ROUS W ATER
Rous Water BASIX Performance
Report
September 2013
ROUS WATER BASIX PERFORMANCE REPORT
Disclaimer:
This report has been prepared on behalf of and for the exclusive use of Rous Water, and is
subject to and issued in accordance with the agreement between Rous Water and Hydrosphere
Consulting. Hydrosphere Consulting accepts no liability or responsibility whatsoever for it in
respect of any use of or reliance upon this report by any third party.
Copying this report without the permission of Rous Water or Hydrosphere Consulting is not
permitted.
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PO Box 7059, BALLINA NSW 2478
Telephone:
02 6686 0006
Facsimile:
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© Copyright 2013 Hydrosphere Consulting
PROJECT 12-037 – ROUS WATER BASIX PERFORMANCE REPORT
REV
DESCRIPTION
AUTHOR
REVIEW
APPROVAL
DATE
0
Draft for Rous Water review
U. Makings
M. Howland
M. Howland
26/4/13
1
Draft for DOP
U. Makings
M. Howland
M. Howland
11/6/13
2
Final for DOP
U. Makings
M. Howland
M. Howland
22/7/13
3b
Final with minor amendments
U. Makings
M. Howland
M. Howland
17/9/13
3c
Final with minor amendments
U. Makings
M. Howland
M. Howland
21/11/13
ROUS WATER BASIX PERFORMANCE REPORT
Executive Summary
This project describes the water demand for single residential homes built under the BASIX legislation
and aims to:
1. Determine the likely future water consumption from single residential dwellings constructed in
the Rous Water Service Area under BASIX legislation, including per capita and per connection
consumption;
2. Determine whether BASIX has achieved its primary water saving objective for BASIX single
residential dwellings in the Rous Water Service Area of 40% reduction in potable water
consumption compared with the average pre-BASIX household) and;
3. Compare the actual metered savings for the dwellings with the predicted savings from BASIX
in the Rous Water Service Area.
Water consumption data, from July 2006 - June 2011, provided by Rous Water was evaluated by
determining average actual BASIX consumption per dwelling and per capita, comparing the BASIX
household usage against the 40% water saving criteria, determining the accuracy of the BASIX tool by
comparing BASIX predicted consumptions with metered consumptions and exploring the effect of
actual occupancy rates on the accuracy of predicted outcomes.
Average household metered water consumption varied across the Rous Water supply area, ranging
from an average of 146 kL/dwelling/year in both the Byron and Ballina areas to 199 kL/dwelling/year in
the Richmond Valley area (although it should be noted that the Richmond Valley sample size was very
small) with an average across the entire Rous Water supply area of 150 kL/dwelling/year. Average per
capita consumptions ranged from 52 kL/person/year in Lismore to 63 kL/person/year in Richmond
Valley with an average across the entire Rous Water supply area of 56 kL/person/year.
Average BASIX Water Savings (metered consumption compared to an average pre-BASIX household)
ranged from 23% in Richmond Valley to 55% in Ballina with an average of 49% across the total Rous
Water supply area. Using BASIX Occupancy data, the percentage of BASIX houses estimated to
achieve the BASIX 40% Savings Objective ranged from 39% in Richmond Valley to 67% in Ballina and
63% across the Rous Water supply area as a whole. Predicted average water savings using Actual
Occupancy data ranged from 30% in Richmond Valley to 48% in Lismore whilst the percentage of
houses estimated to achieve the BASIX 40% savings objective ranged from 53% in Byron to 65% in
Lismore and 60% across the Rous Water supply area as a whole. These figures indicate that BASIX is
successfully achieving its 40% Water Savings Objective in comparison to an average pre-BASIX
household.
When comparing predicted and metered consumptions across the Rous Water service area, both
BASIX Predicted Water Consumption (occupancy assumed in BASIX) and Actual Predicted Water
Consumption (actual occupancy) show very little correlation with Metered Consumption for individual
households and fail to accurately predict the real range in consumption for the data set as a whole.
Despite this, the average consumption predictions from the BASIX tool do reasonably approximate the
metered averages and suggest that use of the long term (4-5 years +) average BASIX predicted
consumptions may be appropriate to provide broad-scale monitoring of BASIX performance if
considering averages alone.
Executive Summary
ROUS WATER BASIX PERFORMANCE REPORT
CONTENTS
1.
AIMS ............................................................................................................................................ 1
2.
METHODOLOGY ........................................................................................................................ 2
2.1
Methodology Variations & Verification .........................................................................................2
2.2
Terms Used .................................................................................................................................3
3.
SAMPLE CHARACTERISTICS ................................................................................................... 5
4.
PERFORMANCE OF LISMORE BASIX DWELLINGS ............................................................... 5
4.1
Metered Consumption .................................................................................................................5
4.2
BASIX Predicted Consumption....................................................................................................6
4.3
Actual Predicted Consumption ....................................................................................................7
4.4
Conclusions from Lismore LGA Analysis ....................................................................................9
5.
PERFORMANCE OF BALLINA BASIX DWELLINGS ................................................................. 9
5.1
Metered Consumption .................................................................................................................9
5.2
BASIX Predicted Consumption....................................................................................................9
5.3
Actual Predicted Consumption ................................................................................................. 11
5.4
Conclusions from Ballina LGA Analysis ................................................................................... 12
6.
PERFORMANCE OF RICHMOND VALLEY BASIX DWELLINGS ........................................... 13
6.1
Metered Consumption .............................................................................................................. 13
6.2
BASIX Predicted Consumptions ............................................................................................... 13
6.3
Actual Predicted Consumptions ............................................................................................... 14
6.4
Conclusions from Richmond Valley LGA Analysis ................................................................... 15
7.
PERFORMANCE OF BYRON BASIX DWELLINGS ................................................................. 16
7.1
Metered Consumption .............................................................................................................. 16
7.2
BASIX Predicted Consumption................................................................................................. 16
7.3
Actual Predicted Consumption ................................................................................................. 17
7.4
Conclusions from Byron LGA Analysis ..................................................................................... 19
8.
9.
PERFORMANCE OF BASIX DWELLINGS ACROSS THE ROUS WATER SERVICE AREA . 19
8.1
Metered Consumption .............................................................................................................. 19
8.2
BASIX Predicted Consumption................................................................................................. 19
8.3
Actual Predicted Consumption ................................................................................................. 21
8.4
Accuracy of Predicted Consumptions ...................................................................................... 22
8.5
Conclusions from Rous Water service area analyses .............................................................. 23
SUMMARY OF FINDINGS ........................................................................................................ 24
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ROUS WATER BASIX PERFORMANCE REPORT
9.1
Metered Consumption............................................................................................................... 24
9.2
Water Savings ........................................................................................................................... 24
9.3
Accuracy of Predicted Consumptions ....................................................................................... 25
10.
