Waikato River Water Take Proposal

Home , Karapiro, Lake Karapiro, Lake Waikare, Pukekawa, Tongariro River, Tuakau

WAIKATO RIVER WATER TAKE PROPOSAL

Lower Waikato River Bathymetry Assessment

Changes Consequent to Development

for

Watercare Services Ltd

December 2020 R.J.Keller & Associates PO Box 2003, Edithvale, VIC 3196

CONTENTS

EXECUTIVE SUMMARY ...... 4 1. INTRODUCTION ...... 5 2. SUMMARY AND CONCLUSIONS ...... 8

2.1 INTRODUCTION ...... 8

2.2 “NATURAL” VARIABILITY IN FLOW RATES ...... 8

2.3 HISTORICAL CHANGES IN BATHYMETRY ...... 9

2.4 HYDRO DAM DEVELOPMENT ...... 9

2.5 SAND EXTRACTION ...... 9

2.6 LOWER WAIKATO FLOOD PROTECTION ...... 10

2.7 LAND USE CHANGES ...... 10

2.8 SEDIMENT REMOVAL THROUGH ADDITIONAL WATER TAKE ...... 11

2.9 CONCLUSIONS...... 11 3. REVIEW OF DEVELOPMENT IN THE WAIKATO RIVER ...... 12 4. “NATURAL” VARIABILITY IN FLOW RATES IN LOWER WAIKATO RIVER...... 15

4.1 ANALYSIS OF FLOW RECORDS BETWEEN 1963 AND 2020 ...... 15

4.2 FUTURE TRENDS ...... 18 5. HISTORICAL CHANGES IN BATHYMETRY IN THE LOWER WAIKATO ...... 23

5.1 INTRODUCTION ...... 23

5.2 BATHYMETRY CHANGES AND ANALYSIS IN MOBILE BED RIVERS ...... 23

5.3 LOWER WAIKATO RIVER - AVAILABLE DATA...... 28

5.4 ANALYSIS OF LOWER WAIKATO RIVER DATA ...... 28

5.5 DISCUSSION ...... 29 6. HYDRO DEVELOPMENT ...... 31

6.1 THE HYDRO DAMS ...... 31

6.2 EFFECT OF THE HYDRO DAMS ON RIVER MORPHOLOGY ...... 32 7. SAND EXTRACTION ...... 33

7.1 AVAILABLE DATA ...... 33

7.2 EFFECT OF SAND EXTRACTION ON BATHYMETRY ...... 36 7.2.1 Mercer Extraction and Downstream Mean Relative Depth ...... 36 7.2.2 Tuakau Extraction and Downstream Mean Relative Depth...... 37 7.2.3 Tuakau and Puni Extraction and Upstream Mean Relative Depth ...... 38 7.2.4 Pukekawa Extraction and Upstream and Downstream Mean Relative Depth ...... 40 7.2.5 Pukekawa Sand Extraction Effect on Local Bathymetry ...... 41 7.2.6 General Discussion ...... 45 8 LOWER WAIKATO FLOOD PROTECTION ...... 46 Page 2 of 110

8.1 INTRODUCTION ...... 46

8.2 LOWER WAIKATO FLOOD PROTECTION SCHEME DESCRIPTION ...... 46

8.3 INFLUENCE OF LOWER WAIKATO FLOOD PROTECTION SCHEME ON WATER LEVELS AND BED LEVELS ...... 48 9 LAND USE CHANGES ...... 49

9.1 INTRODUCTION ...... 49

9.2 EFFECT ON RIVER FLOWS ...... 49

9.3 EFFECT ON SEDIMENT YIELD ...... 50 10 SEDIMENT REMOVAL THROUGH ADDITIONAL WATER TAKE...... 51 11 EFFECT OF PROPOSED ADDITIONAL WATER TAKE IN CONTEXT ...... 52 12 REFERENCES...... 56 APPENDIX A – GRAPHS OF X-SECTION PROFILES AND CHANGES IN MEAN RELATIVE DEPTH ...... 58 APPENDIX B – DETAILED GRAPHS OF X-SECTION PROFILES, CROSS-SECTIONAL AREA AND CHANGES IN MEAN RELATIVE DEPTH LOCAL TO PUKEKAWA SAND EXTRACTION ZONE ...... 93

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EXECUTIVE SUMMARY

This review has examined those changes that may actually be occurring in the Lower Waikato River as a consequence of development, and what the river may look like in the future. Within this context, the effect of the proposed additional water take of up to 150,000 m3/d net is examined.

A number of review elements evolved as being important to understanding how development has affected the hydrology and bathymetry of the Waikato River and how these may continue to be affected into the future. These elements include “natural” variability in flow rates, historical changes in bathymetry, hydro development, sand extraction, flood protection, and land use changes.

The proposed take has been considered in the context of each type of development, and also cumulatively in the context of all types of development together. In reviewing the changes that have occurred within the Lower Waikato River, it is clear that the impact of the proposed 150,000 m3/d water take at the Watercare intake site is negligible within the context of both individual and cumulative development changes that have occurred and will continue into the future.

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1. INTRODUCTION

Watercare Services Limited (“Watercare”) is a lifeline utility providing water and wastewater services to a population of 1.7 million people in Auckland. Its services are vital for life, keep people safe and help communities to flourish. More specifically, Watercare is the council-controlled organisation of Auckland Council responsible for municipal water supply within Auckland, and the provider of bulk water supply services to Pokeno and Tuakau in the Waikato District1.

Watercare supplies approximately 440,000 cubic metres of water per day (“m3/day”) on average across the year, derived from a range of sources and treated to the Ministry of Health Drinking Water Standards for New Zealand 2005 (revised 2018).

Watercare’s three main water supply sources are:2

• Water storage lakes in the Hūnua and Waitākere ranges;

• A groundwater aquifer in Onehunga; and

• The Waikato River.

The exact proportion supplied from each source varies daily, depending on a range of factors including the levels in the storage lakes, forecast rainfall, treatment plant capacity, and maintenance requirements.

In December 2013, Watercare applied to the Waikato Regional Council (“WRC”) for resource consents to authorise abstracting an additional 200,000 m3/day of water from the Waikato River, a new water intake structure and discharges from a new water treatment plant. Since that time, Watercare’s water take application (and the associated applications) have been on hold while the WRC processes and determines other applications to take water from the Waikato River Catchment that were lodged before Watercare’s application.

During the period from late 2019 through to mid-2020, the Auckland region experienced one of the most extreme drought events in modern times with rainfall for the period between January and May 2020 being approximately 30% of what would normally be expected for that period. At Watercare’s recommendation, in May 2020 Auckland Council imposed water use restrictions in Auckland for the first time since the early 1990s. Watercare also took additional steps to improve security of supply during the drought by exercising emergency powers under section 330 of the

1 Under a bulk supply agreement with Waikato District. 2 Watercare also operates individual water supplies from various sources including groundwater and surface water for several other communities such as Muriwai, Algies Bay, Snells Beach, Bombay, Waiuku, Warkworth, Helensville and Wellsford. Page 5 of 110

Resource Management Act 1991 (RMA),3 and by re-establishing supply from previously decommissioned sources.4

While the above steps have been taken to ensure Auckland’s short-term water supply requirements are met, the focus has now turned to the future. Watercare focus remains planning for water demand over the long term by securing sustainably sourced water to achieve:

• Certainty of supply in up to a 1:100-year drought with 15% residual dam storage; and

• Certainty of supply to meet the peak demand.

On 30 June 2020, after considering advice provided by the Environmental Protection Authority, the Minister for Environment issued a direction under section 142(2) of the RMA to call in Watercare’s 2013 application and refer the matter to a Board of Inquiry to determine the application. The Minister direction recognised Watercare’s application as a proposal of national significance.

Given the passage of time since the 2013 application was lodged, Watercare has updated the application to address a range of matters including updates to population and demand assessments, changes to the policy framework within which the application is to be considered, consultation that has taken place, reassessment of potential water supply sources and intake options, and updated assessments of environmental effects including the effect that granting Watercare’s application would have on the allocation available to other users. The updated application will be heard by the Board of Inquiry.

The most significant revision to the 2013 application, resulting directly from Watercare’s ongoing engagement with Waikato-Tainui is a reduction in the volume of the proposed water take from 200,000 m3/day to 150,000 m3/day. This reduction reflects Waikato-Tainui’s special relationship with the Waikato River as outlined in the Waikato-Tainui Raupatu Claims (Waikato River) Settlement Act 2010. It recognises Waikato-Tainui’s relationship with the Waikato River and its respect for the River lies at the heart of Waikato-Tainui’s spiritual and physical wellbeing, tribal identity and culture.

Watercare currently holds three resource consents authorising the abstraction of water from the Waikato River adjacent to the Waikato Water Treatment Plant (“Waikato WTP”) near Tuakau as follows: a) Resource consent 960089.01.04 authorising a net take rate of up to 150,000 m3/day at any time of the year. b) Resource consent 141825.01.01 (referred to as the “Seasonal Water Take” consent) authorising a net take rate of up to:

3 Reduced environmental flows from the Waitakere, Wairoa and Cosseys Storage Lakes, and a short term take from the Waikato River. 4 Groundwater bores at Pukekohe and the Hays Creek Storage Lake in Papakura. Page 6 of 110

i) 100,000 m3/day during the period 1 May to 30 September (inclusive); and

ii) 100,000 m3/day during the period 1 October to 30 April (inclusive) when the 7-day rolling average flow of the Waikato River at Rangiriri exceeds 330.03 m3/second. c) Resource consent 142090.01.01 (referred to as the “Hamilton City Council Water Allocation” consent), authorising a net take rate of up to 25,000 m3/day (or such lesser volume as determined by Hamilton City Council as being available for any given day) during the period 1 October to 30 April (inclusive). This is a short-term consent till 1 May 2023.

In the event that the consent sought through the Board of Inquiry process is granted for the volume sought, Watercare proposes that resource consents 141825.01.01 and 142090.01.01 would be surrendered. Watercare’s combined take from the Waikato River under its existing resource consent 960089.01.04, and the new water take consent sought through the Board of Inquiry would not exceed a year round take volume of 300,000 m3/day.

This report provides an assessment of the changes in the Lower Waikato River consequent to development, prepared to support the application to be considered by the Board of Inquiry.

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2. SUMMARY AND CONCLUSIONS

2.1 Introduction

To assist in meeting water supply for the expected population growth, in Auckland, Watercare is seeking resource consent to increase abstraction from the Lower Waikato River by up to 150,000 m3/d net. This increased take will require construction of an additional intake structure. Following an options assessment process completed in November 2020 it has been decided to seek consent for an additional intake structure located adjacent to the existing intake structure.

2.2 “Natural” Variability in Flow Rates

Mean daily flow records from June 1963 to November 2020 at Mercer Bridge (6 kilometres (km) upstream of the intake site) were analysed. There are negligible inflows between Mercer Bridge and the intake site. Additionally the effect of climate change on flows and water levels was considered.

Analysis of the flow records indicated an average daily flow rate of 401.3 cubic metres per second (m3/s), a median daily flow rate of 358.6 m3/s with a standard deviation of 170.6 m3/s. No statistically significant change with time was noted.

In considering climate change it is likely that high rainfall events and flows (the 2 year Annual Return Interval (ARI) event and greater) – see page 22 - will increase as a result of rising temperatures. Effect on average daily mean flows would be insignificant.

The current daily tidal change at the intake site is approximately 0.5 m. Consequent to predicted sea level rises, the water level at the intake site will rise by about 0.2 m in 2055 for a river flow of 350 m3/s and assuming no sand extraction. Saline intrusion extent is predicted to always remain at least 19km downstream of the intake site – see page 27.

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2.3 Historical Changes in Bathymetry

Detailed cross-section data over a 22.5 km length of river, encompassing the intake site, were analysed and generally showed significant drops in the bed elevation that correlated strongly with sand extraction data. The exception was at the upstream end of the reach, where significant increases in bed elevation were noted. These increases correlated strongly with a reduction in sand extraction upstream at Mercer. Sand extraction at this site ceased in 1995 and the noted bed level increase is due to sedimentation from the upstream sediment supply.

2.4 Hydro Dam Development

Eight hydro-electric dams (hydro dams) have been built along the length of the Waikato River and their construction has resulted in significant effects within the Waikato River – particularly in flow rates and sediment movement. Flow rates in the Lower Waikato River are largely governed by control criteria, especially at Karapiro Dam.

Bed-material sediment load is trapped by the hydro dams, preventing the replenishment of the bed sediment downstream. Because the river flow retains a sediment carrying capacity, the starving of sediment input from upstream results in scouring of the bed downstream to feed the river’s sediment carrying capacity.

This has been a major cause of falling riverbed levels downstream of Karapiro Dam, now extending as far downstream as Ngaruawahia. Downstream of Ngaruawahia, the tendency for bed level reduction is lessened, primarily due to substantial sediment inputs from the Waipa River.

The effect of the hydro dams on bed degradation does not extend into the Lower Waikato River. In any event, the proposed take would not result in any significant bed degradation, with any such effect being negligible when compared with the effects of the hydro dams on bed morphology.

2.5 Sand Extraction

Sand extraction has been carried out since the early 1950s and data since 1962 are summarised. Detailed data on sand extraction between 1988 and October 2020 were available and analysed.

Analysis of the data from Mercer, Tuakau, and Puni show a very strong correlation with bed level changes downstream, but little or no correlation with bed level changes upstream. This is consistent with the effect of sand extraction on the overall movement of sediment in the river.

Sand extraction from Pukekawa by Winstone Aggregates only commenced in January 2013 and has continued to the present time. Using the WRC survey data from 2007 and 2017 and additional survey data from Winstone Aggregates in the vicinity of the Pukekawa sand extraction site, a detailed study of the effect of the sand extraction on upstream and downstream bathymetry was undertaken. This too showed a strong correlation with bed level changes downstream, but little correlation with bed level changes upstream. Page 9 of 110

When sand is removed at an extraction site, the river seeks to recover capacity downstream by eroding the bed and will continue to do so until a new equilibrium is reached. When sand extraction reduces or ceases, the local hole at the extraction site starts to fill through the sediment supply from upstream and this effect propagates downstream.

It is clear that sand extraction is the primary reason for bathymetry changes in the Lower Waikato River. Any change in bathymetry associated with the proposed abstraction is negligible when compared with changes due to sand extraction activities.

2.6 Lower Waikato Flood Protection

The impetus for development of the Lower Waikato Flood Protection Scheme was the major floods experienced in 1952, 1956 and particularly 1958. Work commenced in 1961 and was largely completed by 1982. The design of the scheme was based on mimicking the natural processes within two storage areas, Lake Waikare and the Whangamarino wetland, but in a controlled fashion. In this way, the benefits of the storage areas in reducing peak flows could be retained.

In operation, the scheme increases the magnitude of peak flood flows, but reduces the duration of major floods. There is a probable increase in major flood levels on the riverside of stop banks, but within design limits.

At mean and low river flows, there is no effect on river levels and insignificant or no effect on sediment movement. Similarly, the proposed water take will have a negligible effect on water levels and sand movement in the river.

2.7 Land Use Changes

Historically, extensive clearing of land from forest to pasture increased runoff rates and significantly increased river flows, leading to erosion, increased sediment load and reduced water quality. More recently, there has been a progressive change in land use from forest plantation to pasture in the upper catchment, resulting in an increase in both the rate and total volume of flood runoff. Predictions of the magnitude of increased flood peaks ranged from a factor of two to ten.

