ASHLEY-WAIMAKARIRI:
MAJOR RIVERS
CHARACTERISATION
PREPARED FOR
Environment Canterbury
C16020
11/05/2016
PREPARED BY
Dan Farrow
Disclaimer
This document has been prepared solely for the benefit of Environment Canterbury. No liability is accepted by Aqualinc Research Ltd or
any employee or sub-consultant of this Company with respect to its use by any other person.
This disclaimer shall apply notwithstanding that the document may be made available to other persons for an application for p ermission
or approval or to fulfil a legal requirement.
Quality Control
Client
Environment Canterbury
Document Title
Ashley-Waimakariri: Major Rivers Characterisation
Document Number
C160201
Authors
Dan Farrow
Reviewed By
Julian Weir
Approved By
Helen Rutter
Date Issued
11/05/2016
Project Number
C16020
Document Status
FINAL
File Name
Ashley-Waimakariri_Rivers Report_v3
For more information regarding this document please contact
Dan Farrow
Field Hydrologist
Aqualinc Research Limited
(03) 964 6521
[email protected]
The preferred citation for this document is:
Farrow, D, 2016. Ashley-Waimakariri: Major Rivers Characterisation. Environment Canterbury, C160201. Aqualinc Research Limited.
© All rights reserved. This publication may not be reproduced or copied in any form, without the permission of the Client. Such permission is to be given
only in accordance with the terms of the Client’s contract with Aqualinc Research Ltd. This copyright extends to all forms of copying and any storage of
material in any kind of information retrieval system.
TABLE OF CONTENTS
Executive Summary ........................................................................................................... 1
1
Introduction............................................................................................................... 2
2
Methodology ............................................................................................................. 3
2.1
3
River Bed Hydraulic Conductivity ............................................................................................................ 3
2.1.1
Flow Through the River Bed ...................................................................................................... 4
2.1.2
Vertical Hydraulic Gradient ........................................................................................................ 4
2.1.3
River Bed Area .......................................................................................................................... 5
2.2
River Bed Profiles ................................................................................................................................... 6
2.3
Losing and Gaining River Reach Map ..................................................................................................... 6
2.4
Time Series Stage and Flow Data........................................................................................................... 8
2.4.1
Ashley River at Gorge ................................................................................................................ 8
2.4.2
Coopers Creek at Mountain Road .............................................................................................. 8
2.4.3
Cust River at Carleton Road Bridge ........................................................................................... 9
2.4.4
Eyre River at Trigpole Road ....................................................................................................... 9
2.4.5
Waimakariri River .................................................................................................................... 10
Characteristics for Specific RIvers ........................................................................ 11
3.1
3.2
3.3
3.4
Ashley River .......................................................................................................................................... 11
3.1.1
Reach A1: Ashley River at Gorge to Bowicks Road ................................................................. 13
3.1.2
Reach A2: Ashley River at Bowicks Road to Upstream Okuku Confluence ............................. 15
3.1.3
Reach A3: Ashley River at Upstream Okuku Confluence to Rangiora Traffic Bridge ............... 16
3.1.4
Reach A4: Ashley River at Rangiora Traffic Bridge to Golf Links Road .................................... 19
3.1.5
Reach A5: Ashley River at Golf Links Road to Lowes Corner .................................................. 20
3.1.6
Reach A6: Ashley River at Lowes Corner to State Highway 1 ................................................. 21
Waimakariri River.................................................................................................................................. 23
3.2.1
Reach W1: Waimakariri River at Gorge to Courtenay Road .................................................... 26
3.2.2
Reach W2: Waimakariri at Courtenay Road to Halkett Groyne ................................................ 26
3.2.3
Reach W3: Waimakariri at Halkett Groyne to Weedons Ross Road ........................................ 27
3.2.4
Reach W4: Waimakariri at Weedons Ross Road to Crossbank ............................................... 27
3.2.5
Reach W5: Waimakariri at Crossbank to Wrights Cut .............................................................. 28
3.2.6
Reach W6: Waimakariri at Wrights Cut to Old Highway Bridge ................................................ 28
Eyre River ............................................................................................................................................. 28
3.3.1
Reach E1: Eyre River at Trigpole Road to McGraths Road Ford ............................................. 31
3.3.2
Reach E2: Coopers Creek at Mountain Road to Island Road Ford .......................................... 31
3.3.3
Reach E3: Eyre River at McGraths Road Ford to Depot Gorge Road Bridge .......................... 31
3.3.4
Reach E4: Eyre River at Depot Gorge Road Bridge to Steffens Road ..................................... 32
3.3.5
Reach E5: Eyre River at Steffens Road to Eyre River at Two Chain Road .............................. 32
3.3.6
Reach E6: Eyre River at Two Chain Road to Eyre River Diversion at Waimakariri Confluence 33
Cust River ............................................................................................................................................. 33
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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3.4.1
Reach C1: Cust River at Carleton Road Bridge to Bennetts Road ........................................... 34
3.4.2
Reach C2: Cust River at Bennetts Road to Patersons Road ................................................... 34
3.4.3
Reach C3: Cust River at Patersons Road to Rangiora Oxford Road........................................ 34
3.4.4
Reach C4: Cust River at Rangiora Oxford Road to Cust River at Swannanoa Road ............... 34
3.4.5
Reach C5: Cust River at Swannanoa Road to Cust Main Drain at Threlkelds Road ................ 35
3.4.6
Reach C6: Cust River at Threlkelds Road to Kaiapoi River Confluence ................................... 36
4
Recommendations.................................................................................................. 37
5
Acknowledgements ................................................................................................ 37
References ....................................................................................................................... 38
Appendix A : Cross section model inputs ..................................................................................................................... 39
Appendix B : Time series data extension tool ............................................................................................................... 48
Appendix C : Table of river reach characteristics .......................................................................................................... 49
Appendix D : Map of river reach characteristics ............................................................................................................ 74
Table 1: Concurrent flow gaugings for the Ashley River ............................................................................................... 13
Table 2: Estimated groundwater recharge from the Waimakariri River ......................................................................... 24
Table 3: Eyre River headwater tributary regression equations ...................................................................................... 29
Figure 1: Calculation of river bed hydraulic conductivity ................................................................................................. 3
Figure 2: Calculation of river bed conductance ............................................................................................................... 4
Figure 3: Ashley at SH1 measured wetted channel profiles from flow gauging facecards ............................................. 7
Figure 4: Example cross section profile for Ashley River at SH1 .................................................................................... 7
Figure 5: Regression for Coopers Creek at Mountain Rd versus Ashley River at Gorge ............................................... 8
Figure 6: Regressions for Cust River at Carleton Rd Bridge versus Cust River at Threlkelds Rd and Ashley River at
Gorge ........................................................................................................................................................... 9
Figure 7: Regression for Eyre River at Trigpole Rd versus Ashley River at Gorge ...................................................... 10
Figure 8: Location map of available gaugings, cross sections and groundwater levels for the Ashley River ................. 12
Figure 9: Ashley River at Gorge mean daily flow and Bowicks Road gains and losses (m3/s = cumecs) ...................... 14
Figure 10: Ashley River at Gorge mean daily flow and US Okuku gains/losses ............................................................ 16
Figure 11: Concurrent flows (less than 12 m3/s) for Ashley at Gorge and Ashley at Rangiora Traffic Bridge 1971-2011
................................................................................................................................................................... 18
Figure 12: Ashley River at Gorge mean daily flow and Rangiora Traffic Bridge gains/losses and approximate
uncertainty envelope (dashed line) ............................................................................................................. 18
Figure 13: Ashley River at Gorge mean daily flow and Golf Links Road gains and losses and approximate uncertainty
envelope (dashed line) ............................................................................................................................... 20
Figure 14: Ashley River at Gorge mean daily flow and Lowes Corner observed gains/losses and approximate
uncertainty envelope (dashed lines) ........................................................................................................... 21
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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Figure 15: Ashley River at Gorge mean daily flow and SH 1 Bridge gains/losses and approximate uncertainty envelope
................................................................................................................................................................... 22
Figure 16: Waimakariri River reach locations ............................................................................................................... 25
Figure 17: Eyre and Cust rivers reach locations ........................................................................................................... 30
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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EXECUTIVE SUMMARY
As part of the Canterbury Water Management Strategy, Environment Canterbury (ECan) are
developing a MODFLOW numerical groundwater model for the Waimakariri CWMS zone. Once
calibrated, ECan intend to use this model to explore the likely effects on water quality and quantity from
a range of future development scenarios. It is proposed to build the MODFLOW model using the GMS
(2015) user interface.
Through discussions with ECan and their advisor, Catherine Moore (GNS), it has been proposed that
the major rivers will be modelled using either MODFLOW’s River (RIV) package or stream flow routing
(SFR2) package. As a result, they have requested that Aqualinc characterise the main rivers of the
catchment and prepare input parameters that can be used directly in both of these model packages,
as well as prepare additional values that can be used for calibration targets.
The four major rivers in the Ashley-Waimakariri zone are the Ashley, Cust, Eyre and Waimakariri rivers.
There have been a substantial number of historical investigations into characterising these rivers. This
study brings together that work and develops the relevant data into formats suitable for numerical
model inputs for discrete reaches of the four major rivers.
Key information that is needed to build the numerical model includes river geometry (location, bed
elevation, cross sectional shape, etc.), the locations of gaining and/or losing reaches, river bed
conductivity and/or conductance, and (for the RIV package) river stage. In order to provide this
information, Aqualinc has collated and reviewed existing literature and relevant field data. Where there
was insufficient field data to derive these parameters, coarse estimates have been derived from
textbook values and data from other similar reaches. The finer-scale detail will ultimately be absorbed
into the model calibration process. The information derived provides a useful starting point for model
construction.
The estimates of hydraulic conductivity for model inputs range from 0.006 m/day to 8.5 m/day for the
Ashley, 0.004 to 8.4 m/day for the Waimakariri, 0.005 to 7.1 m/day for the Eyre, and 0.025 to 1,000
m/day for the Cust. There is low confidence in these estimates due to the limited data availability of
concurrent flow gaugings and representative groundwater level data.
The estimates would benefit from an increased number of concurrent gaugings to better estimate river
gains and/or losses. Groundwater levels should be collected at the same time as concurrent gauging
runs from representative shallow groundwater wells adjacent to each river reach, or piezometers
installed in the river bed.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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1
INTRODUCTION
The primary purpose of this Major Rivers Characterisation project is to provide supporting information
for the development of a MODFLOW numerical groundwater model of the Ashley-Waimakariri zone
being developed by Environment Canterbury (ECan). This model will be used to assist in managing
both water quantity and water quality in the catchment and subsequent allocation and land use
practices under the Canterbury Water Management Strategy. To provide robust data for building and
calibrating the surface water components of the model, ECan have engaged Aqualinc Research Ltd
(Aqualinc) to prepare a desktop characterisation of the four major rivers in the Ashley-Waimakariri
zone, these being the Ashley, Cust, Eyre and Waimakariri rivers.
Within the Major Rivers Characterisation project, each of the four major rivers has been divided into
discrete reaches, and information about each reach has then been summarised to inform the model
building and calibration processes. The discrete reaches have been determined based on the
availability of flow gauging data, surveyed channel geometry, and other data required to calculate
various model parameters.
Through discussions with ECan staff and their advisor, Dr Catherine Moore (GNS), it was proposed
that the rivers would be represented using either MODFLOW’s river (RIV) package or stream flow
routing (SFR2) package. ECan propose to use the modelling interface GMS (2015) to assist building
the model.
MODFLOW’s RIV package requires the specification of river stage as an input. Therefore, if the model
is to be used to predict the effects of a future development scenario (e.g. river flow abstractions for
irrigation, or stream depletion from groundwater pumping), then the modeller must adjust the river
stage manually, re-specify this in the model, run the model, calculate losses/gains, then readjust the
river stage again, and iterate until a new hydraulically-balanced solution is reached.
Alternatively, within MODFLOW’s SFR2 package, water is routed downstream and interacts with
groundwater along the way (gains and losses). Hence, flows at specific reaches can be modelled
directly. The package can be constructed to utilise variable-shaped cross sections as an input data
set, which can be entered directly into GMS. The use of the SFR2 package removes the need for
manual hydraulic rebalancing under different future development scenarios, as the package does this
automatically. The SFR2 package may, however, increase run times, depending on the chosen
complexity of the inputs.
As the model scenarios were not fully developed upon commencement of this Major Rivers
Characterisation project, it was decided to provide river inputs for both the RIV and SFR2 packages,
concurrently. ECan’s modeller can therefore choose to build either or both packages to simulate
surface water features within MODFLOW.
The outputs from this project have been derived from existing literature and relevant field data. Where
there was insufficient field data to derive the necessary parameters, approximate estimates have been
derived from text-book values and data from other similar reaches. The finer-scale detail will ultimately
be absorbed into the model calibration process. The information derived provides a useful starting
point for model construction.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
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2
METHODOLOGY
In the following sections, methodologies are outlined for deriving river bed hydraulic conductivity and
conductance, river bed profiles and time series stage and flow data. Other model input parameters
have been described and a summary of the findings has been presented.
2.1
River Bed Hydraulic Conductivity
No direct river bed vertical hydraulic conductivity (K) data is available from aquifer test records, and
only two seepage metering results are available for the Cust. Therefore, river bed conductivities have
been estimated from the more commonly used method using Darcy’s Law, which considers measured
river flow losses and the hydraulic gradient between the river surface and underlying groundwater.
However, this can only be applied where discrete measurements exist. Furthermore, there is
significant spatial and temporal variability in the measured flow losses and gains, and the various inputs
to the equation each have a range of factors that affect data representativeness at the reach-scale.
Despite the limitations of the method, it is a requirement of the groundwater model to set reasonable
bounds for estimates of K, where possible within each river reach. This method achieves this.
The equation used to estimate river bed conductivity is presented in Figure 1 (from Darcy’s Law).
K
Q
h .A
b
Where:
K
= river bed hydraulic conductivity as calculated by Figure 1 [L/T]
ΔQ
= flow through the river bed [L3/T]
h/b
= vertical hydraulic gradient calculated as the ratio of the difference
between the river free surface and the underlying groundwater level
(h) [L] and river bed thickness (b) [L]
A
= plan area of river bed [L2]
Figure 1: Calculation of river bed hydraulic conductivity
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
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Values of river bed conductivity (K) are used directly in MODFLOW’s SFR2 package. For the RIV
package, a bed conductance term (C) is needed. For entry into GMS, bed conductance is entered as
a value per unit length of river reach. GMS then multiplies the unit conductance by the digitised river
length in each model cell to result in the classic definition of bed conductance. For entry into GMS,
bed conductance is calculated as shown in Figure 2.
C
K.A
b.L
Where:
C
= river bed hydraulic conductivity, as entered directly into GMS [L2/T/L]
K
= river bed conductivity [L/T]
A
= plan area of river bed [L2]
b
= river bed thickness [L]
L
= river reach length [L]
Figure 2: Calculation of river bed conductance
A brief discussion on the individual components of the above calculations follows.
2.1.1
Flow Through the River Bed
Flow through the river bed, ΔQ, is derived from simultaneous stream gaugings at the top and bottom
of a given river reach. The accuracy of the method relies on the accurate accounting of incoming
tributary flows and abstractions between the two gauging locations. Corrections for tributary inflows
along a river reach can be applied where the tributary inflows are measured, and some studies have
attempted to ‘naturalise’ flows to account for other interference (e.g. abstraction) (Chater, 2004; White
et al., 2012).
Flow gaugings typically have an inherent measurement error of between 3-10%, and multiple flow
gaugings collected in sequence as part of a ‘run’ may compound this error. These runs may take place
over several days and are typically carried out when rivers are in a steady-state of flow, to avoid
capturing natural flow increases (say from a fresh) or decreases (say from a recession after a fresh).
For this reason, concurrent flow gaugings are usually carried out when rivers are in low flow conditions,
which may differ from estimating bed conductance from higher flow events where flows (and therefore
measurement errors) are greater. The mean flows presented in the report and calibration table for
characterising river reaches are calculated mean flows from the available concurrent gauging results,
unless otherwise stated.
2.1.2
Vertical Hydraulic Gradient
The vertical hydraulic gradient (h/b) is calculated from the difference in elevation between the river free
surface and the underlying groundwater level (h) divided by the bed thickness (b).
Reliable and accurate groundwater data is required from a suitable shallow well nearby with
measurement dates that coincide with flow gaugings. Ideally shallow wells will provide accurate
groundwater level for the gravels under the river. However, where this data is unavailable then
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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© Aqualinc Research Ltd.
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groundwater levels are taken from any wells or interpreted from available piezometric contour maps.
Groundwater levels need to be reported to the same height datum as river stage (e.g. metres above
mean sea level, m amsl) and must be representative of groundwater underlying the reach being
considered.
The groundwater level data used in the bed conductivity calculations are commonly derived from wells
some distance from the river (e.g. > 1 km). However, it is necessary to assume that they represent the
groundwater level immediately adjacent to the river. In reality there will be a gradient between the two
points such that the groundwater level directly beneath the river bed is likely to be higher (for losing
reaches) and lower (for gaining reaches) than that recorded in a well some distance away. Because of
this, the method yields an exaggerated estimate of the hydraulic gradient, which in turn results in river
bed conductivity values that are lower than they are likely to be in reality, possibly significantly so.
These results represent the minimum feasible value1.
Similarly, the elevation of the river free surface is needed relative to the underlying groundwater level.
River stage is measured during river gaugings, and an average channel stage can be determined for
a reach from the concurrent flow gauging records from the upstream and downstream sites.
The height between the river free surface and underlying groundwater level (h) can then be calculated.
The length of flow path (b) over which the vertical head difference occurs is normally the river bed
thickness. As this is rarely known, it has been assumed to be 1 m, consistent with the method assumed
by Sanders (2000).
In order to address the possibility of an unsaturated zone beneath the upper reaches of the rivers
identified as typically losing to groundwater, a vertical hydraulic gradient has been assumed to provide
a wider range in the reported hydraulic conductivity values. In the case of a perched river, the distance
over which the vertical hydraulic gradient is estimated is between the river free surface and the bottom
of the river bed, which is computed as the river stage plus the assumed bed thickness of 1 m.