REFERENCES ......................................................................................................................... 26
FIGURES
Figure 1: Rous Water Bulk Water Service Area ...................................................................................... 1
Figure 2: Distribution of Lismore BASIX % Water Use data (a) and sqrt transformed Lismore
BASIX % Water Use data (b) .................................................................................................................. 7
Figure 3: Distribution of Lismore Actual % Water Use (a) and Lismore Actual % Water Use sqrt
transformed data (b). ............................................................................................................................... 8
Figure 4: Distribution of Ballina BASIX % Water Use data (a) and log10 transformed Ballina BASIX
% Water Use data (b) ............................................................................................................................ 10
Figure 5: Distribution of Ballina Actual % Water Use (a) and Log10 transformed Ballina Actual %
Water Use data (b) ................................................................................................................................ 12
Figure 6: Distribution of Richmond Valley BASIX % Water Use data relative to the BASIX Water
Benchmark ............................................................................................................................................. 14
Figure 7: Distribution of Richmond Valley Actual % Water Use data relative to the Actual Water
Benchmark ............................................................................................................................................. 15
Figure 8: Distribution of Byron BASIX % Water Use data (a) and sqrt transformed Byron BASIX %
Water Use data (b) ................................................................................................................................ 17
Figure 9: Distribution of Byron Actual % Water Use data (a) and sqrt transformed Byron Actual %
Water Use data (b) ................................................................................................................................ 18
Figure 10: Distribution of Rous Water BASIX % Water Use data (a) and sqrt transformed Rous
Water BASIX % Water Use data (b) ...................................................................................................... 21
Figure 11:Distribution of Rous Water Actual % Water Use data (a) and sqrt transformed Rous
Water Actual % Water Use data (b) ...................................................................................................... 22
Figure 12: Box plots illustrating the range in Rous Water Metered and Predicted Consumptions ....... 23
TABLES
Table 1: Data transformations of Water Use/Savings data used for statistical analysis ......................... 3
Table 2: Glossary of key terms used ....................................................................................................... 3
Table 3: Comparison of sample characteristics....................................................................................... 5
Table 4: Average Metered Consumption of Lismore BASIX households ................................................ 6
Table 5: Summary of Lismore BASIX performance based on BASIX Occupancy .................................. 6
Table 6: Comparison of BASIX % Water Use statistics utilising untransformed and sqrt reverse
transformed Lismore BASIX % Water Use/Savings data ........................................................................ 7
Table 7: Summary of Lismore BASIX performance based on Actual Occupancy .................................. 8
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ROUS WATER BASIX PERFORMANCE REPORT
Table 8: Comparison of % Water Use statistics utilising untransformed and sqrt reverse
transformed Lismore Actual % Water Use/Savings data ......................................................................... 8
Table 9: Average Metered Consumption of Ballina BASIX households .................................................. 9
Table 10: Summary of Ballina BASIX performance based on BASIX Occupancy ................................ 10
Table 11: Comparison of BASIX % Water Use statistics utilising untransformed and sqrt reverse
transformed Ballina BASIX % Water Use/Savings data ........................................................................ 11
Table 12: Summary of Ballina BASIX performance based on Actual Occupancy ................................. 11
Table 13: Comparison of % Water Use statistics utilising untransformed and log 10 re-transformed
Ballina Actual Water Savings/Use data .................................................................................................. 12
Table 14: Average Metered Consumptions of Richmond Valley BASIX households ............................ 13
Table 15: Summary of Richmond Valley BASIX performance based on BASIX Occupancy ................ 14
Table 16: Summary of Richmond Valley BASIX performance based on Actual Occupancy ................. 15
Table 17: Average Metered Consumption of Byron BASIX households from 2006/07 - 2010/11 ......... 16
Table 18: Summary of Byron BASIX performance based on BASIX Occupancy .................................. 17
Table 19: Comparison of % Water Use statistics utilising untransformed and sqrt re-transformed
Byron BASIX Water Savings/Use data .................................................................................................. 17
Table 20: Summary of Byron BASIX performance based on Actual Occupancy .................................. 18
Table 21: Comparison of % Water Use statistics utilising untransformed and sqrt re-transformed
Byron Actual Water Savings/Use data ................................................................................................... 18
Table 22: Average Metered Consumption of BASIX households across the total Rous Water bulk
supply area (July 2006 - June 2011) ...................................................................................................... 19
Table 23: Summary of Rous Water BASIX performance based on BASIX Occupancy ........................ 20
Table 24: Comparison of % Water Use statistics utilising untransformed and sqrt re-transformed
Rous Water BASIX Water Savings/Use data ......................................................................................... 21
Table 25: Summary of total Rous Water BASIX performance based on Actual Occupancy ................. 21
Table 26:Comparison of % Water Use statistics utilising untransformed and sqrt re-transformed
Rous Water Actual Water Savings/Use data ......................................................................................... 22
Table 27: Summary of Average Metered Consumption of BASIX households across the total
Rous Water bulk supply area in the 2006/07 - 2010/11 financial years period ...................................... 24
Table 28: Summary of Water Savings ................................................................................................... 25
APPENDICES
APPENDIX 1: DISTRIBUTIONS OF TRANSFORMED AND UNTRANSFORMED WATER USE DATA
APPENDIX 2: ROUS WATER BASIX ASSESSMENT PROJECT METHODOLOGY
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ROUS WATER BASIX PERFORMANCE REPORT
1.
AIMS
The key aims of this report are to:
1. Determine the likely future water consumption from single residential dwellings constructed
under BASIX legislation including per capita and per connection consumption;
2. Determine whether BASIX has achieved its primary water saving objective (40% less water
than the average pre-BASIX household) and;
3. Compare the actual metered savings for the dwellings with the predicted savings from BASIX
in the Rous Water service area (see Figure 1).
Figure 1: Rous Water Bulk Water Service Area
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ROUS WATER BASIX PERFORMANCE REPORT
2.
METHODOLOGY
The methodology used in this project is adopted from the methodology outlined in Rous Water (2010)
and the data used for the current study were provided by Rous Water as an output from that work. The
work presented in Rous Water (2010) is largely based on a report by Sydney Water (2008) where
water savings were analysed for a sample of occupied single dwellings with BASIX certificates. As
outlined in Rous Water (2010), the Department of Planning provided the BASIX Benchmark, BASIX
Target and BASIX Water Score information for each dwelling. Rous Water and its constituent Councils
provided the Metered Consumption data. Mail and telephone surveys on nominated BASIX
households were conducted by Rous Water where questions were asked in relation to set of selection
criteria to determine whether a property was deemed suitable for inclusion in this study. The full list of
selection criteria, as outlined in Rous Water (2010), for the properties in the surveys to be included in
the analysed sample was:
1. Permission of the property owner for their water consumption data to be used for this
study;
2. Dwelling must be completed;
3. Dwelling must not have been occupied before July 2005 (to ensure only BASIX
dwellings have been included);
4. The number of dwellings on the property is no greater than one (multiple dwellings on
one property were excluded from this analysis);
5. The metered water use at the property is for normal residential purposes (e.g. it is not
used for agricultural or commercial purposes);
6. The dwelling must have been occupied prior to the commencement of the first quarter
of the 2009-2010 recording year; and
7. The dwelling must have at least four full quarters of water consumption data including
all four quarters of the 2009-2010 water recording year.
If a property met the criteria and permission was granted by the owner for their water consumption
data to be used in the study, Actual Occupancy and Metered Consumption data was obtained and depersonalised before being included in this study.
2.1
Methodology Variations & Verification
The previous analysis undertaken by Rous Water used ‘R’ software and involved exploratory statistical
analysis to develop the methodology as outlined in Rous Water (2010). The approach utilised by
Hydrosphere Consulting for this project instead utilises Microsoft Excel and is intended to replicate the
Rous Water methodology and provide comparable outcomes. The analysis methodology and
presentation of results aims to be transparent and understandable but also robust in order for it to be
applied to similar data in the future.
To verify the modified methodology a re-analysis of the Lismore LGA data previously evaluated by
Rous Water was conducted. To assist in replicating the methodology and format of the Rous Water
report, a normal distribution macro was developed in Microsoft Excel to reconstruct the distribution
histograms presented in Rous Water (2010b). All the results from the re-analysis yielded identical
results to Rous Water’s analysis of the Lismore LGA data.
As water usage data tend to be skewed and not normally distributed, a simple arithmetic average
(mean) of the data does not provide the best measure of data ‘centrality’. In order to account for this,
Rous Water (2010) transformed the raw Lismore data through square root transformation. Applying
the Rous Water (2010) methodology to data from other LGA’s revealed that the square root
transformation was appropriate in some cases, but for the Ballina LGA this did not provide the best
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ROUS WATER BASIX PERFORMANCE REPORT
estimate of the ‘true’ average. In this case a log10 transformation was determined to be more
appropriate and statistical analysis in these cases was carried out on the results from this
transformation. Square root and log transformation of the Richmond Valley data did little to improve
the distribution and therefore the analysis for this LGA was based on the raw consumption data.
Assessment of the distribution of raw Water Use data, Square root and log10 transformed data was
carried out for all LGA’s (Appendix 1). Table 1 presents which data (transformed or raw) was used for
analysis of each Water Use data set. Due to the limited sample size, transformation of the Richmond
Valley data did little to improve the normalisation of the data.
Table 1: Data transformations of Water Use/Savings data used for statistical analysis
LGA
BASIX Predictions
Actual Predictions
Lismore
Square root
Square root
Ballina
Log10
Log10
RVC
Raw data
Raw data
Byron
Square root
Square root
2.2
Terms Used
Table 2 is a glossary of the terms used throughout this report, providing an explanation of each key
term.
Unless otherwise specified, quoted statistics related to the combined multi-year data set for each LGA.
Table 2: Glossary of key terms used
Term
Definition
Actual Occupancy
The true number of people occupying a household, recorded from the
telephone survey.
Actual Predicted
Consumption
The estimated potable water consumption for a BASIX dwelling using Actual
occupancies. Is equal to the Actual Water Benchmark minus the percentage of
the Actual Water Benchmark given by the BASIX Water Score.
Actual Water
Benchmark
The estimated potable water consumption of an average pre-BASIX household
based on Actual Occupancy. Calculated by multiplying Actual Occupancy by
247.5 L/person/day (the accepted pre-BASIX water consumption).
Actual % Water Use
A measure of the effect of BASIX on water consumption and is calculated as
the Metered Consumption divided by the Actual Water Benchmark multiplied
by 100.
Actual Water Saving
The estimated water saving compared to a non-BASIX household using Actual
occupancies and Metered Consumptions. Is calculated as 100 minus the %
Water Use.
Analysed sample
The final sample taken from the survey sample. The analysed sample satisfies
the selection criteria and is used in the analysis.
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ROUS WATER BASIX PERFORMANCE REPORT
BASIX certificate
Document specifying the sustainability measures that the proposed
development will implement to meet BASIX guidelines.
BASIX Occupancy
The assumed occupancy that is generated by the BASIX tool based on ABS
2001 data on number of bedrooms, type and location of a dwelling.