Predictions of the effect of such land use change of about 4% of the catchment that drains to Rangiriri indicated that, in the Lower Waikato River, on small to medium floods (5 – 20year ARI events), the effect would be insignificant. However, during large floods (100year ARI), the peak flood water level would increase between 0 and 40 mm, and during extreme flood events (500year ARI) an increase between 0 and 270 mm would be expected.

In areas of pastoral land use, erosion of stream banks is a significant sediment source. Estimates indicate that about 7% of Waikato River stream bank length in pastoral zones is subject to erosion and this contributes about 27,000 cubic metres per year (m3/y) from tributaries to the mean sediment load in the Lower Waikato River. However, this represents a small volume when

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compared with the sediment supply from upstream (141,000 m3/y) and the current mean annual sand extraction of approximately 100,000m3/year.

While negligible in terms of sediment loads in the river, the proposed water take would result in a net reduction in sediment in the river, and a consequent positive effect on the bed levels. However, the reduction is negligibly small when compared with erosion loads, upstream sediment supply, and mean annual sand extraction.

2.8 Sediment Removal Through Additional Water Take

The removal of sediment within the water column of the proposed additional take has been estimated to be between 1,300 and 16,700kg/day – see page 60. This translates to an estimate of the volume of sand extracted from the river with the additional water take of between 300 and 3,800m3/year. Even if the maximum rate of removal of sediment through the additional water take of 3,800m3/year is assumed, this represents less than 4% of the projected on-going commercial sand extraction rate of approximately 100,000m3/year.

2.9 Conclusions

The proposed additional take is 150,000 m3/day, with a maximum additional instantaneous take of 3.2 m3/s and a maximum total take of 5.65 m3/s to allow for outages, downtime, maintenance or other situations where the full daily volume will not be taken over a 24-hour period. While the peak rate of taking will not occur at all times, this rate has been used to assess the effect of the 3 take. This take is negligible compared with the median daily flow of 358.6 m /s, and the Q5 flow of 185.9 m3/s.

The proposed take will have a less than minor impact on sediment processes in the Waikato River.

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3. REVIEW OF DEVELOPMENT IN THE WAIKATO RIVER

The major developments in the Waikato River catchment that have affected the characteristics of the Lower Waikato River are identified as hydro dam development, sand extraction, flood protection works, and land use changes. These developments are briefly described in the following, and then linked to measured changes in bathymetry of the Lower Waikato River in later sections of this report.

Hydroelectric power development has been a major factor in the development of the Waikato River. Arapuni was the first dam, commissioned in 1932. Development continued until 1964 when the last of eight dams, Aratiatia, was commissioned.

As a consequence of dam construction, flows in the Waikato River are strongly regulated. In particular, regulation at Karapiro Dam, as the furthest downstream structure, has a major influence on flows in the Lower Waikato River. Flood management rules, generation criteria and conditions of consent for Mercury NZ Ltd (Mercury) at Karapiro largely govern this regulation.

Apart from flow regulation, the main effect of the hydro dams on the Waikato River is a virtual complete blockage to the movement of sediment below Karapiro Dam. This has lead to the creation of an erosion head that is progressively lowering the riverbed below Karapiro Dam. A major source of sediment into the Lower Waikato River is now from the Waipa River, which enters the Waikato River at Ngaruawahia, approximately 45 km downstream of Karapiro. NIWA (2001) estimated the sediment supply from the Waipa River to be 54,000m3/y, compared with a bed material load on the Waikato River just upstream of the Waipa confluence of 99,000 m3/y (Barnett & MacMurray Ltd, 2009) (Note that both figures refer to the bulk volume of sand, including the pore volume).

A further significant impact associated with hydro dam development has been the installation of control gates at Lake Taupō to control outflows from the lake. As a result, flows in the Waikato River are now largely totally controlled to suit electricity generation requirements.

Additionally to the Waikato River dams, a major power scheme was initiated upstream of Lake Taupō on the Tongariro River. The Tongariro Power Scheme also has significant impacts on the hydrology of the Waikato River because of the diversion of water from tributaries of the Whanganui, Rangitikei, Whangaehu, and Tongariro Rivers into Lake Taupō. The average diversion flow into Lake Taupō is 32 m3/s, increasing the mean flows in the Lower Waikato River by about 10%.

Commercial sand extraction has been a major development aspect in the Lower Waikato River since the 1950s. Latterly, in the decade from 1984 to 1994, the main sand extraction occurred between Mercer and Tuakau. As a consequence, there has been a marked lowering of the riverbed in the Lower Waikato River.

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The rate of sand extraction increased slowly to around 200,000 m3/y in the early 1960s, before increasing rapidly to more than 1 million m3/y in 1974. The extraction rate then fell rapidly to about 250,000 m3/y in 1981. The next peak of about 500,000 m3/y was reached in 1987. Since then, the rates have fallen steadily to approximately 100,000 m3/y in 2009 – a level that has been maintained since. In total, some 18 million m3 of sand has been extracted from the Lower Waikato River since 1953.

Sand extraction is now seen as the primary mechanism for maintaining the bed levels sufficiently low to ensure that required flood protection standards in the Lower Waikato catchment are met.

Flood protection works in the Lower Waikato River catchment have had a long history. The first river training works were established between 1911 and 1917, but evidently were not particularly successful.

Floods in 1952, 1956 and particularly 1958 exposed the poor level of natural protection against flooding. In addition to inundating rural agricultural land for long periods, the flood of 1958 caused severe damage within the boroughs of Te Kūiti, Ōtorohanga and Huntly.

As a result of data collected from the 1958 flood event, a comprehensive proposal for a flood protection scheme was created. Work commenced in 1961 and was largely completed by 1982.

The design of the Lower Waikato Flood Protection Scheme (LWFPS) was based on mimicking the natural processes within two storage areas, Lake Waikare and the Whangamarino wetland, but in a controlled fashion. The benefits of the storage areas in reducing peak flows were thus retained.

Land use changes are well known to significantly change the river regime, particularly with regard to flow rates and sediment load.

Within the Waikato River catchment, there has been a progressive change in land use from forest plantation to pasture. Such changes result in both the rate and total volume of flood runoff increasing. The magnitude of these observed increases in flood peaks ranged from a factor of two to ten (Environment Waikato (2009)). The explanation given for this change is the reduction in the infiltration capacities of the soil following conversion to pastoral agriculture as a result of soil compaction due, for example, to grazing animals and vehicle use. While scientific consensus exists for an increase in flood flows from pasture, the increases are highly variable and based on limited and small-scale studies.

The effects of land use changes on sediment yield are less obvious. Certainly, where the vegetal cover is removed from a land surface, the rate of removal of the soil material, at least initially, increases rapidly. In a recent study of the Waikato region (NIWA (2012)), it was found that variations in sediment yield are due mainly to catchment runoff (or rainfall, which is highly correlated with runoff), mean slope, and land-cover. It was noted that, other factors being equal, sediment yields are lower from forested catchments compared with catchments in pasture or horticulture. The tendency for forest land-cover to be associated with steeper, wetter terrain and

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for pasture to be associated with flatter, drier country tend to counter-balance and reduce the range of sediment yields over the region.

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4. “NATURAL” VARIABILITY IN FLOW RATES IN LOWER WAIKATO RIVER

4.1 Analysis of Flow Records Between 1963 and 2020

Flow records at the Mercer Bridge, approximately 6 km upstream of the Watercare intake site, were made available by WRC (2014 & 2020). Between this location and the Watercare intake site, there are no significant inflows to the Waikato River. The total catchment area at Mercer Bridge is 13,861 square kilometres (km2) and at the Watercare intake site, the total catchment area is 2 5 3 3 14,063 km . The corresponding Q5 flows are 185.3 m /sec and 185.9 m /sec, WRC (2014 & 2020). Evidently there are only minor inflows between the Mercer Bridge and the Watercare intake site and, accordingly, the flow records from the Mercer Bridge may be considered as applicable at the intake site for the present purposes.

The flow records were of mean daily flows between 14th June 1963 and 17th November 2020. From the raw daily mean data, monthly means and annual means were developed for the Waikato River at Mercer Bridge. Plots of these data are presented in Figure 4.1 (mean daily flow), Figure 4.2 (mean monthly flow), and Figure 4.3 (mean annual flow). Figures 4.2 and 4.3 are developed from data for complete months and complete years respectively. A summary of statistics is presented in Table 4.1.

About 7.6 km downstream of the Tuakau Bridge, the Whakapipi Stream enters the Waikato River. Mean daily flow records between 5th March 1984 and 17th November 2020 for this stream were also made available by WRC (2014 & 2020).

5 Q5 is the one in five year seven-day low flow, i.e. the stream flow that has a 20% chance of occurring in any one year (or a likelihood of occurrence of once in every five years, also termed a ‘five-year return period’). The Q5 is calculated from the lowest seven consecutive days of flow in each year. Page 15 of 110

Waikato River Flows at Mercer Bridge - Mean Daily 1600

Mean Daily Flows Linear Trend Line 1400 Linear (Mean Daily Flows) y = -0.0005x + 418.94 R² = 0.0003

1200 )

s 1000

(

e 800

o l

F 600

400

200

0 1/1/1963 1/1/1973 2/1/1983 2/1/1993 3/1/2003 3/1/2013 4/1/2023 Date

Figure 4.1: Waikato River Flows at Mercer Bridge – Mean Daily, 1963-2020

Waikato River Flows at Mercer Bridge - Mean Monthly 1,200

1,000 Linear Trend Line

y = -0.0002x + 405.16 R² = 5E-05

800

)

(

e 600

l F 400

200 Mean Monthly Flows

Linear (Mean Monthly Flows) 0 Jan-63 Jan-73 Jan-83 Jan-93 Jan-03 Jan-13 Jan-23 Date

Figure 4.2: Waikato River Flows at Mercer Bridge – Mean Monthly, 1963-2020

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Waikato River Flows at Mercer Bridge - Mean Annual

600 Linear Trend Line y = 0.0001x + 396.52 R² = 0.0002 500

400

)

(

e 300

l F 200 Average Yearly Flow

Linear (Average Yearly Flow) 100

0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 Date

Figure 4.3: Waikato River Flows at Mercer Bridge – Mean Annual, 1963-2020

The flow records for the Whakapipi Stream were also analysed and the mean daily data statistics are included in Table 4.1.

Table 4.1: Statistics for Flow Data at Mercer Bridge and Whakapipi Stream

Whakapipi Waikato River at Mercer Bridge Stream Averaged Averaged Daily Averaged Annual Averaged Daily Parameter Monthly Flow Flow (m3/s) Flow (m3/s) Flow (m3/s) (m3/s) Median 358.6 364.4 396.1 0.505 Mean 401.3 399.4 401.3 0.886 Standard 170.6 149.9 58.4 1.347 Deviation Maximum 1,525.4 1,088.6 569.5 29.858 Minimum 147.1 161.0 304.1 0.036

As expected, the computed mean flows in the Waikato River are similar in Table 4.1. The small differences are due to all daily data being used to calculate the average daily flow, and complete months and complete years of daily data being used to calculate the average monthly and average annual flow respectively. The standard deviations and maximum and minimum flows in Table 4.1

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indicate, however, that the river flow can vary significantly on a daily basis with progressively smaller variations on a monthly and annual basis.

On each of Figures 4.1, 4.2, and 4.3, the red line represents a linear regression trend of the data. The slope of the line implies a very small flow trend in the data with time. However, with the relatively large standard deviations in the data sets, this is not statistically significant.

The daily mean flow statistics for Whakapipi Stream, presented in Table 4.1, indicate that the inflow is negligible compared with measured flows at Mercer Bridge. For this reason, these statistics are not included in the assessment of flows in the Lower Waikato River.

4.2 Future Trends

The remaining consideration is the response of river flows and levels to climate change. Coupled with increases in mean atmospheric temperature, the current scientific evidence – e.g. Intergovernmental Panel on Climate Change (IPCC) (2001) – is that the frequency and severity of extreme rainfall can be expected to increase. The New Zealand Ministry for the Environment (MfE) in MfE (2008a) has correlated these effects and recommends percentage adjustments to apply to extreme rainfall per 1°C of warming, for a range of average recurrence intervals (ARIs) – see Table 5.2 of MfE (2008a).

Barnett & MacMurray Ltd (2010) developed an approximate relationship between extreme rainfall and runoff and applied this to examine the effect of climate change, concluding that the mean runoff response was 2.8 times the increase in rainfall. Utilising this factor in conjunction with the extreme rainfall factors in Table 5.2 of MfE (2008a), Barnett & MacMurray Ltd (2010) predicted percentage increases in high flows due to climate change for various ARIs and for various decades up until 2090-2099. Their results are summarized in Table 4.2.

Table 4.2: Percent increases in high flows due to climate change – from Barnett & MacMurray Ltd (2010)

Event ARI Decade 2 5 10 20 2040-49 9% 12% 15% 18% 2050-59 11% 15% 19% 22% 2090-99 21% 28% 35% 41%

Barnett & MacMurray Ltd (2010) noted further that, while it is likely that extreme rainfall and flows (the 2 year ARI event and greater) will increase as a result of rising temperatures, the same does not apply to low or mean flows. Thus, the effect of climate change on the flow statistics presented in Table 4.1, although positive (i.e. increasing flows) is likely to be small. It is possible,

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however, that the very small positive increase in flows indicated by the linear trend lines in Figures 4.1, 4.2, and 4.3 may be due to climate change.

The effect of climate change on water surface elevations is relevant because the Watercare intake structure is located within the tidal reach of the Tasman Sea. Tonkin & Taylor Ltd (2013, 2020a, 2020b), have noted that these tidal influences extend as far as Rangiriri, some 66 km upstream of the Waikato River mouth. Further, they note that the current daily tidal change at the intake site is approximately 0.5 m. Clearly then, the impact of sea level rise with climate change will be felt at the Watercare intake structure.

MfE (2008b) has addressed this issue in recommending base sea level rise allowances over the present century for planning and development purposes. Table 4.3 is adapted from MfE (2008b).

Table 4.3: Baseline Sea Level Rise Recommendations for Different Future Timeframes – from MfE (2008b)

Timeframe Base Sea Level Rise Allowance (metres relative to 1980-1999 average) 2030-2039 0.15 2040-2049 0.20 2050-2059 0.25 2060-2069 0.31 2070-2079 0.37 2080-2089 0.44 2090-2099 0.50 2100 onwards 0.1/decade

Evidently, all other things being equal, a rise in the sea level will lead to a rise in the water surface elevation at the Watercare intake structure. Barnett & MacMurray Ltd (2010) have modelled the change in water surface elevation in the Lower Waikato River as part of their study of the effects of sand extraction. Table 4.4 is derived from their study, assuming no sand extraction is taking place and presents the computed water surface elevation at Tuakau for a river flow of 350 m3/s. Note that the effect of sand extraction is considered in Section 6 of the current report.

Table 4.4 indicates small and irregular increases in water surface elevation at Tuakau with time up until the year 2047. Between 2047 and 2055, there is a small drop.

The irregularity in the data arises because, despite the assumption of no sand extraction, the modelling allows for variations in bathymetry due to sediment transport within the Waikato River.

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Table 4.4: Computed Water Surface Elevations at Tuakau for River Flow of 350 m3/s and Assuming No Sand Extraction – Extracted from Barnett & MacMurray Ltd (2010)

Year Water Surface Elevation Increase from Year 2007 Reference Figure in at Tuakau (metres (metres) Barnett & referenced to Moturiki MacMurray Ltd Datum) (2010) 2007 101.3 0 2017 101.8 0.5 Figure 30 2027 101.4 0.1 Figure 33 2037 101.9 0.6 Figure 36 2047 101.9 0.6 Figure 39 2055 101.5 0.2 Figure 42

It is noted that the MfE (2008b) report was recently updated MfE (2017). The updated report, based on extensive climate modelling, lead to an updated sea level rise table, reproduced in Table 4.5.