2.1.3
River Bed Area
River bed area (A) is the area of the wetted channel in plan-view (i.e. ‘top down’). To calculate this,
representative estimates of wetted channel width for the full river reach are needed at the time of
gauging, as well as reach length. Sanders (2000) recommends assuming fixed channel widths of 100
m, 35 m and 40 m for the Waimakariri, Eyre and Ashley rivers, respectively. However, these estimates
have been refined for each of the rivers, including the Cust, using available concurrent flow gauging
data and information reported in literature.
ECan have detailed survey information for the Ashley and Waimakariri rivers going back to 1960.
White et al. (2012) carried out a comprehensive assessment of available survey data for the
Waimakariri River to assess river bed cross-sections and channel area for calculating groundwater
recharge in low flow conditions. The results provide average total wetted channel widths (over multiple
channels), and total channel area between reaches. The findings of this study have been used in
calculating hydraulic conductivity.
Smith (2012) uses concurrent gauging data to calculate river flow gains and losses for the Ashley from
2008 to 2009 under a range of flow conditions. The flow gauging data from this period has been used
to estimate mean channel stage and wetted width, and river bed area for six reaches of the Ashley.
This has then been used to estimate stream bed hydraulic conductivity.
Flow gauging facecards have been used to derive average wetted widths and mean channel stage for
the Eyre and Cust rivers for measurements coinciding with average flows of the available concurrent
flow gauging data (typically only available for low flows). LiDAR data has been used for deriving the
channel bed elevations where surveyed cross sections are not available.
1
Personal communication with Zeb Etheridge, Senior Hydrogeologist, ECan
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
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2.2
River Bed Profiles
If MODFLOW’s SFR2 package is used, variable-shaped cross-sections can be entered to more
accurately represent river dynamics. Ideally, river bed cross sections would be derived from detailed
field surveys. However, much of this data either does not exist or has not yet been supplied. Therefore,
profiles have been extracted from LiDAR data and compared to flow gauging cross-section data, where
available.
Some survey data for the Ashley and Waimakariri rivers has been supplied by ECan in the form of
excel spreadsheets. In addition, ECan has also provided *.pdf images that show the locations of
channel cross-sections (this data is available from Aqualinc on request). The spatial data for these
*.pdf cross-section surveys is currently not available, and so profiles have been derived from LiDAR
and gauging facecards.
Appendix A provides the eight-point cross sections for use in MODFLOW’s SFR2 package (as entered
via GMS) and have been generated by providing only one invert channel at the lowest (or near the
lowest) elevation. While the SFR2 package can accommodate multiple channels, cross section
approximations have been restricted to only one channel to minimise the possibility of numerical
instabilities. Furthermore, attempts have been made to ensure that the bed inverts are not too flat,
which further minimises the occurrence of numerical instabilities. Undulations in the river bed have
been linearly smooth and approximated due to the eight-point limit for defining cross-sections in the
SFR2 package.
Examples of wetted channel cross sections for the Ashley River at SH1 as derived from flow gauging
facecards are presented in Figure 3. The wetted channel widths for this site range from 8 m to 42 m
under a range of flows, and the average is 22 m and the average stage is 0.45 m. As can be seen
from Figure 3, the location where flow gauging is carried out can change over time in response to flow
rates and standard gauging practice. Braided rivers like the Ashley and Waimakariri rivers often have
flows in multiple channels, and the channels themselves change over time due to natural meandering,
accretion and erosion. The implications of this for modelling is that some channels may not be
accurately represented by fixed cross-sections.
For simplicity, LiDAR data has been used to generate cross section profiles, and checked against flow
gauging facecards where available. An example cross section derived from the LiDAR data and
interpreted to generate an 8-point cross-section for GMS is presented in Figure 4.
2.3
Losing and Gaining River Reach Map
The study has identified the river reaches that are generally losing or gaining based on the flow gauging
records. This information has been used to create a generalised map of the 4 major rivers, and identify
where the rivers have demonstrated gains and/or losses in flow. The map is provided in Appendix D.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
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Ashley at State Highway 1 Channel Profiles
Width (m)
0
5
10
15
20
25
30
35
40
45
0
0.2
Depth (m)
0.4
0.6
0.8
1
1.2
2/03/2010
7/10/2009
10/11/2010
14/10/2010
23/12/2009
24/03/2010
24/11/2009
28/01/2010
20/04/2010
Figure 3: Ashley at SH1 measured wetted channel profiles from flow gauging facecards
Ashley River at SH1
12
11
10
9
8
7
6
0
50
100
150
200
250
300
350
400
450
Figure 4: Example cross section profile for Ashley River at SH1
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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© Aqualinc Research Ltd.
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2.4
Time Series Stage and Flow Data
To use MODFLOW’s SFR2 package, continuous and complete flow data is required to feed into the
uppermost reach of each river. Where long-term flow data from recorder sites are missing, flows have
been synthesised based on relationships with other rivers. The methods employed to do this are
summarised in the following sections.
If MODFLOW’s RIV package is used, then stage elevation is instead required at the top and bottom of
each river reach. Stage height has been calculated based on the average stage height reported in
each flow gauging facecard.
2.4.1
Ashley River at Gorge
Recorder data is available for the period May 1972-Jul 2015, with only 0.85% of the data missing within
this period. The data was extended and filled using a correlation with Selwyn River at Whitecliffs using
Aqualinc’s extension tool as discussed in Appendix B.
2.4.2
Coopers Creek at Mountain Road
Only 35 spot gaugings were available for Coopers Creek at Mountain Road which spanned the period
2009-2015. This is too few to use Aqualinc’s extension tool. Instead, the available data at Coopers
Creek was correlated with Ashley River at Gorge data to synthesise a time seris. This resulted in a
squared correlation coefficient of 0.90 and the regression plot presented in Figure 5.
3.0
y = 0.035x + 0.1281
R² = 0.899
Coopers Creek at Mountain Road (m3/s)
2.5
2.0
1.5
1.0
0.5
0.0
0
10
20
30
40
50
60
70
80
Ashley River at Gorge (m3/s)
Figure 5: Regression for Coopers Creek at Mountain Rd versus Ashley River at Gorge
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
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Both the correlation coefficient and the regression plot suggest that the flow behaviour of Coopers
Creek is similar to that of the Ashley River. Hence, a time series of daily mean flows for Coopers Creek
at Mountain Road was estimated using this regression.
2.4.3
Cust River at Carleton Road Bridge
In total, only 27 spot gaugings were available for the Cust River at Carleton Road Bridge which
spanned the perod 2009-2011. Again, this is too few to use Aqualinc’s extension tool. Instead, a
synthesised flow series has been generated using a correlation with a nearby site. There is a
downstream recorder site on the Cust River at Threlkelds Road. However, the Ashley River at Gorge
provided a slightly better correlation with the data from Cust River at Carleton Road Bridge. The Ashley
River data resulted in a squared correlation coefficient of 0.92 whereas the data from Cust River at
Threlkelds Road gave a squared correlation coefficient of 0.89. Therefore, the time series has been
based on the correlation with the Ashley River, as given in Figure 6.
0.9
Cust River at Carleton Road Bridge (m3/s)
0.8
y = 0.1463x - 0.0537
R² = 0.885
0.7
0.6
Cust River at Threlkelds Road
y = 0.0254x - 0.056
R² = 0.9224
0.5
Ashley River at Gorge
0.4
Linear (Cust River at Threlkelds
Road)
0.3
Linear (Ashley River at Gorge)
0.2
0.1
0
0
5
10
15
20
Predictor site
25
30
35
40
(m3/s)
Figure 6: Regressions for Cust River at Carleton Rd Bridge versus Cust River at Threlkelds Rd and Ashley River at Gorge
2.4.4
Eyre River at Trigpole Road
A total of 553 days of daily mean stage and flow data are available for Eyre River at Trigpole Road
which span the period 2010-2011. The number of data points is small, but sufficient to use Aqualinc’s
extension tool, in part. The available Eyre River data resulted in a squared correlation coefficient of
0.75 against the Ashley River. This regression is plotted in Figure 7.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
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Eyre River vs Ashley Gorge
10
9
y = 0.044x - 0.0923
R² = 0.7451
Eyre River at Trigpole Rd (m3/s)
8
7
6
5
4
3
2
1
0
0
20
40
60
80
100
120
140
160
180
Ashley River at Gorge (m3/s)
Figure 7: Regression for Eyre River at Trigpole Rd versus Ashley River at Gorge
For this river, the flow data was estimated using the above regression relationship with the Ashley
River.
2.4.5
Waimakariri River
The downstream recorder site Waimakariri at Old Highway Bridge has been in operation since 1967,
and full mean daily flow and stage data is available for the period.
Mean daily flow and stage data from the upstream site Waimakariri at Otarama is available from 2008.
This has been extended back to 1 January 1967 with Waimakariri Old Highway Bridge mean daily flow
data. This resulted in a squared correlation coefficient of 0.893.
The recorder site at Waimakariri Gorge has mean daily stage data from 1967. Due to challenges rating
the site, daily mean flow data is not available. However, the flow gauging record provides 38 flow
readings at Waimakariri Gorge from 1967 to 2015, and 29 of these are concurrent with daily mean flow
estimates at Waimakariri at Otarama recorder site. Again, this is too few readings to use Aqualinc’s
extension tool. Instead, a synthesised flow series has been generated using a correlation with
Waimakariri at Otarama. The correlation resulted in a squared correlation coefficient of 0.95.
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3
CHARACTERISTICS FOR SPECIFIC RIVERS
In this section, descriptions and results for specific river reaches are presented.
information on:
This includes
 The subdivision of the four major rivers into individual reaches based on available cross-section
data and gaining/losing properties;
 Tabulated model input parameters, where data is available; and
 Data gaps and recommendations.
The tabulated results are presented in Appendix C. Results for each main river are presented below.
3.1
Ashley River
The majority of the work completed to date on characterising the Ashley River has been summarised
in Smith (2012), Dodson et al. (2012) and Dodson (2014). The 7-day mean annual low flow (7-day
MALF) calculation for the Ashley River is given in Chater (2004). Smith (2012) analysed all available
concurrent flow gaugings for the Ashley from 2008-2011 to characterise flow losses and/or gains along
six reaches of the Ashley from the Gorge through to SH1. This data has been incorporated in the
stream bed hydraulic conductivity estimations.
Figure 8 provides a map of the Ashley River showing the relevant sites and cross section locations
and groundwater piezometric contours. No new concurrent gaugings have been carried out on the
Ashley River main stem since 2011.
Survey data has been provided by ECan in the form of plan maps of cross-section locations, and
summary changes in minimum bed elevations over years when surveys were carried out (these data
sets are available from Aqualinc on request). Minimum bed elevations derived from surveys completed
at approximately the same time as the concurrent gaugings have been used in this study. The lower
reaches were surveyed in 2008/2009 and the upper reaches were surveyed in 2001 and 2012. No
surveyed channel profiles have been made available, and so channel cross-sections have been
derived from the available LiDAR data and checked using flow gauging facecards.
The concurrent flow gauging data from 2008 to 2011 used by Smith (2012) is presented in Table 1.
Observed river flows for the period at the Gorge vary from 1.4 m3/s to 8.7 m3/s (average 3.38 m 3/s),
compared to a mean flow of approximately 12 m3/s (from the Gorge recorder site). The hydraulic
conductivity values calculated in this study are based on the 2008-2011 data, unless stated otherwise.
The flow gauging results for the Ashley River at Rangiora Traffic Bridge have been adjusted for the
inflow from the Okuku River, as recommended by Smith (2012). Measured reach lengths have been
determined using ECan survey data from the survey periods (2008/2009 or 2001 & 2012).
The results of the specific flow losses and the hydraulic conductivity calculations are described for each
reach individually in the following sections. The Ashley River benefits from concurrent gaugings under
a range of different flow conditions. However, like the other rivers in the study area, there are no
concurrent gaugings under mean flow conditions. In order to make predictions about long term flow
losses and/or gains, the limited flow gauging data for each reach has been compared to the long term
flow record for the Ashley at Gorge. The results have been used to provide an uncertainty envelope
for the loss/gain estimates by either looking at the range in the observed data used in the regression,
or by making a coarse visual estimation.
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Figure 8: Location map of available gaugings, cross sections and groundwater levels for the Ashley River
Piezometric contours (2003) are supplied by ECan and have been used where shallow groundwater data is unavailable
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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Table 1: Concurrent flow gaugings for the Ashley River
Ashley
at
Okuku
River
Okuku
at
Ashley
Ashley
at
Rangiora
TB
Ashley
at Golf
Links
Rd
Ashley
at
Lowes
Corner
Ashley
at SH1
1,615
1,588
125
0
0
0
241
18/1/08
1,395
1,302
102
0
0
0
225
17/3/08
3,456
4,091
1,042
4,002
2,199
2,273
2,574
28/3/08
2,376
2,554
663
2,166
428
636
890
14/4/08
2,131
2,473
726
1,610
14
387
707
27/1/09
1,911
1,677
134
158
0
188
322
7/10/09
8,204
7,826
8,609
3,558
10,945
10,068
9,137
9,145
24/11/09
5,478
5,157
5,432
1,200
5,214
3,784
3,932
3,850
23/12/09
3,300
3,356
3,857
842
2,906
1,402
1,527
1,586
28/1/10
4,841
5,267
5,987
1,661
6,238
4,942
5,068
5,237
2/3/10
1,730
1,571
1,954
404
535
0
321
409
24/3/10
2,342
2,000
2,359
466
899
0
378
626
20/4/10
1,893
2,082
2,325
350
853
0
204
418
14/10/10
8,275
8,856
10,040
2,731
11,940
9,996
10,080
10,550
10/11/10
8,691
8,775
9,688
2,540
10,500
9,046
8,270
8,728
14/12/10
3,077
2,943
3,199
744
2,131
956
822
1,053
12/1/11
2,860
2,651
2,709
459
1,393
139
365
487
11/5/11
8,070
8,574
9,985
3,760
12,548
10,861
10,820
11,402
Date
Ashley at
Gorge
15/1/08
Ashley
at
Bowicks
Rd
(Values reproduced from Smith, 2012)
3.1.1
Reach A1: Ashley River at Gorge to Bowicks Road
The reach between the gauging location at Ashley River at Bowicks Road and the upstream Ashley
River at Gorge (recorder) has been gauged concurrently on 40 occasions from March 1971 to May
2011 (Dodson, 2014). Dodson (2014) calculates that the average difference in mean flows between
these sites is -48 l/s (i.e. the river loses 48 l/s on average), with a maximum observed loss of 530 l/s,
and a maximum observed gain of 2,790 l/s. Dodson (2014) uses regression to estimate that the
average loss increases to 80 l/s when Bowicks Road flows are adjusted to account for inflows of
upstream tributaries of the Ashley (Washpool Stream, Glentui River and an unnamed tributary).
However, further concurrent gaugings are required to verify this relationship, particularly for those
tributaries that have no flow gauging data. The range of losses (48-80 l/s) equates to a range of mean
specific flow losses of 4.29 l/s/km to 7.14 l/s/km across the 11.2 km reach.
Conversely, a subset of 12 concurrent flow gauging results between Bowicks Road and the Gorge
across a range of flows from 2008-2011 (used by Smith, 2012) result in an average gain of 25 l/s and
is sometimes gaining and sometimes losing (-378 l/s to +581 l/s). Smith (2012) calculates an average
specific flow gain of 2.56 l/s/km and suggests that net losses between Bowicks Road and the Gorge
are negligible, especially given that mean flows for Ashley River at Gorge is approximately 12,000 l/s.
The classification of this reach as losing is supported by Chater (2004) who estimates a predicted loss
between the Gorge and Bowicks Road of 160 l/s at low flows (7-day MALF) based on regression and
isohydal mapping. Given the conflicting evidence, the reach will be categorised as sometimes gaining,
sometimes losing, but mostly losing.
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Dodson (2014) carried out a groundwater study in the area to the south of this reach using a number
of wells adjacent to the river, and concluded that the Ashley probably recharged shallow gravel
deposits in this area. Conversely, a shallow well located near Bowicks Road (BW23/0052)
demonstrated some response to changes in river stage, but also responded to other recharge sources.
Dodson (2014) suggests evidence for possible flow from the plains to the river.
Groundwater level data is available for bores M34/0306 and BW23/0053, and an average of the
available data provides a mean groundwater level of approximately 191.5 m amsl for the reach. The
reach is losing, and therefore groundwater levels must, on average, be lower than river stage height.
This is achieved by a groundwater level of 191.5 m amsl. The mean minimum bed elevation for the
reach is 191.8 m amsl based on average surveyed levels at the upstream and downstream reach
boundaries. Using this level returns hydraulic conductivity estimates of 0.03 m/day to 0.05 m/day when
allowing for the range in maximum observed flow losses given by Dodson (2014).
In order to explore the relationship between observed flow gains and losses at Bowicks Road and
mean daily flows at the Ashley Gorge recorder site, the losses and gains observed in the flow gauging
record have been compared to the mean daily flow record in Figure 9.
The squared correlation coefficient is 0.04, and so no meaningful prediction about long-term average
flow losses is possible. Furthermore, Dodson (2014) suggests that losses are likely to increase at
higher flows due to the predicted losses from influent tributaries, and this is not accounted for in the
raw data in Figure 9. The maximum observed loss is 530 l/s, and looking at the spread in the observed
data, it’s plausible to assume that the long term average loss will be within the range of observed
losses.
Figure 9: Ashley River at Gorge mean daily flow and Bowicks Road gains and losses (m3/s = cumecs)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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3.1.2
Reach A2: Ashley River at Bowicks Road to Upstream Okuku Confluence
The Ashley River at Upstream (U/S) Okuku confluence has been gauged 18 times since 2008. The
gaugings were concurrent with Bowicks Road on 12 occasions. This reach gains on average 591 l/s,
with a range of 58 l/s to 1,411 l/s. This gives an average specific flow gain of 52.77 l/s km, ranging from
5.18 l/s/km to 126 l/s/km. A negligible gain in this reach under low flow conditions was predicted by
Chater (2004).
The reach upstream of the Okuku confluence is constrained on the south bank by a remnant Kowai
Formation forming the Mairaki Downs (Brown, 2001). The aquifers around this area are low yielding,
and piezometric contours suggest outflow from the Ashley River occurs between Ashley Gorge and
Mairaki Downs (Sanders, 1997).
