National water allocation statistics
for environmental reporting
Prepared for Ministry for the Environment
June 2016
Prepared by:
Booker, D.J., Henderson, R.D., Whitehead, A.L
For any information regarding this report please contact:
Doug Booker
Scientist
Freshwater Ecology
+64-3-348 8987
[email protected]
National Institute of Water & Atmospheric Research Ltd
PO Box 8602
Riccarton
Christchurch 8011
Phone +64 3 348 8987
NIWA CLIENT REPORT No:
Report date:
NIWA Project:
2017065CH
June 2016
MFE16504
Quality Assurance Statement
Reviewed by:
Charles Pearson
Formatting checked by:
America Holdene
Approved for release by:
Helen Rouse
© All rights reserved. This publication may not be reproduced or copied in any form without the permission of
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during the Project or agreed by NIWA and the Client.
Contents
Executive summary ............................................................................................................. 5
1
Introduction .............................................................................................................. 6
1.1
Background ............................................................................................................... 6
1.2
Aims of this report .................................................................................................... 6
1.3
Spatial framework..................................................................................................... 6
2
Input data.................................................................................................................. 7
3
Methods .................................................................................................................... 9
4
5
3.1
Which consents were included ................................................................................. 9
3.2
Mapping consents onto the river network ............................................................... 9
3.3
Proportioning takes between reaches.................................................................... 10
3.4
Rates and volumes .................................................................................................. 10
3.5
Upstream accumulation ......................................................................................... 10
3.6
Displaying the results .............................................................................................. 11
Results .................................................................................................................... 13
4.1
Summaries by use and source ................................................................................ 13
4.2
Accumulated consents ............................................................................................ 14
Discussion ............................................................................................................... 18
5.1
River flow depletion from groundwater ................................................................. 18
5.2
Regional variations in provided data ...................................................................... 18
5.3
Hydro-power schemes ............................................................................................ 18
5.4
Restrictions ............................................................................................................. 18
5.5
Data curiosities ....................................................................................................... 18
6
Conclusions ............................................................................................................. 19
7
Acknowledgements ................................................................................................. 20
8
References............................................................................................................... 21
Tables
Table 2-1:
Table 4-1:
Obtained variables.
7
Summary statistics for consumptive non-hydro consents by use and source. 13
National environmental indicators for water allocation
Figures
Figure 3-1:
Figure 4-1:
Figure 4-2:
A schematic diagram showing the reach assignment for groundwater and
surface water takes.
9
Map of accumulated upstream consented takes relative to median flow
(standardised AccMaxRate) by river size.
15
Map of accumulated upstream consented rate of take relative to median flow
(standardised AccMaxRate) by use.
17
National environmental indicators for water allocation
Executive summary
The purpose of this work was to develop national level statistics of water allocation for use in
environmental reporting. This report describes data sources, methods and results of analysis of
national environmental indicators for water allocation. Data used in this analysis were sourced
directly from regional council web servers (with the exception of two councils whose data was
sourced via individual requests from the Ministry for the Environment). Automated routines were
used to consistently:

predict consented maximum instantaneous rates and maximum annual volumes in
rare cases where they were missing;

locate surface water takes onto reaches of the national river network;

associate groundwater takes with nearby reaches of the national river network; and

calculate downstream effects by accumulating consented takes down the river
network.
Results are displayed in the following ways:

tables showing summary statistics of consented maximum instantaneous rate and
maximum annual volume by use and source allowing a national-scale comparison of
the number and size of consents between uses and sources;