The four different scenarios in Table 4.5 represent different Representative Concentration Pathways (RCP), where the number following RCP represents a radiative forcing value (Watts/m2), which is essentially the difference between sunlight absorbed by the earth and energy radiated back to space. Each number represents a different level of mitigation of greenhouse gas concentrations. It is current practice for water profile modelling to assume RCP4.5 and RCP8.5 MacMurray (Barnett & MacMurray Ltd) (pers. comm) (2020).

Table 4.5: Decadal increments for projections of sea-level rise (metres above 1986–2005 baseline) for the wider New Zealand region (reproduced from Figure 10 of MfE(2017))

NZ SLR scenario NZ RCP2.6 M NZ RCP4.5 M NZ RCP8.5 M NZ RCP8.5 H+ Year (median) [m] (median) [m] (median) [m] (83rd percentile) [m] 1986–2005 0 0 0 0 2020 0.08 0.08 0.09 0.11 2030 0.13 0.13 0.15 0.18 2040 0.18 0.19 0.21 0.27 2050 0.23 0.24 0.28 0.37 2060 0.27 0.30 0.36 0.48

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2070 0.32 0.36 0.45 0.61 2080 0.37 0.42 0.55 0.75 2090 0.42 0.49 0.67 0.90 2100 0.46 0.55 0.79 1.05 2110 0.51 0.61 0.93 1.20 2120 0.55 0.67 1.06 1.36 2130 0.60* 0.74* 1.18* 1.52 2140 0.65* 0.81* 1.29* 1.69 2150 0.69* 0.88* 1.41* 1.88

The sea level rise adopted by Barnett and MacMurray (2010) for their profile modelling for the year 2059 was 0.25m. Evidently, adopting the updated data in Table 4.5 for the year 2060, a sea level rise of 0.30m (RCP 4.5) or 0.36m (RCP8.5) would be more appropriate. (ie 0.05 to 0.11m higher). The potential effects on the computed water surface elevation at Tuakau for a river flow of 350m3/sec, presented in Table 4.4, is considered to be negligible due to the relative steepness of the river MacMurray (Barnett & MacMurray Ltd) (pers. comm) (2020). Thus, it is considered that the predicted increases in water surface elevation at Tuakau up till 2055, presented in Table 4.4, remain valid.

It is noted, however, that significantly greater water surface elevation rises are predicted in Table 4.5 beyond the year 2060. For example, in the year 2100, water surface elevation rises of 0.55m (RCP4.5) and 0.79m(RCP8.5). These rises continue to increase right up to the last year of prediction of 2150.

Although the water surface elevations at Tuakau presented in Table 4.4 are considered to be appropriate, further water profile modelling, based on the projected sea level rises in Table 4.5, would be required to predict water level rises at Tuakau beyond the year 2060.

There have been few published studies on the physical or ecological characteristics of the Waikato River estuary or delta. Of interest, however, have been two studies involving measurements of saline intrusion upstream of the mouth of the estuary.

A survey of the Waikato River estuary in 1977, undertaken by Heath and Shakespeare (1977) and referenced by Jones and Hamilton (2014) involved one-off measurements of temperature and salinity at seven stations in mid-summer. These measurements indicated that salinity declined rapidly (from salt to nearly freshwater) between 3 and 6 km from the mouth of the estuary.

The measurements of Jones and Hamilton (2014) indicated that the limit of saltwater intrusion was at least 12 km from the entrance. It is not clear if this greater intrusion represents a significant change in salinity conditions. Jones and Hamilton (2014) note that it is likely that over the full range of possible river flows and tidal cycles the extent of saline intrusion will be highly variable, Page 21 of 110

potentially ranging from close to the entrance to at least 13 km upstream. Thus, there is no conclusive evidence that saline intrusion is extending further upstream than it has in the past. Watercare’s intake structure is located 34 km upstream of the Waikato River mouth.

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5. HISTORICAL CHANGES IN BATHYMETRY IN THE LOWER WAIKATO

5.1 Introduction

In this section some general aspects of bathymetry changes in rivers are first discussed. Attention is then turned to the Lower Waikato River and a methodology is developed for analysing temporal changes in river depth. Detailed bathymetric cross-sections are surveyed by WRC on a nominal 10- year cycle. The latest WRC survey data available were obtained in 2017. However, these data are supplemented by some additional surveys at WRC cross-section locations, local to the Pukekawa quarry, up to 2020.

The available bathymetric survey data in the Lower Waikato River are discussed and a summary of changes between 1986 and 2017 over a 22.5 km length of the Lower Waikato River, encompassing the Watercare intake is presented and briefly discussed.

5.2 Bathymetry Changes and Analysis in Mobile Bed Rivers

Rivers are classified according to their pattern in plan. The index used to describe the river’s plan form is the sinuosity, defined as the ratio of the valley slope to the channel slope, or the ratio of channel length to valley length.

Alluvial rivers generally exhibit one or more of three basic shapes – straight (or sinuous), meandering, or braided. Truly straight rivers are rare in nature.

According to this classification, a “straight” river is one that does not have a distinct meandering pattern. Typically, such a river has a sinuosity less than about 1.5 (Chang, 1988).

A Google Map image of the Waikato River in the region of Tuakau is presented in Figure 5.1. It is clear that curves are generally relatively gentle and there is little or no evidence of periodic meandering. It is evident that the Waikato River may be classified as a “straight” (or sinuous) river. In Figure 5.1, two cross-sections are highlighted – XS-20 and XS-35. These cross-sections are utilised in the morphology discussion that follows.

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Figure 5.1: Waikato River in the Tuakau locale, highlighting cross-sections XS-20 and XS-35

Although the Waikato River does have a relatively straight alignment, its thalweg – i.e. the locus of the deepest part of the channel between the riverbanks – may wander back and forth from one bank to the other. This wandering behaviour is a dynamic process, changing the shape of the bed both temporally and spatially as the meandering shape migrates downstream. As a consequence, at a particular river location, the cross-sectional shape changes with time as the meandering thalweg moves through the cross-section.

This behaviour is illustrated in Figure 5.2. This figure shows the survey results of cross-section measurements obtained between 1973 and 2017 at Location XS-20, which, as shown in Figure 5.1, is located on a relatively straight reach of the Waikato River. It is evident that, at the time of the 1973 survey, the thalweg was against the right bank. In 1980, it is against the left bank; in 1986, the thalweg was again against the right bank; in 1998 close to the left bank; and in 2007 and 2017 back against the right bank.

At some cross-sections, however, the thalweg does not wander back and forth between the banks, instead remaining against one bank. This is illustrated in Figure 5.3, which shows the survey results of cross-section measurements obtained between 1986 and 2017 at Location XS-35. As shown in Figure 5.1, this cross-section is located at the apex of a river bend.

Figure 5.3 shows that the thalweg remains generally against, or close to, the left bank. This behaviour is typical of flows through bends in alluvial rivers and is due to the presence of secondary currents. These currents act to scour the outside of the bend and deposit sediment on the inside of the bend, leading to the relatively stable cross-sectional shape shown in Figure 5.3. Page 24 of 110

Although this discussion helps to explain observed bathymetric behaviour in alluvial rivers, it is noted that a number of other factors can modify the observed behaviour. These factors include the presence of islands, non-erodible bank features such as rock bluffs, bank and bed protection measures and so on. Nevertheless, the descriptions above do explain in general how the morphology of an alluvial river varies (in straight reaches), or doesn’t vary (in bends), with time. In particular these descriptions illustrate how an apparent change in depth at a given location in the river may, in fact, represent simply the movement of the thalweg with time.

The changes in cross-section shape with the movement of the thalweg illustrate a difficulty in determining readily how the depth of flow (or the bed elevation) may be changing with time. For the present study, where bathymetric changes in response to development, this is a major issue, hence a suitable methodology was developed and is described in the following.

XS - 20

6.00

4.00

2.00

0.00 )

m -2.00

(

i t

a -4.00 1913

l E

1962 d

e -6.00

B 1973

-8.00 1980 1986 -10.00 1998 2007 -12.00 2017 -14.00 0 50 100 150 200 250 300 350

Transverse Distance (m)

Figure 5.2: Results of Cross-section Surveys at XS-20

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XS-35 5.00

4.00

3.00

2.00

) 1.00

m (

1964

n o

i 1969 t

a 0.00

v 1975

l E

1986 d e -1.00 B 1991 1993 -2.00 1998 2007 -3.00 2017

-4.00

-5.00 0 50 100 150 200 250 300 350 400 Transverse Distance (m)

Figure 5.3: Results of Cross-section Surveys at XS-35

The methodology is based on the determination of the change in the mean relative depth (MRD). The mean depth is defined as the cross-sectional area below a pre-determined level divided by the channel width at the top of the bank. For a given river location, the level and the channel width remain constant for each measured cross-section at that location. Consequently, the value of the defined mean depth has no physical meaning because it is relative to an arbitrary lid level. Because the lid level is defined arbitrarily, the defined mean depth is also arbitrary. Nevertheless, changes in the defined mean depth with time are relevant and represent quantitative measures of the distance by which the bed elevation is raised or lowered with time. It is for this reason that the methodology is described as identifying the change in MRD.

The methodology is illustrated with reference to Figure 5.4. Figure 5.4(a) shows six measured profiles at Cross-section XS-28 obtained for surveys conducted between 1962 and 2017. Figure 5.4(b) importantly provides a quantitative indication of the change in bed elevation with time. For the survey of 1962, the mean relative bed elevation was computed to be -3.74 m – i.e. the mean elevation of the bed was 3.74 m below the arbitrary lid level of 4 m and was calculated as the total cross-sectional area below this lid level divided by the assessed width at the top of bank of 270 m. As shown by the dashed construction lines in Figure 5.4(b) the mean relative bed elevation reduced from -3.74 m to -4.56 m over the period of 13 years between the surveys of 1962 and 1975. Thus, the mean bed level dropped by 0.82 m (4.56 – 3.74 m). A downward trending line indicates a lowering of the bed and, hence, an increase in the depth while an upward trending line indicates that the bed is rising and the depth decreasing with time. It is evident that, at this cross-

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section, the bed level dropped relatively quickly between 1962 and 1975, slowly between 1975 and 1986, quickly again between 1986 and 1998, then rose slightly between 1998 and 2007 and dropping again between 2007 and 2017. Overall, however at XS-28, the river has deepened between 1962 and 2017 by 1.91m (5.65 – 3.74m).

XS-28

5.00

3.00

1.00

)

(

i t

a -1.00

e 1962 B 1975 -3.00 1986 1998 2007 -5.00 2017

-7.00 0 50 100 150 200 250 300 350 Transverse Distance (m)

(a)

XS-28 - CHANGE IN MEAN RELATIVE DEPTH

-3

-3.5 1962 13years -3.74 1975

-4

) m

( 0.82m

e v

i -4.5

t -4.56

a l

e -4.65

a e

M -5

-5.25 -5.35 -5.5

-5.65

-6 1950 1960 1970 1980 Date 1990 2000 2010 2020

(b) Page 27 of 110

Figure 5.4: Cross-section XS-28 – (a) Measured Cross-section Surveys and (b) Analysed Change in Mean Relative Depth

5.3 Lower Waikato River - Available Data

Extensive periodic cross-section surveys of the Waikato River have been undertaken by WRC, with some dating back to 1913. For the purposes of this study, data from 1962 onwards were considered. For earlier surveys some significant anomalies were noted, particularly in measured river width, indicating that cross-section locations may have been shifted.

It is noted that Barnett & MacMurray Ltd (2010) use the date identifier of 1988 to represent cross- section data obtained between Ngaruawahia and the Elbow (XS-20) in 1986 and between XS-20 and the Waikato River mouth in 1989. The analysis presented in this report covers only cross- section data between XS-20 (downstream) and XS-57 (upstream) and, all of these data were obtained in 1986. Thus, the date identifier of 1986 is used in the present study to indicate measurements that are identified as 1988 by Barnett & MacMurray Ltd (2010).

For the present study, use was made of all available cross-section information between XS-20 and XS-56 – a distance of 22.5 km. Generally, these data comprised the results of surveys undertaken at various intervals up until 2017 and were sourced from WRC. However, the detailed cross- sections for the 2007 survey between XS-20 and XS-38 were undertaken by Winstone Aggregates Ltd and were eventually only made available under tight restrictions.

Additionally, Winstone Aggregates Ltd provided limited reports and surveys of bathymetric data between XS-39 and XS-48 at two-year intervals between 2012 and 2020. The data analysis in Section 7 makes use of all available data. 5.4 Analysis of Lower Waikato River Data

The analytical methodology developed in Section 5.2 was applied at nearly all cross-sections between XS-20 and XS-56. This analysis enabled the determination of the change in MRD with time at each cross-section. Full graphs of the cross-sections and their temporal change, of which Figure 5.4 is an example, were developed and are presented in full in Appendix A.

It is noted that an earlier version of the current report (Keller, R.J. & Associates (2017)) only made use of survey data up until 2007. To clearly identify changes between the surveys of 2007 and 2017, the cross-sections for each of these surveys are emphasised in the cross-section graphs in Appendix A by a thick blue line for 2007 and a thick red line for 2017. Additionally, for cross- sections XS-39 to XS-48, supplementary graphs are presented for the period between 2007 and 2020 in Appendix B, incorporating the additional data provided by Winstone Aggregates Ltd.

The results of the analysis are summarised for the period 1986 to 2017 in Table 5.1 and discussed briefly in Section 5.5. This period was chosen because detailed sand extraction quantities are

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available, and sand extraction has been cited as a primary reason for bed level changes (several sources, e.g. Hicks and Hill (2010)).

It is noted, however, that sand mining has been carried out since the early 1950s and data since 1962 have been summarised by Hill (2011). These data are presented and discussed in more detail in Section 7. The analysis of the relative mean bed elevation covers all available and verified cross- section data. 5.5 Discussion

The second, third, fourth and fifth columns of Table 5.1 list the MRD at each cross section for the years 1986, 1998, 2007, and 2017 respectively. It is emphasised that the values in each column cannot necessarily be correlated for different cross-sections because different lid levels may have been used for different cross sections. However, comparisons for different years for a given cross section are valid as the same lid level is used for each year.

The final five columns, (6) to (10), of Table 5.1 show the change in MRD and specifically indicate a net aggradation (+ve) or degradation (-ve) of the bed. Considering XS-30 as an example, there is a net bed degradation of 300 mm between 1986 and 1998, a net aggradation between 1998 and 2007 of 100 mm, a net degradation of 200 mm between 1986 and 2007, a net degradation of 190mm between 1986 and 2017, and a net aggradation of 10mm between 2007 and 2017.

Table 5.1 indicates different extents and directions of bed level changes over the period of detailed record at different cross sections. These data are used in Section 7 to relate bathymetric changes with sand extraction levels.