BASIX Predicted
Consumption
The estimated potable water consumption for a BASIX dwelling using BASIX
assumed occupancies. Is equal to the BASIX Water Benchmark minus the
percentage of the BASIX Water Benchmark given by the BASIX Water Score.
BASIX Water
Benchmark
The estimated potable water consumption of an average pre-BASIX household
based on BASIX Occupancy. Calculated by multiplying BASIX assumed
occupancy by 247.5 L/person/day (the accepted non BASIX water
consumption).
BASIX Water Score
The BASIX tool predicted water saving compared to an average pre-BASIX
household.
BASIX 40% Savings
Objective
Minimum reduction requirement for all new dwellings, 40% less than the
average NSW pre-BASIX household.
BASIX % Water Use
A measure of the effect of BASIX on water consumption and is calculated as
the Metered Consumption divided by the BASIX Water Benchmark multiplied
by 100.
BASIX Water Saving
The estimated water saving compared to a non-BASIX household using BASIX
assumed occupancies and Metered Consumptions. Is calculated as 100 minus
the % Water Use.
Dwelling
A single BASIX dwelling.
Dwelling/year
A particular dwelling in a particular year.
Log10 transformation
Where the log of each observation in the data set was taken.
Mean
Statistical term equivalent to ‘Average’
Metered
Consumption
Actual water consumption recorded by household meters.
Normalisation
Transformation of the data set to achieve a better fit to the normal distribution.
Normal distribution
Describes the way that data are spread above and below the mean. A normal
distribution is required in order for the mean to accurately reflect the central
point of the data set.
Period analysed
Refers to data from the 2006/07 - 2010/11 financial years except Lismore
which only spans the 2007/08 - 2010/11 financial years.
Square root
transformation
Where the square root of each observation in the data set was taken.
Transformed data
Data that has had a statistical transformation applied to it.
Untransformed data
Raw data that has had no statistical transformation applied to it.
Year
Refers to the financial year. e.g. 2006/07 is from July 2006 - June 2007
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ROUS WATER BASIX PERFORMANCE REPORT
3.
S AMPLE CHAR ACTERISTI CS
A total of 302 surveys were received for this study. Of these, 205 were used in the analysed sample as
97 did not meet the selection criteria as outlined in Rous water (2010). To ensure the analysed sample
was representative of the total survey sample, the characteristics of the total survey and analysed
sample groups were compared as presented in Table 3. This analysis only evaluates the
representativeness of the analysed sample relative to the total sample, not all BASIX single residential
dwellings. Checking the representativeness of the analysed sample relative to all BASIX dwellings is
not possible due to the absence of metered and occupancy data.
Table 3 shows that the analysed sample was representative of the total survey sample as there was
no significant difference between any of the means, except the proportion of houses connected to dual
reticulation. In this case, the slightly higher percentage of dual reticulated houses in the analysed
sample may fractionally over-estimate the Average BASIX Water Saving statistic for areas with dual
reticulation.
Table 3: Comparison of sample characteristics
Survey Characteristic
Total Sample (Mean ± 1.96 SE) Analysed Sample (Mean ± 1.96 SE)
(n= 302)
(n= 205)
722.7 ± 13.09
738.2 ± 14.13
Number of bedrooms
3.6 ± 0.10
3.7 ± 0.09
BASIX Occupancy
2.9 ± 0.05
3.0 ± 0.06
Actual Occupancy
2.8 ± 0.09
2.9 ± 0.09
12.9 ± 0.04
15.1 ± 0.05
BASIX Water Benchmark (L/dwelling/day)
Proportion of dual reticulation (%)
Note: The 1.96 multiple of the standard error (SE), provides an estimate of the confidence limits of the sample mean.
Note: Dual reticulation ‘purple pipes’ are currently connected to potable water.
4.
PERFORMANCE OF LISMO RE BASIX DWELLINGS
Data from Byron, Ballina and Richmond Valley encompasses the 2006/07 to 2010/11 financial years.
The Lismore data set does not include the first year as data from 2006/07 was unavailable at the time
of publication. In general, 2006/07 was a high water consumption year therefore the absence of data
from this year in the Lismore data set may result in slightly lower averages than if 2006/07 data was
available. However, analysis of data from the other LGA’s reveals that the removal of 2006/07 data
has minimal effect (a 1% change or less) on overall averages, except for Richmond Valley due to its
minimal sample size. As a result the absence of 2006/07 from the Lismore analysis was deemed to
have a negligible impact on the overall results from Lismore.
4.1
Metered Consumption
Table 4 presents average Metered Consumption data for Lismore BASIX households from July 2007
until June 2011. Average Metered Consumption ranged from 131 kL/year to 178 kL/year with an
average of 152 kL/year for 2007/08 - 2010/11 financial years. Consumption on a per person basis
ranged from 43 kL/person/year to 61 kL/person/year with an average of 52 kL/person/year.
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ROUS WATER BASIX PERFORMANCE REPORT
Table 4: Average Metered Consumption of Lismore BASIX households
Year
2007/08
2008/09
2009/10
2010/11
2007/08-2010/11
4.2
Number of
Dwellings
23
52
79
96
250
Average Metered
Consumption
(kL/dwelling/year)
178
145
175
131
152
Average Metered
Consumption
(kL/person/year)
55
53
61
43
52
BASIX Predicted Consumption
Table 5 presents data used to derive BASIX Water Saving estimates based on BASIX Occupancy.
Across the 2007/08 - 2010/11 financial year period, the averaged BASIX Occupancy was 3.04
persons per dwelling. These people were assumed to consume 247.5 L/p/day of potable water in an
average pre-BASIX house, giving an average BASIX Water Benchmark of 275 kL/dwelling/year across
the period.
Table 5 shows that the BASIX Water Score for Lismore between the 2007/08 and 2010/11 financial
years averaged 42.3%. This indicates that BASIX predicts water consumption to be 42.3% less than
the BASIX Benchmark, therefore the average BASIX Predicted Consumption was 159
kL/dwelling/year. The average Metered Consumption across the period was 152 kL/dwelling/year.
The analysis of the distribution of Metered Consumption against the BASIX 40% Savings Objective
reveals that the majority of dwellings (64%) achieved a BASIX % Water Use of 60% or less (or BASIX
Water Saving of 40% or more) relative to the BASIX Water Benchmark. The average estimated BASIX
Water Saving across the period was 44.5%. This estimation is a slightly higher saving than that
calculated by the BASIX tool (BASIX Water Score, 42.3%), which suggests that BASIX dwellings are
actually performing better than expected.
Table 5: Summary of Lismore BASIX performance based on BASIX Occupancy
Average
Average BASIX
Average
Average
BASIX
Average BASIX
Average
Predicted Water Average Metered
BASIX
BASIX
Number of Occupancy Water Benchmark BASIX Water
Consumption
Consumption
Water Use
Water
Year
Dwellings (persons) (kL/dwelling/year) Score (%) (kL/dwelling/year) (kL/dwelling/year)
(%)
Saving (%)
2007/08
23
3.09
280
43.1
160
178
62.9
37.1
2008/09
52
3.02
273
42.6
157
145
53.9
46.1
2009/10
79
3.04
274
42.4
158
175
64.3
35.7
2010/11
96
3.05
275
41.8
160
131
47.2
52.8
2007/08-2010/11
250
3.04
275
42.3
159
152
55.5
44.5
As illustrated in Figure 2 the distribution of BASIX % Water Use relative to the BASIX Water
Benchmark is slightly right skewed so the true average BASIX % Water Use will tend to be overestimated and BASIX Water Saving under-estimated. To normalise this skewed distribution, square
root (sqrt) transformation and base ten logarithmic (log) transformations were applied to the data to
improve the goodness of fit to the normal distribution curve. Visual assessment (see Appendix 1)
revealed that the distribution of the sqrt transformed data closely matches the symmetrical normal
distribution curve which therefore allows statistical analysis to be more accurate than for
untransformed or log transformed data. Utilising the sqrt transformed data gives an average BASIX
Water Saving of 48.7% (Table 6) with 64% of dwellings achieving the BASIX 40% Water Savings
Objective. The average BASIX Water Saving is higher than the untransformed average of 44.5% and
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ROUS WATER BASIX PERFORMANCE REPORT
similar to the results for the untransformed data, indicating that significantly greater than half of the
BASIX households are achieving a 40% or more water saving.
(a)
(b)
Figure 2: Distribution of Lismore BASIX % Water Use data (a) and sqrt transformed Lismore
BASIX % Water Use data (b)
Table 6: Comparison of BASIX % Water Use statistics utilising untransformed and sqrt reverse
transformed Lismore BASIX % Water Use/Savings data
Untransformed
Sqrt Transformed
Average BASIX % Use
55.5
51.3
Average BASIX Saving (%)
44.5
48.7
4.3
Actual Predicted Consumption
In the BASIX tool the number of occupants is a key variable in calculating the Water Benchmark,
Predicted Consumption and the corresponding percentage Water Use/Saving for each household. The
phone survey conducted by Rous Water (2010) gathered information on Actual Occupancy of each
BASIX house in the analysed sample. This allows a recalculation of the Benchmark, Predicted
Consumption and Water Use/Saving using Actual Occupancy instead of BASIX Occupancy data. The
use of Actual Occupancy rates is an attempt to more accurately predict water consumption and Water
Use/Savings in BASIX dwellings.