maps of accumulated consented rates upstream of each river reach, allowing potential
changes to river flows to be visualised.
These results can be used to quantify patterns in water allocation. Results showed that surface water
consents are distributed around the country whereas groundwater consents are concentrated in
particular zones where aquifers are present and groundwater demand is high. Results also indicated
that irrigation has by far the greatest potential to cause widespread alteration to river flows.
National environmental indicators for water allocation
5
1
Introduction
1.1
Background
The purpose of this work was to develop national level statistics of water allocation for use in
environmental reporting. Quantifying pressures on river flows is important because river flow is a
vital component for the provision of life supporting capacity in aquatic ecosystems. This work
provided quantitative and spatial information to answer the questions: what activities cause
pressures on river flows; are pressures on river flows mainly from abstraction of groundwater or
surface water; and where in the country are these pressures most concentrated?
1.2
Aims of this report
The aim of this report is to provide the Ministry for the Environment (MfE) with supporting
information in relation to possible national indicators (hereafter referred to as indicators) on water
allocation and impacts on river flows. It is important that indicators are calculated using transparent,
defensible and nationally consistent methods. The objectives of this report were therefore as
follows:
1.3
1.
To document the sources of raw data used to calculate indicators.
2.
To document any post-processing of these data.
3.
To document the methods used to calculate indicators, including assumptions made,
as well as advantages and disadvantages of the methods applied.
4.
To provide commentary regarding the potential purpose of the indicators.
5.
To provide non-spatial indicators for a particular reporting period (i.e., the 2013-2014
hydrological year) and demonstrate how these might be communicated.
6.
To provide spatial indicators for a particular reporting period (i.e., the 2013-2014
hydrological year) and demonstrate how these might be mapped.
7.
To provide a written summary of the results for each indicator.
Spatial framework
The River Environment Classification (REC; Snelder & Biggs 2002) is a deductive (i.e., a priori defined)
natural flow regime classification of New Zealand’s rivers mapped onto a digital representation of the
river network. This river network comprises 570,000 reaches. Each reach is associated with a suite of
attributes. These attributes include those that pertain to local conditions (e.g., altitude), attributes
that pertain to the upstream catchment (e.g., upstream catchment area), and attributes that
describe inter-connectivity (upstream and downstream connections). These attributes are often
available for all reaches within the network. This has allowed the river network to provide a basis for
various national-level analyses of hydrology (Booker & Woods 2014), geomorphology (Booker 2010),
invertebrates (Booker et al. 2014) and fish (Crow et al. 2012). The nationwide nature of these data
allows methods to be applied consistently, and for results to be reported at national, regional or
catchment levels. New Zealand’s national river network, as defined in the REC (version 1) was
therefore used as the spatial framework for all analysis in this project.
6
National environmental indicators for water allocation
2
Input data
In New Zealand, regional councils and unitary authorities are responsible for various aspects of
managing freshwater resources. They administer consents to take and use water and they hold
records of water use and observed river flows. They also delineate management units, and set
planning provisions in regional plans. These agencies therefore hold a great deal of information that
is critical for the calculation of indicators. The data used to calculate indicators in this work were
obtained from two sources. These were: a) by remotely accessing data from council servers; and b)
by requesting specified data from two councils (Gisborne and Otago) directly. These data included
various information types, and required some post-processing (Table 2-1).
Table 2-1:
Obtained variables.
Variable
Description
Post-processing
Maximum annual
volume (maxAnnual)
The maximum volume of water
that can be abstracted in a year in
cubic metres per year.
Should not exceed volume obtained by
constantly exercising maximum
instantaneous rate.
Maximum
instantaneous rate
(maxRate)
The maximum rate at which
abstraction may occur in litres per
second.
Should not exceed maximum annual volume
if exercised constantly for less than one week.
Use
The primary purpose for which the
water is being used (e.g., irrigation,
industrial, drinking, hydro, mixed
etc.).
All uses that were concatenations of various
uses were labelled as being in the “Combined
/ Mixed” category.
Source
The primary source from which the
water has been abstracted
(groundwater or surface water).
All sources that were not labelled as
Groundwater (Not Specified, Storage, Stream
Depleting) were assumed to be Surface
Water.
Co-ordinates
Latitude and Longitude.
Transformation on NZTM grid system.