Table 5.1: Change in MRD (metres) for Cross-section Surveys in 1986, 1998, 2007, 2017

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) Mean Relative Depth (m) Change in MRD (m) Cross- 1986- 1998- 1986- 1986- 2007- section 1986 1998 2007 2017 1998 2007 2007 2017 2017 XS-20 -6.16 -5.9 -7.77 -6.79 +0.26 -1.87 -1.61 -0.63 +0.98 XS-21 -4.23 -4.71 -5.12 -5.32 -0.48 -0.41 -0.89 -1.09 -0.20 XS-23 -4.22 -4.97 -4.70 -5.34 -0.75 +0.27 -0.48 -1.12 -0.64 XS-25 -3.79 -4.3 -5.27 -5.35 -0.51 -0.97 -1.48 -1.56 -0.08 XS-26A -2.43 -2.59 -2.5 -2.98 -0.16 +0.09 -0.07 -0.55 -0.48 XS-27 -4.50 -5.13 -4.60 -5.27 -0.63 +0.53 -0.10 -0.77 -0.67 XS-28 -4.65 -5.35 -5.26 -5.65 -0.70 +0.09 -0.61 -1.00 -0.39 XS-29 -2.89 -3.23 -2.96 -3.56 -0.34 +0.27 -0.07 -0.67 -0.60 XS-30 -4.52 -4.82 -4.72 -4.71 -0.30 +0.10 -0.20 -0.19 +0.01 XS-31 -4.85 -4.81 -4.85 -4.94 +0.04 -0.04 0 -0.09 -0.09 XS-31A -6.38 -6.17 -6.13 -6.7 +0.21 +0.04 +0.25 -0.32 -0.57 XS-33 -5.51 -6.24 -5.85 -7.14 -0.73 +0.39 -0.34 -1.63 -1.29 XS-35 -3.63 -4.15 -4.06 -4.09 -0.52 +0.09 -0.43 -0.46 -0.03 XS-37 -4.65 -5.06 -5.10 -5.19 -0.41 -0.04 -0.45 -0.54 -0.09 XS-37A -3.77 -4.27 -4.37 -4.69 -0.50 -0.10 -0.60 -0.92 -0.32 XS-38 -3.15 -3.49 -3.49 -3.61 -0.34 0 -0.34 -0.46 -0.12 XS-39 -2.92 -3.20 -3.62 -4.15 -0.28 -0.42 -0.70 -1.23 -0.53 Page 29 of 110

XS-40 -3.75 -4.38 -4.8 -4.94 -0.63 -0.42 -1.05 -1.19 -0.14 XS-41 -4.17 -4.56 -4.42 -4.52 -0.39 +0.14 -0.25 -0.35 -0.10 XS-43 -5.25 -5.75 -5.67 -5.74 -0.50 +0.08 -0.42 -0.49 -0.07 XS-44 -8.29 -6.94 -6.49 -6.66 +1.35 +0.45 +1.80 +1.63 -0.17 XS-45 -3.75 -4.30 -4.67 -4.83 -0.55 -0.37 -0.92 -1.08 -0.16 XS-46 -7.65 -8.68 -7.84 -8.63 -1.03 +0.84 -0.19 -0.98 -0.79 XS-47 -6.28 -7.18 -5.88 -6.45 -0.9 +1.3 +0.40 -0.17 -0.57 XS-48 -5.16 -6.09 -5.35 -5.48 -0.93 +0.74 -0.19 -0.32 -0.13 XS-49 -3.09 -3.31 -3.29 -3.41 -0.22 +0.02 -0.20 -0.32 -0.12 XS-50 -5.84 -5.92 -5.48 -5.45 -0.08 0.44 0.36 0.39 0.03 XS-51 -9.77 -8.18 -7.25 -8.17 +1.59 +0.93 +2.52 +1.60 -0.92 XS-52 -6.24 -5.94 -5.35 -5.77 +0.3 +0.59 +0.89 +0.47 -0.42 XS-53 -4.11 -4.10 -3.94 -3.97 +0.01 +0.16 +0.17 +0.14 -0.03 XS-55 -4.89 -4.40 -4.23 -4.21 +0.49 +0.17 +0.66 +0.68 +0.02 XS-56 -5.48 -5.32 -5.00 -5.01 +0.16 +0.32 +0.48 +0.47 -0.01

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6. HYDRO DEVELOPMENT

6.1 The Hydro Dams

There are eight hydro dams along the length of the Waikato River, from Aratiatia (upstream) to Karapiro (downstream). Construction of the dams has resulted in significant effects within the Waikato River and its catchment. Among these are changes to fisheries, and changes to the ecology, hydrology, sedimentology, and morphology of the river.

Table 6.1 lists the dams from upstream (Aratiatia) to downstream (Karapiro) with their years of construction and generating capacity.

Table 6.1: Waikato River Dams (adapted from NIWA (2010))

Dam First Operated (Year) Capacity (MWatts)

Aratiatia 1964 84

Ohakuri 1961 112

Atiamuri 1958 84

Whakamaru 1956 100

Maraetai 1953-62 360

Waipapa 1961 51

Arapuni 1929-46 197

Karapiro 1947 90

Karapiro Dam is the furthest downstream. The eight hydro dams within the Waikato River are managed by Mercury and, together with the Taupō Outlet Gates, regulate the Waikato River flows from Lake Taupō. Additionally, flows diverted from the headwaters of the Whanganui and Rangitikei Rivers by the Tongariro Power Scheme enter Lake Taupō and are managed by Genesis Energy Ltd.

Regulation at Karapiro Dam, as the furthest downstream structure, has a major influence on flows in the Lower Waikato River. Flood management rules, generation criteria and conditions of consent for Mercury at Karapiro largely govern this regulation.

The hydro dams act as sediment traps, storing on average 280,000 tonnes of sediment per year (t/y). Of this total, 167,000 t/y is sand and gravel that would nourish the bed of the Lower Waikato

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River in the absence of the dams, and 112,000 t/y is silt and clay that would be transported along the Lower Waikato River as suspended load. Lake Ohakuri stores the greatest single component of the total storage with about 125,000 t/y, followed by Maraetai, Karapiro and Whakamaru, storing about 40,000 t/y each. 6.2 Effect of the Hydro Dams on River Morphology

The interception of the bed-material load by the hydro dams prevents the replenishment of the bed sediment downstream. Because the river flow retains a sediment carrying capacity, the starving of sediment input from upstream means that the Waikato River scours the bed downstream to feed its sediment carrying capacity.

For this reason, the interception of the bed-material load upstream has been a major cause of falling riverbed levels downstream of Karapiro Dam. The progressive reduction in downstream sediment transport below Karapiro Dam has resulted in a drop in the bed elevation that now extends as far downstream as Ngaruawahia.

Initially, the bed level reduction was confined upstream from Hamilton and the bed-material scoured from there served to replace that trapped in the reservoirs upstream. Since Karapiro Dam was built in 1947, riverbed surveys have shown that the erosion head has migrated downstream as a wave.

With time, the preferential entrainment of the fine component of the bed sediment results in a bed surface layer that is coarser than the underlying sediment. This results in a so-called “armour layer” that, to some extent, resists further erosion. Over recent decades, at Hamilton, the reduction in the bed level has averaged 25–35 mm per year. Some sections have deepened at a faster rate while others have been more stable, evidently in response to at least partial armour development.

Downstream of Ngaruawahia, the tendency for bed level reduction is lessened owing in part to restoration of the bed-material load from the sediment scoured from upstream, but primarily from substantial sediment inputs from the Waipa River. Barnett & MacMurray Ltd (2009) estimated the sediment transport rate by volume in the Waikato River immediately upstream of the confluence with the Waipa River as 99,000 m3/y. This compares with an estimate by NIWA (2001) of the sediment transport rate by volume in the Waipa River of 54,000 m3/y. A subsequent study by NIWA, quoted by Barnett & MacMurray Ltd (2010), indicated an average sediment transport rate by volume in the Waipa River of 60,000 m3/y. It is clear that a substantial proportion of the total sediment load in the Waikato River downstream of Ngaruawahia is due to sediment inflows from the Waipa River.

Further downstream, as examined in Section 7, riverbed down-cutting has for the most part coincided with sand extraction; when this has ceased, riverbed levels have generally recovered.

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7. SAND EXTRACTION

7.1 Available Data

Detailed data on sand extraction are available between 1988 and 2007 (Barnett & MacMurray Ltd (2010). Additional sand extraction data from 2007 to 2012 have also been made available (pers. comm. Lamb, R. (WRC) (2018)). Sand extraction commenced at Pukekawa in 2013 and detailed monthly records to September 2020 have been made available (pers. comm. Twidle, R. (Winstone Aggregates) (2018) (pers. comm. Macpherson, N. (Winstone Aggregates) (2020). All yearly data from 1988 to 2019 are summarised in Figure 7.1.

However, sand mining has been carried out since the early 1950s and data since 1962 have been summarised by Hill (2011). Figure 7.2 summarises the extraction data and is taken from Hill (2011).

Figure 7.3 shows the same Google map of the Tuakau reach of the Lower Waikato River as in Figure 5.1, but with the extents of the study reach shown (XS-20 to XS-56) and with the sand extraction sites indicated. These sites are located at XS-20 (Winstone’s – Puni), XS-35 (Winstone’s – Tuakau), and XS-56 (Winstone’s and Stevenson’s – Mercer). These locations were provided by MacMurray (Barnett & MacMurray Ltd) (pers. comm) (2016) and correspond to the locations used in the major modelling study of Barnett & MacMurray Ltd (2010). The Pukekawa Quarry site located 195m downstream of XS-43 is also shown.

Sand extraction from Mercer ceased in 1996, from Tuakau in 2004, and from Puni in 2012. In January 2013 sand extraction commenced at Winstone’s Pukekawa Quarry site.

Sand Extraction in Lower Waikato 1988 - 2019

500000

450000 Winstones (Puni) 400000 Winstones (Mercer) Winstones (Tuakau)

350000 Stevensons (Mercer)

Winstones Pukekawa

) 3

^ 300000 Total Sand Extraction

(

i t

c 250000

d 200000

a S

150000

100000

50000

0 1985 1990 1995 2000 2005 2010 2015 2020 Year

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Figure 7.1: Annual Sand Extraction in the Lower Waikato River 1988 - 2019

Figure 7.2: Historical and Forecast Volumes of Sand and Gravel Annually Extracted from Various Reaches of the Lower Waikato River (Hill, 2011)

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Figure 7.3: Waikato River in the Tuakau Region, Highlighting the Data Analysis Extents and Sand Extraction Locations

Figure 7.2 was analysed to determine the volume of sand mining each year between 1962 and 2007 from each of the three sites at Puni, Tuakau, and Mercer respectively. These data overlap the more precise data of Barnett & MacMurray Ltd (2010) and comparisons, showing the overlap, for each site are presented in Figures 7.4, 7.5, and 7.6.

Figure 7.4: Sand Extraction from Puni

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Figure 7.5: Sand Extraction from Tuakau

Figure 7.6: Sand Extraction from Mercer

Although there are some minor differences in detail between the overlapped records in Figures 7.4, 7.5, and 7.6, for the purposes of the current study, the long term records obtained from Figure 7.2 can be considered to be validated and can be used to investigate the changes in bathymetry in the vicinity of the sites. This investigation is presented and discussed in the following. 7.2 Effect of Sand Extraction on Bathymetry

The locations for sand extraction from Puni (XS-20) and Mercer (XS-56), coincidentally, represent the downstream and upstream boundaries respectively of the study area. The Tuakau sand extraction location is situated at XS-35 and is about half way along the study area. These locations permit the influence of sand extraction on local bathymetry upstream of the extraction location (XS-20), downstream of the extraction location (XS-56), and upstream and downstream of the extraction location (XS-35). 7.2.1 Mercer Extraction and Downstream Mean Relative Depth

Figure 7.7 shows the sand extraction record at Mercer (XS-56) with plots of the variation in MRD up to 6.7 km downstream. The extraction record commences in 1958 and shows substantial peaks of extraction in 1974 and 1987 with extraction ceasing in 1995.

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Sand Extraction & MRD - Mercer - Downstream

480000 0

Sand Extraction Record 420000 MRD - XS-56-0m -1 MRD - XS-55-827m D/S MRD - XS-53-1,395m D/S 360000 -2 MRD - XS-49-3,261m D/S

MRD - XS-41-6,712m D/S

)

) 3

300000 -3 m

(

v i

r 240000 -4

e n

A 180000 -5 M

120000 -6

60000 -7

0 -8 1950 1960 1970 1980 1990 2000 2010 2020 Year

Figure 7.7: Sand Extraction and MRD Records Downstream of XS-56

The MRD record at XS-56 commences in 1975, one year after the peak level of extraction in 1974. It shows a sharp rise (reduction in MRD), correlated with a steep reduction in extraction volume between 1974 and 1981. As the extraction volume rises again between 1981 and 1987, the local bed level drops again, before a continuous rise until 1995 when sand extraction ceased. From 1995 to 2007, with no sand extraction, the bed level rises more steeply. From 2007 to 2017 there is a very small reduction in MRD.

Between 1975 and 2007, the bed level has risen from -6.7 m to -5 m, representing a reduction in MRD of 1.7 m. This is clearly a direct outcome of sand extraction from the site.

The four MRD records downstream of the sand extraction site all commence in 1964. There is some inconsistency in these records, in that the MRD traces for XS-55, XS-49, and XS-41 all show a deepening trend with increasing sand extraction, while the MRD trace for XS-53 shows virtually no change between 1964 and 1975. However, with all traces there is a clear deepening trend with sand extraction and a clear shallowing trend with reduction and cessation of sand extraction.

7.2.2 Tuakau Extraction and Downstream Mean Relative Depth

Figure 7.8 shows the sand extraction record at Tuakau (XS-35) with plots of the variation in MRD up to 10 km downstream. The extraction record commences in 1960, shows substantial peaks of extraction in 1977 and 1986 with extraction ceasing in 2005.

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Unfortunately, good quality bathymetry records were not available within the first few kilometres downstream of the extraction site. Four traces are presented and, although there is some inconsistency, the same trends of a deepening of the bed during periods of substantial sand extraction and a shallowing during periods of reduced or no sand extraction are evident.

Sand Extraction & MRD - Tuakau - Downstream

160000 0

Sand Extraction Record

140000 MRD - XS-31-2,917m D/S -1

MRD - XS-29-4,818m D/S

120000 MRD - XS-27-6,524m D/S -2

MRD - XS-25-10,045m D/S

)

) 3

100000 -3 m

(

v a

80000 -4 i

e n

A 60000 -5 M

40000 -6

20000 -7

0 -8 1950 1960 1970 1980 1990 2000 2010 2020 Year

Figure 7.8: Sand Extraction and MRD Records Downstream of XS-35

7.2.3 Tuakau and Puni Extraction and Upstream Mean Relative Depth

Figure 7.9 shows the sand extraction record at Tuakau (XS-35) with plots of the variation in MRD up to 3.4 km upstream. In Figure 7.10, the sand extraction record at Puni (XS-20) is presented, together with plots of the MRD up to 9 km upstream.

In contrast to Figures 7.7 and 7.8, Figures 7.9 and 7.10 show little direct correlation between sand extraction and bathymetry changes upstream. This is not surprising when the effect of sand extraction on the overall sediment movement in the Waikato River is considered. The Waikato River has a sediment transport capacity and when sand is removed at an extraction site, the river seeks to recover capacity downstream of the extraction site. It does this by eroding the bed and will continue to do so until a new equilibrium is reached.

When sand extraction reduces or ceases, the local hole at the extraction site starts to fill through the sediment supply from upstream and this effect propagates downstream.