Table 7 presents data used to derive Actual Water Use/Saving estimates based on Actual Occupancy
figures gathered in the survey, per year and across the period. The average Actual Occupancy across
the period was found to be higher (3.19) than the BASIX Occupancy (3.04). As a result, the Water
Benchmark rises from the BASIX calculated average of 275 kL/dwelling/year to the average Actual
Water Benchmark of 289 kL/dwelling/year. The BASIX Water Score remains the same, as does the
Metered Consumption, but the average Actual Predicted Consumption increases from 159
kL/dwelling/year to 166 kL/dwelling/year.
The distribution of Actual Water % Use relative to the Actual Water Benchmark is illustrated in Figure
3. The majority of dwellings (65.1%) achieved savings of 40% or more compared to the Actual
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ROUS WATER BASIX PERFORMANCE REPORT
Benchmark, with an average saving of 42.8% across the period. This average Actual Water Saving
estimation compares very closely to the average BASIX Water Score of 42.3%.
Table 7: Summary of Lismore BASIX performance based on Actual Occupancy
Average Actual
Average
Average
Number Average Actual Average Actual
Average
Predicted Water Average Metered
Actual
Actual
of
Occupancy
Water Benchmark BASIX Water
Consumption
Consumption
Water Use
Water
Year
Dwellings
(persons)
(kL/dwelling/year) Score (%) (kL/dwelling/year) (kL/dwelling/year)
(%)
Saving (%)
2007/08
23
3.47
314
43.1
180
178
60.4
39.6
2008/09
52
3.07
278
42.6
159
145
58.1
41.9
2009/10
79
3.18
287
42.4
165
175
67.2
32.8
2010/11
96
3.20
289
41.8
168
131
47.6
52.4
2007/08-2010/11
250
3.19
289
42.3
166
152
57.2
42.8
(a)
(b)
Figure 3: Distribution of Lismore Actual % Water Use (a) and Lismore Actual % Water Use sqrt
transformed data (b).
Table 8: Comparison of % Water Use statistics utilising untransformed and sqrt reverse
transformed Lismore Actual % Water Use/Savings data
Average Actual % Use
Average Actual Saving
(%)
Untransformed
Sqrt
Transformed
57.2
52.5
42.8
47.5
As illustrated in Figure 3a, the distribution of Actual Water Use relative to the Actual Water Benchmark
is right skewed. To normalise these data a square root transformation was applied to yield a more
symmetrical distribution closely matching the normal distribution curve (Figure 3b). Reverse
transformation of these data revealed that 65.2% of dwellings achieved the BASIX 40% Water Saving
Objective with an average Actual Water Saving of 47.5% (Table 8). This saving compares relatively
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ROUS WATER BASIX PERFORMANCE REPORT
closely to the average BASIX Water Saving of 48.7%, drawing the same conclusion that BASIX is
achieving the BASIX 40% Savings Objective in the Lismore LGA.
4.4
Conclusions from Lismore LG A Analysis

Average Metered Consumption per dwelling per year was 152 kL and per person per year was
52 kL.

Using square root transformed data, the average BASIX Water Saving was 48.7% with 64% of
households reaching the 40% savings target and the average Actual Water Saving was 47.5%
with 65.2% of households achieving the BASIX 40% Savings Objective. Both analyses
indicate that BASIX is achieving its BASIX 40% Water Savings Objective in the Lismore LGA.
5.
PERFORMANCE OF BALLI NA BASIX DWELLINGS
5.1
Metered Consumption
Table 9 presents average Metered Consumption data for Ballina BASIX households for the period
from July 2006 until June 2011. Average Metered Consumption ranged from 124 kL/dwelling/year to
170 kL/dwelling/year with an average of 146 kL/dwelling/year for 2006/07 - 2010/11. Consumption on
a per person basis ranged from 49 kL/person/year to 70 kL/person/year with an average of 59
kL/person/year.
Table 9: Average Metered Consumption of Ballina BASIX households
Average Metered
Number of
Consumption
Dwellings (kL/dwelling/year)
12
156
31
135
48
149
62
170
68
124
Year
2006/07
2007/08
2008/09
2009/10
2010/11
2006/07-2010/11
221
Average Metered
Consumption
(kL/person/year)
70
58
59
68
49
146
59
Note: The data from a single household in 2008/09 was excluded from the analysis due to the Metered
Consumption being 0 kL/dwelling/year. This consumption value was deemed non-representative of that
household as in other years consumption was consistently higher.
5.2
BASIX Predicted Consumption
Table 10 presents data used to derive BASIX Water Saving estimates based on BASIX Occupancy.
Across the period (2006/07 - 2010/11) the average BASIX Occupancy was 3.00 persons per dwelling.
These people were assumed to consume 247.5 L/p/day of potable water in an average pre-BASIX
house, giving an average BASIX Water Benchmark of 271 kL/dwelling/year across the period.
The BASIX Water Score for Ballina between 2006/07 and 2010/11 averaged 42.4%, therefore the
average BASIX Predicted Consumption was 156 kL/dwelling/year. The average Metered Consumption
across the period was 146 kL/dwelling/year.
Analysis of Figure 4a reveals that 67% of dwellings achieved a BASIX Water Use of 60% or less,
hence a BASIX Water Saving of 40% or more, relative to the average BASIX Water Benchmark. The
average estimated BASIX Water Saving across the period was 46.0 %. This value is slightly higher
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ROUS WATER BASIX PERFORMANCE REPORT
than the BASIX tool calculated saving (Average BASIX Water Score) of 42.5%, suggesting that Ballina
BASIX dwellings are performing better than expected.
As illustrated in Figure 4a, the distribution of BASIX Water % Use relative to the BASIX Water
Benchmark is right skewed therefore the true average BASIX % Water Use will tend to be overestimated and average BASIX Water Saving under-estimated. To normalise this skewed distribution, a
sqrt transformation and a log10 transformation were applied to the data to improve the goodness of fit
to the normal distribution curve (Appendix 1). Visual assessment of Figure 4b revealed that the
distribution of the log10 transformed data closely matches the symmetrical normal distribution curve
which allows statistical analysis to be more accurate than for untransformed or sqrt transformed data.
Utilising the log10 transformed data gives an average BASIX Water Saving of 55% (Table 11) with 67%
of dwellings achieving the BASIX 40% Water Savings Objective, indicating that significantly greater
than half of the BASIX households are achieving a water saving of 40% or more. The log10
transformed BASIX Water Saving of 55% is considerably higher than the average BASIX Water Score
(42.4%), suggesting that Ballina BASIX households are performing significantly better than expected.
Table 10: Summary of Ballina BASIX performance based on BASIX Occupancy
Average Average BASIX
Number
BASIX
Average BASIX
BASIX
Predicted Water Average Metered Average
Average
of
occupancy Water Benchmark
Water
Consumption
Consumption BASIX Water BASIX Water
Year
Dwellings (persons) (kL/dwelling/year) Score (%) (kL/dwelling/year) (kL/dwelling/year)
Use (%)
Saving (%)
2006/07
12
2.89
261
41.5
153
156
60.4
39.6
2007/08
31
3.04
276
42.3
159
135
48.6
51.4
2008/09
48
3.01
272
42.1
157
149
54.3
45.7
2009/10
62
3.00
271
42.6
156
170
63.5
36.5
2010/11
68
3.00
271
42.6
156
124
46.4
53.6
2006/07-2010/11
221
3.00
271
42.4
156
146
54.0
46.0
(a)
(b)
Figure 4: Distribution of Ballina BASIX % Water Use data (a) and log10 transformed Ballina
BASIX % Water Use data (b)
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ROUS WATER BASIX PERFORMANCE REPORT
Table 11: Comparison of BASIX % Water Use statistics utilising untransformed and sqrt
reverse transformed Ballina BASIX % Water Use/Savings data
Untransformed
Log10 Transformed
Average BASIX % Use
54.0
45.0
Average BASIX Saving (%)
46.0
55.0
5.3
Actual Predicted Consumption
As discussed in section 4.3 the number of occupants is a key input into the BASIX tool when
calculating the Water Benchmark, Predicted Consumption and the corresponding % Water Use/Saving
for each household. Table 12 presents data used to derive Actual Water Use/Saving estimates based
on Actual Occupancy figures from Ballina BASIX households gathered in the surveys, per year and
across the period. The average Actual Occupancy across the period was found to be lower (2.57) than
the BASIX Occupancy of 3.00 persons. As a result, the average Actual Water Benchmark decreases
from the average BASIX Water Benchmark of 271 kL/dwelling/year (Table 10) to 232 kL/dwelling/year.
