 30 September 2020. Waitaki Catchment Water and Allocation Board. Waitaki Catchment Water Allocation Regional Plan Revised 5 Feb 2019. Waitaki Catchment Water Allocation Board, 2005. Waitaki Catchment Water and Allocation Regional Plan Section 32 Report. Young, J., 1983. Awakino Catchment Hydrology. Unpublished Report Waitaki Catchment Commission, December 1983. PU1C/4109.

26 Environment Canterbury Technical Report

Environment CanterburyTechnical Report Appendix 1: River gaugings

Site 29/01/2018 18/04/2018 7/08/2018 25/09/2018 19/10/2018 11/01/2019 31/01/2019 22/02/2019 3/05/2019 9/05/2019 20/08/2019 10/09/2019 27/11/2019 13/01/2020 21/02/2020 2/03/2020 Site Name Number Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s) Flow (m3/s)

Awakino River Lower East Branch Above Upper Intake 1711458 0.102 0.463 0.169 0.189 0.186 0.307 0.184 0.107 0.220 0.181 0.319 0.168 SH 83 (Boraman rec) 71105 0.390 1.283 0.443 0.545 0.617 0.995 0.494 0.355 0.659 0.552 0.775 0.504 0.892 0.678 0.525 0.417 Kurow River Waitaki Gorge 1841 0.153 0.487 0.205 0.275 0.379 0.303 0.184 0.247 0.191 0.474 0.303 0.318 0.318 0.173 Curries 2367 0.157 0.549 0.238 0.296 0.276 0.510 0.328 0.269 0.301 0.216 0.527 0.329 0.383 0.341 0.200 SH 83 (rec) 171147 Dry 0.224 0.006 0.105 Dry Dry Dry Dry Dry 0.242 0.002 Dry Dry Dry Dry

Otiake River River Lower Gorge 71111 0.199 0.526 0.281 0.316 0.274 0.738 0.521 0.339 0.313 0.271 0.614 0.390 0.457 0.386 0.268 0.258 Mt Bell Station 1711435 Dry 0.367 0.101 0.158 0.054 0.532 0.178 0.007 0.119 0.079 0.461 0.201 0.191 0.063 0.001 0.018

SH 83 1711453 Dry Dry Dry Dry Dry 0.192 Dry Dry Dry Dry Dry Dry Dry Dry Dry Dry southern tributaries Otekaieke River Upstream Weir (rec) 71178 0.193 0.922 0.406 0.707 0.554 0.944 0.535 0.344 0.467 0.326 1.290 0.629 0.611 0.400 0.267 0.202

Eastern Road Bridge 171159 0.010 0.898 0.391 0.702 0.366 0.923 0.367 0.168 0.428 0.297 1.364 0.606 SH 83 1711011 Dry 0.514 0.039 0.416 0.040 0.615 0.072 Dry 0.005 Dry 0.910 0.252 0.044 Dry Dry Maerewhenua River Kellys Gully (rec) 71106 0.526 2.761 1.515 2.249 1.313 2.480 1.338 0.800 1.039 0.741 2.981 1.717 1.008 0.798 0.572 SH83 2005 1.412 2.579 1.141 2.349 0.931 0.451 1.233 0.608 3.031 1.538 Dry = zero flow Hatched = not gauged –

mining privileges

27

28

Lower Waitaki

River

southern tributaries

Environment CanterburyTechnical Report –

mining

privileges

Environment CanterburyTechnical Report Appendix 2: Low flow frequency analysis

Environment Canterbury HYLOWFL V106 Output 01/03/2021

Low Flow Frequency Analysis 7 Day Duration Events Distribution

Annual Series (in days) Lower 71106 Maerewhenua River at Kellys Gully

04/03/1970 to 10/02/2021

Overall: 2% Missing Data Waitaki

Worst Included Year: 34% Missing Data

Weibull plotting positions

River Log Pearson 3 distribution Probability of Lower Flows

99 95 90 80 50 20 10 5.0 2.0 1.0 0.5 0.1 3.3618196 southern tributaries

2.6894557

2.0170918

1.6809098

1.3447278 –

mining privileges

0.6723639 Stream Discharge in Cubic metres/second Cubic in Discharge Stream

0.3361820 1.01 1.1 2.0 2.5 3.3 5.0 10 50.0 100 1000

Average recurrence Interval (Years) 29

30

Environment Canterbury HYLOWFL V106 Output 01/03/2021

Low Flow Frequency Analysis 7 Day Duration Events Distribution

Annual Series (in days)