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Sand Extraction & MRD - Tuakau - Upstream

160000 0 Sand Extraction Record

MRD - XS-37-653m U/S 140000 -1 MRD - XS-38-1,597m U/S

MRD - XS-39-2,134m U/S 120000 -2 MRD - XS-40-2,730m U/S

MRD - XS-41-3,381m U/S

)

) 3

100000 -3 m

(

v a

80000 -4 i

e n

A 60000 -5 M

40000 -6

20000 -7

0 -8 1950 1960 1970 1980 1990 2000 2010 2020 Year

Figure 7.9: Sand Extraction and MRD Records Upstream of XS-35

Sand Extraction & MRD - Puni - Upstream

200000 0 Sand Extraction Record

MRD - XS-20-0m 175000 -1 MRD - XS-21-519m U/S

MRD - XS-25-2,373m U/S 150000 -2 MRD - XS-27-5,894m U/S

MRD - XS-29-7,600m U/S

)

) m

3 125000 -3

(

^ MRD - XS-30-9,048m U/S

(

v a

100000 -4 i

n e

A 75000 -5 M

50000 -6

25000 -7

0 -8 1950 1960 1970 1980 1990 2000 2010 2020 Year

Figure 7.10: Sand Extraction and MRD Records Upstream of XS-20

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7.2.4 Pukekawa Extraction and Upstream and Downstream Mean Relative Depth

Figure 7.11 shows the sand extraction record at Pukekawa with plots of the variation in MRD up to 1.65 km upstream. Figure 7.12 shows the sand extraction record at Pukekawa with plots of the variation in MRD up to 1.71 km downstream.

The sand extraction record is very short with extraction only commencing in January 2013. The extraction rate has been highly variable with a minimum of 70,860 cubic metres in 2015 and a maximum of 141,700 cubic metres in 2018. Since 2018, the annual extraction rate has dropped to about 100,000 cubic metres, estimated in 2020. It is understood that this extraction rate is likely to continue into the future.

Initially, only the latest (2017) cross-section survey data were available for analysis at this site. Thus, it was not feasible to draw any definitive conclusions on the effect of Pukekawa sand extraction on the bathymetry. Both Figure 7.11 and 7.12 show an increase in depth in the adjacent cross-sections, but this generally continues a trend that predates the commencement of sand extraction.

Sand Extraction & MRD - Pukekawa - Upstream 160000 -1

Sand Extraction Record 140000 -2 MRD - XS-43-195m U/S MRD - XS-44-714m U/S

120000 MRD - XS-45-1,241m U/S -3

MRD - XS-46-1,645m U/S

) )

3 100000 -4

(

v a

80000 -5 i

n A 60000 -6 M

40000 -7

20000 -8

0 -9 1960 1970 1980 1990 2000 2010 2020 2030 Year

Figure 7.11: Sand Extraction and MRD Records Upstream of Pukekawa

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Sand Extraction & MRD - Pukekawa - Downstream 160000 0

140000 -1

120000 -2

) )

3 100000 -3

(

v a

80000 -4 i

n A 60000 -5 M

Sand Extraction Record 40000 -6 MRD - XS-41-451m D/S

MRD - XS-40-1,110m D/S 20000 -7 MRD - XS-39-1,705m D/S

0 -8 1960 1970 1980 1990 2000 2010 2020 2030 Year

Figure 7.12: Sand Extraction and MRD Records Downstream of Pukekawa

However, further detailed survey information was provided by Winstone Aggregates in 2020 and a detailed examination of the effect of Pukekawa sand extraction on local bathymetry between 2007 and 2020 was carried out. This is presented in the following section. 7.2.5 Pukekawa Sand Extraction Effect on Local Bathymetry

The further cross-sectional data were provided by Winstones (Winstone Aggregates, 2020), following the preparation of the draft of this report. These data were obtained at locations shown in Figure 7.13. Almost all locations coincide with WRC cross-sections. The two exceptions are SECTION PL1 and SECTION PL2 which are located between Cross-sections 39 and 40 and are, respectively, 50m downstream and upstream of the Vector Pipeline Bridge.

It is noted that the WRC surveys are conducted at approximately 10-year intervals, with the latest surveys in 2007 and 2017. The Winstones surveys include dates within the last 10-year period.

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Figure 7.13: Cross-section Locations for Winstone Aggregates Study

Figure 7.14 indicates the consented sand extraction zone utilised by Winstone Aggregates. Extraction generally takes place between cross sections 41 and 43, shown on Figures 7.13 and 7.14.

Figure 7.14: Consented Sand Extraction Area - Pukekawa

Figure 7.13 indicates five cross-sections (XS-39 to XS-41) downstream of the principal sand extraction area. Figure 7.15 shows the sand extraction record at Pukekawa with plots of the

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variation in MRD at these five cross-sections. In Figure 7.16, the sand extraction record at Pukekawa with plots of the variation in MRD for the six cross-sections (XS-43 to XS-48) upstream of the principal sand extraction area are presented. The full graphs for all eleven cross-sections are presented in Appendix 2.

In each of Figures 7.15 and 7.16 the same scale is used for Mean Relative Depth to enable easy comparison. Additionally, all analyses used the same lid level of +4m for the computation of Mean Relative Depth.

In undertaking the computations, it was noted that, for each cross-section, the profiles for different surveys did not necessarily match with respect to start and end locations and, hence, cross-section width. Care was taken to ensure that only common parts of each profile were used to ensure that valid temporal variations of Mean Relative Depth could be made.

Sand Extraction and MRD - Pukekawa Downstream of Normal Extraction Zone 200,000 -4

180,000

-4.5 )

160,000 m

(

) 140,000

-5 d

(

t n

120,000

t e

x 100,000 -5.5

l 80,000

i n

Annual Sand Extraction -6 t

a A 60,000 l

MRD-XS-39 e

MRD-XS-PL1 n a 40,000 MRD-XS-PL2 e -6.5 M MRD-XS-40 20,000 MRD-XS-41

0 -7 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey & Annual Extraction

Figure 7.15: Refined Sand Extraction and MRD Records Downstream of Pukekawa Extraction Zone

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Sand Extraction and MRD - Pukekawa U/S of Normal Extraction Zone 200,000 -4

180,000

-4.5

160,000 )

(

) 140,000

-5 d

(

t n

120,000

t e

x 100,000 -5.5

l 80,000

e n

Annual Sand Extraction v

i n

-6 t

a A MRD-XS-43 l

60,000 e R

MRD-XS-44

n a

MRD-XS-45 e

40,000 M MRD-XS-46 -6.5 MRD-XS-47 20,000 MRD-XS-48

0 -7 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey & Annual Extraction

Figure 7.16: Refined Sand Extraction and MRD Records Upstream of Pukekawa Extraction Zone

In general, Figure 7.15 supports the previous observations of correlation of changes in the bathymetry downstream with changes in sand extraction – deepening with increase in extraction and bed rising with a decrease in sand extraction. The effect appears to be more pronounced with distance downstream – the MRD at XS-39 shows a significant drop in the MRD and subsequent rise in the bed consequent to an increase and decrease respectively in the annual sand extraction. Further upstream, the changes in MRD with changes in sand extraction is present, but less pronounced and may reflect the time required for changes to move through the system and a difference in the location of sand extraction.

Figure 7.16 shows more mixed results and shows little direct correlation between sand extraction and bathymetry changes upstream. As noted earlier, this is not surprising when the effect of sand extraction on the overall sediment movement in the Waikato River is considered. The Waikato River has a sediment transport capacity and when sand is removed at an extraction site, the river seeks to recover capacity downstream of the extraction site. It does this by eroding the bed and will continue to do so until a new equilibrium is reached. It is interesting to note, however, that the bed level at XS-47 drops as the sand extraction increases, but that the bed level at XS-44 rises as the sand extraction increases. The reason is not immediately obvious but may reflect local unrelated interactions between the bathymetry and hydraulic conditions.

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7.2.6 General Discussion

There is no doubt that the deepening of the bed levels downstream of the extraction sites is a direct consequence of the sand extraction. Hicks (2010) has considered bed level changes between the Karapiro Dam and Port Waikato, making use of data on bed material load, tributary sediment supply, and sand and gravel extraction and developed the sediment load budget presented in Figure 7.17.

Figure 7.17: Sediment Load Budget in Waikato River (Hicks (2010))

Considering the Lower Waikato River below Ngaruawahia, Hicks (2010) notes a sediment supply across the upstream boundary of 141,000 m3/y, 27,000 m3/y from tributaries, 417,000 m3/y of bed degradation, 484,000 m3/y of sand extraction leaving a supply to Port Waikato of 101,000 m3/y. Hicks (2010) suggests that the good match between the volume of bed degradation and sand extraction indicates a direct correlation between the two.

Barnett & MacMurray Ltd (2010) demonstrated that the bed degradation downstream of Tuakau between the surveys of 1998 and 2007 was consistent with the sand extraction records at Tuakau and Puni over the same period.

Barnett and MacMurray Ltd (2020) also reviewed the bed degradation in the Pukekawa Reach (XS- 39 to XS-48) and found reasonable correlation between the sand extraction records and their modelling of bed degradation.

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8 LOWER WAIKATO FLOOD PROTECTION

8.1 Introduction

The impetus for development of the LWFPS was the major floods experienced in 1952, 1956 and particularly 1958. Work commenced in 1961 and was largely completed by 1982.

The design of the LWFPS was based on mimicking the natural processes within two storage areas, Lake Waikare and the Whangamarino wetland, but in a controlled fashion. In this way, the benefits of the storage areas in reducing peak flows could be retained.

In this section, an outline of the LWFPS and how it operates is presented first to provide context. The effect of the LWFPS on Waikato River water levels and bed levels is then assessed. 8.2 Lower Waikato Flood Protection Scheme Description

Prior to the development of the LWFPS, the floodplain of the Lower Waikato River contained many wetlands and shallow lakes. These wetlands, collectively known as the Whangamarino Swamp, combined with Lake Waikare, represented a natural reservoir for floodwaters passing down the Waikato River. These features, acting as major storages, helped to attenuate peak flows in the Lower Waikato River.

Despite the clear beneficial impact of these natural storages on peak flood flows, their natural action was uncontrolled, and this aspect contributed to the widespread flooding associated with large flow events. When the Lower Waikato River rose in flood, overland flow would occur from the Waikato River into Lake Waikare, raising its water surface elevation. This in turn led to the overtopping of the low peat ridge along its northern foreshore with water spilling into the Whangamarino Swamp. In the same manner, a sufficient increase in the Waikato River level would cause the Whangamarino River to reverse, with flow from the Waikato River into the Whangamarino Swamp.

The storage capacity of both Lake Waikare and the Whangamarino Swamp results in significant attenuation of the flood peaks in the Waikato River. However, the corollary was that the river was in flood for long periods of time due to the large volumes of stored water and their relatively slow release back into the Waikato River.

Essentially, the design of the LWFPS results in the reproduction of the natural water storage functions of Lake Waikare and the Whangamarino Swamp but in a controlled manner. Thus, the benefits of the storage areas in reducing peak flows were retained but their filling and subsequent release back into the Waikato River were controlled. Figure 8.1 shows the main features of the LWFPS. This figure and the following description of the scheme operation are taken from (WRC (2011)).

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With reference to Figure 8.1, the two dominant flood storage features are Lake Waikare and the renamed Whangamarino wetland. A new outlet canal was constructed from Lake Waikare to the Whangamarino wetland with a control gate that could be varied to permit control of the lake level. The addition of a stopbank along the northern foreshore prevented overflow from Lake Waikare. Under normal circumstances, the outlet canal and control gate provided the means to permanently lower Lake Waikare, thereby providing more flood storage within the lake. Lake Waikare is then the primary flood storage for the LWFPS.

Additional structures included a raised spillway at Rangiriri to control the spilling of water from the Waikato River into Lake Waikare and the Whangamarino control gate to prevent backflows from the Waikato River in to the Whangamarino wetland during floods.

In addition to the construction of the spillways and control gates depicted in Figure 8.1, the LWFPS incorporated a major river training program, with stopbanks designed to narrow the Lower Waikato River with the aim of scouring a deeper more hydraulically efficient channel. The stopbanks are also shown in Figure 8.1.

Figure 8.1 Lower Waikato Flood Scheme (Waikato Regional Council (2011))

Under flood conditions, when the Waikato River starts to backflow in to the Whangamarino wetland, the Whangamarino control gates are closed. The Lake Waikare outlet gate is also normally closed, essentially isolating the two major storage areas. Flood runoff from the local Whangamarino and Maramarua catchments is retained in the wetland storage area. Page 47 of 110

The trigger level for operation of the Rangiriri spillway occurs when the water level at Rangiriri reaches 8.8 m above sea level. This corresponds to a flow in the Waikato River of 1,300 m3/s (Works Consultancy Services, 1996) which is a flood with an ARI of 50 years. When this level is exceeded, water will spill from the Waikato River over the Rangiriri spillway and pass overland into Lake Waikare. Because the Lake Waikare gate is closed, any water spilling from the Waikato River and any runoff from the lake’s own catchment must be stored in the lake. In very large events, once the lake level exceeds 7.37 m, the Waikare Spillway is activated, passing water from Lake Waikare into the Whangamarino Wetlands.

Following the peak of the flood when the Waikato River level starts to fall, the Whangamarino gates are opened when the Waikato River level drops below the level of water impounded in the wetland. This allows water to drain from the wetland. The Lake Waikare control gate is then opened to commence the release of water stored in Lake Waikare to the Waikato River via the Whangamarino wetland. 8.3 Influence of Lower Waikato Flood Protection Scheme on Water Levels and Bed Levels

The impact of the LWFPS on the hydrology of the Waikato River has been to increase peak flood flows, but reduce the duration of major floods. Because of the loss of floodplain storage, the peak flows are not smoothed out as much as they used to be, but less water is now ponded for long periods of time.

Construction of the LWFPS has probably caused flood levels on the riverside of stop banks to rise within design limits. However, at mean and low river flows, the LWFPS has no effect on river levels.

Although the ultimate purpose of the LWFPS is to reduce flooding within the Waikato River, during low flows it is unlikely that the LWFPS has any major effect on water levels within the river. It is also unlikely that the LWFPS has any significant effect on sediment movement.

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9 LAND USE CHANGES

9.1 Introduction

It is known that land use changes can significantly alter the river regime, particularly with regard to flow rates and sediment load. Historically, following the arrival of the first Europeans, extensive clearing of land from forest to pasture occurred within the Waikato River catchment. With increased runoff rates from pasture, this historical change would have significantly increased river flows, leading to erosion and associated increased sediment load and reduced water quality (Environment Waikato (2008)).

Noting that the Lower Waikato River carries all waters flowing into the Waikato River catchment, it follows that this part of the river is significantly impacted by land use activities throughout the catchment. In the context of the present study, the effect of land use changes on flow rates and sediment yield – and consequent bathymetry changes - is of particular importance.

More recently, within the upper Waikato catchment, there has been a progressive change in land use from forest plantation to pasture. Such changes result in both the rate and total volume of flood runoff increasing. The magnitude of these observed increases in flood peaks ranged from a factor of two to ten (Environment Waikato (2009)). The explanation given for this change is the reduction in the infiltration capacities of the soil following conversion to pastoral agriculture as a result of soil compaction due, for example, to grazing animals and vehicle use. While scientific consensus exists for an increase in flood flows from pasture, the increases are highly variable and based on limited and small-scale studies.

The topography of the Lower Waikato River catchment, downstream of Lake Karapiro, is predominantly rolling or gently sloped land. Currently 74% of this catchment is primarily pasture, 4% is planted forest, 6% is indigenous forest, and the balance is classified as “other” (scrub, inland water, horticulture, willows, and poplar (Collier et al, 2010)). Considering the entire Waikato River catchment, 62% is pasture, 19% is planted forest, and 10% is native forest (Collier et al, 2010)).