The BASIX Water Score remains the same (42.4%), as does the Metered Consumption (146
kL/dwelling/year), but the average Actual Predicted Consumption decreases from 156 kL/dwelling/year
to 133 kL/dwelling/year.
Analysis of Figure 5a reveals that 57.5% of households achieved water savings of 40% or more
compared to the average Actual Water Benchmark, with an average Actual Water Saving of 34.7%,
relative to the average Actual Water Benchmark, across the period. More than half of the households
are achieving the BASIX 40% Savings Objective although the low average of the untransformed data
indicates that in general BASIX households are performing poorly. However, assessment of Figure 5a
shows that the distribution of Actual % Water Use relative to the Actual Water Benchmark is right
skewed which means that the average is likely to be over-estimated and therefore the average Actual
Water Saving under-estimated. To normalise these data, a log10 transformation was applied to yield a
more symmetrical distribution closely matching the normal distribution curve (Figure 5b). Reverse
transformation of these data revealed that the average Actual Water Saving was 43.3% (Table 13),
which compares closely to the average BASIX Water Score (42.4%), with 57% of households
achieving a 40% water saving. It can therefore be concluded that with the use of Actual Occupancy
figures BASIX is achieving its 40% Water Savings Objective in the Ballina LGA.
Table 12: Summary of Ballina BASIX performance based on Actual Occupancy
Year
2006/07
2007/08
2008/09
2009/10
2010/11
2006/07-2010/11
Number of
Dwellings
12
31
48
62
68
221
Average Actual
Occupancy
(persons)
2.33
2.50
2.58
2.56
2.63
2.57
Average Actual
Water Benchmark
(kL/dwelling/year)
211
226
233
231
238
232
Average
BASIX Water
Score (%)
41.5
42.3
42.1
42.6
42.6
42.4
Average Actual
Predicted Water
Consumption
(kL/dwelling/year)
124
131
135
132
136
133
Average Metered
Consumption
(kL/dwelling/year)
156
135
149
170
124
146
Average
Average
Actual Water Actual Water
Use (%)
Saving (%)
77.1
22.9
64.4
35.6
64.9
35.1
75.5
24.5
54.7
45.3
65.3
34.7
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ROUS WATER BASIX PERFORMANCE REPORT
(a)
(b)
Figure 5: Distribution of Ballina Actual % Water Use (a) and Log10 transformed Ballina Actual %
Water Use data (b)
Table 13: Comparison of % Water Use statistics utilising untransformed and log10 retransformed Ballina Actual Water Savings/Use data
Average Actual % Use
Average Actual Saving (%)
5.4
Untransformed Log10 Transformed
65.3
56.7
34.7
43.3
Conclusions from Ballina LG A Anal ysis

Average consumption in the Ballina LGA per BASIX dwelling was 146 kL/year and per person
was 59 kL/year.

The average BASIX Water Saving was 55% with 67% of households achieving the BASIX
40% Savings Objective and the average Actual Water Saving was 43.3% with 57% of house
achieving the BASIX 40% Savings Objective. Both analyses indicate that BASIX is achieving
its 40% water savings objective in the Ballina LGA.
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ROUS WATER BASIX PERFORMANCE REPORT
6.
PERFORMANCE OF RICHMOND V ALLEY BASIX DWELLINGS
The limited amount of data available for the Richmond Valley LGA means that little meaningful
analysis can be applied to the data and any conclusions drawn from this analysis may not be
indicative of the true future performance of BASIX households in the Richmond Valley Shire. The
financial years 2006/07 and 2007/08 have data from the same single house therefore the results are
biased towards this particular dwelling. This section is still included in this report for the sake of
completeness and to provide a basis for future comparative analysis, however caution should be
applied when drawing any conclusions from the Richmond Valley statistics.
6.1
Metered Consumption
Table 14 presents average Metered Consumptions of Richmond Valley BASIX households from July
2006 to June 2011. Average Metered Consumption ranged from 140 kL/dwelling/year to 483
kL/dwelling/year with an average of 199 kL/dwelling/year. Consumption on a per person basis ranged
from 42 kL/person/year to 80 kL/person/year with an average of 63 kL/person/year across the period.
Table 14: Average Metered Consumptions of Richmond Valley BASIX households
Average Metered Average Metered
Number of
Consumption
Consumption
Year
Dwellings (kL/dwelling/year) (kL/person/year)
2006/07
1
483
80
2007/08
1
252
42
2008/09
4
240
69
2009/10
8
202
74
2010/11
9
140
52
2006/07-2010/11
23
199
63
6.2
BASIX Predicted Consumptions
Table 15 presents data used to derive BASIX Water Saving estimates based on BASIX Occupancy
data. Across the period the average BASIX Occupancy was 2.80 persons per dwelling. These people
were assumed to have consumed 247.5 L/day in an average pre-BASIX household, producing an
average BASIX Water Benchmark of 253 kL/dwelling/year across the period.
The average BASIX Water Score across the period was 42.7% (Table 15). This indicates that BASIX
predicts water consumption to be 42.7% less than the average BASIX Water Benchmark, therefore the
average BASIX Predicted Consumption was 146 kL/dwelling/year. The average Metered Consumption
across the period was relatively higher at 199 kL/dwelling/year.
Analysis of Figure 6 reveals that only 39% of households achieved a BASIX Water Use figure of 60%
or less, or a BASIX Water Saving of 40% or more, relative to the average BASIX Water Benchmark.
The average estimated BASIX Water Saving across the period was only 23.1%, compared to the
average BASIX Water Score of 42.7%. This suggests that BASIX households are performing poorly in
the RVC LGA with a significant majority of households not achieving the BASIX 40% Water saving
objective.
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ROUS WATER BASIX PERFORMANCE REPORT
Table 15: Summary of Richmond Valley BASIX performance based on BASIX Occupancy
Number of
Year
Dwellings
2006/07
1
2007/08
1
2008/09
4
2009/10
8
2010/11
9
2006/07-2010/11
23
Average
BASIX
Occupancy
(persons)
3.23
3.23
2.92
2.73
2.71
2.80
Average BASIX
Average BASIX
Average
Predicted Water Average Metered
Water Benchmark BASIX Water
Consumption
Consumption
(kL/dwelling/year) Score (%) (kL/dwelling/year) (kL/dwelling/year)
292
40.0
175
483
293
40.0
176
252
263
40.8
156
240
247
43.0
141
202
245
44.0
138
140
253
42.7
146
199
Average
BASIX
Water Use
(%)
165.2
85.9
92.5
80.9
55.7
76.9
As illustrated in Figure 6, the distribution of BASIX Water Use relative to the BASIX Water Benchmark
is not symmetrical and has very few data. In an attempt to normalise this distribution, sqrt and log10
transformations were conducted. Not surprising, given the limited data, visual assessment of the
results (see Appendix 1) revealed that the transformation yielded no improvement in the distribution of
the data. As a result, the original untransformed data was used for statistical analysis of Richmond
Valley BASIX Water Use data.
Figure 6: Distribution of Richmond Valley BASIX % Water Use data relative to the BASIX Water
Benchmark
6.3
Actual Predicted Consumptions
Table 16 presents data used to derive Actual Water % Use/Saving based on Actual Occupancy figures
per year and across the period. The average Actual Occupancy across the period was found to be
(3.3) which was higher than the BASIX Occupancy (2.8). As a result, the average Actual Water
Benchmark (300 kL/dwelling/year) is increased from the average BASIX Water Benchmark of 253
kL/dwelling/year. The average BASIX Water Score (42.7%) remains the same, as does the Metered
Consumption (199 kL/dwelling/year), but the average Predicted Consumption increases from the
BASIX Predicted 146 kL/dwelling/year to the Actual Predicted 175 kL/dwelling/year.
Page 14
Average
BASIX Water
Saving (%)
-65.2
14.1
7.5
19.1
44.3
23.1
ROUS WATER BASIX PERFORMANCE REPORT
Table 16: Summary of Richmond Valley BASIX performance based on Actual Occupancy
Average
Average Actual
Average Average
Actual
Average Actual
Average
Predicted Water
Average Metered
Actual
Actual
Number of Occupancy Water Benchmark BASIX Water
Consumption
Consumption
Water
Water
Year
Dwellings (persons) (kL/dwelling/year) Score (%)
(kL/dwelling/year) (kL/dwelling/year) Use (%) Saving (%)
2006/07
1
6.0
538
40.0
323
483
89.7
10.3
2007/08
1
6.0
540
40.0
324
252
46.6
53.4
2008/09
4
3.8
336
40.8
200
240
77.0
23.0
2009/10
8
3.0
269
43.0
155
202
82.2
17.8
2010/11
9
2.9
259
44.0
148
140
58.5
41.5
2006/07-2010/11
23
3.3
300
42.7
175
199
70.8
29.2
Figure 7 illustrates the distribution of Actual % Water Use data relative to the Actual Water
Benchmark. Analysis of this distribution reveals that 57% of BASIX households are achieving the
BASIX 40% Savings Objective with an average Actual Water Saving of 29.2% (relative to the average
Actual Water Benchmark), well below the BASIX tool predicted Water Score of 42.7%. Even though
over half the households are achieving the 40% saving, on average, they are achieving less than the
40% target saving. On the limited data available, this indicates, as did the BASIX Occupancy figures,
that BASIX is performing poorly in the Richmond Valley LGA, however, the very minimal sample size
means that this conclusion may not accurately represent future trends within the Richmond Valley
LGA.