Due to the lack of suitable groundwater data from a nearby well, piezometric contours have been used
to estimate representative groundwater levels for the reach. This reduces confidence in the result.
The piezometric contours suggest that groundwater levels are approximately 130 m amsl at the midpoint of the reach. The mean bed elevation for the reach is 125.7 m amsl. This groundwater level
gradient is consistent with flow gains from the reach (i.e. the groundwater level is higher than the
channel stage and the river is typically gaining).
An estimation of hydraulic conductivity for this reach returns a value of 0.05 m/day, ranging from 0.0060.15 m/day when the minimum and maximum observed flow gains are used in the calculation.
There are surface water inflows along this reach from the Garry River, Mt Thomas Stream and Bullock
Creek, which may be contributing to the observed gains. In the absence of concurrent gauging data,
and due to the groundwater level gradient established for the reach, these inflows have been assumed
to be negligible for the purpose of estimating hydraulic conductivity. It is recommended that concurrent
gaugings are undertaken on these tributary inflows in order to test this assumption. In order to highlight
the uncertainty of whether the reach is gaining solely from groundwater, the reach has been
categorised as sometimes gaining, sometimes losing, but mostly gaining. This lowers confidence in
the results.
Figure 10 presents the observed flow losses and gains at the Ashley at U/S Okuku and the mean daily
flows recorded at the Gorge. The data suggests a weak positive correlation, with gains increasing as
Ashley Gorge flows increase, and an estimated gain at U/S Okuku of approximately 1.75 m3/s at the
long term average flow of 12 m 3/s.
The unanswered question remains about the relative contribution of the influent tributaries of the Garry
River, Mt Thomas Stream and Bullock Creek. If there are significant gains from surface water in this
reach then the apparent gains from groundwater are being over estimated. This is can be determined
with additional concurrent gaugings.
One way to deal with this in the model calibration is to expand the uncertainty envelope for the longterm average gain using the maximum observed gain of 1.41 m 3/sec to provide both the upper and
lower uncertainty thresholds. Therefore, a conservative approach would be to adopt a long term
average gain estimate of 1.5 m3/s, with an uncertainty envelope of 0.1-2.9 m3/s.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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Figure 10: Ashley River at Gorge mean daily flow and US Okuku gains/losses
3.1.3
Reach A3: Ashley River at Upstream Okuku Confluence to Rangiora Traffic Bridge
The Ashley River is widely reported to lose to groundwater from downstream of the Okuku confluence
to the Rangiora Traffic Bridge, and the river is often dry near Rangiora in summer (Dodson et al. 2012;
Sanders, 1997; Brown, 2001). The flow gauging records for this site reveal that the Ashley River was
dry in May 2001 and January 2008. The Okuku River flows into the Ashley within this reach and the
relative flow contribution can be estimated from concurrent gaugings. The Makerikeri River also flows
into the Ashley along this reach but no concurrent gaugings are available to assess the relative flow
contribution. However, Brown (2001) suggests that the majority of flow losses in this reach occur
downstream of the Makerikeri confluence. Piezometric contours suggest that seepage from the Ashley
flows south east towards Woodend.
The flows have been gauged at the Rangiora Traffic Bridge concurrently with the upstream Okuku
confluence 18 times since 2008. A subset of 16 concurrent gaugings from 2008-2011 (adjusted for
inflows from Okuku River) give an average flow loss of 1,511 l/s, with a range of 1,926 l/s to 831 l/s.
This gives an average specific flow loss of 142.6 l/s/km, ranging from 182 l/s/km to 78 l/s/km.
An estimation of hydraulic conductivity for this reach returns a value of 0.19 m/day, ranging from 0.1
m/day to 0.24 m/day when maximum and minimum losses are used in the equation. Groundwater
data from M35/2679 has been used in the calculation, and a coarse adjustment of +7 m has been
applied to the average recorded level of 53 m amsl to account for the distance and slope from the well
location to the reach mid-point. This adjustment is supported by the piezometric contours which
suggest that groundwater levels at the mid-point of the reach are between 55 m amsl and 65 m amsl.
The mean bed elevation for the reach is 62.81 m amsl.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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If the groundwater level adjustment was not made, then the mean average groundwater level of 53 m
amsl returns lower hydraulic conductivity estimates in the range of 0.03 m/day to 0.08 m/day, which
could be less representative of the reach. It is suggested the minimum and maximum range of 0.030.24 m/day be used for guiding model calibration.
Mosley (2001) identified that the Ashley naturally dried in the vicinity of Rangiora during summer low
flows (< 2.5 m3/s) as a result of losses to groundwater. Mosley (2001) used aerial photography to
assess the extent of the reach that is subject to periodic dewatering. The results suggest that at flows
less than 2.5 m 3/s the reach from Priors Road (5.4 km upstream of Rangiora Traffic Bridge) to Lowes
Corner was completely dry, and continuous flow is observed in the channel at State Highway 1 Bridge
(Mosley, 2001).
The concurrent gauging record between Ashley at Gorge and Ashley at Rangiora Traffic Bridge is
presented in Figure 11. This includes all the historic records, and does not account for inflows from
Okuku River. The lowest flow recorded at the Gorge was 1.73 m 3/s with concurrent flows at Rangiora
Traffic Bridge of 0.54 m 3/s. The trend line on the plot suggests that the average cease-to-flow for the
Rangiora Traffic Bridge site occurs when flows at the Gorge are less than 1.65 m3/s. The implication
for modelling is that when the Gorge flow approaches this low flow rate, the river is typically dry at
Rangiora Traffic Bridge down to the Lowes Corner site.
Figure 12 plots the Ashley at Gorge mean daily flow and the observed flow losses at Rangiora Traffic
Bridge (adjusted for Okuku inflows). The regression suggests a weak positive relationship (r2=0.28)
and as Ashley Gorge flows increase the average loss at Rangiora Traffic Bridge seems to decrease
(i.e. moves towards a positive direction). A visual assessment of the scatter in the limited observed
data and the trend line extrapolation in Figure 12 suggests that the average long term loss estimate is
approximately 1 m3/s, with an uncertainty envelope of +/- 0.6 m3/s (represented as the dashed lines
on Figure 12).
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
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Figure 11: Concurrent flows (less than 12 m3/s) for Ashley at Gorge and Ashley at Rangiora Traffic Bridge 1971-2011
Figure 12: Ashley River at Gorge mean daily flow and Rangiora Traffic Bridge gains/losses and approximate uncertainty
envelope (dashed line)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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© Aqualinc Research Ltd.
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3.1.4
Reach A4: Ashley River at Rangiora Traffic Bridge to Golf Links Road
There is a negligible average flow gain of 67 l/s from 16 concurrent gaugings between Golf Links Road
and Rangiora Traffic Bridge from 2008-2009 (-1,075 l/s to +2,681 l/s), when Rangiora Traffic Bridge
flows are adjusted for Okuku inflows. The average is skewed by two extreme gaining events on
07/10/2009 and 11/05/2011, and when these are removed there is an average flow loss of -263 l/s,
ranging from a loss of 1,075 l/s to a gain of 1,086 l/s. This exclusion is considered justified on the basis
of limited data availability, and on the evidence that this reach is subject to periodic dewatering (Mosley,
2001). Furthermore, the concurrent gauging record demonstrates losses more frequently than gains.
On 8 occasions in the concurrent gauging record when the Ashley Gorge flows were less than 2.5 m3/s
(average 1.9 m3/s), the river was dry at Golf Links Road (2003 to 2010), and this site has gone dry on
more occasions than any other site in the gauging record, notably in January 2008, January 2009 and
March 2010. Dodson et al. (2012) classifies this as a losing reach due to the intermittently dry river
bed, however the available data suggest that this reach is sometimes gaining and sometimes losing,
but mostly losing.
Due to the lack of suitable groundwater data from a nearby well, piezometric contours have been used
to estimate representative groundwater levels for the reach. The piezometric contours suggest that
groundwater levels are approximately 28 m amsl at the mid-point of the reach. The mean bed elevation
for the reach is 29.6 m amsl. This groundwater level gradient is consistent with flow losses from the
reach.
An estimation of hydraulic conductivity for this reach returns a value of 0.21 m/day, ranging from 0.02
m/day to 0.87 m/day when the minimum and maximum observed losses from the concurrent gauging
record are used.
The observed range in the gains and losses at Golf Links Road are larger than at any other site in the
study. Figure 13 plots the observed gains and losses from the gauging record at Golf Links Road and
the gauging day mean daily flow for the Gorge recorder. The plot demonstrates that the Golf Links
Road site typically loses to groundwater when flows at the Gorge are less than approximately 5 m3/s.
The river on average starts to gain at Golf Links Road when Ashley Gorge flows are above 5 m 3/s.
There is a moderate positive correlation in the data (r2=0.65). A visual assessment of the scatter in the
limited observed data and the trend line extrapolation in Figure 14 suggests that the average long term
gain estimate is approximately 1.5 m 3/s, with an uncertainty envelope of 1 m 3/s to 2.4 m3/s (represented
as the dashed lines).
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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Figure 13: Ashley River at Gorge mean daily flow and Golf Links Road gains and losses and approximate uncertainty envelope
(dashed line)
3.1.5
Reach A5: Ashley River at Golf Links Road to Lowes Corner
There is an average flow gain of 36 l/s from 16 concurrent gaugings between Gold Links Road and
Lowes Corner from 2008-2009 (-931 l/s to +378 l/s). This equates to an average specific gain of 14.94
l/s/km, ranging from a loss of 157 l/s/km to a gain of 386 l/s/km.
Flow was recorded as zero at Lowes Corner in January 2008. On four occasions there was flow
recorded at Lowes Corner when flow was absent at the upstream Golf Links Road, and these events
coincide with flows at the gorge of less than 2.4 m3/s (average of 1.97 m 3/s), which suggests that this
reach typically gains under low flow conditions. Conversely, the biggest loss observed at this site on
7 October 2009 coincided with a much higher flow at the gorge of 8,204 l/s. Mosley (2001) highlighted
that this reach is subject to periodic dewatering.
Measurements suggests that the reach is sometimes losing and sometimes gaining. Smith (2012) used
a subset of 12 concurrent flow gaugings between Golf Links Road and Lowes Corner from 2009 to
2012 and found that the reach is losing on average 22.5 l/s, ranging from -931 l/s to +378 l/s. This
equates to an average specific loss of 9.24 l/s/km, ranging from a loss of 157 l/s/km to a gain of 386
l/s/km.
Concurrent groundwater level data from M35/0366 (located on Golf Links Road), and M35/2677
(upstream Lowes Corner) have been averaged to provide a representative groundwater level for the
reach of 20 m amsl. This is supported by the piezometric contours. The average mean channel stage
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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for the reach is 21.25 m amsl. The surface water-groundwater level gradient established with these
levels is inconsistent with flow gains, and so to calculate hydraulic conductivity the Smith (2012) subset
data has been used.
An estimate of 0.03 m/day hydraulic conductivity has been derived, with a range of 0.02 to 1.34 m/day
when adjusted for the maximum observed flow loss, and assuming a range of groundwater levels
between 19-20 m amsl.
Figure 14: Ashley River at Gorge mean daily flow and Lowes Corner observed gains/losses and approximate uncertainty
envelope (dashed lines)
Figure 14 plots the observed gains and losses from the gauging record at Lowes Corner and the
gauging day mean daily flow for the Gorge recorder. The plot demonstrates that the Lowes Corner site
sometimes gains and sometimes loses under a range of flow conditions. However, there is a very poor
positive correlation in the limited data set (r2=0.07). A visual assessment of the scatter in the limited
observed data and the trend line extrapolation in Figure 14 suggests that the average long term gain
estimate is approximately 0.4 m 3/s, with an uncertainty envelope of -0.6 m3 to 0.8 m3/s (represented
as the dashed lines).
3.1.6
Reach A6: Ashley River at Lowes Corner to State Highway 1
There is an average flow gain of 224 l/s from 16 concurrent gaugings between Ashley River at Lowes
Corner and Ashley River at State Highway 1 from 2008-2009 with a range of -82 l/s to +582 l/s. This
equates to an average specific gain of 69.6 l/s/km, ranging from a loss of 25.5 l/s/km to a gain of 180.7
l/s/km.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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Concurrent groundwater level data from M35/17982 (located near to State Highway 1 Bridge), and
M35/2677 (upstream Lowes Corner) have been averaged to provide a representative groundwater
level for the reach of 11.7 m amsl, which is supported by the piezometric contours. The mean bed
elevation is 10.9 m amsl.
Hydraulic conductivity has been estimated at 0.84 m/day based on the average flow gain of 224 l/s,
and ranges from 0.46 m/day to 2.17 m/day when adjusted for maximum observed flow gain and using
a range of groundwater levels from 11.7 m amsl to 12 m amsl.
Dodson et al. (2012) classify this as a gaining reach, and Mosley (2001) noted that even when
observed flows at the Gorge were as low as 1.23 m3/s, there was continuous flow observed at State
Highway 1.
Figure 15 plots the observed gains and losses from the gauging record at SH1 Bridge and the gauging
day mean daily flow for the Gorge recorder. The plot demonstrates that the SH1 Bridge site sometimes
gains and sometimes loses under a range of flow conditions. However there is a very poor positive
correlation in the limited data set (r2=0.15). A visual assessment of the scatter in the limited observed
data and the trend line extrapolation in Figure 15 suggests that the average long term gain estimate is
approximately 0.4 m3/s, with an uncertainty envelope of 0.1 m3 to 0.7 m3/s (represented as the dashed
lines).
Figure 15: Ashley River at Gorge mean daily flow and SH 1 Bridge gains/losses and approximate uncertainty envelope
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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3.2
Waimakariri River
A comprehensive study of groundwater and surface water interactions along the Waimakariri River
under low flow conditions is provided by White et al. (2011) and White et al. (2012). This study provides
a detailed analysis of the available flow gaugings from 1953 and 2009 for six reaches of the Waimakariri
River, from the Gorge down to the Old Highway Bridge. The reach boundaries have been selected
based on the locations of ECan’s flow gauging locations, entrainment works, and groundwater
catchment areas (White et al., 2012). The concurrent flow gaugings used in White et al. (2012) were
selected when flows at the gorge were less than 80 m 3/s (there were 63 of these), and average daily
flows were less than the mean flow of 120 m3/s. The reason for this is that flows in the river are not
generally stable over time above this flow: flows are typically rising or receding over the course of the
gauging run, with average mean daily flows at the Gorge differing by more than 12 m 3/s compared to
the preceding day (White et al., 2012).
White et al. (2012) estimates the long-term average Waimakariri River flow gains and losses between
the river and the river bed gravels, and also between the river-bed gravels and the adjacent Springston
formation gravels beside the river bed. The results of this steady-state groundwater budget estimates
that the river is losing approximately 12.9 m 3/s to the Springston formation gravels beside the river bed,
between Courtenay Road and the Old Highway Bridge, and this equates to seepage rates in losing
reaches of between 38-230 mm/day, with an average of 109 mm/day (White et al., 2012).
The average Waimakariri river gains from, or losses to, groundwater in the river-bed gravels presented
in White et al. (2012) have been used in the calculation of vertical hydraulic conductivity estimates. In
using this data, it has been assumed that the ‘gravel bed’ of the river is essentially shallow unconfined
groundwater. This distinction differs from White et al. (2012) but is consistent with the methodology
applied to the other major rivers in this report. The estimates of long-term river bed inflows and outflows
provided by White et al. (2012) have been used herein.
White et al. (2012) estimates a net surface water loss to the gravels between the Gorge and the Old
Highway Bridge of 11.2 m 3/s. The surface water gains and losses have been naturalised to account
for surface water inflows and outflows, where possible. The upper reaches from the gorge down to
Crossbank demonstrate net losses to gravel of 11.8 m 3/s, and the two lower reaches between
Crossbank and Old Highway Bridge demonstrate a net gain of 0.6 m3/s, when accounting for tributary
inflows of 3.5 m 3/s. Surface water abstractions make a large contribution to flow losses in the upper
reaches, with an estimated total of 4 m 3/s (White et al., 2012).
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In order to calculate seepage rates, extensive modelling by White et al. (2011) of the wetted channel
was required based on survey data of the river bed profile as surveyed between 1995 and 2007. This
is because the braided channel geometry of the Waimakariri River frequently encompasses several
channels within the fairway, and the number of ‘wetted areas’ is related to flow rate and rise in river
stage. The average channel depths and widths under low flows have are estimated for each reach
(White et al., 2011), and used in the calculation of vertical hydraulic conductivity.
Table 2 provides summary details of the White et al. (2011, 2012) analysis showing groundwater
recharge estimates, gauged losses/gains, surface outflows and surface inflows. Figure 16 provides a
map of the river and the reach boundaries.
Table 2: Estimated groundwater recharge from the Waimakariri River
Gauged river
flow gain (-) or
loss (+) (m3/s)
Surface outflow
(to irrigation)
(m3/s)
River
tributary
inflow (m3/s)
Inflow from (+) or
discharge to (-) the
river (m3/s)
Gorge to Courtenay Rd
4.5
1.7
0
2.8
Courtenay Rd to Halkett
4.1
1.4
0
1.1
Halkett to Weedons Ross Rd
1.5
0.9
0
2.2
Weedons Ross Rd to Crossbank
5.6
0
0
5.7
Crossbank to Wrights Cut
-0.1
0
0
-0.1
Wrights Cut to Old Highway Bridge
-4.9
0
3.5
-0.5
Total
10.7
4
3.5
11.2
Waimakariri River reach
(Values reproduced from White et al., 2011 and White et al., 2012)
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Figure 16: Waimakariri River reach locations
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3.2.1
Reach W1: Waimakariri River at Gorge to Courtenay Road
White et al. (2012) estimates an average loss of 2.8 m 3/s in this reach from the gauging record (2
measurements), and calculates a corresponding seepage rate of 55 mm/day at low flows.
PDP (2015) highlights that shallow groundwater in this area is typically more than 20 m deep, and the
direction of groundwater flow cannot be reliably determined. The piezometric contours mostly suggest
that the river is losing to groundwater and the movement of water is an east-south-east flow direction
(PDP, 2015).