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Within the upper Waikato River Catchment (Taupō to Karapiro), it is proposed to convert 567 km2 of forest land to pastoral agriculture in the period to 2025. This represents an area of land use change of about 4% of the catchment that drains to Rangiriri. A major simulation study (WRC (2009)) was undertaken to examine the effect of this land use change on flows within the Waikato River. The study predicted that, in the lower Waikato River from Ngaruawahia to Rangiriri, the impact of the land use change on small to medium floods (5 – 20 year ARI events) would be insignificant. During large floods (100 year ARI), the peak flood water level would increase between 0 and 40 mm, and during extreme flood events (500 year ARI) an increase between 0 and 270 mm would be expected. 9.3 Effect on Sediment Yield

Historically, land use changes in the Waikato River catchment have involved the removal of forest and scrub with conversion to agricultural pasture. Changes to ground cover, and particularly to bare soil exposure, lead to large increases in sediment loads. Of the areas affected by land use, most bare soil relates to tracks, and cultivation, with bare soil greatest on pastoral land.

Hicks (2004) reported on a survey that showed that about 10% of the Waikato River catchment was subject to soil disturbance, of which two thirds was due to land use activities and the balance to natural erosion. Farm and forestry tracks and poor pasture cover were the main elements in land use activities. Of the natural erosion processes, bare soil is associated mostly with sheetwash, landslides and rockfalls.

Erosion of stream banks is perceived to be a significant sediment source in areas of pastoral land use, particularly along unfenced banks accessible to stock (Hicks and Hill, 2010). Estimates indicate that about 7% of Waikato River stream bank length in pasture regions is subject to erosion. However, fencing of stream banks was noted to significantly reduce bank disturbance and represents an effective management practice for reducing sediment supply to the Waikato River.

As noted in Figure 7.17, the mean sediment load into the Lower Waikato River from tributaries is estimated to be 27,000 m3/y. Much if not all of this is due to erosion, both through land use activities and natural processes. Although significant, this represents a small volume when compared with the sediment supply from upstream (141,000 m3/y) and the mean annual sand extraction, calculated by Hicks (2010) to be 484,000 m3/y.

It is noted that Winstone Aggregates is the only company that currently extracts sand from the Lower Waikato River. Their current rate of extraction is about 100,000 m3/year, about one half of their consented extraction. It is understood that this reduced extraction rate will continue into the future.

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10 SEDIMENT REMOVAL THROUGH ADDITIONAL WATER TAKE

The removal of sediment within the water column of the proposed additional take has been estimated to be between 1,300 and 16,700kg/day (pers. comm. Bhamji, T., WaterCare) (2020)). Following Barnett & MacMurray Ltd (2010), the density of the sediment is assumed to be 2,650kg/m3, and the porosity of the bulk sediment is assumed to be 0.4. This leads to an estimate of the volume of sand extracted from the river with the additional water take of between 300 and 3,800m3/year.

Even if the maximum rate of removal of sediment through the additional water take of 3,800m3/year is assumed, this represents less than 4% of the projected on-going commercial sand extraction rate of 100,000m3/year.

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11 EFFECT OF PROPOSED ADDITIONAL WATER TAKE IN CONTEXT

Changes to the flow regime and water surface elevation resulting from the proposed take have been considered specifically by Tonkin and Taylor (2017). The present report has examined a broader picture - those changes that may actually be occurring in the Lower Waikato River and what the river may look like in the future. In the following, the effect of the proposed additional water take is examined within this broader context.

The current resource consent authorises the abstraction of up to 150,000 m3/d at a rate of 2,450 litres per second (L/s). The current application is for an increased instantaneous rate of taking (5,650 L/s) to provide for outages, downtime, maintenance activities or other situations where the full daily volume will not be taken over a 24-hour period. While the peak rate of taking will not occur at all times, this rate has been used to assess the effect of the take.

Addressing specifically the impact in the Lower Waikato River, the particular issues reviewed have been:

• “Natural” Variability in Flow Rates

• Historical Changes in Bathymetry

• Hydro Development

• Commercial sand Extraction

• Flood Protection

• Land Use Changes

• Sand Extraction with Proposed Additional Water Take

Any impact of the proposed consent on permissible water abstractions or other pending consent applications is outside of the scope of this report. Accordingly, herein only the impact of the proposed consent to take up to 150,000m3/day within the context of the issues reviewed is considered. In particular, cumulative effects (i.e. the effects of the proposed consent in combination with these issues/effects of other activities) have been considered.

Table 10.1 summarises the main conclusions for each of the issues reviewed. The impact of the proposed consent in context of the issue reviewed is then stated.

In all cases, this impact represents a negligible effect on both flow rates and bathymetry.

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Table 10.1: Summary of Review and Impact of Proposed Water Abstraction in Context

Issue Reviewed Summary of Review Impact of Proposed Consent in Context of Issue Reviewed “Natural” Variability Review of Mean Daily Flow Records • Negligible in Flow Rates in Lower • Records from June 1963 to November 2020 at Mercer Bridge analysed. reduction in flow Waikato River • Record site is 6 km upstream of proposed Watercare intake site, with negligible inflows in this 6 km reach. rates • Average Daily Mean Flow 401.3 m3/s, standard deviation of 170.6 m3/s. • No effect on 3 • Q5 at intake site 185.9 m /s. bathymetry • Statistically insignificant flow increase with time Effect of Climate Change • Negligible • Likely that extreme rainfall and flows (the 2 year ARI event and greater) will increase as a result of rising reduction in flow temperatures. rates • This does not apply to low or mean flows, so effect on average daily mean flow insignificant. • No effect on • Effect of climate change on water surface elevations considered because the Watercare intake structure is bathymetry located within the tidal reach of the Tasman Sea. • Current daily tidal change at the intake site is approximately 0.5 m. • Baseline sea level rise prediction varies from 0.19 m (RCP4.5) and 0.21m (RCP8.5)(2040) to 0.55 m (RCP4.5) and 0.79m (RCP8.5)(2100). • Corresponding rise in water surface levels at proposed Watercare intake structure for river flow of 350 m3/s with no sand extraction predicted to vary from 0.5 m (2017) to 0.2 m (2055). Increases referenced to baseline level in 2007. • Although the water surface elevations at Tuakau presented in Table 4.4 are considered to be appropriate, further water profile modelling, based on the projected sea level rises in Table 4.5, would be required to predict water level rises at Tuakau beyond the year 2060. • Over the full range of possible river flows and tidal cycles the extent of saline intrusion upstream is highly variable, ranging from close to the entrance to at least 13 km upstream. • Watercare’s proposed intake structure is located 34 km upstream of the Waikato River mouth. Historical Changes in • Use was made of all available cross-section information between XS-20 and XS-56 – a distance of 22.5 km – • Negligible Bathymetry in the encompassing the Watercare intake. reduction in flow Lower Waikato River • Generally, these data comprised the results of surveys undertaken at various intervals up until 2007. rates

• Analyses of these data for surveys undertaken in 1986, 1998, and 2007 enabled the determination of the • No effect on change in relative mean depth with time at each cross-section. bathymetry • Generally, these analyses showed significant drops in bed elevation between 1986 and 2007 throughout the reach that correlated strongly with sand extraction data (see comments below). • The exception was at the upstream end of the reach where significant increases in bed elevation were noted (XS-51 to XS-56). • However, this correlated strongly with a reduction in sand extraction at Mercer (upstream). • Sand extraction at this site ceased in 1995 and the noted bed level increase is due to sedimentation from upstream sediment supply Hydro Development • Eight hydro dams have been built along the length of the Waikato River. • Negligible • Construction of the dams has resulted in significant effects within the Waikato River. reduction in flow • In the present context, changes to the flow rates and sediment movement within the river are important. rates • Flow rates in the Lower Waikato River are largely governed by control criteria, especially at Karapiro Dam. • No effect on • Bed-material sediment load is trapped by the hydro dams, preventing the replenishment of the bed sediment bathymetry downstream. • Because the Waikato River flow retains a sediment carrying capacity, the starving of sediment input from upstream results in scouring of the bed downstream to feed the river’s sediment carrying capacity. • This has been a major cause of falling riverbed levels downstream of Karapiro Dam, now extending as far downstream as Ngaruawahia. • Downstream of Ngaruawahia, the tendency for bed level reduction is lessened, primarily due to substantial sediment inputs from the Waipa River. • The effect of the hydro dams on bed degradation does not extend into the Lower Waikato River. Commercial Sand • Detailed data on sand extraction are available between 1988 and 2020. • Negligible • However, sand mining has been carried out since the early 1950s and data since 1962 are summarised. reduction in flow Extraction • Analysis of sand extraction data from Mercer, Tuakau, and Puni show a very strong correlation with bed level rates changes downstream, but little or no correlation with bed level changes upstream. • Very small effect • This is consistent with the effect of sand extraction on the overall movement of sediment in the Waikato River. on bathymetry • When sand is removed at an extraction site, the river seeks to recover capacity downstream by eroding the bed through small and will continue to do so until a new equilibrium is reached. increase in total • When sand extraction reduces or ceases, the local hole at the extraction site starts to fill through the sediment sediment supply from upstream and this effect propagates downstream. extraction

Page 54 of 110

Lower Waikato River • Increase in peak flood flows, but reduction in duration of major floods. • Negligible • Probable rise in major flood levels on the riverside of stop banks, but within design limits. reduction in flow Flood Protection • At mean and low river flows no effect on river levels. rates • Insignificant or no effect on sediment movement. • No effect on bathymetry

Land Use Changes • Land use changes can significantly alter the river regime, particularly with regard to flow rates and sediment • Negligible load. reduction in flow • Historically, extensive clearing of land from forest to pasture increased runoff rates and significantly increased rates river flows, leading to erosion, increased sediment load and reduced water quality. • No effect on • More recently, there has been a progressive change in land use from forest plantation to pasture in the upper bathymetry catchment, resulting in an increase in both the rate and total volume of flood runoff. • Predictions of the magnitude of increased flood peaks ranged from a factor of two to ten. • Predictions of the effect of such land use change of about 4% of the catchment that drains to Rangiriri indicated that, in the lower Waikato, on small to medium floods (5 – 20 year ARI events), the effect would be insignificant. • During large floods (100 year ARI), the peak flood water level would increase between 0 and 40 mm, and during extreme flood events (500 year ARI) an increase between 0 and 270 mm would be expected. • Erosion of stream banks is a significant sediment source in areas of pastoral land use. • Estimates indicate that about 7% of Waikato River stream bank length in pasture regions is subject to erosion. • The mean sediment load into the Lower Waikato River from tributaries is estimated to be 27,000 m3/year. • Much if not all of this is due to erosion. • This represents a small volume when compared with the sediment supply from upstream (141,000m3/year) and the current and projected mean annual sand extraction of 100,000 m3/year).

Page 55 of 110

12 REFERENCES

Barnett & MacMurray Ltd (2009): Preliminary assessment of effects of proposed sand extraction from Waikato River, report prepared for Winstone Aggregates, a division of Fletcher Concrete and Infrastructure Ltd.

Barnett & MacMurray Ltd (2010): Assessment of effects of Waikato River sand extraction, report prepared for Winstone Aggregates, a division of Fletcher Concrete and Infrastructure Ltd.

Barnett & MacMurray Ltd (2020): Waikato Pukekawa Bed Monitoring Analysis 2020, report prepared for Winstone Aggregates Ltd, October

Bhamji, T., (WaterCare) (2020): Personal Communication, 11th May

Collier, K. J., Watene-Rawiri, E. M., and McCraw, J. D. (2010): Geography and History; in Waikato Regional Council, The Waters of the Waikato, Environment Waikato and the Centre for Biodiversity and Ecology Research, The University of Waikato

Environment Waikato (2008): The Health of the Waikato River and Catchment – Information for the Guardians Establishment Committee, March

Environment Waikato (2009): Summary of the effects of land use change between Taupō and Karapiro on the flood hydrology of the Waikato River catchment, Environment Waikato Technical Report 2009/21

Greening, S. (WaterCare) (2017): Personal Communication, 24th October

Heath, R. A. and B. S. Shakespeare. (1977): Summer temperatures and salinity distribution on three small inlets on the west coast, North Island, New Zealand. New Zealand Oceanographic Institute, Wellington, New Zealand 3:151-157.

Hicks, D. L. (2004): Soil Intactness Assessment of the Waikato Region: 2003, Environment Waikato Technical Report No 2003/14, Environment Waikato, Hamilton

Hicks, D. M. and Hill, R. B. (2010): Sediment Regime: Sources, Transport and Changes in the Riverbed; in Waikato Regional Council, The Waters of the Waikato, Environment Waikato and the Centre for Biodiversity and Ecology Research, The University of Waikato

Hill, R. (2011): Sediment management in the Waikato region, New Zealand, Journal of Hydrology (NZ), vol 50, no 1, pp 227-240

Intergovernmental Panel on Climate Change (IPCC) (2001): Climate Change 2001: The Scientific Basis. Contribution of Working Group 1 to the Third Assessment Report of IPCC, Section 9.3.6.2 – Precipitation and Convection

Internet Google Search (2018): http://winstoneaggregates.co.nz/sites-locations/pukekawa/

Jones, H.F.P. and Hamilton, D.P. (2014): Assessment of the Waikato River estuary and delta

for whitebait habitat management: field survey, GIS modelling and hydrodynamic modelling, ERI Report 27 prepared for Waikato Regional Council, Environmental Research Institute, Faculty of Science and Engineering, University of Waikato, January

Keller, R.J. & Associates (2017): Waikato River Take, Lower Waikato River – Changes Consequent to Development for WaterCare Services Ltd, (Interim Final Draft), November

Lamb, R. (WRC) (2018): Personal Communication, 8th May

MacMurray, H. (Barnett and MacMurray Ltd) (2016): Personal Communication, 14th October

MacMurray, H. (Barnett and MacMurray Ltd) (2020): Personal Communication, 28th April

Ministry for the Environment (2008a): Climate Change Effects and Impacts Assessment; A guidance manual for local government in New Zealand, 2nd Ed., May

Ministry for the Environment (2008b): Coastal Hazards and Climate Change; a guidance manual for local government in New Zealand, July

Ministry for the Environment (2017): Coastal Hazards and Climate Change; a guidance manual for local government in New Zealand, December

NIWA (2001): Waikato River sediment budget and processes. Report for Mighty River Power. NIWA Client Report: CHC01/24. Project No.: MRP00506

NIWA (2010): Waikato River Independent Scoping Study, report prepared for Waikato Regional Council, NIWA Client Report HAM2010-032

Tonkin and Taylor (2013): Hydrology and Ecology Assessment associated with the extension of the Waikato Intake, report prepared for Watercare Services Ltd, (August)

Tonkin and Taylor (2020a): Waikato Seasonal Water Take, Hydrology and Ecology, report prepared for Watercare Services Ltd, (April)

Tonkin and Taylor (2020b): Waikato Intake, Hydrology and River Hydraulics Assessment, report prepared for Watercare Services Ltd, (November)

Twidle, R. (Winstone Aggregates) (2018): Personal Communication, 30th July

Waikato Regional Council (2011): Lower Waikato Zone Management Plan, Waikato Regional Council Policy Series – 2011/04, May

Waikato Regional Council (2014): Personal Communication

Waikato Regional Council (2020): Personal Communication

Winstone Aggregates (2020): Email from Nicola Macpherson to Tanvir Bhamji (Watercare) and Robert Keller (R.J.Keller & Associates) with attachments, 7th October

Page 57 of 110

APPENDIX A – GRAPHS OF X-SECTION PROFILES AND CHANGES IN MEAN RELATIVE DEPTH

Page 58 of 110

XS - 20

6.00

4.00

2.00

0.00 )

m -2.00

(

i t

a -4.00 1913

l E

1962 d

e -6.00

B 1973

-8.00 1980 1986 -10.00 1998 2007 -12.00 2017 -14.00 0 50 100 150 200 250 300 350

Transverse Distance (m)

XS-20 - CHANGE IN MEAN RELATIVE DEPTH

-3.00

-3.50

-4.00

-4.50

)