As evident in Figure 7 the distribution of the Actual % Water Use data relative to the Actual Water
Benchmark is slightly right skewed. In attempt to normalise this distribution, sqrt and log 10
transformations were conducted on the data (See Appendix 1). Visual assessment of the results
revealed that the transformations did little to normalise the data, once again due to the low number of
data points and hence, the raw data was used to complete the statistical analyses as above.
Figure 7: Distribution of Richmond Valley Actual % Water Use data relative to the Actual Water
Benchmark
6.4
Conclusions from Richmond Valle y LG A Anal ysis

Average consumption per dwelling over the period was 199 kL/year and per person was 63
kL/year.

The average BASIX Water Saving across the period was 23.1% with 39% of households
achieving the BASIX 40% Savings Objective and the Actual Water Saving was 29.1% with
Page 15
ROUS WATER BASIX PERFORMANCE REPORT
57% of houses achieving the BASIX 40% Savings Objective. Both indicate that BASIX is not
achieving its 40% Water Savings Objective in the Richmond Valley LGA.

The limited amount of data available for the Richmond Valley LGA means that any
conclusions drawn from this analysis may not be indicative of the true future performance of
BASIX households in the Richmond Valley Shire.
7.
PERFORMANCE OF BYRON BASIX DWELLINGS
7.1
Metered Consumption
The average Metered Consumption in the Byron LGA ranged from 122 kL/year to 166 kL/year with an
average of 146 kL/year (Table 17). Consumptions on a per person basis ranged from 51
kL/person/year to 73 kL/person/year with an average of 61 kL/person/year.
Table 17: Average Metered Consumption of Byron BASIX households from 2006/07 - 2010/11
Year
2006/07
2007/08
2008/09
2009/10
2010/11
2006/07-2010/11
7.2
Number of
Dwellings
6
15
22
29
31
103
Average Metered
Consumption
(kL/dwelling/year)
122
137
162
166
123
146
Average Metered
Consumption
(kL/person/year)
73
56
65
69
51
61
BASIX Predicted Consumption
Table 18 presents data used to derive BASIX Water Saving estimates based on BASIX Occupancy.
Across the period (2006/07 - 2010/11) the average BASIX Occupancy was 2.84 persons per dwelling.
These people were assumed to have consumed 247.5 L/p/day of potable water in an average preBASIX house, giving an average BASIX Water Benchmark of 254 kL/dwelling/year.
The average BASIX Water Score across the period was 41.4% indicating that BASIX predicts water
consumption to be 41.4% less than the average BASIX Water Benchmark, therefore the average
BASIX Predicted Consumption across the period was 149 kL/dwelling/year. Comparably, the average
Metered Consumption across the period was 146 kL/dwelling/year.
Analysis of the distribution of BASIX % Water Use relative to the BASIX Water Benchmark (Figure 8a)
reveals that 64% of BASIX households achieved the BASIX 40% Savings Objective over the five year
period. On average they saved 42.7% compared to the average BASIX Water Benchmark which is
slightly higher than the average BASIX water score of 41.4%, suggesting that BASIX dwellings are
performing slightly better than expected. However, visual assessment of Figure 8a reveals that the
distribution of BASIX % Water Use data is right skewed, therefore the average BASIX Water Saving is
likely to be underestimated.
To normalise this skewed distribution, sqrt transformation and log10 transformations were applied to
the data to in an attempt to improve the goodness of fit (Appendix 1). Visual assessment of the results
revealed that the distribution of the sqrt transformed data is still right skewed, but is closer to the
symmetrical normal distribution curve (Figure 8b). This allows statistical analysis to be more accurate
than if performed on untransformed or log10 transformed data. Utilising the sqrt transformed data gave
Page 16
ROUS WATER BASIX PERFORMANCE REPORT
an average BASIX Water Saving of 48.1% (Table 19) (with 64% achieving a BASIX Water Saving of
40% or more) which indicates that BASIX houses are performing on average 16% better than the
BASIX tool suggests.
Table 18: Summary of Byron BASIX performance based on BASIX Occupancy
Average
Average BASIX
Number Average BASIX Average BASIX
BASIX
Predicted Water Average Metered
of
Occupancy
Water Benchmark Water Score
Consumption
Consumption
Average BASIX Average BASIX
Year
Dwellings
(persons)
(kL/dwelling/year)
(%)
(kL/dwelling/year) (kL/dwelling/year) Water Use (%) Water Saving (%)
2006/07
6
2.89
259
41.3
153
122
44.4
55.6
2007/08
15
2.87
258
41.8
150
137
52.7
47.3
2008/09
22
2.86
256
41.5
150
162
63.8
36.2
2009/10
29
2.83
254
41.3
149
166
66.4
33.6
2010/11
31
2.80
251
41.3
147
123
48.9
51.1
2006/07-2010/11
103
2.84
254
41.4
149
146
57.3
42.7
(a)
(b)
Figure 8: Distribution of Byron BASIX % Water Use data (a) and sqrt transformed Byron BASIX
% Water Use data (b)
Table 19: Comparison of % Water Use statistics utilising untransformed and sqrt retransformed Byron BASIX Water Savings/Use data
Average BASIX % Use
Average BASIX Saving (%)
7.3
Untransformed Sqrt Transformed
57.3
51.9
42.7
48.1
Actual Predicted Consumption
Table 20 presents data used to derive Actual Water Use/Saving estimates based on Actual
Occupancy figures. The average Actual Occupancy across the period was 2.42 persons/dwelling,
down from the BASIX Occupancy of 2.84 persons/dwelling. As a result the average Actual Water
Benchmark decreases from the average BASIX Water Benchmark of 254 kL/ dwelling/year to the
average Actual Water Benchmark of 219 kL/dwelling/year. The average BASIX Water Score remains
the same at 41.4% as does the average Metered Consumption at 146 kL/dwelling/year, but the
average Predicted Consumption decreases from the average BASIX Predicted Consumption of 149
kL/dwelling/year to the average Actual Predicted Consumption of 128 kL/dwelling/year.
Page 17
ROUS WATER BASIX PERFORMANCE REPORT
Table 20: Summary of Byron BASIX performance based on Actual Occupancy
Average Actual Average Actual
Average
Number of
Occupancy
Water Benchmark BASIX Water
Year
Dwellings
(persons)
(kL/dwelling/year)
Score (%)
2006/07
6
1.50
136
41.3
2007/08
15
2.30
208
41.8
2008/09
22
2.48
224
41.5
2009/10
29
2.59
234
41.3
2010/11
31
2.48
224
41.3
2006/07-2010/11
103
2.42
219
41.4
Average Actual
Predicted Water
Consumption
(kL/dwelling/year)
80
120
130
137
131
128
Average Metered
Average
Average Actual
Consumption
Actual Water Water Saving
(kL/dwelling/year)
Use (%)
(%)
122
81.3
18.7
137
61.8
38.2
162
72.3
27.7
166
76.0
24.0
123
56.9
43.1
146
67.7
32.3
Analysis of Figure 9a reveals that 54% of BASIX dwellings are achieving the BASIX 40% Savings
Objective when compared to the average Actual Water Benchmark with an average Actual Water
Saving of 32.3% (relative to the average Actual Water Benchmark) (Table 20). This saving is much
lower than the average BASIX Water Score and the average BASIX Water Saving of 42.7%
suggesting that actually, BASIX households aren’t achieving the BASIX savings target of 40%.
However, as Figure 9a illustrates, the distribution of the Water Use data is right skewed. This means
that the average Actual Water Saving value is likely to be an under-estimate of the true average.
To normalise this skewed distribution, sqrt transformation and log10 transformations were applied to
the data to improve the goodness of fit (Appendix 1). Visual assessment of the results (See Appendix
1) revealed that the distribution of the sqrt transformed data is closer to the symmetrical normal
distribution curve therefore allows statistical analysis to be more accurate than if performed on
untransformed or log10 transformed data. Utilising the sqrt transformed data gives an average Actual
Water Saving of 36.8% with 53% of households achieving the BASIX 40% Savings Objective. This
value is higher than the average of the untransformed data (32.3%) but is still less than the BASIX
40% Savings Objective, therefore, still concluding that on average BASIX households in the Byron
LGA aren’t achieving the BASIX 40% Savings Objective.