71178 Otekaieke River at Weir

10/07/1984 to 10/02/2021 Lower

Overall: 9% Missing Data

Worst Included Year: 52% Missing Data Waitaki

Weibull plotting positions

Log Pearson 3 distribution Probability of Lower Flows

River

99 95 90 80 50 20 10 5.0 2.0 1.0 0.5 0.1 1.3221107

southern tributaries

1.0576885

0.7932664

0.6610553 Environment CanterburyTechnical Report 0.5288443 –

mining privileges

0.2644221 Stream Discharge in Cubic metres/second Cubic in Discharge Stream

0.1322111 1.01 1.1 2.0 2.5 3.3 5.0 10 50.0 100 1000

Average recurrence Interval (Years)

Environment CanterburyTechnical Report Appendix 3: Dry reach mapping using Google Earth Awakino Kurow Otiake Otekaieke Maerewhenua Recorded Recorded Recorded Recorded Recorded Date flow Flow status flow Flow status flow Flow status flow Flow status flow Flow status (m3/s) (m3/s) (m3/s) (m3/s) (m3/s) dry at ford but flowing again d/s, 12/04/2003 n/a by hill to u/s SH83 n/a dry Doctors Ck Rd to Waitaki 0.556 dry at lower ford road Lower 16/03/2012 n/a flows all the way n/a flows all the way 2.814 4/04/2012 n/a flows all the way 1.061 19/02/2015 0.715 flows all the way Waitaki 14/01/2018 n/a dry u/s Settlement Rd to Waitaki n/a dry u/s ford to Waitaki 0.33 dry pond d/s Eastern Rd to Waita 0.671 dry? at lower ford 29/01/2018 n/a flows all the way n/a dry d/s Curries? to Waitaki n/a dry d/s lower gorge to Waitaki 0.173 dry Eastern Rd to Waitaki 0.551

30/04/2018 3.638 8.65 flows all the way River 21/07/2018 0.449 1.498 flows all the way 27/09/2018 0.538 flows all the way 1.665 flows all the way

15/10/2018 0.019 0.591 1.501 flows all the way southern tributaries 31/10/2018 n/a flows all the way 0.315 flows all the way 1.993 3.389 16/12/2018 1.304 flows all the way 0.308 dry d/s SH83 to Waitaki n/a flows all way 2.149 flows all the way 4.433 flows all the way 4/01/2019 1.066 flows all the way 0.129 dry u/s Settlement Rd to Waitaki? n/a flows all way? 1.374 flows all the way 2.242

15/01/2019 1.069 0.042 3.818 flows all the way dry hill u/s SH83, flows a reach u/s 30/01/2019 0.546 flows all the way 0 dry u/s Settlement Rd to Waitaki n/a of SH83 flows all the way 1.376 5/04/2019 0.393 flows all the way 0 dry u/s Settlement Rd to Waitaki n/a dry d/s ford to Waitaki 0.354 dry pond d/s Eastern Rd to Waita 0.749 12/04/2019 0.86 0.134 0.632 1.646 –

16/04/2019 0.507 0.02 0.315 dry u/s Doctors Creek Rd to Waita 0.827 flows all the way mining 29/04/2019 0.685 flows all the way 0.154 flows all the way n/a dry hill u/s SH83 to Waitaki 0.779 flows all the way 3.497 flows to edge of image (d/s 30/04/2019 0.714 0.159 0.664 Doctors Creek Rd to Waitaki) 2.517 12/05/2019 0.517 0 0.305 0.693 flows all the way privileges 4/07/2019 0.464 0.023 0.374 dry u/s SH83 to Waitaki 1.329 flows all the way 3/10/2019 0.016 1.1 flow to edge of image (u/s SH83) 2.892 flows all the way 3/11/2019 n/a flows all the way 0.004 1.218 2.806

25/11/2019 0 0.689 1.837 flows all the way 30/11/2019 0 0.563 1.506 only partial images available - dry 20/02/2020 0 in available image n/a dry Gards Road to Waitaki only partial images available - dry 28/02/2020 0 in available image n/a dry Gards Road to Waitaki 31

Facilitating sustainable development in the Canterbury region ecan.govt.nz