PDP (2015) analysed data from a groundwater transect across the river from north to south, located
approximately 5 km upstream of Courtenay Road. The following conclusions relating to surface watergroundwater interactions were derived from this analysis:
 Groundwater is generally higher on the north side of the river compared to the south, which
indicates a north-to-south gradient; and
 There appears to be a downward gradient from shallow groundwater (< 25 m) to deep
groundwater (> 25 m). This could indicate a ‘perched’ water system that permits only limited
interactions between shallow and deep aquifers. Alternatively, the groundwater level difference
could be a result of groundwater mounding where the river acts as a hydraulic barrier to
groundwater flowing from north to south.
There is limited groundwater data available to provide a representative groundwater level for the
vertical hydraulic conductivity calculation, and in the absence of suitable measurements the
groundwater has been estimated from piezometric contours, and this reduces confidence in the results.
The mean bed elevation for this reach is 203 m amsl, which is the average surveyed bed elevation at
the upstream and downstream sites. White et al. (2011) estimates an average water depth in the reach
of 0.4 m. The piezometric contours suggest that the groundwater level is between 200-205 m amsl at
the midpoint of this reach. However, data for bore L35/0085 from 1981 to 2015 suggests that the
average groundwater level is around 193 m amsl, and so this has been incorporated into the range of
groundwater levels used in the calculation of hydraulic conductivity. The groundwater gradient
established using these groundwater levels is consistent with losses to groundwater in this reach.
The resulting hydraulic conductivity estimate for this reach is 0.016 m/day (based on a mid-point
groundwater level of 200 m amsl) and ranges between 0.006-0.119 m/day based on a range of
groundwater levels from 193-203 m amsl. The estimate of K appears to be low assuming the river bed
comprises free gravels. However, this estimate also assumes a bed thickness of 1 m (taken from
Sanders, 2000). If the bed thickness was greater, then so too would be the calculated river bed
hydraulic conductivity.
If a vertical hydraulic gradient is assumed to explore the scenario of an unsaturated zone under the
river, the resulting hydraulic conductivity is 0.04 m/day, which is within the estimated range.
The White et al. (2012) steady-state groundwater model predicts a net groundwater inflow to the subsurface gravels beneath the river in this reach of 1.2 m 3/s.
3.2.2
Reach W2: Waimakariri at Courtenay Road to Halkett Groyne
White et al. (2012) estimates an average loss in this reach of 1.1 m3/s from the gauging record and
calculates a corresponding seepage rate of 159 mm/day at low flows. The losses have been estimated
from the differences between gaugings at the Gorge to Courtenay Road and the Gorge to Halkett
Groyne (White et al., 2012).
The piezometric contours downstream of Courtenay Road start to indicate a change to a more easterly
gradient, which is linked to the effects of seepage from the Waimakariri River, particularly on the south
side of the river (PDP, 2015).
The mean bed elevation for the reach is 137.3 m amsl, based on survey data, average water depth is
0.3 m (White et al., 2012). The piezometric contours suggest that groundwater levels are between 135-
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140 m amsl. However, average groundwater level data for bore M35/8967 from 2001 to 2015 suggest
an average groundwater level of 135 m amsl.
The hydraulic conductivity estimate for this reach is 0.025 m/day (based on a mid-point groundwater
level of 135 m amsl) and ranges between 0.009-0.101 m/day when groundwater levels are adjusted
over the range of 130-137 m amsl.
If we assume a vertical hydraulic gradient to explore the scenario of an unsaturated zone under the
river, the resulting hydraulic conductivity is 0.05 m/day, which is within the estimated range.
The White et al. (2012) steady-state groundwater model predicts a net groundwater outflow to the
Springston formation gravels next to the river in this reach of 1.2 m 3/s.
3.2.3
Reach W3: Waimakariri at Halkett Groyne to Weedons Ross Road
White et al. (2012) estimates an average loss in this reach of 2.2 m3/s from the gauging records, and
calculates a corresponding seepage rate of 38 mm/day at low flows. The concurrent flow gauging
average loss for this reach has been calculated by White et al. (2012) as the difference from the
average losses measured between the Gorge and Halkett Groyne, and the Gorge and Weedons Ross
Road.
The mean surveyed bed elevation for the reach is 102.1 m amsl and the average channel stage is 0.3
m. The groundwater level at the midpoint is between 95-105 m amsl based on the piezometric contours
given in White et al. (2012). Limited groundwater level data from nearby shallow wells is available.
However, average groundwater levels in bores M35/0962 and M35/0930 suggest an average water
level around 95 m amsl, which is supported by the piezometric contours.
The hydraulic conductivity estimate for this reach is 0.058 m/day (based on a mid-point groundwater
level of 100 m amsl) and ranges between 0.019-0.359 m/day when groundwater levels are adjusted
over the range of 95-102 m amsl.
If a vertical hydraulic gradient is assumed, the resulting hydraulic conductivity is 0.108 m/day, which is
within the estimated range.
The White et al. (2012) steady-state groundwater model predicts a net groundwater outflow to the
Springston formation gravels next to the river in this reach of 2.5 m 3/s.
3.2.4
Reach W4: Waimakariri at Weedons Ross Road to Crossbank
White et al. (2012) estimates an average loss in this reach of 5.7 m3/s from one gauging record, and
calculates a corresponding seepage rate of 230 mm/day at low flows.
The mean bed elevation for the reach is 63.1 m amsl and the average channel stage is 0.3 m (White
et al., 2012). The average of groundwater level for bores M35/8968 and M35/0931 is approximately
62 m amsl, which is consistent with the piezometric contours at the reach midpoint located between
60-65 m amsl.
The hydraulic conductivity calculated for this reach is 0.162 m/day with a range of 0.036-0.527 m/day
by accounting for groundwater levels within the range 60 to 65 m amsl.
If we assume a vertical hydraulic gradient, the resulting hydraulic conductivity is 0.180 m/day, which is
within the estimated range. White et al. (2012) highlights that flow losses in this reach are estimated
to be the highest for the river, and suggests that this water will flow to springs and streams that feed
the Old South Branch and the Crossbank–Wrights Cut reach.
The White et al. (2012) steady-state groundwater model predicts a net groundwater outflow to the
Springston formation gravels next to the river in this reach of 5.5 m3/s.
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3.2.5
Reach W5: Waimakariri at Crossbank to Wrights Cut
White et al. (2012) estimates that the reach between Crossbank and Wrights Cut gains on average 0.1
m3/s. White et al. (2012) suggest that gains in flow could be sourced from seepage from the upper
reaches returning to the river, but also suggest that the reach is likely to be losing to springs and
streams that feed the Old South Branch.
Seepage rates are not considered by White et al. (2012) as the reach gains groundwater from the
Springston formation. The mean bed elevation is 20.7 m amsl and the average water depth is 0.4 m
(White et al., 2012). The average of groundwater level data from bores M35/1692 and M35/8969 is
approximately 22 m amsl. The hydraulic conductivity calculation for this reach returns an estimate of
0.006 m/day and ranges from 0.004-0.014 m/day when groundwater levels are adjusted within the
range 21.5 m amsl to 22.5 m amsl.
The White et al. (2012) steady-state groundwater model predicts a net groundwater outflow to the
Springston formation gravels next to the river in this reach of 2.8 m 3/s.
3.2.6
Reach W6: Waimakariri at Wrights Cut to Old Highway Bridge
White et al. (2012) estimates that the reach between Wrights Cut and the Old Highway Bridge is gaining
on average 4.9 m3/s. Seepage rates are not considered by White et al. (2012) as the reach gains
groundwater from the Springston formation.
The mean bed elevation for the reach is 2.47 m amsl. The groundwater level data for M35/5144 has
been averaged and adjusted for the change in slope and distance from the well to the reach mid-point,
which provides a mean groundwater level of between 3.3 m amsl to 4 m amsl. The hydraulic
conductivity estimate for the reach returns a value of 1.955 m/day, and ranges from 0.348 m/day to
8.471 m/day when adjusting the groundwater level between 3.3 m amsl and 4 m amsl.
The White et al. (2012) steady-state groundwater model predicts a net groundwater outflow to the
Springston formation gravels next to the river in this reach of 0.9 m 3/s.
3.3
Eyre River
The Eyre River has permanent flow in the upper reaches but rarely flows along its full length (Dodson
et al. 2012). The Eyre River is referred to as a ‘foothill’ river, and the headwater tributaries are fed by
rainfall in the Eyre foothills (Dodson et al., 2012). The Eyre foothills give rise to the tributaries Eyre
River, White Stream, Mounseys Stream, Coopers Creek, Gammons Creek and Trout Stream, which
confluence with the Eyre River near Oxford.
The river loses flow as it crosses over the plains and is typically dry near Oxford. Subsequently, it has
been classified as a losing river from Depot Gorge Road Bridge down to the confluence with the
Waimakariri River (Dodson et al., 2012). The piezometric contours suggest an east-south-east
gradient, turning more easterly towards the coastal confined zone (Dodson et al., 2012).
A series of concurrent gauging runs were carried out on foothill tributaries of the Eyre River between
April 2004 and January 2005 (Davey & Smith, 2005). The study found that the most upstream location
of zero flow observed in the Eyre River was at Pesters Road, located approximately 14 km south of
Oxford, when cumulative tributary inflow to the Eyre was 1,899 l/s.
The Eyre River historical gauging record sometimes provides flow readings, and sometimes provides
a visual assessment of where the river is dry and where it is flowing. The relationship between the
flows in the upper reaches and the location where the river goes dry is variable. The gauging record
suggests that on average when summer flows at the Trigpole Road site are less than 141 l/s then the
Eyre is dry at Depot Gorge Road, and when flows are between 141 l/s and 292 l/s the river runs dry
before Steffens Road.
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PDP (2005) carried out an aquifer recharge test releasing 2.7 m 3/s into the Eyre River in 2005 and
concluded that the Eyre River recharges groundwater along its length, and has a river bed conductance
in the order of 7 to 44 m/day. The most upstream location of zero flow observed during the PDP trial
was Poyntzs Road, approximately 12.5 km south of Oxford.
Figure 17 provides a plan map of the Eyre and Cust Rivers and highlights the reach boundaries.
Davey & Smith (2005) used regression to predict flow in the Eyre River at Trigpole Road Ford from
flows at recorder site Ashley River at Gorge. This is shown in Table 3 (reproduced from Smith, 2012)
along with regressions for other gauging sites. Using this equation, and the mean flow of 11,880 l/s
for the Ashley River, the mean flow in the Eyre River at Trigpole Road is estimated to be 438 l/s (Smith,
2010).
Table 3: Eyre River headwater tributary regression equations
Gauging site
No. of
gaugings
Regression equation
y = site flow
x = flow at Ashley River gorge
Adjusted
R Square
Standard
error (l/s)
Eyre
8
y = 0.0387x - 22.261
0.87
68
White
8
y = 0.0136x - 11.752
0.61
40
Mounseys
12
y = 0.0261x + 2.469
0.90
32
Coopers
13
y = 0.0322x + 154.150
0.69
153
Trout
8
y = 0.0083x - 2.094
0.52
29
Gammans
8
y = 0.0106x + 29.502
0.32
51
(reproduced from Smith, 2012)
Smith (2012), in calculating a surface water balance for the Ashley-Waimakariri catchment, predicts
that flows in the Eyre River Diversion (the most downstream site before the confluence with the
Waimakariri River) will equal zero when flows in the Cust River at Threlkelds Road are approximately
equal to or less than the mean flow of 1,611 l/s. Smith (2012) states that the Eyre River Diversion
flows only every 2 years on average in response to flood events, and therefore should be ignored from
the groundwater water balance. Smith (2012) recommends monitoring of the Eyre River Diversion in
future to test this conclusion.
Dodson et al. (2012) investigated groundwater discharge from the upper Eyre River and concluded
that flow losses recharged deeper groundwater aquifers in the area north of Oxford, and a downward
vertical gradient exists which decreases closer to the river (supporting the claim of recharge). This
downward vertical gradient shifts to an upward direction closer to the coast near Kaiapoi as deeper
groundwater discharges to the Ohoka and Silverstream Rivers, which form part of the Kaiapoi River
system (Dodson et al. 2012).
The implications of the findings for modelling are that flows in the upper Eyre River could be treated as
direct groundwater inputs around Oxford. Alternatively, flows (where present) could be routed down
the river, and the model could be calibrated to replicate where the river goes dry in the flow records.
The headwaters of the Eyre River benefit from two water level recorders, one at Eyre River at Trigpole
Road (2010-2011) and one at Coopers Creek at Mountain Road (2009-2015). Flow gauging data from
the Eyre River can be used to indicate the most downstream presence of flow in the model.
PDP (2007) conducted a recharge trial in 2005 and estimated stream-bed conductance using
concurrent gaugings of stream flow losses from the release of 2.7 m 3/s of water at Warren Road. The
range of values derived have been included in the calibration ranges provided.
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Figure 17: Eyre and Cust rivers reach locations
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3.3.1
Reach E1: Eyre River at Trigpole Road to McGraths Road Ford
Seven concurrent flow gaugings for the Eyre River at Trigpole Road and McGraths Road Ford from
2004 to 2005 result in an average mean loss of 90 l/s (losses ranging from 55 to 171 l/s), at an average
flow at Trigpole Road of 243 l/s (Davey & Smith, 2005). This suggests that flows in the Eyre River
reduces on average by more than 50 % by the time it reaches McGraths Road Ford, which equates to
a loss of 90 l/s over a reach length of approximately 9.5 km. This gives an average specific flow loss
of 9.5 l/s/km.
Piezometric contours suggest that the average groundwater level near the mid-point of the reach is
315 m amsl. Averages of available groundwater level data for L35/0050 and L35/0025 are consistent
with this estimate. There is an assumed bed thickness of 1 m, which is same as the value assumed
for the Ashley and Waimakariri rivers. Channel width (5.5 m) and depth (0.18 m) have been taken from
flow gauging facecards for the Eyre River at Trigpole Road at the mean flow from the concurrent
gaugings, and are assumed to be representative of the reach.
The mean bed elevation has been taken as an average between the minimum bed elevations of the
upstream and downstream reach taken from the LiDAR, as no survey data is available. The average
bed elevation is 333.5 m amsl.
This results in an estimated hydraulic conductivity of 0.008 m/day, with a range of 0.005-0.015 m/day
when adjusted for the range of observed flow losses. When a vertical hydraulic gradient is assumed,
the upper range of hydraulic conductivity estimates increases to 0.24 m/day.
3.3.2
Reach E2: Coopers Creek at Mountain Road to Island Road Ford
The upmost reach of the Coopers Creek at Mountain Road to Island Road Ford is upstream of the
confluence with the other Eyre tributaries. The eight concurrent flow gaugings for Coopers Creek at
Mountain Road and Island Road from 2004 to 2005 give a mean loss of 305 l/s (losses range from
146-499 l/s), at an average flow in Coopers Creek at Mountain Road of 384 l/s (Davey & Smith, 2005).
This suggests that flows in Coopers Creek reduce on average by 80% by the time it reaches Island
Road Ford, which equates to a loss of 305 l/s over a reach length of approximately 4.6 km. This
equates to an average specific flow loss of 66.3 l/s/km.
Piezometric contours suggest that the average groundwater level near the mid-point of the reach is
305 m amsl. This is approximately consistent with average groundwater level data for bore L35/0058
(1977-1986) when adjusted for the slope and relative distance to the reach mid-point. The mean bed
elevation is 312.6 m amsl based on LiDAR data.
There is an assumed bed thickness of 1 m, and channel width (4 m) and depth (0.2 m) have been
taken from flow gauging facecards for Coopers Creek at Mountain Road, and are assumed to be
representative of the reach.
This results in an estimated hydraulic conductivity of 0.18 m/day, with a range of 0.09-0.30 m/day when
adjusted for the full range of flow losses. When a vertical hydraulic gradient is assumed, the upper
range of hydraulic conductivity estimates increases to 1.95 m/day.
3.3.3
Reach E3: Eyre River at McGraths Road Ford to Depot Gorge Road Bridge
The Eyre River at Depot Gorge Road Bridge is downstream of the confluence of all of the major Eyre
River tributaries, including Coopers Creek, Gammons Creek and Trout Stream. Eight concurrent
gaugings for the reach from 2004-2005 suggest that there is a negligible average flow gain of 2.9 l/s in
this reach, with a range of -90 l/s to 154 l/s. This takes into account the measured inflows of the
tributaries and the residual flow of the Eyre main-stem from Eyre at U/S Coopers Creek Junction.
There are 6 historical observations of zero flow at Depot Gorge Road concurrent with flow readings at
Trigpole Road during summer months between 2004 and 2011, with the average flow at Trigpole Road
being 118 l/s, ranging from 76 l/s to 299 l/s. The length of the reach from Trigpole Road to Depot Gorge
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Road is 14.68 km, so a loss of 118 l/s over the reach gives a mean specific flow loss of 8.04 l/s/km.
This is similar to the result reported for Trigpole Road to McGraths Road. When the losses are adjusted
to the proportion of the reach length from McGraths Road to Depot Gorge Road, this returns a loss
estimate of 41.6 l/s over 5.18 km, returning a mean specific loss of 8.2 l/s/km. This is assuming that
flow is lost from the river uniformly over the reach.
The implications for modelling are that when flow at Trigpole Road approaches 118 l/s during summer
months, the river has been observed to go dry at Depot Gorge Road.
The piezometric contours suggest an average groundwater level of approximately 262 m amsl. The
average channel width and stage have been approximated from flow gauging facecards as 0.18 m and
5.5 m respectively. The mean bed elevation for the reach is 265 m amsl based on LiDAR data. The
groundwater gradient is inconsistent with flow gains along the reach and so the hydraulic conductivity
calculation has been applied only to the calculated losses between Depot Gorge Road and Trigpole
Road scaled to the reach length between McGraths Road and Depot Gorge Road.
This results in in a hydraulic conductivity estimate of 0.04 m/day, ranging from 0.013-0.71 m/day by
using the full range of flow losses and adjusting mean groundwater level between 255-265 m amsl.
When a vertical hydraulic gradient is assumed, the resulting hydraulic conductivity is 0.11 m/day, which
is within the estimated range.
3.3.4
Reach E4: Eyre River at Depot Gorge Road Bridge to Steffens Road
There are five historical concurrent gaugings of the Eyre River at Depot Gorge Road and Steffens
Road from January 1994 to November 1994 with an average flow loss of 341 l/s, with losses ranging
from 157-586 l/s. During this time, the average flow at Depot Gorge Road was 642 l/s, ranging from
264 to 1,165 l/s. This results in an average specific loss of 35.9 l/s/km.