(

t -5.00

e v

i -5.50

n -6.00

e M -6.50

-7.00

-7.50

-8.00 1900 1920 1940 1960 1980 2000 2020 2040 Year

Page 59 of 110

XS-21

3.00

2.00

1.00

)

(

n o

i 0.00

d e

B -1.00 1962 1975 -2.00 1981 1986

-3.00 1998 2007 2017 -4.00 -50 0 50 100 150 200 250 300 350 400

Transverse Distance (m)

XS-21 - CHANGE IN MEAN RELATIVE DEPTH

-2

-2.5

-3

-3.5

)

(

t -4

e v

i -4.5

n -5

e M -5.5

-6

-6.5

-7 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 60 of 110

XS-22 - CHANGE IN MEAN RELATIVE DEPTH

-1

-1.5

-2

-2.5

)

(

h -3

e v

i -3.5

n -4

e M -4.5

-5

-5.5

-6 1960 1965 1970 1975 1980 1985 1990 Date

Page 61 of 110

XS-23

2.50

1.50

)

(

i t

a 0.50

d e

B 1962 -0.50 1975 1981 1986 -1.50 1998 2007 2017 -2.50 0 50 100 150 200 250 300 350 400 450

Transverse Distance (m)

XS-23 - CHANGE IN MEAN RELATIVE DEPTH -3

-3.5

-4

-4.5

)

(

h -5

e v

i -5.5

n -6

e M -6.5

-7

-7.5

-8 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 62 of 110

XS-25

3.00

2.00

1.00

) 0.00

(

i t

a -1.00

d e 1965 B -2.00 1975 1986 -3.00 1998 2007 -4.00 2017

-5.00 0 50 100 150 200 250 300 350 400

Transverse Distance (m)

XS-25 - CHANGE IN MEAN RELATIVE DEPTH

-0.5

-1

-1.5

-2

-2.5

-3

-3.5

-4

-4.5

-5

-5.5 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020

Page 63 of 110

XS-26A

4.00

3.00

2.00

) 1.00

(

n o

i 1962 t

a 0.00 v

e 1975

d 1986

e B -1.00 1998 2007 -2.00 2017

-3.00

-4.00 0 100 200 300 400 500 600 700 800 900 1,000 Transverse Distance (m)

XS-26A - CHANGE IN MEAN RELATIVE DEPTH

-0.5

-1

-1.5

)

(

t -2

e v

i -2.5

n -3

e M -3.5

-4

-4.5

-5 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 64 of 110

XS-27

4.00

1913 3.00 1962 1975

2.00 1981 1986

) 1998

m ( 1.00

n 2007

i t

a 2017

d 0.00

e B

-1.00

-2.00

-3.00 0 50 100 150 200 250 300 350 400 Transverse Distance (m)

XS-27 - CHANGE IN MEAN RELATIVE DEPTH

-2

-2.5

-3

-3.5

)

(

t -4

e v

i -4.5

n -5

e M -5.5

-6

-6.5

-7 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 65 of 110

XS-28

5.00

3.00

1.00

)

(

i t

a -1.00

e 1962 B 1975 -3.00 1986 1998 2007 -5.00 2017

-7.00 0 50 100 150 200 250 300 350 Transverse Distance (m)

XS-28 - CHANGE IN MEAN RELATIVE DEPTH

-3

-3.5

-4

-4.5

)

(

h -5

e v

i -5.5

n -6

e M

-6.5

-7

-7.5

-8 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 66 of 110

XS-29

5.00

4.00

3.00

2.00

)

(

n 1.00 o

i 1913

v e

l 1962 E

0.00

d 1975

e B 1986 -1.00 1998 2007 -2.00 2017

-3.00

-4.00 0 100 200 300 400 500 600 700 Transverse Distance (m)

XS-29 - CHANGE IN MEAN RELATIVE DEPTH

-1

-1.5

-2

-2.5

)

(

h -3

e v

i -3.5

n -4

e M

-4.5

-5

-5.5

-6 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 67 of 110

XS-30

5.00

4.00

3.00

2.00

)

(

n 1.00 o

i 1913

v e

l 1962 E

0.00

d 1975

e B 1986 -1.00 1991 1993 -2.00 1998 2007 -3.00 2017

-4.00 -50 0 50 100 150 200 250 300 350 400 Transverse Distance (m)

XS-30 - CHANGE IN MEAN RELATIVE DEPTH

-2

-2.5

-3

-3.5

)

(

t -4

e v

i -4.5

n -5

e M -5.5

-6

-6.5

-7 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 68 of 110

XS-31

6.00

4.00

2.00

) 1962

(

n 1975

i t

a 0.00 1983

e l

E 1986

d e

B 1988 -2.00 1989 1991 1993 -4.00 1998 2007 2017

-6.00 0 50 100 150 200 250 300 350 400 Transverse Distance (m)

XS-31 - CHANGE IN MEAN RELATIVE DEPTH

-2

-2.5

-3

-3.5

)

(

t -4

e v

i -4.5

n -5

e M -5.5

-6

-6.5

-7 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 69 of 110

XS-31A 5.00

3.00

1.00

)

(

i t

a -1.00

e 1962 B 1975 -3.00 1981 1986 1993 -5.00 1998 2007 2017

-7.00 0 100 200 300 400 500 600 700 Transverse Distance (m)

XS-31A - CHANGE IN MEAN RELATIVE DEPTH -3

-3.5

-4

-4.5

)

(

h -5

e v

i -5.5

n -6

e M

-6.5

-7

-7.5

-8 1950 1960 1970 1980 1990 2000 2010 2020 Date

Page 70 of 110

XS-33 6.00

4.00

2.00

)

m (

0.00 1913

o i

t 1962

a v

e 1975

d -2.00 1983 e

B 1986 1991

-4.00 1993 1998 2007

-6.00 2017

-8.00 0 20 40 60 80 100 120 140 160 180 200 Transverse Distance (m)

XS-33 - CHANGE IN MEAN RELATIVE DEPTH -3

-3.5

-4

-4.5

)

(

h -5

e v

i -5.5

n -6

e M -6.5

-7

-7.5

-8 1900 1920 1940 1960 1980 2000 2020 2040 Date

Page 71 of 110

XS-35 5.00

4.00

3.00

2.00

) 1.00

m (

1964

n o

i 1969 t a 0.00

v 1975

l E

1986 d e -1.00 B 1991 1993 -2.00 1998 2007 -3.00 2017

-4.00

-5.00 0 50 100 150 200 250 300 350 400 Transverse Distance (m)

XS-35 - CHANGE IN MEAN RELATIVE DEPTH -1

-1.5

-2

-2.5

)

(

h -3

e v

i -3.5

n -4

e M

-4.5

-5

-5.5

-6 1960 1970 1980 1990 2000 2010 2020 Date

Page 72 of 110

XS-37

5.00

4.00

3.00

) 2.00

(

i t

a 1.00

v e

l 1964

d 1975

e B 0.00 1981 1986 -1.00 1991 1993

-2.00 1998 2007 2017 -3.00 0 50 100 150 200 250 300 350 400 450 Transverse Distance (m)

XS-37 - CHANGE IN MEAN RELATIVE DEPTH

-3

-3.5

-4

-4.5

)

(

h -5

e v

i -5.5

n -6

e M -6.5

-7

-7.5

-8 1960 1970 1980 1990 2000 2010 2020 Date

Page 73 of 110

XS-37A

6.00

5.00

4.00

3.00

)

(

n 2.00

l E

1.00 1964

d e

B 1975 0.00 1986 1993 -1.00 1998 2007

-2.00 2017

-3.00 -100 0 100 200 300 400 500 600 Transverse Distance (m)

XS-37A - CHANGE IN MEAN RELATIVE DEPTH -2

-2.5

-3

-3.5

)

(

h -4

e v

i -4.5

n -5

e M -5.5

-6

-6.5

-7 1960 1970 1980 1990 2000 2010 2020 Date

Page 74 of 110

XS-38

4.00

3.00

2.00

)

(

o i t 1938

a 1.00

v e

l 1964

e 1969 B 0.00 1975 1986 1991

-1.00 1993 2007 2017 -2.00 0 50 100 150 200 250 300 350 400 450 500 Transverse Distance (m)

XS-38 - CHANGE IN MEAN RELATIVE DEPTH

-1

-1.5

-2

-2.5

)

(

t -3

e v

i -3.5

n -4

e M -4.5

-5

-5.5

-6 1960 1970 1980 1990 2000 2010 2020

Date

Page 75 of 110

XS-39

7.00

6.00 1964 1975 5.00 1981 1986 4.00 1991

) 1993

m 3.00

(

o 1998

i t

a 2.00

v 2007

l E

2017 d

e 1.00 B

0.00

-1.00

-2.00

-3.00 0 50 100 150 200 250 300 350 400 Transverse Distance (m)

XS-39 - CHANGE IN MEAN RELATIVE DEPTH

-1

-1.5

-2

-2.5

)

(

t -3

e v

i -3.5

n -4

e M -4.5

-5

-5.5

-6 1960 1970 1980 1990 2000 2010 2020 Date

Page 76 of 110

XS-40

5.00

4.00

3.00

2.00

1.00

1964

) m

( 0.00

1969

n o

i 1975

t a

v -1.00 1986

l E

1988

d e

B -2.00 1991 1993 -3.00 1998 2007 -4.00 2017

-5.00 0 50 100 150 200 250 300 350 400 450 Transverse Distance (m)

XS-40 - CHANGE IN MEAN RELATIVE DEPTH

-2

-2.5

-3

-3.5

)

(

t -4

e v

i -4.5

n -5

e M -5.5

-6

-6.5

-7 1960 1970 1980 1990 2000 2010 2020 Date

Page 77 of 110

XS-41

6.00

5.00 1964

4.00 1969 1975 3.00 1986 1998

) 2.00 m

( 2007

n o

i 2017 t

a 1.00

e 0.00 B

-1.00

-2.00

-3.00

-4.00 0 50 100 150 200 250 Transverse Distance (m)

XS-41 - CHANGE IN MEAN RELATIVE DEPTH

-1

-1.5

-2

-2.5

)

m (

-3

e v

i -3.5

n a

e -4 M

-4.5

-5

-5.5

-6 1960 1970 1980 1990 2000 2010 2020

Date

Page 78 of 110

XS-42

6.00

5.00

4.00

) 3.00

(

o i

t 1964

a 2.00

v e

l 1969

e 1975 B 1.00 1986

0.00

-1.00

-2.00 0 50 100 150 200 250 300 350 400 450 Date

XS-42 - CHANGE IN MEAN RELATIVE DEPTH

-1

-1.5

-2

-2.5

)

(

t -3

e v

i -3.5

n -4

e M -4.5

-5

-5.5

-6 1960 1965 1970 1975 1980 1985 1990 Date

Page 79 of 110

XS - 43 6.00

4.00

2.00

1964

) m

( 1969

n o

i 1975 t

a 0.00

v e

l 1986

d 1998

e B 2007 -2.00 2017

-4.00

-6.00 0 50 100 150 200 250 300 Transverse Distance (m)

XS-43 - CHANGE IN MEAN RELATIVE DEPTH

-3.00

-3.50

-4.00

-4.50

)

(

h -5.00

e v

i -5.50

n -6.00

e M -6.50

-7.00

-7.50

-8.00 1960 1970 1980 1990 2000 2010 2020 Date

Page 80 of 110

XS-44

6.00

4.00

2.00

)

m (

0.00

e v

i -2.00

t a

l 1964

e R

1969 n

a -4.00

e 1975 M 1981 -6.00 1986 1998

-8.00 2007 2017

-10.00 0 50 100 150 200 250 300 Date

XS-44 - CHANGE IN MEAN RELATIVE DEPTH

-4

-4.5

-5

-5.5

)

(

h -6

e v

i -6.5

n -7

e M

-7.5

-8

-8.5

-9 1960 1970 1980 1990 2000 2010 2020 Date

Page 81 of 110

XS-45

5.00

4.00

3.00

2.00

) 1.00

(

i t

a 0.00

v e

l 1964

d 1975

e -1.00 B 1981

-2.00 1986 1998 -3.00 2007 2017 -4.00

-5.00 0 50 100 150 200 250 300 350 400 Date

XS-45 - CHANGE IN MEAN RELATIVE DEPTH

-1

-1.5

-2

-2.5

)

(

h -3

a -3.5

v i

t -4

e R -4.5

-5

-5.5

-6 1960 1970 1980 1990 2000 2010 2020 Date

Page 82 of 110

XS-46

8.00

6.00

4.00

2.00

) 0.00

(

i t

a -2.00

d e -4.00 B 1964 1975 -6.00 1981

-8.00 1986 1998 -10.00 2007 2017 -12.00 0 20 40 60 80 100 120 140 Date

XS-46 - CHANGE IN MEAN RELATIVE DEPTH

-5

-5.5

-6

-6.5

)

(

t -7

e v

i -7.5

n -8

e M -8.5

-9

-9.5

-10 1960 1970 1980 1990 2000 2010 2020 Date

Page 83 of 110

XS-47

6.00

5.00

4.00

3.00

) 2.00

(

o 1964

i t a 1.00

v 1975

l E

1986 d e 0.00 B 1996 1998 -1.00 2007 -2.00 2017

-3.00

-4.00 0 20 40 60 80 100 120 140 160 180 Transverse Distance (m)

XS-47 - CHANGE IN MEAN RELATIVE DEPTH

-4

-4.5

-5

-5.5

)

(

h -6

e v

i -6.5

n -7

e M -7.5

-8

-8.5

-9 1960 1970 1980 1990 2000 2010 2020 Date

Page 84 of 110

XS-48

6.00

4.00

2.00

)

(

i t

a 0.00

l E

1964

d e

B 1975

-2.00 1986 1998 2007

-4.00 2017

-6.00 0 50 100 150 200 250 Transverse Distance (m)

XS-48 - CHANGE IN MEAN RELATIVE DEPTH

-3

-3.5

-4

-4.5

)

(

h -5

e v

i -5.5

n -6

e M -6.5

-7

-7.5

-8 1960 1970 1980 1990 2000 2010 2020 Date

Page 85 of 110

XS-49

6.00

5.00

4.00

3.00

2.00

)

(

o 1.00

e l

E 0.00

e 1964 B -1.00 1975 1986 -2.00 1998 -3.00 2007 2017 -4.00

-5.00 0 100 200 300 400 500 600 Transverse Distance (m)

XS-49 - CHANGE IN MEAN RELATIVE DEPTH

-0.5

-1

-1.5

)

(

h -2

e v

i -2.5

n -3

e M -3.5

-4

-4.5

-5 1960 1970 1980 1990 2000 2010 2020 Date

Page 86 of 110

XS-50 6.00

5.00

1964 4.00 1970 1975 3.00 1986 1996 ) 2.00

m 1998

(

o 2007

i t a 1.00

v 2017

d e

B 0.00

-1.00

-2.00

-3.00

-4.00 0 50 100 150 200 250 300 350 Transverse Distance (m)

XS-50 - CHANGE IN MEAN RELATIVE DEPTH -3

-3.5

-4

-4.5

)

(

h -5

e v

i -5.5

n -6

e M

-6.5

-7

-7.5

-8 1960 1970 1980 1990 2000 2010 2020 Date

Page 87 of 110

XS-51

10.00

5.00

) 0.00

(

o i

t 1964

v e

l 1975

e -5.00 1981 B 1982 1983 1986 -10.00 1998 2007 2017

-15.00 0 20 40 60 80 100 120 140 160 Transverse Distance (m)

XS-51 - CHANGE IN MEAN RELATIVE DEPTH

-5.5

-6

-6.5

-7

)