We inspected the consent database and found 102 consents describing hydro-power schemes. We
classified these into consumptive and non-consumptive. We defined consumptive hydro-power
schemes as those that depleted river flows for some length of the river network over the long term.
This definition captured diversions within the same catchment, inter-catchment diversions, and
diversions to the sea. This definition did not capture dams that store water, but release that water
immediately downstream. These comprised the non-consumptive hydro-power schemes. We
removed non-consumptive consents from the analysis.
We compared the consumptive hydro-power consents with information describing hydro-power
schemes supplied by MfE, the Electricity Authority dataset of New Zealand power stations1, and
power scheme lists used in compiling the national water accounts2. From this information, we added
the relevant data (Table 2-1) describing 126 pieces of consumptive hydro-power infrastructure to the
1http://www.emi.ea.govt.nz/Datasets/Browse?directory=%2FStationList&parentDirectory=%2FDatasets%2FWholesale%2FArchive%2F2013
10_Centralised_dataset%2FCentralisedDataset%2FNetworkConfiguration%2FGeneration
2http://www.stats.govt.nz/browse_for_stats/environment/environmental-economic-accounts/water-physical-stock-account-19952010.aspx
National environmental indicators for water allocation
7
analysis. For each piece of consumptive hydro-power infrastructure, we used location information to
identify reaches of the REC river network that the water was sourced from, and reaches of the REC
river network that the water was directed to. Positive values of take were associated with reaches of
the REC river network that the water was taken from. Negative values of take were associated with
reaches of the REC river network that the water was directed to. Negative rates of take represented
augmentation of river flows from flow diversions. Rates of take for consumptive hydro-power
consents summed to one except where the scheme discharges to the sea (Manapouri and a small
Taranaki scheme).
8
National environmental indicators for water allocation
3
Methods
3.1
Which consents were included
The majority of consents do not allow the indefinite right to abstract or use water. Each consent has
a commencement and termination date. In order to avoid including expired consents in our analysis
we selected a particular “analysis date”. This date was 14 February 2014. Results were only reported
for consents that were active on this date. We selected this date because it falls near to the likely
peak of the irrigation season for the target reporting water year (July 2013 to June 2014).
3.2
Mapping consents onto the river network
Co-ordinates describing the position of the point of take were supplied for each consent. This
information was used to assign each non-hydro consent to one (for surface water takes) or many (for
groundwater takes) reaches of the REC river network using an automated procedure. Each
groundwater consent was associated with all reaches on the New Zealand river network whose
centroid was within a 2000 m radius of the coordinates describing the groundwater take point. This
method assumed that a groundwater take would deplete river flows within the specified radius
(Figure 3-1).
Figure 3-1: A schematic diagram showing the reach assignment for groundwater and surface water takes.
The colour of the reach depicts the take it has been assigned to. For groundwater consents, all reaches within
2000m were assigned to a given take (red), while surface water consents were assigned to the nearest reach
(blue). If more than one reach was within 100m of a surface water consent, the consent was assigned to the
reach with the greatest mean annual flow (MALF) (grey).
Non-hydro surface water consents were assigned to a single reach on the New Zealand river network
by identifying the nearest reach based on the distance to points describing river lines. Where more
than one reach had some part of its river line within 100m of the consent location, the reach with the
largest estimated (MALF) from Booker and Woods (2014) was assigned to the consent (Figure 3-1).
This method was used in an attempt to avoid incorrectly associating surface water takes with very
small streams, and therefore overestimating the effect of abstraction. All hydro consents were
manually assigned to a reach on the New Zealand river network using the sources of information
given in Section 2.
National environmental indicators for water allocation
9
3.3
Proportioning takes between reaches
We proportioned each groundwater take between its assigned reaches as a function of distance and
river low flow. The inverse distance squared was used to represent distance from groundwater take
to each river reach. The seven day (MALF) from Booker and Woods (2014) was used to represent
river low flows. Assuming 𝑇𝑗 is the jth groundwater take, 𝑄𝑖𝑗 is river depletion rate at reach i resulting
from the jth groundwater take, 𝑑𝑖𝑗 is distance from the jth groundwater take to the ith reach, and 𝑄𝑖 is
the river depletion rate of the ith reach with 𝑄𝑖 = ∑𝑗 𝑄𝑖𝑗 . River depletion from each groundwater take
was proportional to the (MALF) of reaches multiplying by inverse squared distance as follows:
𝑤𝑖𝑗 =
2
𝑀𝐴𝐿𝐹𝑖 /𝑑𝑖𝑗