The available groundwater data available for bore L35/0058 provides an average groundwater level of
207.3 m amsl, which has been assumed to be representative of the reach. The average channel width
and stage have been approximated from flow gauging facecards as 5.5 m and 0.18 m respectively.
The mean bed elevation for the reach is 213 m amsl based on LiDAR data.
This results in an estimated hydraulic conductivity of 0.09 m/day, with a range of 0.04-0.15 m/day when
adjusted for the full range of flow losses.
The recharge trial carried out by PDP in 2005 provides hydraulic conductivity values for the reach
between Warrens Road and Steffens Road of between 0.6 m/day and 4.9 m/day, which is substantially
more than the values derived here, and it is recommended that the full range of values are considered
when calibrating the model.
The reach between Depot Gorge Road and Steffens Road is subject to periodic dewatering, with
summer flows in the Eyre typically going to ground within this reach. Between 2004 and 2011 there
are 7 observations of the Eyre at Steffens Road during summer months concurrent with flow data at
Trigpole Road, and only 5 observations suggest that the river is flowing at Steffens Road. The average
flow at Trigpole Road when flows at Steffens Road have reduced to zero is 147 l/s, and the minimum
flow at Trigpole Road when flow is observed at Steffens Road is 292 l/s (on 13/01/2005).
The length of the reach from Trigpole Road to Steffens Road is approximately 31 km, so a loss of 292
l/s over the reach gives a specific flow loss of 9.4 l/s/km, which is similar to the result reported for
Trigpole Road to McGraths Road. The implications for modelling are that when flow at Trigpole Road
approaches 292 l/s during summer months, the river has been observed to go dry at Steffens Road,
and is typically dry before Steffens Road at flows of 147 l/s.
3.3.5
Reach E5: Eyre River at Steffens Road to Eyre River at Two Chain Road
There is one concurrent gauging for Eyre River at Steffens Road and Two Chain Road (04/08/1994),
due to the Eyre River mostly being dry at this point. The gauging was carried out on August 4 1994
and resulted in a flow loss of 2,239 l/s across the reach. Piezometric contours suggest that the average
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groundwater level is between 115-120 m amsl at the reach mid-point, and an average of 117 m amsl
has been assumed to represent the reach. The average bed elevation for the reach is 121.3 m amsl.
These values return a hydraulic conductivity estimate of 0.40 m/day, ranging from 0.28-1.23 m/day
when adjusted for groundwater levels in the range 115-120 m amsl.
This compares to the results from the PDP recharge trial (2007) which provide hydraulic conductivity
estimates of 3.2 m/day to 7.1 m/day for the reach between Steffens Road and Poyntzs Road. It is
recommended that the full range of values are considered when calibrating the model.
3.3.6
Reach E6: Eyre River at Two Chain Road to Eyre River Diversion at Waimakariri Confluence
There are no concurrent flow gaugings for Eyre River downstream of Two Chain Road. From here the
Eyre River passes into a diversion that flows to the Waimakariri River approximately 9 km upstream of
the Old Highway Bridge. The diversion is typically dry except during flood events, and flows on average
only every 2 years (Smith, 2012). It is suggested that a river bed conductivity from the upstream reach
be assumed to apply to this reach.
3.4
Cust River
The Cust River originates in swampy areas to the north west of Oxford (Brown, 2001), and is referred
to as a ‘foothill’ river, collecting rain-fed inflows from the Ashley foothills (Dodson et al., 2012). Brown
(2001) suggests that the Cust River flows within a former last-glaciation Ashley River course. The Cust
River rarely flows with sufficient frequency and force to incise the floodway in which it currently flows
(Dodson et al., 2012). Figure 17 provides a plan map of the Cust River and the reach boundaries.
In order to reduce the influence of Cust River flows recharging swampy areas west of Rangiora, the
course of the Cust River is constrained by the Cust Main Drain, which diverts the Cust River near
Fernside bypassing Rangiora, and follows the channelised course down to the confluence with the
Kaiapoi River to the west of Kaiapoi (Brown, 2001).
A recorder site is located on the downstream reach of the Cust at Threlkelds Road, which is
approximately 2.3 km upstream of the confluence with the Kaiapoi River. The recorder has stage and
flow data from November 1980 to September 2015.
Dodson et al. (2012) classifies the Cust River as ephemeral in the upper reaches, but gains flow along
its length between Carleton Road Bridge (located approximately 5.5 km east of Oxford) and the
confluence with the Kaiapoi River. The Cust River at Carleton Road Bridge has 22 flow gaugings from
the period 2009 to 2011, with flows ranging from 0-849 l/s (Smith, 2012). Smith (2012) estimates a
mean flow at this site of 0.25 m 3/s, with a median flow of 0.13 m 3/s based on a regression with the
Ashley River at the Gorge (Smith, 2012).
A visual survey of flows in the Cust and Ashley foothill rivers was carried out in 2012-2013, and the
visual surveys suggest that although the Cust at Carleton Road Bridge can go dry in summer, there is
typically always some flow in the downstream Cust at Bennetts Road site (based on eight gaugings),
suggesting that the reach is gaining (Dodson, 2014). The presence of surveyed springs around
Steffens Road and Bennetts Road approximately coincide with a historically swampy area, and this
upwelling supports the claim that the Cust River is gaining along this reach (Dodson, 2014).
Further investigations into surface water-groundwater interactions in the Cust River reveal that losses
from the Ashley River possibly flow into the Cust River area (Dodson et al., 2012). Dodson et al. (2012)
reports that the limited groundwater monitoring data available from the Cust River area does not
suggest a significant downward hydraulic gradient from shallow to deep. The water quality
investigations that have been carried out also suggest that nitrate concentrations in wells near the Cust
River demonstrate an elevated signature independent of river flows, which is consistent with discharge
of groundwater with a land-surface recharge signature in the lower reaches (Dodson et al., 2012).
In determining a water balance for the Cust groundwater allocation zone (GAZ), Dodson et al. (2012)
assumes that mean flows estimated for the Cust River at Carleton Road Bridge of 248 l/s are lost to
groundwater, and this recharges the GAZ by a volume of approximately 7.8x106 m3/year.
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3.4.1
Reach C1: Cust River at Carleton Road Bridge to Bennetts Road
The Cust River at Carleton Road Bridge has 22 flow gaugings over the period 2009 to 2011, with flows
ranging from 0 l/s to 849 l/s (Smith, 2012). Smith (2012) estimates a mean flow at this site of 250 l/s,
with a median flow of 130 l/s, using a regression with the Ashley River at Gorge (Smith, 2012). No
concurrent flow gauging data is available for this reach, but a visual observation survey undertaken
from 2012 to 2013 suggests that this reach is typically gaining (Dodson, 2014).
It is suggested that bed conductance for downstream reaches be used to categorise this reach.
3.4.2
Reach C2: Cust River at Bennetts Road to Patersons Road
This reach encompasses the Tippings Road and Swamps Road flow gauging sites. Direct river bed
conductance surveys were carried out at the Tippings Road site and reported in Dodson et al. (2012).
The average river bed conductance across this reach was 40 m/day and ranged from 6-90 m/day.
The Dodson et al. (2012) study reported that concurrent gauging from 2001 for the Tippings Road and
Swamps Road reach demonstrated a net loss to groundwater, however no data is available. Due to
the lack of data, it is difficult to categorise this as a losing or a gaining reach. Concurrent flow data for
the upstream Carleton Road Bridge and the downstream Rangiora Oxford Road (discussed in the next
section) suggest that this reach is typically gaining.
3.4.3
Reach C3: Cust River at Patersons Road to Rangiora Oxford Road
There are 111 flow records for the Rangiora Oxford Road site, with a mean flow of 412 l/s and flows
ranging from 1 l/s to 3,924 l/s from 1970 to 2012. Smith (2012) estimated a mean flow for the Rangiora
Oxford Road site of 912 l/s using regression with the Cust Main Drain at Threlkelds recorder. There
are no concurrent gaugings with Patersons Road.
Concurrent gaugings (21) with the distant upstream Cust at Carleton Road Bridge site reveal average
gains in flow of 766 l/s, ranging from 272 to 1,995 l/s, with average flow at Rangiora Oxford Road of
942 l/s for the period. This equates to average specific flow gains of 13.4 l/s/km over a reach length
of approximately 17 km between Carleton Road Bridge and Rangiora Oxford Road. This evidence
supports the classification by Dodson et al. (2012) that this is a gaining reach.
The hydraulic conductivity estimate for the reach is based on an average bed elevation between the
upstream Cust at Carleton Road Bridge and downstream Rangiora Oxford Road of 135 m amsl,
derived from LiDAR, and assumed channel geometry based on flow gauging surveys at Carleton Road
Bridge (channel width of approximately 4.5 m, and approximate channel depth of 0.25 m for mean
concurrent flow gauging). The piezometric contours have been used to estimate an average
groundwater level estimate of 140 m amsl, and this is assumed to be representative of the reach. The
resulting estimate of K returns a value of 0.18 m/day, ranging from 0.06 m/day to 0.47 m/day when the
full range of observed flow gains are used in the equation.
River bed conductance surveys were carried out at the Kennedys Hill Road site, located upstream of
the Rangiora Oxford Road site, and reported in Dodson et al. (2012). The average river bed
conductance across this reach was 500 m/day, ranging from 50-1,000 m/day. It is recommended that
the full range of values are considered when calibrating the model (0.06 m/day to 1,000 m/day).
3.4.4
Reach C4: Cust River at Rangiora Oxford Road to Cust River at Swannanoa Road
There are no concurrent flow gaugings between Rangiora Oxford Road and Swannanoa Road in the
flow gauging record. However, groundwater level records for well BW23/0134 and visual flow
observations of the Cust dating back to 2013 suggest that the Cust is periodically dry at Swannanoa
Road. There are 6 visual observations of the Cust being dry, and one observation of ponding but no
flow, at Swannanoa Road from 25/11/2014 to 02/06/2015. The average mean daily flow recorded at
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the Cust at Threlkelds Road recorder site during this period was 522 l/s, ranging from 338 l/s to 668
l/s, which is around one third of the long term average mean daily flow of approximately 1,500 l/s.
None of the visual records from BW23/0134 are concurrent with flow gaugings at the upstream
Rangiora Oxford Road. In order to estimate the relative flow loss along this reach during periodically
dry periods, we can average the flows recorded at Rangiora Oxford Road between the months of
November to March between 1984 and 2012 which coincide with mean daily flows at the Threlkelds
Road recorder of less than 522 l/s (n= 25). The result gives an estimated average November to March
flow at Rangiora Oxford Road of approximately 143 l/s, ranging from 6 l/s to 307 l/s, and this data can
be used to approximate losses between Rangiora Oxford Road and Swannanoa Road under low flow
conditions. This equates to an average specific flow loss during periodically dry periods of up to 23.8
l/s/km, ranging from 1 to 51.2 l/s/km over the 6 km reach.
In order to estimate hydraulic conductivity, a groundwater level of between 55 m amsl and 60 m amsl
has been assumed from the piezometric contours. The estimated average minimum bed elevation for
the reach is 66.07 m amsl. This hydraulic gradient is consistent with predicted losses to groundwater
(143 l/s). The resulting estimate of K returns a value of 0.039 m/day, ranging from 0.02 m/day to 0.084
m/day when adjusting the representative groundwater level between 55 m amsl and 60 m amsl.
It is recommended that concurrent gaugings are carried out to determine at what flow the Cust is likely
to be periodically dry in the summer at Swannanoa Road. A flow of 522 l/s at the Cust at Threlkelds
Road recorder has an exceedance probability of 81 % based on long term flow records for the site
(1980-2015). It should also be noted that the subset of flow readings identified for Rangiora Oxford
Road when the Threlkelds Road recorder was at or below 522 l/s; when subtracted from the Threlkelds
Recorder mean daily flows results in an average flow gain of 184 l/s. This suggests that even under
conditions when the Cust has been observed to go dry at Swannanoa Road there is still an average
gain in flow between Swannanoa Road and the downstream Threlkelds Road recorder, and this is
discussed further in section 3.4.5.
3.4.5
Reach C5: Cust River at Swannanoa Road to Cust Main Drain at Threlkelds Road
This reach largely encompasses the Cust River transition to the Cust Main Drain. There are no
concurrent gaugings between Swannanoa Road and Threlkelds Road. The upstream site Cust River
at Rangiora Oxford Road has 88 flow gauging records going back to 1988 that coincide with daily mean
flow records available for Cust at Threlkelds Road recorder. The average flow at downstream
Threlkelds Road for the period of concurrent data is 955 l/s. The average flow for Rangiora Oxford
Road for the period is 508 l/s, ranging from 6 l/s to 3,924 l/s.
The concurrent flow records suggest an average gain in flow of 447 l/s between Rangiora Oxford Road
and the Threlkelds Road recorder, ranging from 26 l/s to 4,836 l/s. This equates to an average specific
flow gain of 29.8 l/s/km over the estimated reach length of 15 km. However the previous section
identified that the river is periodically dry around Swannanoa Road, and in that situation all of the
apparent flow gains would occur across a shorter reach length between Swannanoa Road and
Threlkelds Road. Consequently two scenarios have been used to get an estimate of hydraulic
conductivity: one for Rangiora Oxford Road to Threlkelds Road, and one for Swannanoa Road to
Threlkelds Road.
In the first scenario the hydraulic conductivity estimate for the reach is based on an average bed
elevation between Rangiora Oxford Road and Threlkelds Road of 45 m amsl, derived from LiDAR, and
assumed channel geometry based on flow gauging surveys at Threlkelds Road (channel width of
approximately 8 m, and approximate channel depth of 0.24 m for mean flows from the concurrent
gaugings). The piezometric contours have been used to estimate an average groundwater level
estimate of 46 m amsl, and this is assumed to be representative of the reach. The resulting estimate
of K returns a value of 0.4 m/day, ranging from 0.03 m/day to 4.6 m/day when the full range of observed
flow gains are used in the equation.
The previous section highlighted that under low flow conditions the Cust has gone dry at Swannanoa
Road, which lies within the Rangiora Oxford Road to Threlkelds Road reach. However, even under low
flow conditions the flow gauging record suggests an average flow gain of 184 l/s between Rangiora
Oxford Road and the Threlkelds Road recorder site. One way to account for this is to attribute the
average flow gain of 447 l/s observed in the flow gauging record (Rangiora Oxford Road) to a shorter
reach length from Swannanoa Road to Threlkelds Road. This equates to an average specific flow gain
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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35
of 48.6 l/s/km over a reach length of 9.2 km. In this scenario, the average bed elevation between
Swannanoa Road and Threlkelds Road is 27.78 m amsl, derived from LiDAR. The piezometric
contours have been used to estimate an average groundwater level estimate of 30 m amsl, and this is
assumed to be representative of the reach. The resulting estimate of K returns a value of 9.4 m/day,
ranging from 0.51 m/day to 95.33 m/day when the full range of observed flow gains are used in the
equation.
It is recommended that the full range of hydraulic conductivity values are considered when calibrating
the model.
3.4.6
Reach C6: Cust River at Threlkelds Road to Kaiapoi River Confluence
The Cust River joins the Kaiapoi River west of Kaiapoi. No concurrent gaugings are available to
characterise this reach, although the presence of spring fed rivers such as the Cam River and the
Ohoka River that emerge to the west of Kaiapoi suggest that most of the lowland rivers are gaining in
this area (Dodson et al., 2012). It is therefore recommended that the bed conductance from the reach
above be used to represent this site.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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4
RECOMMENDATIONS
The estimates of hydraulic conductivity for model inputs range from 0.006 m/day to 8.5 m/day for the
Ashley, 0.004 to 8.471 m/day for the Waimakariri, 0.005 to 7.1 m/day for the Eyre, and 0.025 to 1,000
m/day for the Cust. There is low confidence in these estimates due to the limited data availability of
concurrent flow gaugings and representative groundwater level data.
The estimates would benefit from an increased number of concurrent gaugings to better estimate river
gains and/or losses. Groundwater levels should be collected at the same time as concurrent gauging
runs from representative shallow groundwater wells adjacent to each river reach, or piezometers
installed in the river bed.
5
ACKNOWLEDGEMENTS
The contributions to this report from the staff at Environment Canterbury are much appreciated, in
particular the members of the modelling team; Zeb Etheridge, Matt Dodson, Fouad Alkhaier, Carl
Hanson and Maureen Whalen are gratefully acknowledged for their comments and contributions.
Thanks also to Phil Downes, Tony Gray, Kirsty Duff and Andrew Howes from ECan for their advice
and timely provision of data. The non-ECan members of the modelling team who have provided input
to this work are also acknowledged, in particular Lee Burbery (ESR), Peter Callander (PDP) and Scott
Wilson (Lincoln Agritech).
The following authors, whose reports and data were interpreted and heavily utilised herein, are thanked
for their publications: Jeff Smith, and Paul White, Erika Kovacova, Gil Zemansky, Nadia Jebbour,
Magali Moreau-Fournier.
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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REFERENCES
Brown, LJ (2001): Groundwaters of the Canterbury Region. Revised by J H Weeber, May 2002;
Environment Canterbury Technical Report No. R00/10.
Chater, M (2004): 7-day Mean Annual Low Flow Mapping for the Ashley Catchment Area. Environment
Canterbury Report No. U04/16. April 2004.
Davey, G and Smith, E (2005): Losses to Groundwater from headwater tributaries of the Eyre River.
Environment Canterbury Technical Report U05/50.
Dodson, M, Aitchison-Earl, P, Scott, L. (2014): Ashley-Waimakariri groundwater resources
investigation. Environment Canterbury Report No. R12/69. ISBN 978-1-927222-04-1
Dodson, M (2014): Investigating the significance of river recharge from the Ashley River/Rakahuri to
the
upper
Cust
groundwater
allocation
zone.
Memorandum
File
Reference
WATR/INGW/QUAN/ASH/1-5.
GMS (2015): Groundwater Modelling System. Software developed and distributed by Aquaveo LLC,
USA.
Hicks DM and Mason PB (1991): Roughness Characteristics of New Zealand Rivers. Water Resources
Survey, DSIR Marine and Freshwater, Wellington.
Mosley, M P (2011): Ashley River: Flow Management Regime. Environment Canterbury Technical
Report number UO1/4.