(a)
(b)
Figure 9: Distribution of Byron Actual % Water Use data (a) and sqrt transformed Byron Actual
% Water Use data (b)
Table 21: Comparison of % Water Use statistics utilising untransformed and sqrt retransformed Byron Actual Water Savings/Use data
Average Actual % Use
Average Actual Saving (%)
Untransformed Sqrt Transformed
67.7
63.2
32.3
36.8
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ROUS WATER BASIX PERFORMANCE REPORT
7.4
Conclusions from Byron LG A Anal ysis

Average Metered Consumption of a BASIX dwelling across the 2006/07 to 2010/11 financial
year period in the Byron LGA was 146 kL/dwelling/year or 61 kL/person/year.

The average BASIX Water Saving was 48.1% with 64% of households achieving the BASIX
40% Savings Objective and the Actual Water Saving was 36.8% with 53% of houses
achieving the BASIX 40% Savings Objective.
8.
PERFORMANCE OF BASIX DWELLINGS ACROSS THE ROUS
WATER SERVICE ARE A
Data from Byron, Ballina and Richmond Valley encompasses the 2006/07 to 2010/11 financial years.
The Lismore data set does not include the first year as data from 2006/07 was unavailable at the time
of publication (See Section 4).
8.1
Metered Consumption
Table 22 presents the average Metered Consumption data for BASIX households across the total
Rous Water bulk supply area from July 2006 - June 2011. Average Metered Consumption ranged from
146 kL/dwelling/year in the Ballina and Byron supply areas to 199 kL/dwelling/year in Richmond
Valley, with an average of 150 kL/dwelling/year across the total bulk supply area. Average
consumption per person ranged from 52 kL/person/year across the Lismore supply area to 63
kL/person/year across Richmond Valley, with an average of 56 kL/person/year across the total bulk
supply area.
Table 22: Average Metered Consumption of BASIX households across the total Rous Water
bulk supply area (July 2006 - June 2011)
Number Average Metered Average Metered
of
Consumption
Consumption
LGA
Dwellings (kL/dwelling/year (kL/person/year)
Ballina
221
146
59
Byron
103
146
61
Lismore
250
152
52
Richmond Valley
23
199*
63*
Total Bulk Supply
Area
597
150
56
* Calculated from limited data and unlikely to provide a true reflection of consumption in Richmond Valley.
Note: Lismore data are from the period July 2007- June 2011 only.
8.2
BASIX Predicted Consumption
Table 23 presents data used to derive BASIX Water Saving estimates based on BASIX Occupancy.
The average BASIX Occupancy across the 2006/07 to 2010/11 financial year period was 2.98
persons/dwelling. These people were assumed to have used 247.5 L/p/day in an average pre-BASIX
house, giving an average BASIX Water Benchmark of 269 kL/dwelling/year across the period.
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ROUS WATER BASIX PERFORMANCE REPORT
The average BASIX Water Score for BASIX households across the Rous Water bulk water supply
area was 42.2% (Table 23). This means that the average BASIX Predicted Consumption was found to
be 42.2% less than the average BASIX Water Benchmark, therefore the average BASIX Predicted
Consumption was 156 kL/dwelling/year.
Analysis of the distribution of BASIX % Water Use data relative to the BASIX Water Benchmark
(Figure 10a) reveals that 64% of BASIX households across the Rous Water total bulk supply area
have achieved a BASIX Water % Use of 60% or less (or water saving of 40% or more) relative to the
average BASIX Water Benchmark. On average, BASIX households saved 44.0% relative to the
average BASIX Water Benchmark across the period. This value is slightly higher than the average
saving estimated by the BASIX tool (42.2%), which suggests that BASIX houses in the Rous Water
bulk supply area are on average performing better than expected.
Table 23: Summary of Rous Water BASIX performance based on BASIX Occupancy
Number of
LGA
Dwellings
Ballina
221
Byron
103
Lismore
250
Richmond Valley
23
Total Bulk Supply
Area
597
Average
BASIX
Occupancy
(persons)
3.00
2.84
3.04
2.80*
Average BASIX
Average BASIX
Predicted Water
Average Metered
Water Benchmark Average BASIX
Consumption
Consumption
Average BASIX Average BASIX
(kL/dwelling/year) Water Score (%) (kL/dwelling/year) (kL/dwelling/year) Water Use (%) Water Saving (%)
271
42.4
156
146
54.0
46.0
254
41.4
149
146
57.3
42.7
275
42.3
159
152
55.5
44.5
253*
42.7*
146*
199*
76.9*
23.1*
*
2.98
269
42.2
156
150
56.0
* Calculated from limited data and unlikely to provide a true reflection of consumption in Richmond Valley.
Note: Lismore data are from the period July 2007 - June 2011 only.
As illustrated in Figure 10a the distribution of BASIX Water Use data is right skewed so the average
water saving value discussed above (44.0%) is likely to be under-estimated, hence the actual true
water saving is likely to be higher than this figure. To normalise this skewed distribution, sqrt
transformation and log10 transformations were applied to the data to improve the goodness of fit.
Visual assessment of the results (See Appendix 1) revealed that the distribution of the sqrt
transformed data is closer to the symmetrical normal distribution curve (Figure 10b) therefore allows
statistical analysis to be more accurate than if performed on untransformed or log 10 transformed data.
Utilising the sqrt transformed data gives an average BASIX Water Saving of 48.6% (Table 24) with
63% of households achieving a BASIX Water Saving of 40% or more. These estimations using BASIX
Occupancy reveal that BASIX houses in the Rous Water bulk supply area are on average saving
48.6% of water when compared to the average BASIX Water Benchmark and that significantly more
than half of BASIX houses (63%) are achieving the BASIX 40% Savings Objective or more.
Page 20
44.0
ROUS WATER BASIX PERFORMANCE REPORT
(a)
(b)
Figure 10: Distribution of Rous Water BASIX % Water Use data (a) and sqrt transformed Rous
Water BASIX % Water Use data (b)
Table 24: Comparison of % Water Use statistics utilising untransformed and sqrt retransformed Rous Water BASIX Water Savings/Use data
Average BASIX % Use
Average BASIX Saving (%)
8.3
Untransformed Sqrt Transformed
56.0
51.4
44.0
48.6
Actual Predicted Consumption
As discussed in section 4.3 the use of Actual Occupancy data in savings calculations is an attempt to
make a more accurate estimate of the benchmark value and hence the savings value. The average
Actual Occupancy per dwelling across the region (2.83) (Table 25) was found to be lower than the
average BASIX Occupancy of 2.98 (Table 23). This resulted in an average Actual Water Benchmark of
256 kL/dwelling/year which was lower than the average BASIX Water Benchmark of 269
kL/dwelling/year (Table 23). As a result the average Actual Predicted Consumption (148
kL/dwelling/year) was lower than the average BASIX Predicted Consumption of 156 kL/dwelling/year
(Table 23). The average BASIX Water Score remains the same (42.2%), as does the average Metered
Consumption (150 kL/dwelling/year).
Table 25: Summary of total Rous Water BASIX performance based on Actual Occupancy
LGA
Ballina
Byron
Lismore
Richmond Valley
Total Bulk Supply Area
Average Actual
Average Actual
Average
Number of
Occupancy
Water Benchmark BASIX Water
Dwellings
(persons)
(kL/dwelling/year) Score (%)
221
2.57
232
42.4
103
2.42
219
41.4
250
3.19
289
42.3
23
3.35*
300*
42.7 *
597
2.83
256
42.2
Average Actual
Average
Predicted Water
Metered
Average
Average Actual
Consumption
Consumption Actual Water Water Saving
(kL/dwelling/year) (kL/dwelling/year)
Use (%)
(%)
133
146
65.3
34.7
128
146
67.7
32.3
166
152
57.2
42.8
175*
199*
70.8*
29.2*
148
150
62.5
37.5
* Calculated from limited data and unlikely to provide a true reflection of consumption in Richmond Valley.
Note: Lismore data are from the period July 2007- June 2011 only.
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ROUS WATER BASIX PERFORMANCE REPORT
The distribution of the Actual Water use data is illustrated in Figure 11a. Analysis of this distribution
reveals that 60% of BASIX households achieved the 40% BASIX water saving objective. The use of
Actual Occupancy data in the estimation of water savings figures reveals that the average Actual
Water Saving (relative to the Actual Water Benchmark) across the region across the period was 37.5%
(Table 25). This value is below the BASIX 40% Savings Objective, suggesting that on average, BASIX
houses are not achieving the objective. However, assessment of the distribution of Actual % Water
Use data in Figure 11a demonstrates that the distribution of the data is right skewed, which suggests
that the savings figure is likely to be under-estimated.