(

t -7.5

e v

i -8

n -8.5

e M -9

-9.5

-10

-10.5 1960 1970 1980 1990 2000 2010 2020 Date

Page 88 of 110

XS-52

6.00

4.00

2.00

0.00

)

(

n -2.00 o

i 1964

a v

e 1975

l E

-4.00

d 1981 e B 1982 -6.00 1983 1986 -8.00 1998 2007 -10.00 2017

-12.00 0 50 100 150 200 250 300 Transverse Distance (m)

XS-52 - CHANGE IN MEAN RELATIVE DEPTH -3

-3.5

-4

-4.5

)

(

h -5

e v

i -5.5

n -6

e M

-6.5

-7

-7.5

-8 1960 1970 1980 1990 2000 2010 2020 Date

Page 89 of 110

XS-53

5.00

4.00

3.00

2.00 1964

) 1975

(

n 1.00

o 1981

t a

v 1982

l E

0.00 1983

d e B 1985 -1.00 1986 1988 -2.00 1996 1998 -3.00 2007 2017 -4.00 0 50 100 150 200 250 300 350 400 450 Transverse Distance (m)

XS-53 - CHANGE IN MEAN RELATIVE DEPTH

-1

-1.5

-2

-2.5

)

(

h -3

a -3.5

v i

t -4

e R -4.5

-5

-5.5

-6 1960 1970 1980 1990 2000 2010 2020 Date

Page 90 of 110

XS-55

6.00

4.00

2.00

) m

( 1964

n o

i 1975 t

a 0.00 v

e 1982

d 1986 e B 1988 -2.00 1996 1998 2007 -4.00 2017

0 50 100 150 200 250 300 350 -6.00

Transverse Distance (m)

XS-55 - CHANGE IN MEAN RELATIVE DEPTH

-2

-2.5

-3

-3.5

)

(

t -4

a -4.5

v i

t -5

e R -5.5

-6

-6.5

-7 1960 1970 1980 1990 2000 2010 2020 Date

Page 91 of 110

XS-56

10.00

8.00

6.00

4.00

)

(

o i

t 1964

a 2.00

v e

l 1975

e 1981 B 0.00 1982 1983

-2.00 1986 1996 1998 -4.00 2007 2017 -6.00 0 50 100 150 200 250 300 350 Transverse Distance (m)

XS-56 - CHANGE IN MEAN RELATIVE DEPTH

-3

-3.5

-4

-4.5

)

(

t -5

e v

i -5.5

n -6

e M -6.5

-7

-7.5

-8 1960 1970 1980 1990 2000 2010 2020 Date

Page 92 of 110

APPENDIX B – DETAILED GRAPHS OF X-SECTION PROFILES, CROSS-SECTIONAL AREA AND CHANGES IN MEAN RELATIVE DEPTH LOCAL TO PUKEKAWA SAND EXTRACTION ZONE

Page 93 of 110

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 39

4.5 4.0

3.5 2007 Survey 2012 Survey 3.0 2014 Survey 2.5 2016 Survey 2.0 2017 Survey

1.5 2018 Survey

) 1.0 2020 Survey

(

l 0.5

e v

e 0.0

e -0.5

u d

e -1.0 R -1.5

-2.0 -2.5 -3.0

-3.5

-4.0

-4.5 100 150 200 250 300 350

Distance (m)

XS-39 Cross-Sectional Area and MRD

1250 -4.7

-4.8

1200 -4.9

)

(

m -5

(

o w

1150 X-Sectional Area -5.1 l

B e

Mean Relative Depth

a p

e -5.2

t o

1100 -5.3 a

s a

s -5.4

M C 1050 -5.5

-5.6

1000 -5.7 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 94 of 110

XS-39 MRD and Sand Extraction

-4.7 200,000

-4.8 180,000

-4.9 160,000

)

m )

( -5 140,000

(

n o

l -5.1 120,000

r t

Mean Relative Depth t

p x

e -5.2 100,000 E

Annual Sand Extraction

a -5.3 80,000

a A

e -5.4 60,000 M

-5.5 40,000

-5.6 20,000

-5.7 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: PL1 (Down Stream)

3.5

3.0

2.5

2.0 2012 Survey 2014 Survey 1.5 2016_Survey

1.0 2018 Survey

0.5 2020 Survey

)

(

l 0.0

v e

L -0.5

d e

c -1.0

u d

e -1.5 R

-2.0

-2.5

-3.0

-3.5

-4.0

-4.5 50 100 150 200 250 300 350

Distance (m)

Page 95 of 110

XS-PL1 Cross-Sectional Area and MRD

1250 -4.5

-4.6

1200 -4.7

)

^ m

-4.8 (

(

o w

1150 -4.9 l

a p

e -5

a i

1100 -5.1 l

s e

o -5.2 r

X-Sectional Area M C Mean Relative Depth 1050 -5.3

-5.4

1000 -5.5 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 Year of Survey

XS-PL1 MRD and Sand Extraction -4.5 200,000

-4.6 180,000

-4.7 160,000 )

m -4.8 140,000

(

)

(

w o

-4.9 120,000 n

p x

e -5 100,000

a l

l -5.1 80,000

a A e -5.2 60,000

M Mean Relative Depth Annual Sand Extraction -5.3 40,000

-5.4 20,000

-5.5 0 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 Year of Survey

Page 96 of 110

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: PL2 (Up Stream)

4.5 4.0 3.5

3.0 2012 Survey 2.5 2014 Survey 2.0 2016 Survey 1.5 2018 Survey 2020 Survey

) 1.0

(

l 0.5

v e

L 0.0

d e

c -0.5

u d

e -1.0 R -1.5 -2.0

-2.5

-3.0

-3.5 -4.0

-4.5 50 100 150 200 250 300 350

Distance (m)

XS-PL2 Cross-Sectional Area and MRD

1400 -3.9

-4

1350 -4.1

X-Sectional Area

)

) 2

^ Mean Relative Depth m

-4.2 (

(

o w

1300 -4.3 l

p e

-4.4 e

o a

i 1250 -4.5

a s

-4.6 e

M C

1200 -4.7

-4.8

1150 -4.9 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 Year of Survey

Page 97 of 110

XS-PL2 MRD and Sand Extraction -3.9 200,000

-4 180,000

-4.1 160,000 Mean Relative Depth

) Annual Sand Extraction

m -4.2 140,000

(

)

(

-4.3 120,000 n

t p

-4.4 100,000 x

a l

l -4.5 80,000

a A

e -4.6 60,000 M

-4.7 40,000

-4.8 20,000

-4.9 0 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 Year of Survey

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 40

4.5

4.0

3.5 2007 Survey 3.0 2012 Survey 2014 Survey 2.5 2016 Survey 2.0 2017 Survey

) 2018 Survey

m (

1.5

l 2020 Survey

v e

L 1.0

d e

c 0.5

d e

R 0.0

-0.5

-1.0

-1.5

-2.0

-2.5 50 100 150 200 250 300 350

Distance (m)

Page 98 of 110

XS-40 Cross-Sectional Area and MRD

1500 -3.7

-3.8

1450 -3.9 )

2 X-Sectional Area

m (

m -4

Mean Relative Depth

(

w o

1400 -4.1 l

e r

-4.2 e

o i

1350 -4.3 a

s e

o -4.4

M C

1300 -4.5

-4.6

1250 -4.7 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

XS-40 MRD and Sand Extraction

-3.7 200,000

-3.8 180,000

-3.9 160,000

)

m (

-4 140,000 )

(

o n

l -4.1 Mean Relative Depth 120,000

Annual Sand Extraction c

p x

e -4.2 100,000

-4.3 80,000 l

a A

e -4.4 60,000 M

-4.5 40,000

-4.6 20,000

-4.7 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 99 of 110

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 41

4.5

4.0

3.5

3.0 2007 Survey 2016 Survey 2.5 2017 Survey

2.0 2020 Survey

1.5

)

(

l 1.0

v e

L 0.5

d e

c 0.0

u d

e -0.5 R

-1.0

-1.5

-2.0

-2.5

-3.0

-3.5 0 50 100 150 200 250

Distance (m)

XS-41 Cross-Sectional Area and MRD 1220 -4.2

1200 -4.3

1180 -4.4

X-Sectional Area

) )

2 1160 Mean Relative Depth

^ m

-4.5 (

(

L 1140

o w

-4.6 l

B 1120

a p

e -4.7

A D

1100 e

o a

i -4.8

c e

1080 R

a s

-4.9 e

r M

C 1060

-5 1040

1020 -5.1

1000 -5.2 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 100 of 110

XS-41 MRD and Sand Extraction -4.2 200,000

-4.3 180,000

-4.4 160,000

)

m (

-4.5 140,000 )

(

o n

l -4.6 120,000

p x

e -4.7 100,000

a l

l -4.8 80,000

a A

e -4.9 Mean Relative Depth 60,000 M Annual Sand Extraction -5 40,000

-5.1 20,000

-5.2 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 43

3.5 3.0

2.5 2007 Survey

2.0 2016 Survey

1.5 2017 Survey

1.0 2020 Survey 0.5

0.0

)

m (

-0.5

e v

e -1.0

e -1.5

c u

d -2.0 e R -2.5 -3.0

-3.5 -4.0 -4.5 -5.0 -5.5 -6.0 0 50 100 150 200 250

Distance (m)

Page 101 of 110

XS-43 Cross-Sectional Area and MRD 1250 -4

-4.1

1200 -4.2

X-Sectional Area

)

2 ^ Mean Relative Depth m

-4.3 (

(

o w

1150 -4.4 l

a p

e -4.5

o a

i 1100 -4.6

a s

-4.7 e

M C

1050 -4.8

-4.9

1000 -5 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

XS-43 MRD and Sand Extraction -4 200,000

-4.1 180,000

-4.2 160,000

)

m (

-4.3 140,000 )

(

o n

l -4.4 120,000

t p

-4.5 100,000 x

-4.6 80,000 l

a A

e -4.7 60,000 M

-4.8 40,000

-4.9 20,000

-5 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 102 of 110

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 44

3.5 3.0 2.5 2.0 2007 Survey 1.5 2016 Survey 1.0 2017 Survey 0.5 2020 Survey 0.0

) -0.5

(

e -1.0 v

e -1.5

e -2.0

c u

d -2.5 e

R -3.0 -3.5 -4.0 -4.5 -5.0 -5.5 -6.0 -6.5 -7.0 0 50 100 150 Distance (m)

XS-44 Cross-Sectional Area and MRD

950 -5.5

-5.6

900 -5.7

)

2 ^

X-Sectional Area m

(

m -5.8

(

Mean Relative Depth i

o w

850 -5.9 l

a p

e -6

o a

i 800 -6.1

a s

-6.2 e

M C 750 -6.3

-6.4

700 -6.5 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 103 of 110

XS-44 MRD and Sand Extraction -5.5 160,000

-5.6 140,000

-5.7

Mean Relative Depth 120,000 )

m -5.8 (

Annual Sand Extraction )

100,000 (

-5.9 n

t p

-6 80,000 x

a l

l -6.1

a e

60,000 u

a A

e -6.2 M 40,000 -6.3

20,000 -6.4

-6.5 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 45

4.0

3.5

3.0 2007 Survey 2.5 2016 Survey 2.0 2017 Survey 2020 Survey 1.5

1.0

)

(

l 0.5

e v

e 0.0

d e

c -0.5

u d

e -1.0 R

-1.5

-2.0

-2.5

-3.0

-3.5

-4.0 100.00 150.00 200.00 250.00 300.00 350.00

Distance (m)

Page 104 of 110

XS-45 Cross-Sectional Area and MRD 1250 -4

-4.1

1200 -4.2

)

2 ^

-4.3 m

(

w o

w 1150 -4.4

a p

e -4.5

a i

1100 -4.6 l

s e

o -4.7

M C

1050 -4.8

-4.9

1000 -5 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

XS-45 MRD and Sand Extraction -4 200,000

-4.1 180,000

-4.2 160,000 )

m -4.3 140,000

(

)

(

-4.4 120,000 n

o e

Mean Relative Depth i

c a

h Annual Sand Extraction

t p

-4.5 100,000 x

a l

l -4.6 80,000

a A

e -4.7 60,000 M

-4.8 40,000

-4.9 20,000

-5 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 105 of 110

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 46 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 2007 Survey 1.0 0.5 2016 Survey 0.0 2017 Survey -0.5 2020 Survey

) -1.0

m (

-1.5

l e

v -2.0 e

L -2.5

d -3.0

e c

u -3.5 d

e -4.0 R -4.5 -5.0 -5.5 -6.0 -6.5 -7.0 -7.5 -8.0 -8.5 -9.0 -9.5 -10.0 -10 40 90 140 Distance (m)

XS-46 Cross-Sectional Area and MRD 950 -5.7

-5.8

900 -5.9

)

2 ^

-6 m

(

w o

w 850 -6.1

a p

e -6.2

a i

800 -6.3 l

s e

o -6.4

M C

750 -6.5

-6.6

700 -6.7 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 106 of 110

XS-46 MRD and Sand Extraction -5.7 200,000

-5.8 180,000

-5.9 160,000 )

m -6 140,000

(

)

(

-6.1 120,000 n

t p

-6.2 100,000 x

a l

l -6.3 80,000

a e

Mean Relative Depth u

n n

Annual Sand Extraction n

a A

e -6.4 60,000 M

-6.5 40,000

-6.6 20,000

-6.7 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 47

3.5

3.0

2.5

2007 Survey 2.0 2016 Survey 1.5 2017 Survey 2020 Survey

) 1.0

(

e 0.5

e 0.0

u d

e -0.5 R

-1.0

-1.5

-2.0

-2.5

-3.0 -20 30 80 130 180

Distance (m)

Page 107 of 110

XS-47 Cross-Sectional Area and MRD 950 -5

-5.1

900 -5.2

)

2 ^

-5.3 m

(

w o

w 850 -5.4

a p

e -5.5

a i

800 -5.6 l

s e

o -5.7

M C

750 -5.8

-5.9

700 -6 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

XS-47 MRD and Sand Extraction -5 200,000

-5.1 180,000

-5.2 160,000

)

m (

-5.3 140,000 )

(

o n

l -5.4 120,000

r t

Mean Relative Depth t p

-5.5 100,000 x

D Annual Sand Extraction

-5.6 80,000 l

a A

e -5.7 60,000 M

-5.8 40,000

-5.9 20,000

-6 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 108 of 110

2020 Winstones Aggregates Cross Section Survey: CROSS SECTION: 48

4.0

3.5

3.0

2.5 2007 Survey 2016 Survey 2.0 2017 Survey

1.5 2020 Survey

)

m (

1.0

v e

L 0.5

d e

c 0.0

d e

R -0.5

-1.0

-1.5

-2.0

-2.5

-3.0 0 50 100 150 200 250

Distance (m)

XS-48 Cross-Sectional Area and MRD 1150 -4

-4.1

1100 -4.2

)

^ m

-4.3 (

(

X-Sectional Area i

Mean Relative Depth w

o w

1050 -4.4 l

a p

e -4.5

a i

1000 -4.6 l

s e

o -4.7

M C

950 -4.8

-4.9

900 -5 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 109 of 110

XS-48 MRD and Sand Extraction -4 200,000

-4.1 180,000

-4.2 160,000

) Mean Relative Depth

m -4.3 140,000

(

)

d Annual Sand Extraction

(

-4.4 120,000 n

p x

e -4.5 100,000

a l

l -4.6 80,000

a A

e -4.7 60,000 M

-4.8 40,000

-4.9 20,000

-5 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 Year of Survey

Page 110 of 110