2)
∑𝑖 (𝑀𝐴𝐿𝐹𝑖 /𝑑𝑖𝑗
𝑄𝑖𝑗 = {
𝑤𝑖𝑗 𝑇𝑗
0
(𝑑𝑖𝑗 < 2𝑘𝑚)
𝑜𝑡ℎ𝑒𝑟𝑤𝑖𝑠𝑒
3.4
Rates and volumes
(1)
(2)
The dataset included the maxAnnual and the maxRate for each consent in the majority of cases.
However, not all consents were associated with both a maximum annual volume and a maximum
instantaneous rate. There were 16,068 active consents in total, of which 12,730 had a maxRate and a
maxAnnual that were both not zero.
Where maxRate and maxAnnual were both available, we compared these values against each other
in order to apply a check on the supplied numbers. We calculated the time it would take for the
maxRate to accrue a volume equal to the maxAnnual. When this time period was less than one week
we reduced the maxRate to be the rate that would result in the maxAnnual being accrued in one
week. This was the case for 401 consents (3 per cent of those with values) for which both maxAnnual
and the maxRate were supplied. We applied this method in order to reduce the influence of very
large maxRate values that could only be exercised for short durations according to their maxAnnual
values.
Of all consents, 1 per cent had a missing maxAnnual or a maxAnnual that was zero even though
maxRate was not zero. For these “missing maxAnnuals” we predicted maxAnnual from maxRate,
source, use and region (see Table 2-1 for details). We applied a linear regression (in log10 space) to
predict maxAnnual. This linear model produced an r2 value of 0.83 (F= 2655 on 24 and 12705 d.f., p <
0.001), and all predictors were statistically significant (p < 0.001). We then predicted missing
maxAnnual values after having applied an appropriate smearing factor to avoid any potential bias in
back-transformation (Duan 1983) using the method described by Costello et al. (2014).
Of all consents, 12 per cent had a missing maxRate or a maxRate that was zero even though
maxAnnual was not zero. For these “missing maxRates” we predicted maxRate from maxAnnual,
source, use and region. We applied a linear regression (in log10 space) to predict maxRate. This linear
model produced an r2 value of 0.87 (f = 3590 on 24 and 12705 d.f. p < 0.001), and all predictors were
statistically significant (p < 0.001). We then predicted missing maxRate values using the method
described above when back-transforming.
3.5
Upstream accumulation
After having predicted missing values where possible, 94 per cent of consents were associated with a
maxAnnual and a maxRate. We then calculated the accumulated maximum rate (AccMaxRate) for
each reach in the New Zealand river network. After assigning each take (or a proportion of each take
10
National environmental indicators for water allocation
in the case of groundwater takes) to a reach, we routed each of these values downstream to
calculate the cumulative effects of all upstream consents. This procedure was repeated separately
for each category of use (e.g., irrigation consents, industrial consents) and separately for each
category of source (e.g., all groundwater consents, all surface water consents). This allowed the
cumulative effects of any category of either use or source as well as the total AccMaxRate to be
expressed.
Values of AccMaxRate can be expressed as rates in litres per second (or cubic meters per second) to
indicate the magnitude of stream depletion regardless of stream size or river flows. However, this
magnitude does not take into account the relative size (or flow rate) of the river being depleted.
Therefore we also calculated the standardised AccMaxRate by dividing the AccMaxRate by the
estimated naturalised median flow, where the median flow is the flow that is exceeded for 50 per
cent of the time over the long-term. The standardised AccMaxRate represents the proportion of the
median flow that is consented upstream for each reach. For example, for a particular reach, a value
of 0.1 indicates that one tenth of the median flow at that reach would be abstracted from upstream
if all consents were being exercised at their maximum instantaneous rates. A value of one indicates
that the median flow at that reach would be abstracted from upstream if all consents were being
exercised at their maximum instantaneous rates. Negative AccMaxRate values indicate that flow
augmentation resulting from hydro-power diversions exceeds upstream accumulated abstractions.
Naturalised estimates of various hydrological indices were available following the work of Booker
and Woods (2014). These represent the best available estimates of flow indices such as the seven
day (MALF), mean flow and median flow in the absence of major abstractions. See Booker and
Woods (2014) for details of how these hydrological indices were calculated and tested. We chose to
standardise by the median flow rather than (MALF) because during low flow abstractions may be
restricted and because some rivers can experience extremely low flows for limited periods, but still
exhibit large flows at other times.
No data describing restriction of consents (i.e., where abstractions are required to cease or be
reduced due to low river flow, low groundwater level, or other specified conditions) were available
for this dataset. When accumulating we therefore assumed a worst-case scenario where all consents
are unrestricted.
3.6
Displaying the results
Results were displayed using several methods:

Tables showing summary statistics of consented maxRate and maxAnnual use and
source. These tables gives a national-scale comparison of the number and size of
consents between uses and sources.

Maps of consent locations by use and source. These maps showed the spatial
distribution of consented takes. They illustrate in which locations certain uses and
types are most concentrated across the country.

Maps of accumulated consented rates. These maps allow assessment of potential
changes to river flows. They represent a worst case scenario of changes to river flows.
These maps can show absolute rates, indicating the amount of water supplied.
Alternatively standardised rates can be shown to indicate the relative effect on stream
flows.
National environmental indicators for water allocation
11
The proportion of consents without maximum annual volumes and without maximum instantaneous
rates was calculated. For consents with maximum annual volumes and maximum instantaneous
rates, summary results were given showing the median, mean and count for each category. Results
were tabulated for the whole country and by source and use.
All consents were associated with grid location co-ordinates, except 463 of 1485 active consents in
the Otago region. Therefore, these 463 consents and their contribution to accumulated flows could
not be displayed on any maps. For each map all keys and panels were ordered alphabetically.
Symbols were plotted in the order in which they appear in the map key. We noted that this resulted
in some overplotting when many points are located in close proximity. In order to avoid overplotting
and to aid interpretation of results, we categorised rivers based on Strahler stream order where
Small was stream orders 1 to 3, Medium was stream orders 4 and 5, and Large was stream orders 6
to 8.
12
National environmental indicators for water allocation
4
Results
4.1
Summaries by use and source
Quantifying patterns in numbers and size of consents by use gives an indication of what abstracted
water is being used for. Quantifying patterns by source gives an indication of where abstracted water
is being taken from.
Table 4-1 shows summary statistics by use and source. Some findings of these results include:

only small proportions of consents did not have maxRate and maxAnnual values;

industrial uses had the highest mean maxRates, due to a few large takes for this use;

the sum of maxRates for industrial and drinking uses was relatively low because there
were relatively few consents for these uses;

the mean and median maxRate for irrigation uses was similar to other uses (such as
drinking);

the sum of irrigation was by far the greatest of any use (excluding hydro) due to the
high number of consents for this use;

there were approximately twice as many groundwater consents than surface water
consents;

total groundwater rates were less than total surface water rates;

there were differences in the ratios of maxRate to maxAnnual between sources and
between uses;