To normalise this skewed distribution, sqrt transformation and log10 transformations were applied to
the data to improve the goodness of fit (Appendix 1). Visual assessment of the results (See Appendix
1) revealed that the distribution of the sqrt transformed data is closer to the symmetrical normal
distribution curve (Figure 11a) therefore allows statistical analysis to be more accurate than if
performed on untransformed or log10 transformed data. Utilising the sqrt transformed data gives an
average Actual Water Saving of 42.2% with 60% of BASIX houses achieving a water saving of 40% or
greater. Therefore BASIX houses in the Rous Water bulk water supply area are achieving the 40%
water savings objective.
(a)
(b)
Figure 11:Distribution of Rous Water Actual % Water Use data (a) and sqrt transformed Rous
Water Actual % Water Use data (b)
Table 26:Comparison of % Water Use statistics utilising untransformed and sqrt retransformed Rous Water Actual Water Savings/Use data
Average Actual % Use
Average Actual Saving (%)
8.4
Untransformed Sqrt Transformed
62.5
57.8
37.5
42.2
Accurac y of Predicted Consumptions
Figure 12 illustrates the range and averages of BASIX Predicted, Actual Predicted and Metered
Consumptions across the five year period. A comparison of averages reveals that both BASIX and
Actual Predicted Consumptions provide reasonable estimates of Metered Consumption over the five
year period. The average BASIX Predicted Consumption (156 kL/dwelling/year) overestimates the
Page 22
ROUS WATER BASIX PERFORMANCE REPORT
average Metered Consumption of 150 kL/dwelling/year by 4% and the average Actual Predicted
Consumption of 148 kL/dwelling/year underestimates it by 1.3%. Therefore, both methods provide a
reasonable estimation of average Metered Consumption over a five year period. However, the Actual
Predicted Consumption provides a larger range in estimated values (closer to that of the range in
Metered Consumption Values) emphasising that the number of actual occupants is one of the major
factors that contribute to the difference between Metered and BASIX Predicted Consumptions.
The ability of Predicted Consumptions to accurately predict Metered Consumptions of an individual
dwelling in a particular year was also statistically explored. These analyses revealed that the range in
error when using BASIX Occupancy to predict Metered Consumption varies significantly with an
average of error of +94%. The Actual Predicted Consumption improves the range of the error, but still
results in large individual deviations from Metered Consumption, with errors in Actual Predicted
Consumption averaging +59%.This demonstrates that both BASIX and Actual Predicted
Consumptions have limited ability in predicting Metered Consumptions for a single dwelling in a single
year. Variations in Metered Consumptions are influenced by a range of factors including variations in
customer behaviour which cannot be effectively captured by the BASIX tool or incorporated into
BASIX Predicted Consumptions. Overall, BASIX Predicted Consumption provides a reasonable
estimation of average Metered Consumption over a five year period, but should not be used to
evaluate consumption changes on a dwelling by dwelling basis.
600
kL/dwelling/year
500
400
300
200
150
156
148
100
0
Metered Consumption
BASIX Predicted
Actual Predicted
Figure 12: Box plots illustrating the range in Rous Water Metered and Predicted Consumptions
8.5
Conclusions from Rous Water service area anal yses

Average Metered Consumption of BASIX dwellings across the 2006/07 to 2010/11 financial
year period in the Rous Water total bulk supply area was 150 kL/dwelling/year or 56
kL/person/year.

The average BASIX Water Saving was 48.6% with 63% of households achieving the BASIX
40% Savings Objective and the average Actual Water Saving was 42.2% with 60% of
households achieving the 40% savings target. Both analyses indicate that BASIX is achieving
its 40% water saving objective across the Rous Water bulk water supply area as a whole.
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ROUS WATER BASIX PERFORMANCE REPORT

Both BASIX Predicted Consumptions and Actual Predicted Consumptions provide reasonable
estimations of average Metered Consumption over a five year period.
9.
SUMMARY OF FINDINGS
9.1
Metered Consumption
Table 27 provides a summary of average Metered Consumptions across all the Rous Water supply
LGA’s and the total Rous Water bulk water supply area. These values can be interpreted as likely
future water consumption for BASIX dwellings.
Table 27: Summary of Average Metered Consumption of BASIX households across the total
Rous Water bulk supply area in the 2006/07 - 2010/11 financial years period
Number Average Metered Average Metered
of
Consumption
Consumption
LGA
Dwellings (kL/dwelling/year (kL/person/year)
Ballina
221
146
59
Byron
103
146
61
Lismore
250
152
52
Richmond Valley
23
199*
63*
Total Bulk Supply
Area
597
150
56
* Calculated from limited data and unlikely to provide a true reflection of consumption in Richmond Valley.
Note: Lismore data are from the period July 2007- June 2011 only
9.2
Water Savings
The BASIX Water Score is the amount of water that the BASIX tool estimates a house will save
compared to an average pre-BASIX house. The average Water Score ranged from 41.4% in Byron to
42.7% in Richmond Valley with an average of 42.2% across the total Rous Water bulk water supply
area (Table 28).The overall objective of BASIX is to achieve a 40% Water Saving and the BASIX tool
indicates that this is being achieved.
Average BASIX Water Savings ranged from 23% in Richmond Valley to 55% in Ballina with an
average Water Saving of 49% across the total Rous Water supply area. Using BASIX Occupancy data
the percentage of BASIX houses achieving the BASIX 40% Savings Objective ranged from 39% in
Richmond Valley to 67% in Ballina. Average Actual Water Savings ranged from 30% in Richmond
Valley to 48% in Lismore where the percentage of houses achieving the BASIX 40% Savings
Objective ranged from 53% in Byron to 65% in Lismore.
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ROUS WATER BASIX PERFORMANCE REPORT
Table 28: Summary of Water Savings
Region
Average
Average BASIX
% of BASIX houses
Average
% of BASIX houses
BASIX Water
Water Saving
Achieving BASIX 40%
Actual Water
Achieving BASIX 40%
Score (%)
(%)
Saving Objective a
Saving (%)
Saving Objective b
Lismorec
42.3
49
64
48
65
Ballina*
42.4
55
67
43
57
Richmond
42.7
23
39
30
57
Byron*
41.4
48
64
37
53
Total Rous*
42.2
49
63
42
60
Valley
a
using BASIX Occupancy
b
using Actual Occupancy
* Utilising transformed data. Lismore (square root transformed); Byron (square root
transformed); Ballina (log10 transformed).
c
Lismore data are from the period July 2007- June 2011 only.
9.3
Accurac y of Predicted Consumptions
In the Rous Water supply area as a whole, both BASIX Predicted and Actual Predicted Consumptions
did not reflect Metered Consumption on a dwelling/year basis (i.e. the consumption of a single house
in a given year). BASIX Predicted Consumptions also had a limited ability in predicting the real range
in consumption that is evident in Metered Consumption data. This is partly due to the BASIX
occupancies only being assumptions based on number of bedrooms and locations, where in reality
there is more variability than the BASIX Occupancy. The use of Actual Occupancy data attempts to
close this gap by using the actual number of people living in each house. This method increased the
range in Predicted Consumptions to closer match the Metered Consumption data, however, this was
still not as broad as the range observed in Metered Consumption and dwelling/year predictions and
correlation of BASIX or Actual Predicted Consumptions against Metered Consumption data on an
individual household basis was poor. Variations in Metered Consumptions are influenced by a range
of factors, not only occupancy but also variations in customer behaviour which cannot be effectively
captured by or incorporated into BASIX or Actual Predicted Consumptions.
When five-year BASIX Predicted, Actual Predicted and Metered Consumption averages were
compared it was revealed that the average BASIX Predicted Consumption average did not
significantly differ from the average Metered Consumption. This suggests that BASIX Predicted
Consumption provides a reasonable estimate of average Metered Consumption over a five year period
and therefore may be appropriate to estimate average water savings of BASIX households over the
long term.
Five-year average Actual Predicted Consumption also did not significantly differ from the average
Metered Consumption and was closer to the average Metered Consumption than the BASIX Predicted
average. In general, the use of Actual Occupancies provides more realistic BASIX model outcomes,
but to gain real occupancy data is a time-consuming process as identified in Rous Water (2010).
Utilisation of updated census information in the prediction of BASIX Occupancy as it becomes
available will help to improve the accuracy of BASIX tool predictions.
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ROUS WATER BASIX PERFORMANCE REPORT
10.
REFERENCES
Rous Water (2010). Rous Water BASIX Water Assessment Project- Methodology. Rous Water.
Rous Water (2010b). Rous Water BASIX Water Assessment Project: Performance of Lismore BASIX
Dwellings. Rous Water.
Sydney Water (2008). BASIX Monitoring Report Water Savings for 2007-08. Final Report. Sydney
Water,
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ROUS WATER BASIX PERFORMANCE REPORT
APPENDIX 1 - Distributions of untransformed and transformed % Water Use data sets.
BASIX
Sqrt BASIX
LOG10 BASIX
Actual
Sqrt Actual
LOG10 Actual
Lismore
Ballina
RVC
Byron
Appendix 1
ROUS WATER BASIX PERFORMANCE REPORT
APPENDIX 2 – Rous Water BASIX Assessment Project Methodology.
Appendix 2