Oliver, T (2008): Waimakariri District Flood Hazard Management Strategy – Ashley River Floodplain
Investigation. Report R08/23. ISBN 978-1-86937-804-2
PDP (2007): Report on September 2005 Eyre River recharge trial. Environment Canterbury Report
U07/31, prepared by Pattle Delamore Partners for Waimakariri Irrigation Ltd and Environment
Canterbury.
PDP (2015): Review of Eyre River - Christchurch West Melton Groundwater Allocation Zone
Interaction. Currently in draft. Prepared for Environment Canterbury
Sanders, R (1997): Groundwater of the Waimakariri - Ashley Plains, a Resource Summary Report.
Canterbury Regional Council Unpublished Report U97/43.
Sanders, R (2000): Ashley-Waimakariri Groundwater Investigation 1999/2000 Report on Development
of Groundwater Model (Year 3 of a 4 Year Programme). Canterbury Regional Council Unpublished
Report IN6C-0040
Souhangir, A (1997): Water-table geometry and related groundwater recharge near Halkett,
Waimakariri River, New Zealand. A thesis submitted in partial fulfilment of the requirements for the
degree of Masters of Agricultural Science in water resources engineering in the University of
Canterbury.
Smith J (2010): Ashley-Waimakariri Water Resources Investigation (AWWRI) update of surface water
monitoring. Memorandum Ref. 027503. June 2010.
Smith (2012): Surface Water Balance Components of the Ashley-Waimakariri Plains. Environment
Canterbury report R12/58. July 2012.
White, PA, Jebbour, N, Kovacova, E, Tschritter, C (2011): Waimakariri River bed and groundwater –
surface water interaction. GNS Science Report 20009/41
White, PA, Kovacova, N, Zemansky, G, Jebbour,N , Moreau-Fournier, M. (2012) Groundwater-surface
water interaction in the Waimakariri River, New Zealand, and groundwater outflow from the river
bed. Journal of Hydrology (NZ) 51 (1): 1-24
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
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Appendix A: Cross section model inputs
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Ashley River at Bowicks Rd
Ashley River at Gorge
54
165
53
164
52
163
51
162
50
161
49
160
48
159
47
158
0
5
10
15
20
25
30
35
40
45
500
50
600
700
800
900
1000
1100
Ashley River at Rangiora TB
Ashley River U/S Okuku
41
96
40
95
40
39
94
39
38
93
38
37
92
37
36
91
36
35
90
0
100
200
300
400
500
600
700
800
900
1000
0
50
100
150
200
250
300
350
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Ashley River at Golf Links Rd
Ashley River at Lowes Cnr
31
20.0
19.5
30
19.0
29
18.5
18.0
28
17.5
27
17.0
16.5
26
16.0
25
15.5
24
15.0
0
100
200
300
400
500
600
700
800
900
0
1000
50
100
Ashley River at SH1
150
200
250
300
350
400
450
500
Cust River at Carleton Rd Bridge
12
188.6
188.4
11
188.2
188.0
10
187.8
9
187.6
187.4
8
187.2
7
187.0
186.8
6
0
50
100
150
200
250
300
350
400
450
0
50
100
150
200
250
300
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Cust River at Bennetts Rd
164.8
164.6
164.4
164.2
164.0
163.8
163.6
163.4
163.2
163.0
162.8
0
20
40
60
80
100
120
1000
1200
Cust River at Patersons Rd
110
109
109
108
108
107
0
200
400
600
800
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Cust at Threlkelds Rd
12
10
8
6
4
2
0
0
20
40
60
Kaiapoi at Rail bridge
80
100
120
140
160
180
200
Eyre at Trigpole Rd
5.0
392
4.5
391
4.0
390
3.5
389
3.0
388
2.5
387
2.0
386
1.5
385
1.0
384
0.5
383
382
0.0
0
20
40
60
80
100
120
140
160
180
0
10
20
30
40
50
60
70
80
90
100
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Eyre at McGraths Rd Ford
Coopers Creek at Mountain Road
291
350
290
349
289
348
288
347
287
346
286
345
285
344
284
283
343
0
50
100
150
200
250
300
350
400
450
500
0
10
20
Coopers Creek at Mountain Road
30
40
50
60
Eyre River at Depot Gorge Road
285.0
250.0
249.5
284.5
249.0
284.0
248.5
283.5
248.0
283.0
247.5
247.0
282.5
246.5
282.0
246.0
281.5
245.5
0
20
40
60
80
100
120
140
0
50
100
150
200
250
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Eyre River at Carleton Road
Eyre River at Steffens Rd
197.0
183.5
196.5
183.0
196.0
182.5
195.5
195.0
182.0
194.5
181.5
194.0
193.5
181.0
193.0
180.5
192.5
192.0
180.0
0
100
200
300
400
500
600
700
0
50
100
150
200
250
300
Eyre Diversion at Waimakariri Confluence
Eyre River at Two Chain Road
66.0
34
65.5
33
65.0
32
64.5
64.0
31
63.5
30
63.0
29
62.5
28
62.0
61.5
27
0
50
100
150
200
250
300
350
0
20
40
60
80
100
120
140
160
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Waimakariri River at Gorge
Waimakariri River at Halkett
251.0
128
250.5
126
124
250.0
122
249.5
120
249.0
118
248.5
116
248.0
114
112
247.5
0
10
20
30
40
50
0
60
200
400
Waimakariri River at Weedons Ross Rd
600
800
1000
1200
1400
1600
1200
1400
1600
Waimakariri River at Crossbank
94
45
93
44
92
43
91
42
90
41
89
40
88
39
87
38
86
37
0
200
400
600
800
1000
1200
1400
1600
0
200
400
600
800
1000
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Waimakariri River at Wrights Cut
Waimakariri River at Old HW Bridge
12
4.5
4.0
10
3.5
8
3.0
2.5
6
2.0
4
1.5
1.0
2
0.5
0
0.0
0
50
100
150
200
250
300
350
400
450
500
0
50
100
150
200
250
300
350
400
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Appendix B: Time series data extension tool
Aqualinc’s time-series extension tool is a tool for correcting and extending daily climate/river flow time
series. A time series that is short or missing a significant amount of data (TS1) is extended using
correlations with longer time series (TS2). The program first runs through the time series and
calculates the ratio TS1/TS2 for each calendar month, for the period where there is overlap between
the two datasets. The program then runs through the time series a second time and extends or fills
TS1 by multiplying TS2 by the monthly ratios (refer to Table 1).
Table 1: Output value given data availability
Data for day i
TS1
TS2
Yes
Irrelevant
No
Yes
Output value
TS1 [day i]
TS2 [day i]×(TS1/TS2 for relevant calendar month)
Both TS1 and TS2 may have gaps in the data, and can have different start and end dates. The output
time series extends from the first day of data from either TS1 or TS2, to the last day of data from either
TS1 or TS2.
When neither TS1 nor TS2 has data for a certain day, the program first runs through TS1 and calculates
mean monthly averages for each calendar month. The program then runs through TS1 a second time
and fills any missing gaps with the long term monthly average.
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Appendix C: Table of river reach characteristics
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Ashley River (Reach A1): Ashley Gorge to Bowicks Road
Attribute
Description, count or value
Range
Measured flows (m3/s) at US site
4.38 (mean from concurrent
gaugings)
1.3 to 10.3
4.33 (mean from concurrent
gaugings)
1.01 to 10.5
Gaining or losing (l/s)
Loss 48 (difference in mean flows)
Loss 80 (based on concurrent
gaugings and tributary inflows*)
-530 to 2,590*
Long term gain/loss estimate (l/s)
Loss 265
0 to -530
Length (km)
11.2
Width (m)
20 (average)
Average specific river flow change
Loss of 5.714 l/s/km
Cross-sections
11
Area (m2) (plan view)
224,000
Low
Calculated from length and width
Average stage height (m)
0.3 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
224 m amsl
Low
Estimated using Topo map (not covered by LiDAR)
Stage elevations US
224.3 m amsl
Bed elevation DS
159.6 m amsl
Stage elevations DS
159.9 m amsl
Moderate
Bed gradient (m/m)
0.007
High
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
191.5
Low
Average of data for bores M34/0306 and
BW23/0053
Bed vertical hydraulic
conductivity (k) (m/day)
0.04
0.03 to 0.05
Low
Calculated based on Sanders (2000) method, as
given in main report
Bed thickness (m)
1
-
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
0.80
0.60 to 1.0
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.047
0.03 to 0.046
Hicks & Mason (1991),
Oliver (2008)
Moderate
Similar to Gowan at Lake Rotorua (Hicks & Mason,
1991, p190)
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008)
Measured flow
(m3/s)
at DS site
Source
Quality
Dodson (2014)
Uncertainty
envelope +/20%
(uncertainty of
gauging error
and
measurement
bias)
40 concurrent measurements 1971-2011
(*adjusting for estimated tributary inflows, see
Dodson, 2014). Ashley Gorge recorder extended
flow data available from 1964-2015; long term
mean flow 11.47 m3/s.
Based on observed range of losses
ECan Survey , LiDAR
4.92 to 8.21
l/s/km
Comments
Dodson (2014)
Moderate
Low
Estimated from flow gauging facecards
Low
Dodson (2014)
2 provided with gauging data; 3 more available;
see spreadsheet for model cross sections.
Survey
Topo map
Moderate
ECan Survey 2001 &
2012
M34/0306 and
BW23/0053
Sanders (2000)
ECan Survey 2001 & 2012, and Topo map
Calculated using average stage height (m)
High
Calculated using average stage height (m)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
50
Ashley River (Reach A2): Bowicks Road to US Okuku Confluence
Attribute
Description, count or value
Range
Measured flows (m3/s) at US site
4.92 (mean from concurrent
gaugings)
1.57 to 8.86
4.81 (mean from concurrent
gaugings)
1.95 to 10
Gaining or losing (l/s)
Gain 591 l/s
(mean from concurrent gaugings)
58 to 1,411
Long term gain/loss estimate (l/s)
Gain 1,500
100 to 2,900
Length (km)
11.2
Width (m)
20 (average)
Average specific river flow change
Gain 54.9 l/s/km
Cross-sections
11
Area (m2) (plan view)
224,000
Low
Calculated from length and width
Average stage height (m)
0.45 (Average)
Low
Estimated from flow gauging facecards
Bed elevation US
159.5 m amsl
Stage elevations US
160 m amsl
Bed elevation DS
91.9 m amsl
Stage elevations DS
92.4 amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.006
High
Calculated from bed elevations and length
Representative GW level (m amsl)
130
Low
Piezometric contours provided by ECan
Bed vertical hydraulic
conductivity (k) (m/day)
0.05
0.006 to 0.15
Low
Calculated based on Sanders (2000) method, as
given in main report
Bed thickness (m)
1
-
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
1
0.12 to 3
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.047
0.03 to 0.046
Hicks & Mason (1991),
Oliver (2008)
Moderate
Similar to Gowan at Lake Rotorua (Hicks &
Mason, 1991, p190)
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008)
Measured flow
(m3/s)
at DS site
Source
Quality
Smith (2012)
Uncertainty
envelope +/20%
(uncertainty of
gauging error
and
measurement
bias)
Comments
12 concurrent measurements with Bowicks Road
(2008-2011). Evidence in literature suggests that
this reach may be sometimes gaining and
sometimes losing, but typically gaining (see
report).
Based on regression and observed range
ECan Survey 2001 &
2012
5.18 to 126
l/s/km
High
ECan Survey 2001 & 2012
Low
Estimated from flow gauging facecards
Low
N=12 concurrent flow gaugings
2 provided with gauging data; 4 more available;
see spreadsheet for model cross sections.
Survey
ECan Survey 2001 &
2012
High
Moderate
ECan Survey 2001 &
2012
Piezo contours (2003)
Sanders (2000)
Calculated using average stage height (m)
High
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
51
Ashley River (Reach A3): US Okuku Confluence to Rangiora Traffic Bridge
Attribute
Description, count or value
Range
Source
Quality
Smith (2012)
Uncertainty
envelope +/20% (uncertainty
of gauging error
and
measurement
bias)
Comments
Measured flows (m3/s) at US site
4.81 (mean from concurrent
gaugings)
1.7 to 10
Measured flow (m3/s) at DS site
3.3 (mean from concurrent
gaugings)
0.02 to 9.21
Gaining or losing (l/s)
Loss -1,511 l/s
(mean from concurrent gaugings)
-1,926 l/s to 831 l/s
Long term gain/loss estimate (l/s)
Loss 1,000
400 to 2,400
Length (km)
10.6
Width (m)
20 (average)
Average specific river flow change
Gain 142.55 l/s/km
Cross-sections
11
Area (m2) (plan view)
212,000
Low
Calculated from length and width
Average stage height (m)
0.45
Low
Estimated from flow gauging facecards
Bed elevation US
91.9 m amsl
Stage elevations US
92.4 m amsl
Bed elevation DS
33.7 m amsl
Stage elevations DS
34.2 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.0055
High
Calculated from bed elevations and length
Representative GW level (m amsl)
60
Low
Based on bore M35/2679 adjusted for slope and
distance to mid-point of reach. Piezo contours
confirm.
Bed vertical hydraulic
conductivity (k) (m/day)
0.19
0.03 to 0.24
Low
Calculated based on Sanders (2000) method, as
given in main report
Bed thickness (m)
1
-
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
3.8
2 to 4.8
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.047
0.03 to 0.046
Hicks & Mason (1991),
Oliver (2008)
Moderate
Similar to Gowan at Lake Rotorua (Hicks &
Mason, 1991, p190)
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008)
16 of 18 concurrent measurements (2008-2011).
Rangiora Traffic Bridge flows adjusted for Okuku
inflows (i.e. concurrent Okuku measured flow is
subtracted from RTB measured flow). Typically
when Ashley at Gorge flow is <1.23 m3/s the river
is dry from RTB to Lowes Corner.
Based on regression and observed range
ECan Survey 2008/2009
182 to 78
l/s/km
High
Low
Estimated from flow gauging facecards
Low
N=16 concurrent flow gaugings
2 provided with gauging data; 9 more available;
see spreadsheet for model cross sections.
Survey
ECan Survey 2008/09
High
Moderate
ECan Survey 2008/09
Sanders (2000)
Calculated using average stage height (m)
High
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
52
Ashley River (Reach A4): Rangiora Traffic Bridge to Golf Links Road
Attribute
Description, count or value
Range
Measured flows (m3/s) at US site
3.12 (mean from concurrent
gaugings)
0.13 to 9.2
3.03 (mean from concurrent
gaugings)
0 to 10
Gaining or losing (l/s)
Loss 263 l/s
(mean from concurrent gaugings)
-1,075 l/s to
1,086 l/s
Long term gain/loss estimate (l/s)
Gain 1,500
1,000 to 2,400
Length (km)
2.65
Width (m)
20 (average)
Average specific river flow change
Loss 102.3 l/s/km
Cross-sections
4
Area (m2) (plan view)
53,000
Average stage height (m)
0.45 (average)
Bed elevation US
33.7 m amsl
Stage elevations US
34.2 m amsl
Bed elevation DS
25.5 m amsl
Stage elevations DS
26 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.0044
High
Calculated from bed elevations and length
Representative GW level (m amsl)
28
25 to 30
Low
Estimated from piezo contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.21
0.02 to 0.87
Low
Calculated based on Sanders (2000) method.
Bed thickness (m)
1
-
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
4.2
0.4 to 17.4
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.047
0.03 to 0.046
Hicks & Mason (1991),
Oliver (2008)
Moderate
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Measured flow
(m3/s)
at DS site
Source
Quality
Comments
Smith (2012)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error
and
measurement
bias)
14 of 16 concurrent measurements (2008-2011).
Rangiora Traffic Bridge flows adjusted for Okuku
inflows (i.e. concurrent Okuku measured flow is
subtracted from RTB measured flow). Two outliers
removed for October 2009 and May 2011.
Based on regression and observed range
ECan Survey
2008/2009
-405.7 to 409.8
l/s/km
High
Low
Estimated from flow gauging facecards
Low
N=16 concurrent flow gaugings
2 provided with gauging data; 2 more available, but
not yet supplied; see spreadsheet for model cross
sections.
Survey
ECan Survey 2008/09
Low
Calculated from length and width
Low
Estimated from flow gauging facecards
High
Moderate
ECan Survey 2008/09
Sanders (2000)
Calculated using average stage height (m)
High
Similar to Gowan at Lake Rotorua (Hicks & Mason,
1991, p190)
Range given by Oliver (2008)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
53
Ashley River (Reach A5): Golf Links Road to Lowes Corner
Attribute
Description, count or value
Range
Measured flows (m3/s) at US site
4.266 (mean from concurrent
gaugings)
0 to 10.9
Measured flow (m3/s) at DS site
4.244 (mean from concurrent
gaugings)
0.19 to 10.8
Gaining or losing (l/s)
Loss 22.5 l/s
(mean from concurrent gaugings)
-931 l/s to 378
l/s
Long term gain/loss estimate (l/s)
Gain 400
-600 to 800
Length (km)
2.41
Width (m)
20 (average)
Average specific river flow change
Loss 9.24 l/s/km
Cross-sections
4
Area (m2) (plan view)
48,200
Source
Quality
Comments
Smith (2012)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement bias)
12 of 18 concurrent measurements (2009-2011)
from Smith (2012). The subset data has been
used due to the negative groundwater gradient
identified in the report. The evidence suggests
the reach is sometimes gaining and sometimes
losing.
Based on regression and observed range
ECan Survey
2008/2009
-157 to 386
l/s/km
High
Low
Estimated from flow gauging facecards
Low
N=16 concurrent flow gaugings
2 provided with gauging data; 2 more available,
but not yet supplied; see spreadsheet for model
cross sections.
Survey
Low
Calculated from length and width
Low
Estimated from flow gauging facecards
Average stage height (m)
0.45
Bed elevation US
25.5 m amsl
Stage elevations US
26 m amsl
Bed elevation DS
16.1 m amsl
Stage elevations DS
16.5 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.004
High
Calculated from bed elevations and length
Representative GW level (m
amsl)
20
15-25
Low
Based on averages for bores M35/2677 and
M35/0366 and piezo contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.03
0.02 to 1.34
Low
Calculated based on Sanders (2000) method, as
given in main report.