many maxAnnual values equated to the volume taken over a year if maxRate was
exercised constantly, but some maxAnnual values equate to less volume than could be
taken over a year at maxRate.
Table 4-1:
Summary statistics for consumptive non-hydro consents by use and source. Other comprises
uses labelled as Combined/Mixed, Frost Protection, Not Specified, Other or Stock.
Maximum instantaneous rate (l s-1)
Maximum annual volume (m3)
Count Missing Median Mean
Sum
15,920
975
9.1
43.5
649,700 15,920
1,337
88
4.2
47.6
59,500
Industrial
812
62
5.2
111.2
83,380
Irrigation
10,490
352
13.0
40.6
3,281
473
1.8
33.8
Groundwater
10,860
245
7.6
Surface Water
5,064
730
15.0
National
Count Missing
Median
Mean
Sum
966
61,600
660,300
9,874,000,000
1,337
85
55,510
1,079,000
1,350,000,000
812
61
64,970
1,738,000
1,305,000,000
412,100 10,490
348
84,500
497,600
5,047,000,000
3,281
472
31,200
773,200
2,172,000,000
23.0
243,800 10,860
237
51,870
241,400
2,564,000,000
93.7
405,900
729
142,400
1,686,000
7,311,000,000
Use
Drinking
Other
94,760
Source
National environmental indicators for water allocation
5,064
13
4.2
Accumulated consents
The total upstream accumulated maximum take (AccMaxRate) of each reach in the New Zealand
river network standardised by naturalised median flow was calculated. This is a useful indicator of
pressure on stream flows because it reflects the likely proportional reduction in flow that would
result from maximum consented use regardless of restrictions.
Maps of the standardised AccMaxRate show the highest effects occur in smaller rivers, where
proportionally more water is consented (Figure 4-1). The disbursed pattern of surface water takes
often results in high standardised AccMaxRates in the headwaters of smaller streams, which then
often reduce with distance downstream because of increases in the median flow. In contrast, the
concentrated pattern in groundwater takes in lowland areas often results in high standardised
AccMaxRates across particular catchments. This is particularly the case across the Canterbury Plains,
coastal areas of Hawke’s Bay and in lowland catchments in the Horizons region.
14
National environmental indicators for water allocation
Figure 4-1: Map of accumulated upstream consented takes relative to median flow (standardised
AccMaxRate) by river size. Small rivers = stream orders 1 to 3; Medium rivers = stream orders 4 and 5;
Large rivers = stream orders 6 to 8.
National environmental indicators for water allocation
15
Maps of accumulated standardised AccMaxRate gave further evidence that irrigation uses resulted in
the highest rates of stream depletion across the country, although takes for hydro, industrial and
drinking uses are important in some catchments (Figure 4-2). Results indicated that consumptive
hydro-power uses have the potential to greatly deplete some large rivers (e.g., the Southland
Waiau). In many cases these schemes also augmented river flows (e.g., Waikato River), although in
some locations depletion from other uses exceeded flow augmentation from non-consumptive
hydro-power uses (e.g., Lower Rakaia) (Figure 4-1).
16
National environmental indicators for water allocation
Figure 4-2: Map of accumulated upstream consented rate of take relative to median flow (standardised
AccMaxRate) by use. Other comprises uses labelled as Combined/Mixed, Frost Protection, Not
Specified, Other or Stock.
National environmental indicators for water allocation
17
5
Discussion
5.1
River flow depletion from groundwater
No data describing the depths of groundwater bores, or the connectivity of groundwater to surface
water (e.g., where groundwater was being taken from a confined aquifer) were available. We
therefore assumed that all groundwater takes would result in some level of stream flow depletion.
This method can be viewed as a worst case scenario for impacts on river flows.
5.2
Regional variations in provided data
Results indicate regional variations in the type of activities that require consents or the type of
consents that were included in the supplied datasets. This was particularly the case for stock water
and hydro consents. Many consents for stock water uses were included in the supplied datasets from
the Southland, Waikato and Horizons regions. In contrast, very few consents for stock water were
included in the remaining regions. Aside from including stock water consents in our analysis, we did
not attempt to estimate the influence of water taken for stock water as a permitted activity.
5.3
Hydro-power schemes
Some hydro-power schemes (e.g., Manapouri) were included in the supplied datasets. We added
known information on consents for large consumptive hydro-power schemes when these schemes
were not included in the supplied datasets. This included the Waikato dams and Tongariro Power
Development scheme that were not supplied. We did not include non-consumptive hydro-power
schemes in this analysis because those schemes do not deplete river flows over the long-term.
However, non-consumptive hydro-power schemes do have the ability to greatly alter river flows in
the short-term mainly through storage in reservoirs followed by release at a later time.
5.4
Restrictions
Consents to abstract water can include the enforcement of restrictions. (i.e., where abstractions
cease or are reduced due to low river flow, low groundwater levels or other specified conditions).
Enforcement of restrictions are designed to reduce stream depletion in situations where demand to
take water is large compared with supply. No data describing restriction of consents were available
for this dataset. When accumulating we therefore assumed a worst-case scenario where all consents
are unrestricted.
5.5
Data curiosities
Generally, we assumed that the supplied data were accurate and fit for the purposes of national
environmental reporting. However, we also applied our own quality checks. These included
comparison between maximum instantaneous rate and maximum annual volume.
We noticed some curious features within the dataset whilst conducting our analysis. These included:
18

81 consents where maxAnnual was zero and maxRate was either zero or missing

For some consents maxAnnual was greater than maxRate multiplied by the number of
seconds in a year. We did not change either value in this case, as it was unknown
which value was incorrect.
National environmental indicators for water allocation
6
Conclusions
The analysis provided in this report can be used to represent several indicators of water allocation
and pressure on river flows. The analysis is nationally consistent because the same methods were
applied universally across the country. The results provide defensible indicators of nationwide
patterns in water allocation, including where water has been consented, what water is being used
for, and the likely influence of unrestricted consented water abstraction on river flows.
National environmental indicators for water allocation
19
7
Acknowledgements
Many thanks to James King of MfE for discussion and assistance in providing data. Many thanks to
various regional council staff for assistance in providing data.
20
National environmental indicators for water allocation
8
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and Landforms, 35: 828-841.
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empirically-based approaches for estimating the hydrology of ungauged catchments.
Journal of Hydrology, 10.1016/j.jhydrol.2013.11.007.
Costello, C., Deschênes, O., Larsen, A., Gaines, S. (2014) Removing biases in forecasts of
fishery status. Journal of Bioeconomics, 16, 2: 213-219.
Crow, S.K., Booker, D.J., Snelder, T.H. (2012) Contrasting influence of flow regime on
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