Bed thickness (m)
1
-
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
0.6
0.4 to 26.8
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.047
0.03 to 0.046
Hicks & Mason (1991),
Oliver (2008)
Moderate
Similar to Gowan at Lake Rotorua (Hicks &
Mason, 1991, p190)
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008)
ECan Survey 2008/09
High
Moderate
ECan Survey 2008/09
Sanders (2000)
Calculated using average stage height (m)
High
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
54
Ashley River (Reach A6): Lowes Corner to State Highway 1
Attribute
Description, count or value
Range
Source
Quality
Comments
Measured flows (m3/s) at US site
3.40 (mean from concurrent
gaugings)
0.19 to 10.82
Measured flow (m3/s) at DS site
3.62 (mean from concurrent
gaugings)
Smith (2012)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement bias)
16 of 18 concurrent measurements (2008-2011)
(Smith, 2012); additional stage recorder data
available spanning 2012-2015 (flood
monitoring). Ashley at SH1 recorder mean flow
17.3 m3/s based on mean daily flows.
0.32 to 11.40
Gaining or losing (l/s)
Gain 224 l/s
(mean from concurrent gaugings)
-82 l/s to 582 l/s
Long term gain/loss estimate (l/s)
Gain 400
100 to 700
Length (km)
3.32
Width (m)
20 (average)
Average specific river flow change
Gain 69.6 l/s/km
Cross-sections
5
Area (m2) (plan view)
64,400
Average stage height (m)
0.45 (median)
flow gauging
Moderate
Bed elevation US
16.1 m amsl
ECan Survey 2008/09
High
Stage elevations US
16.6 m amsl
Bed elevation DS
5.7 m amsl
Stage elevations DS
6.2 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.0032
High
Calculated from bed elevations and length
Representative GW level (m amsl)
11.7
10-13
Low
Based on averages for bores M35/17982 and
M35/2677 and piezo contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.84
0.46 to 2.17
Low
Calculated based on Sanders (2000) method,
as given in main report. Based on observed
flow gains only.
Bed thickness (m)
1
-
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
16.3
8.9 to 42.1
Low
For GMS: traditional conductance (k*A/b)
divided by reach length
Mannings n for main channel
0.047
0.03 to 0.046
Hicks & Mason (1991)
Moderate
Similar to Gowan at Lake Rotorua (Hicks &
Mason, 1991, p190)
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008)
Based on regression and observed range
ECan Survey
2008/2009
-25.5 to 181
l/s/km
High
Low
Estimated from flow gauging facecards
Low
From 16 concurrent flow gaugings
2 provided with gauging data; 3 more available
from survey; see spreadsheet for model cross
sections.
Survey
Low
Moderate
ECan Survey 2008/09
Sanders (2000)
High
Calculated from length and width
Estimated from flow gauging facecards
Survey and LiDAR data
Calculated using average stage height (m)
Survey and LiDAR data
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
55
Eyre River (Reach E1): Trigpole Road to McGraths Road Ford
Attribute
Description, count or value
Range
Measured flows (m3/s) at US site
0.244 (mean from concurrent
gaugings)
0.067 to 0.578
Measured flow (m3/s) at DS site
0.125 (mean from concurrent
gaugings)
0.002 to 0.5
Gaining or losing (l/s)
Loss 90.1 (mean from
concurrent gaugings)
-55 to -171
Length (km)
9.5
Width (m)
5.5 (estimated)
Average specific river flow change
Loss 9.49 l/s/km
Source
Quality
Comments
Davey & Smith (2005)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
6 concurrent measurements 2004-2005 (Davey
& Smith, 2005). Trigpole Road recorder stage
and flow data available from 2010-2011, with
mean daily flow of 0.454 m3/s. Record
extension with Ashley Gorge recorder provides
flow records from 1971-2011.
LiDAR
Moderate
Low
5.79 to 18 l/s/km
Davey & Smith (2005)
LiDAR data
Estimated from flow gauging facecards
Low
LiDAR & gauging
data
2 derived from LiDAR and checked with
gauging data
Cross-sections
2
Area (m2) (plan view)
52,250
Low
Calculated from length and estimated width
Average stage height (m)
0.18 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
383 m amsl
Stage elevations US
383.2 m amsl
LiDAR
LiDAR
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Bed elevation DS
284 m amsl
Moderate
Estimated using LiDAR data
Stage elevations DS
284.2 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.01
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
315
L35/0025 and
L35/0050
Low
Estimated average of data from bores L35/0025
and L35/0050
Bed vertical hydraulic
conductivity (k) (m/day)
0.008
0.005 to 0.24
Low
Calculated based on Sanders (2000) method,
as given in main report
Bed thickness (m)
1
-
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
0.04
0.03 to 1.32
Low
For GMS: traditional conductance (k*A/b)
divided by reach length
Mannings n for main channel
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Mannings n for bank
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Sanders (2000)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
56
Eyre River (Reach E2): Coopers Creek at Mountain Road to Island Road Ford
Attribute
Description, count or value
Range
Measured flows (m3/s) at US site
0.384 (mean from concurrent
gaugings)
0.146 to 0.723
Measured flow (m3/s) at DS site
0.078 (mean from concurrent
gaugings)
0 to 0.224
Gaining or losing (l/s)
Loss 305 (mean from
concurrent gaugings)
-146 to -499
Length (km)
4.6
Width (m)
4 (estimated)
Average specific river flow change
Loss 66.4 l/s/km
Cross-sections
2
Area (m2) (plan view)
18,400
Average stage height (m)
0.20 (average)
Bed elevation US
343.5 m amsl
Stage elevations US
343.7 m amsl
Bed elevation DS
281.7 m amsl
Stage elevations DS
Source
Quality
Davey & Smith (2005)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement bias)
LiDAR
Moderate
Low
31.7 to 108.5
l/s/km
Davey & Smith (2005)
8 concurrent measurements 2004-2005
(Davey & Smith, 2005).
LiDAR data
Estimated from flow gauging facecards
Low
LiDAR & gauging
data
LiDAR
Comments
2 derived from LiDAR and checked with
gauging data
Low
Calculated from length and estimated width
Low
Estimated from flow gauging facecards
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
281.9 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.013
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
305
Bed vertical hydraulic
conductivity (k) (m/day)
0.18
0.09 to 1.95
Bed thickness (m)
1
-
Bed conductance (m2/day/m)
0.72
0.36 to 7.8
Mannings n for main channel
0.05
0.027 to 0.15
Mannings n for bank
0.05
0.027 to 0.15
LiDAR
L35/0025 and
L35/0050 & Piezo
contours
Low
Estimated average of data from bores
L35/0025 and L35/0050 and piezo contours
Low
Calculated based on Sanders (2000) method,
as given in main report
Low
Unknown - 1 m assumed
Low
For GMS: traditional conductance (k*A/b)
divided by reach length
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Sanders (2000)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
57
Eyre River (Reach E3): McGraths Road Ford to Depot Gorge Road
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
0.125 (mean from
concurrent gaugings)
0.002 to 0.5
Measured flow (m3/s) at DS site
0.39 (mean from concurrent
gaugings)
0 to 1.311
Gaining or losing (l/s)
Loss 118 l/s*
-90 to 154
Length (km)
5.18
Width (m)
5.5 (estimated)
Average specific river flow change
Loss 8.04 l/s/km
Cross-sections
2
Area (m2) (plan view)
28,490
Low
Calculated from length and estimated width
Average stage height (m)
0.18 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
284 m amsl
Stage elevations US
284.18 m amsl
Bed elevation DS
246 m amsl
Stage elevations DS
Source
Quality
Comments
Davey & Smith (2005)
& calculated flow
losses from
concurrent flow
readings at Trigpole
Road and Depot
Gorge Road
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
8 concurrent measurements 2004-2005 (Davey
& Smith, 2005). *The average flow loss has
been calculated from 6 concurrent flows
between Trigpole Road and Depot Gorge Road
(see report). River typically dry at Depot Gorge
Road in summer when Eyre at Trigpole Road
flows are < 118 l/s.
LiDAR
Moderate
Low
-29.7 to 17.38
l/s/km
Davey & Smith (2005)
Estimated from flow gauging facecards
Low
LiDAR & gauging
data
LiDAR
LiDAR data
2 derived from LiDAR and checked with
gauging data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
246.18 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.007
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
262
260 to 265
Bed vertical hydraulic
conductivity (k) (m/day)
0.04
0.013 to 0.11
Bed thickness (m)
1
-
Bed conductance (m2/day/m)
0.22
0.07 to 3.91
Mannings n for main channel
0.05
0.027 to 0.15
Mannings n for bank
0.05
0.027 to 0.15
LiDAR
Piezo contours
Low
Estimated average from piezo contours
Low
Calculated based on Sanders (2000) method,
as given in main report. Based on calculated
flow losses.
Low
Unknown - 1 m assumed
Low
For GMS: traditional conductance (k*A/b)
divided by reach length
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Sanders (2000)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
58
Eyre River (Reach E4): Depot Gorge Road to Steffens Road
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
0.64 (mean from
concurrent gaugings)
0.264 to 1.648
Measured flow (m3/s) at DS site
0.301 (mean from
concurrent gaugings)
0 to 1.062
Gaining or losing (l/s)
Loss 341 (calculated from
concurrent gaugings)
-157 to -586
Length (km)
9.5
Width (m)
5.5 (estimated)
Average specific river flow change
Loss 35.9 l/s/km
Cross-sections
2
Area (m2) (plan view)
52,250
Low
Calculated from length and estimated width
Average stage height (m)
0.18 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
246 m amsl
Stage elevations US
246.18 m amsl
Bed elevation DS
180.3 m amsl
Stage elevations DS
Source
Quality
ECan
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
LiDAR
Moderate
Low
16.5 to 61.7 l/s/km
Comments
5 concurrent measurements from 1994 (ECan).
River typically dry at Steffens Road in summer
when Eyre at Trigpole Road flows are < 147 l/s.
LiDAR data
Estimated from flow gauging facecards
Low
LiDAR & gauging
data
LiDAR
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
180.48 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.007
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
207
Bed vertical hydraulic
conductivity (k) (m/day)
0.09
Bed thickness (m)
LiDAR
L35/0058 & Piezo
contours
Low
Estimated average from L35/0058 & piezo
contours
0.04 to 4.9
ECan data; PDP
(2007)
Low
Calculated based on Sanders (2000) method, as
given in main report. ECan data and PDP results
included in range.
1
-
Sanders (2000)
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
0.5
0.22 to 44
Low
Including estimates from ECan data and PDP
results.
Mannings n for main channel
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Mannings n for bank
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
59
Eyre River (Reach E5): Steffens Road to Two Chain Road
Attribute
Description, count or
value
Measured flows (m3/s) at US site
2.76
Measured flow
(m3/s)
at DS site
Gaining or losing (l/s)
Range
Source
Quality
ECan
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
LiDAR
Moderate
0.517
Loss 2,239
Comments
1 concurrent measurement from 1994 (ECan).
Length (km)
19.6
Width (m)
5.5 (estimated)
Low
Average specific river flow change
Loss 114.2 l/s/km
Low
Cross-sections
2
Area (m2) (plan view)
107,800
Low
Calculated from length and estimated width
Average stage height (m)
0.18 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
180.3 m amsl
Stage elevations US
180.5 m amsl
Bed elevation DS
62.3 m amsl
Stage elevations DS
LiDAR & gauging
data
LiDAR
LiDAR data
Estimated from flow gauging facecards
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
62.5 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.006
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
117
115 to 120
Piezo contours
Low
Estimated average from piezo contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.4
0.28 to 7.1
ECan data; PDP
(2007)
Low
Calculated based on Sanders (2000) method, as
given in main report. Average of ECan data and
PDP results.
Bed thickness (m)
Sanders (2000)
Low
Unknown - 1 m assumed
Low
Average of ECan data and PDP results.
LiDAR
1
-
(m2/day/m)
2.2
1.54 to 57
Mannings n for main channel
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Mannings n for bank
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Bed conductance
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
60
Eyre River (Reach E6): Two Chain Road to Eyre River Diversion at Waimakariri Confluence
Description, count or
value
Attribute
Range
Source
Quality
ECan
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
LiDAR
Moderate
Measured flows (m3/s) at US site
Measured flow
(m3/s)
at DS site
Gaining or losing (l/s)
Losing*
Comments
*No concurrent gaugings, assumed losing based
on upstream reaches.
Length (km)
7.1
Width (m)
5.5 (estimated)
Average specific river flow change
N/A
Cross-sections
2
Area (m2) (plan view)
39,050
Low
Calculated from length and estimated width
Average stage height (m)
0.18 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
62.3 m amsl
Stage elevations US
62.5 m amsl
Bed elevation DS
28.2 m amsl
Stage elevations DS
Low
LiDAR & gauging
data
LiDAR
LiDAR data
Estimated from flow gauging facecards
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
28.4 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.005
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
27
Bed vertical hydraulic
conductivity (k) (m/day)
N/A
Bed thickness (m)
1
LiDAR
25 to 30
Low
Estimated from piezo contours
Use same as upstream reach
Low
Unknown - 1 m assumed
(m2/day/m)
N/A
Mannings n for main channel
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Mannings n for bank
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna
(p25) (Hicks & Mason, 1991)
Bed conductance
Use same as upstream reach
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
61
Cust River (Reach C1): Carleton Road Bridge to Bennetts Road
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
0.425 (average from
gaugings)
0 to 0.849
Measured flow (m3/s) at DS site
N/A
Gaining or losing (l/s)
Gaining*
Source
Quality
Smith (2012)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
LiDAR
Moderate
Comments
22 flow gaugings from 2009-2011 for Carleton
Road. *No concurrent gaugings – visual
observations only.
Length (km)
3.55
Width (m)
4.5 (estimated)
Average specific river flow change
N/A
Cross-sections
2
Area (m2) (plan view)
15,975
Low
Calculated from length and estimated width
Average stage height (m)
0.25 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
186.9 m amsl
Stage elevations US
187.3 m amsl
Bed elevation DS
162.9 m amsl
Stage elevations DS
Low
LiDAR & gauging
data
LiDAR
LiDAR data
Estimated from flow gauging facecards
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
163.3 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.007
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
170
Bed vertical hydraulic
conductivity (k) (m/day)
N/A
Bed thickness (m)
1
Bed conductance (m2/day/m)
N/A
Mannings n for main channel
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
Mannings n for bank
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
LiDAR
165 to 175
Low
Estimated average from piezo contours
Low
Unknown - 1 m assumed
For GMS: traditional conductance (k*A/b) divided
by reach length
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
62
Cust River (Reach C2): Bennetts Road to Patersons Road
Attribute
Description, count or
value
Measured flows (m3/s) at US site
N/A
Measured flow
(m3/s)
at DS site
Range
Source
Quality
Comments
Dodson et al.
(2012)
Uncertainty
envelope +/20% (uncertainty
of gauging error
and
measurement
bias)
No concurrent gaugings – visual observations only.
*Dodson et al. (2012) p26.
LiDAR
Moderate
N/A
Gaining or losing (l/s)
Gaining*
Length (km)
9.75
Width (m)
4.5 (estimated)
Average specific river flow change
N/A
Cross-sections
2
Area (m2) (plan view)
58,500
Low
Calculated from length and estimated width
Average stage height (m)
0.25 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
162.0 m amsl
Stage elevations US
163.3 m amsl
Bed elevation DS
107.2 m amsl
Stage elevations DS
Low
LiDAR & gauging
data
LiDAR
LiDAR data
Estimated from flow gauging facecards
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
107.5 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.006
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
132
130 to 135
Bed vertical hydraulic
conductivity (k) (m/day)
40
6 to 90 m/day
Bed thickness (m)
1
Bed conductance (m2/day/m)
240
36 to 540
Mannings n for main channel
0.05
0.027 to 0.15
Mannings n for bank
0.05
0.027 to 0.15
LiDAR
Low
Estimated average from piezo contours
Low
Field results from Tippings Road site by Smith and
reported in Dodson et al. (2012)
Low
Unknown - 1 m assumed
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
Dodson et al.
(2012)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
63
Cust River (Reach C3): Patersons Road to Rangiora Oxford Road
Attribute
Description, count or
value
Measured flows (m3/s) at US site
N/A
Measured flow (m3/s) at DS site
0.412 (average of
gaugings)
Gaining or losing (l/s)
Gaining*
Range
0.001 to 3.92
Source
Quality
Comments
Dodson et al.
(2012)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
111 gaugings for Rangiora Oxford from 1970-2012.
No concurrent gaugings. *Dodson et al. (2012) p26.
Concurrent gaugings between the reach above and
below suggest that the reach is typically gaining.
LiDAR
Moderate
Length (km)
3.5
Width (m)
6 (estimated)
Average specific river flow change
N/A
Cross-sections
2
Area (m2) (plan view)
15,750
Low
Calculated from length and estimated width
Average stage height (m)
0.25 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
107.2 m amsl
Stage elevations US
107.5 m amsl
Bed elevation DS
83.3 m amsl
Stage elevations DS
Low
LiDAR & gauging
data
LiDAR
LiDAR data
Estimated from flow gauging facecards
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
83.5 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.007
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
97
LiDAR
90 to 100
Dodson et al.
(2012)
Low
Estimated from piezo contours
Low
Based on concurrent gaugings between Carleton
Road Bridge an Rangiora Oxford Road (see report,)
and Field results from Kennedys Road site by
Smith and reported in Dodson et al. (2012)
Low
Unknown - 1 m assumed
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Bed vertical hydraulic
conductivity (k) (m/day)
0.18
Bed thickness (m)
1
Bed conductance (m2/day/m)
3,000
300 to 6,000
Mannings n for main channel
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
Mannings n for bank
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
0.06 to 1,000
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
64
Cust River (Reach C4): Rangiora Oxford Road to Swannanoa Road
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
0.412 (average of
gaugings)
0.001 to 3.92
Measured flow (m3/s) at DS site
NA (no concurrent
gaugings)
Gaining or losing (l/s)
Predicted average loss of
143 l/s *
Length (km)
6
Width (m)
6 (estimated)
Average specific river flow change
-23.9 l/s/km
Cross-sections
2
Area (m2) (plan view)
36,000
Low
Calculated from length and estimated width
Average stage height (m)
0.25 (estimated)
Low
Estimated from flow gauging facecards
Bed elevation US
83.3 m amsl
Stage elevations US
83.55 m amsl
Bed elevation DS
48.85 m amsl
Stage elevations DS
Source
Quality
ECan
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
LiDAR
Moderate
6 to 307*
Low
-1 to -51.2 l/s/km
Comments
25 flow gaugings at Rangiora Oxford Road are
concurrent with mean daily flows available for
Threlkelds Road recorder of less than 522 l/s.
*Visual observations of Cust going dry at
BW23/0134 (Swannanoa Road) when Threlkelds
Road flow < 522 l/s
LiDAR data
Estimated from flow gauging facecards
Low
LiDAR & gauging
data
LiDAR
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
49.1 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.006
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
57.5
55 to 60
Low
Estimated average from piezo contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.039
0.002 to 0.084
Low
Calculated based on Sanders (2000) method, as
given in main report.
Bed thickness (m)
1
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
0.23
0.01 to 0.5
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
Mannings n for bank
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
LiDAR
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
65
Cust River (Reach C5): Swannanoa Road to Main Drain at Threlkelds Road
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
NA
NA
1.55 (recorder data mean
daily flow)
0.095 to 8.760
Gain 447*
26 to 4,836
Measured flow
(m3/s)
at DS site
Gaining or losing (l/s)
Source
Quality
Comments
ECan
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
No concurrent gaugings available. *88 flow
gaugings at Rangiora Oxford Road are concurrent
with mean daily flows available for Threlkelds Road
recorder. Additional recorder stage and flow data
available from 1980-2015.
LiDAR
Moderate
Length (km)
9.2
Width (m)
8 (average)
Average specific river flow change
48.6 l/s/km
Cross-sections
2
Area (m2) (plan view)
73,600
Low
Calculated from length and estimated width
Average stage height (m)
0.24 (average)
Low
Estimated from flow gauging facecards
Bed elevation US
48.85 m amsl
Stage elevations US
49.1 m amsl
Bed elevation DS
6.7 m amsl
Stage elevations DS
Low
2.83 to 526 l/s/km
LiDAR data
Estimated from flow gauging facecards
Low
LiDAR & gauging
data
LiDAR
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Calculated using average stage height (m)
Moderate
Estimated using LiDAR data
6.94 m amsl
Moderate
Calculated using average stage height (m)
Bed gradient (m/m)
0.051
Moderate
Calculated from estimated bed elevations and
length
Representative GW level (m amsl)
42
40 to 45
Low
Estimated average from piezo contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.282
0.015 to 4.55
Low
Calculated based on Sanders (2000) method, as
given in main report.
Bed thickness (m)
1
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
1.69
0.09 to 27.30
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
Mannings n for bank
0.05
0.027 to 0.15
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
LiDAR
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
66
Cust River (Reach C6): Threlkelds Road to Kaiapoi River Railway Bridge
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
1.55
0.095 to 8.760
NA
NA
Measured flow
(m3/s)
at DS site
Source
Quality
ECan
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement bias)
LiDAR
Moderate
Comments
Threlkelds Road recorder stage and flow data
available from 1980-2015. Daily mean flow 1.55
m3/s
Gaining or losing (l/s)
Assumed gaining
Length (km)
2.39
Width (m)
10 (average)
Average specific river flow change
N/A
Cross-sections
2
Area (m2) (plan view)
23,900
Low
Calculated from length and estimated width
Average stage height (m)
0.2 (average)
Low
Estimated from flow gauging facecards for
Threlkelds
Bed elevation US
6.70 m amsl
Stage elevations US
6.90 m amsl
Bed elevation DS
0.52 m amsl
Stage elevations DS
Bed gradient (m/m)
Low
LiDAR & gauging
data
LiDAR
Estimated from flow gauging facecards for
Threlkelds
2 derived from LiDAR and checked with gauging
data
Moderate
Estimated using LiDAR data
Moderate
Estimated from flow gauging facecards for
Threlkelds
Moderate
Estimated using LiDAR data
0.7 m amsl
Moderate
Estimated from flow gauging facecards for
Threlkelds
0.003
Moderate
Calculated from estimated bed elevations and
length
LiDAR
Representative GW level (m amsl)
No data available
Bed vertical hydraulic
conductivity (k) (m/day)
N/A
Bed thickness (m)
1
(m2/day/m)
N/A
Mannings n for main channel
0.05
0.027 to 0.15
Mannings n for bank
0.05
0.027 to 0.15
Bed conductance
LiDAR data
Low
Unknown - 1 m assumed
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
Hicks & Mason
(1991)
Low
Average of Waiau (p110) and Ruakokaputuna (p25)
(Hicks & Mason, 1991)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
67
Waimakariri River (Reach W1): Gorge to Courtenay Road
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
51 (average daily flow
rounded)
N/A
Measured flow (m3/s) at DS site
51 (average daily flow
rounded)
N/A
Gaining or losing (l/s)
Loss of 2,800
N=2
Length (km)
17.4
Width (m)
224
Average specific river flow change
N/A
White et al. (2012)
Seepage rate 55 mm/day at low flows
Cross-sections
10
ECan Survey data
10 available, none yet provided.
Area (m2) (plan view)
4,370,000
Average stage height (m)
Low flows
Source
Quality
Comments
White et al. (2012)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
Average of 2 concurrent measurements reported in
White et al. (2012). Adjusted for inflows and
outflows. Stage records from Gorge site available
(1971 to present). Daily mean flow at upstream
Otarama site available from 2008; mean flow 114.8
m3/s. Synthesised record available going back to
1967.
ECan Survey data
Moderate
White et al. (2012)
High
Average of 9 surveys from 1960-2014
Average total wetted channel width for low flow
records. Average of 8.1 channels.
White et al. (2012)
High
Estimated for low flow wetted channel width and
length
0.4
White et al. (2012)
High
Average water depth in observed channels
Bed elevation US
247
ECan Survey data
& Topo map
Moderate
Estimate based on Topo map and ECan survey
results
Stage elevations US
247.4
Moderate
Calculated using average stage height (m)
Bed elevation DS
159.13
Stage elevations DS
Low flows
ECan Survey data
High
Average of 9 surveys from 1960-2014
159.43
High
Calculated using average stage height (m)
Bed gradient (m/m)
0.005
Moderate
Calculated from bed elevations and length
Representative GW level (m amsl)
200
193.5 to 203
Bed vertical hydraulic
conductivity (k) (m/day)
0.016
0.006 to 0.119
Bed thickness (m)
1
Bed conductance (m2/day/m)
4.02
1.51 to 29.89
Mannings n for main channel
0.040
0.034 to 0.048
Mannings n for bank
0.075 (average)
0.03 to 0.12
L35/0085 & Piezo
contours
Low
Estimated average from bore L35/0085 and piezo
contours
Low
Calculated based on Sanders (2000) method, as
given in main report
Low
Unknown - 1 m assumed
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Hicks & Mason
(1991)
Low
Taken from the Rangitikei Hicks & Mason (1991)
p142
Oliver (2008)
Low
Range given by Oliver (2008) for the Ashley
Sanders (2000)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
68
Waimakariri River (Reach W2): Courtenay Road to Halkett Groyne
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
49 (average daily flow
rounded)
N/A
Measured flow (m3/s) at DS site
49 (average daily flow
rounded)
N/A
Gaining or losing (l/s)
Loss of 1,100
Estimated
Length (km)
8.04
Width (m)
186
Average specific river flow change
N/A
White et al. (2012)
Cross-sections
6
Survey
Area (m2) (plan view)
1,470,000
Low flows
Low flows
Source
Quality
Comments
White et al. (2012)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement
bias)
Estimate based on difference between concurrent
gaugings for upstream and downstream reaches
reported in White et al. (2012). Adjusted for inflows
and outflows.
ECan Survey data
High
Average of 9 surveys from 1960-2014
White et al. (2012)
High
Average total wetted channel width for low flow
records. Average of 7 channels.
Seepage rate 159 mm/day at low flows
6 available, none yet provided. Halkett Groyne
profile derived from LiDAR and provided in
Appendix.
White et al. (2012)
High
Estimated for low flow wetted channel width and
length
Average stage height (m)
0.3
White et al. (2012)
High
Average water depth in observed channels
Bed elevation US
159.13
ECan Survey data
High
Average of 9 surveys from 1960-2014
Stage elevations US
159.43
High
Calculated using average stage height (m)
Bed elevation DS
115.55
High
Average of 9 surveys from 1960-2014
Stage elevations DS
115.85
High
Calculated using average stage height (m)
Bed gradient (m/m)
0.005
High
Calculated from bed elevations and length
Representative GW level (m amsl)
135
130 to 137
Low
Estimated average from bore M35/8967 and piezo
contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.025
0.009 to 0.101
Low
Calculated based on Sanders (2000) method, as
given in main report
Bed thickness (m)
1
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
4.57
1.65 to 18.47
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.040
0.034 to 0.048
Hicks & Mason
(1991)
Moderate
Taken from the Rangitikei Hicks & Mason (1991)
p142
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008) for the Ashley
ECan Survey data
M35/8967 &Piezo
contours
Sanders (2000)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
69
Waimakariri River (Reach W3): Halkett Groyne to Weedons Ross Road
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
48 (average daily flow
rounded)
N/A
Measured flow (m3/s) at DS site
48 (average daily flow
rounded)
N/A
Gaining or losing (l/s)
Loss of 2,200
Estimated
Length (km)
5.23
Width (m)
200
Average specific river flow change
N/A
White et al. (2012)
Cross-sections
6
Survey
Area (m2) (plan view)
1,360,000
Average stage height (m)
Low flows
Source
Quality
Comments
White et al. (2012)
Uncertainty
envelope +/- 20%
(uncertainty of
gauging error and
measurement bias)
Estimate based on difference between concurrent
gaugings for upstream and downstream reaches
reported in White et al. (2012). Adjusted for
inflows and outflows.
ECan Survey data
High
Average of 9 surveys from 1960-2014
White et al. (2012)
High
Average total wetted channel width for low flow
records. Average of 6.3 channels.
Seepage rate 38 mm/day at low flows
6 available, none yet provided. 2 provided from
LiDAR data in Appendix.
White et al. (2012)
High
Estimated for low flow wetted channel width and
length
0.3
White et al. (2012)
High
Average water depth in observed channels
Bed elevation US
115.55
ECan Survey data
High
Average of 9 surveys from 1960-2014
Stage elevations US
115.85
High
Calculated using average stage height (m)
Bed elevation DS
88.63
High
Average of 9 surveys from 1960-2014
Stage elevations DS
88.93
High
Calculated using average stage height (m)
Bed gradient (m/m)
0.005
High
Calculated from bed elevations and length
Representative GW level (m amsl)
100
95 to 102
Low
Estimated average from bores M35/0962 and
M35/0930 and Piezo contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.058
0.019 to 0.359
Low
Calculated based on Sanders (2000) method, as
given in main report
Bed thickness (m)
1
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
15.08
4.94 to 93.35
Low
For GMS: traditional conductance (k*A/b) divided
by reach length
Mannings n for main channel
0.040
0.034 to 0.048
Hicks & Mason
(1991)
Moderate
Taken from the Rangitikei Hicks & Mason (1991)
p142
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008) for the Ashley
Low flows
ECan Survey data
M35/0962 and
M35/0930 & Piezo
contours
Sanders (2000)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
70
Waimakariri River (Reach W4): Weedons Ross Road to Crossbank
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
64 (average daily flow
rounded)
N/A
Measured flow (m3/s) at DS site
64 (average daily flow
rounded)
N/A
Gaining or losing (l/s)
Loss of 5,700 (n=1)
Length (km)
10.3
Width (m)
230
Average specific river flow change
N/A
White et al. (2012)
Cross-sections
10
Survey
Area (m2) (plan view)
2,100,000
Average stage height (m)
Low flows
Source
Quality
Comments
White et al. (2012)
Uncertainty envelope
+/- 20% (uncertainty
of gauging error and
measurement bias)
ECan Survey data
High
Average of 9 surveys from 1960-2014
White et al. (2012)
High
Average total wetted channel width for low flow
records. Average of 8.9 channels.
1 concurrent measurement reported in White et
al. (2012). Adjusted for inflows and outflows.
Seepage rate 230 mm/day at low flows
10 available, none yet provided. 2 provided from
LiDAR data in Appendix.
White et al. (2012)
High
Estimated for low flow wetted channel width and
length
0.3
White et al. (2012)
High
Average water depth in observed channels
Bed elevation US
88.63
ECan Survey data
High
Average of 9 surveys from 1960-2014
Stage elevations US
88.93
High
Calculated using average stage height (m)
Bed elevation DS
37.66
High
Average of 9 surveys from 1960-2014
Stage elevations DS
37.96
High
Calculated using average stage height (m)
Bed gradient (m/m)
0.005
High
Calculated from bed elevations and length
Representative GW level (m amsl)
62
57 to 63
Low
Estimated average from bores M35/8968 and
M35/0931 and Piezo contours
Bed vertical hydraulic
conductivity (k) (m/day)
0.162
0.036 to 0.527
Low
Calculated based on Sanders (2000) method, as
given in main report
Bed thickness (m)
1
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
33.03
7.34 to 107.45
Low
For GMS: traditional conductance (k*A/b)
divided by reach length
Mannings n for main channel
0.040
0.034 to 0.048
Hicks & Mason
(1991)
Moderate
Taken from the Rangitikei Hicks & Mason (1991)
p142
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008) for the Ashley
Low flows
ECan Survey data
M35/8968 and
M35/0931 & Piezo
contours
Sanders (2000)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
71
Waimakariri River (Reach W5): Crossbank to Wrights Cut
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
37 (average daily flow
rounded)
N/A
Measured flow
(m3/s)
at DS site
37 (average daily flow
rounded)
Gaining or losing (l/s)
Gain of 100 (n=4)
Length (km)
9.82
Width (m)
149
Average specific river flow change
N/A
Cross-sections
14
Area (m2) (plan view)
1,470,000
Average stage height (m)
N/A
Low flows
Source
Quality
Comments
White et al. (2012)
Uncertainty envelope
+/- 20% (uncertainty
of gauging error and
measurement bias)
ECan Survey data
High
Average of 9 surveys from 1960-2014
White et al. (2012)
High
Average total wetted channel width for low flow
records. Average of 5.2 channels.
Average of 4 concurrent measurements
reported in White et al. (2012). Adjusted for
inflows and outflows.
14 available, none yet provided. 2 provided
from LiDAR data in Appendix.
Survey
White et al. (2012)
High
Estimated for low flow wetted channel width
and length
0.4
White et al. (2012)
High
Average water depth in observed channels
Bed elevation US
37.66
ECan Survey data
High
Average of 9 surveys from 1960-2014
Stage elevations US
38.06
High
Calculated using average stage height (m)
Bed elevation DS
3.68
High
Average of 9 surveys from 1960-2014
Low flows
ECan Survey data
Stage elevations DS
4.08
High
Calculated using average stage height (m)
Bed gradient (m/m)
0.003
High
Calculated from bed elevations and length
Representative GW level (m amsl)
22
21.5 to 22.5
Low
Estimated average from bores M35/1692 and
M35/8969
Bed vertical hydraulic
conductivity (k) (m/day)
0.006
0.004 to 0.014
Low
Calculated based on Sanders (2000) method,
as given in main report
Bed thickness (m)
1
Low
Unknown - 1 m assumed
Bed conductance (m2/day/m)
0.9
0.6 to 2.1
Low
For GMS: traditional conductance (k*A/b)
divided by reach length
Mannings n for main channel
0.040
0.034 to 0.048
Hicks & Mason
(1991)
Moderate
Taken from the Rangitikei Hicks & Mason
(1991) p142
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008) for the Ashley
M35/1692 and
M35/8969
Sanders (2000)
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
72
Waimakariri River (Reach W6): Wrights Cut to Old Highway Bridge
Attribute
Description, count or
value
Range
Measured flows (m3/s) at US site
51 (average daily flow
rounded)
N/A
Measured flow (m3/s) at DS site
51 (average daily flow
rounded)
N/A
Gaining or losing (l/s)
Gain of 500 (n=2)
Length (km)
1.21
Width (m)
111
Average specific river flow change
N/A
Cross-sections
6
Area (m2) (plan view)
170,000
Average stage height (m)
Low flows
Source
Quality
Comments
White et al. (2012)
Uncertainty envelope
+/- 20% (uncertainty of
gauging error and
measurement bias)
Average of 2 concurrent measurements
reported in White et al. (2012). Adjusted for
inflows and outflows. Recorder data from Old
Highway Bridge available from 1967, mean
daily flow 119.3 m3/s.
ECan Survey data
High
Average of 9 surveys from 1960-2014
White et al. (2012)
High
Average total wetted channel width for low
flow records. Average of 1.9 channels.
6 available, none yet provided. 2 provided
from LiDAR data in Appendix.
Survey
White et al. (2012)
High
Estimated for low flow wetted channel width
and length
0.4
White et al. (2012)
High
Average water depth in observed channels
Bed elevation US
3.68
ECan Survey data
High
Average of 9 surveys from 1960-2014
Stage elevations US
4.08
High
Calculated using average stage height (m)
Bed elevation DS
1.261
High
Average of 9 surveys from 1960-2014
Stage elevations DS
1.661
High
Calculated using average stage height (m)
Bed gradient (m/m)
0.002
High
Calculated from bed elevations and length
Representative GW level (m amsl)
3.4
3.3-4
Low
Estimated average from bore M35/5144
adjusted for reach mid-point, and piezometric
contours
Bed vertical hydraulic
conductivity (k) (m/day)
1.955
0.348 to 8.471
Low
Calculated based on Sanders (2000) method,
as given in main report
Bed thickness (m)
1
Low
Unknown - 1 m assumed
Low
Use same as upstream reach
Bed conductance
(m2/day/m)
Low flows
ECan Survey data
Sanders (2000)
275
49 to 1,190
Mannings n for main channel
0.040
0.034 to 0.048
Hicks & Mason
(1991)
Moderate
Taken from the Rangitikei Hicks & Mason
(1991) p142
Mannings n for bank
0.075 (average)
0.03 to 0.12
Oliver (2008)
Moderate
Range given by Oliver (2008) for the Ashley
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
73
Appendix D: Map of river reach characteristics
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
74
A1
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
75
Water Management Report / Ashley-Waimakariri: Major Rivers Characterisation
Environment Canterbury / C160201 / 11/05/2016
© Aqualinc Research Ltd.
76