14 years experience of using iwa best practice...
TRANSCRIPT
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14 Years Experience of using IWA Best Practice Water Balance and Water Loss Performance Indicators in Europe
A Lambert*,B Charalambous**,M Fantozzi***,J Kovac****,A Rizzo*****,S Galea St John******
* Water Loss Research & Analysis Ltd, Llanrhos, Llandudno, LL30 1SL, UK, WWW.leakssuite.com
** Hydrocontrol Ltd, POBox 71044, CY3840 Lemesos, Cyprus, [email protected]
*** Studio Marco Fantozzi, Via Forcella, 29 - 25064 Gussago (Brescia) Italy. [email protected]
**** Aqua Libera Ltd, Ribnica 146c, 10415 Novo Cice, Croatia, [email protected]
***** Institute of Applied Science, MCAST, Kordin Road; Paola, PLA9032, [email protected]
****** Water Services Corporation, Malta. [email protected]
Keywords: Water Loss; Water Balance; Performance Indicators; ILI
Abstract
The IWA Best Practice Water Balance and Performance Indicators were published in 1999 by the 1st IWA Water Loss Task Force, and in 2000 by the Performance Indicators Group. The objective - to provide a long overdue standardised international approach to the calculation of Non-Revenue Water, its components, and performance – has been substantially achieved in an ever-increasing number of countries internationally. However, adoption of the approach in European countries has been rather mixed; and the 2013 European Commission’s Water Blueprint’s proposed tool box approach allows each country to choose its own performance measures for improved water loss management. The first section of the paper highlights some common practices which are producing misleading conclusions for water loss management performance assessment and improvement – in particular, serious inherent problems with using %s of System Input Volume as a performance indicator. Appendix A suggests a guideline approach to defaults for assessed components of NRW, which could be considered as applicable to Europe. The second section discusses Technical Minimum Real Losses - ‘How Low Could You Go’ – assessed using IWA Water Loss Task Force equations for UARL (Unavoidable Annual Real Losses). UARL is used in calculating the Infrastructure Leakage Index (ILI), specifically designed to compare technical real losses management between Utilities. Key aspects of the fundamental role of pressure management in Real Losses management and Sustainable Economic Real Losses calculations will be in a separate future paper. The third section summarises new developments and practical experiences since 1999 which the authors consider have clearly identified the most appropriate choices of water loss Performance Indicators for two different purposes:
tracking progress and setting targets within a single Utility or system
comparing technical performance between Utilities with different key characteristics. The fourth section contains updated European ILI data sets from 71 Utility systems in 12 High Income countries, and 9 Utility systems from 3 Low/Middle Income countries. Appendix B contains a brief initial draft review of the extent to which these countries have adopted the IWA Water Loss Specialist Group best practices relating to Water Balance and Performance Indicators. Contributions to extend these ILI data sets to more Countries, and to correct, update and improve Appendix B, are welcomed. Links are given
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to a free access website which will hold and update international ILI data sets for Europe, and other international regions and countries. .
1. Current practices which can produce misleading conclusions
1.1 IWA Best Practice Water Balance: Water Supplied, and System Input Volume
The IWA Best Practice Water Balance developed by the 1st Water Loss Task Force is shown in Figure 1, as originally published (Hirner & Lambert, 2000; Alegre et al, 2000),
‘System Input Volume’ was defined as ‘the annual volume input to that part of the water supply system to which the water balance calculation relates.’ This broad definition, adopted for reasons of simplicity and flexibility, has caused some problems.
Also, Water Exported was specifically shown as a component of Billed Metered Consumption (and also of Authorised Consumption, and System Input Volume).
System
Input
Volume
Authorised
Consumption
Billed
Authorised
Consumption
Billed Metered Consumption
(including water exported)
Revenue
Water
Billed Unmetered Consumption
Unbilled
Authorised
Consumption
Unbilled Metered Consumption
Non-
Revenue
Water
Unbilled Unmetered Consumption
Water
Losses
Apparent
Losses
Unauthorised Consumption
Customer Metering Inaccuracies
Real
Losses
Leakage on Transmission and/or
Distribution Mains
Leakage and Overflows at Storage Tanks
Leakage on Service Connections up to
point of Customer metering
Figure 1 IWA Water Balance as originally published (Hirner & Lambert 2000; Alegre et al 2000)
The first Performance Indicators Report (Alegre et al, 2000) contained an additional diagram (Figure 2) which clearly identified ‘Water Supplied’, and numerous options for ‘System Input Volume’. Unfortunately this figure seems to be rarely referred to or used.
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oper
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metering
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*)
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Point of measurement for water balance
purposesM
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(*) - can be located anywhere between the water intake and the treatment
(**) - can be located anywhere downstream treatment
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Figure 2: Definition of water supply system inputs and outputs (Fig. 7 of Alegre at al, 2000)
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Unintended consequences and problems arising can be summarised as follows:
5 (or more) different values of ‘System Input Volume’ exist for each Utility (Fig. 3).
copies of the IWA Water Balance often omit the words ‘Water Exported’
the Standard Water Balance should have included a separate column for
‘Water Supplied’ = ‘Distribution Input’ minus ‘Water Exported’
Figure 3: Water balance of water supply system inputs and outputs (after Fig. 7, Alegre at al, 2000)
The most meaningful results (and best practice) for quantifying and interpreting NRW and its components will be obtained by calculating separate water balances for:
raw water systems (up to treatment works outputs)
treated water transmission mains
individual distribution systems
1.2 Best practice for estimating annual volumes of UAC and Apparent Losses
In any ‘top-down’ water balance, real losses volume will be under-estimated if excessively high estimates are used for the assessed components of Unbilled Authorised Consumption (UAC) and Apparent Losses (AL). Conversion of UAC and AL volumes into monetary values can help to identify inefficient customer metering and revenue collection, but it is also good practice to suggest maximum ‘default’ limits on what can be claimed for UAC and AL, without auditable Utility-specific data to justify higher assessed volumes.
Some countries (e,g. Australia, National Performance Reporting, 2009) have specified low maximum ‘default’ values for UAC and AL, and experience shows that few Utilities try to justify higher figures without good reason. German DVGW in revising the W392 Guideline, and this type of approach should be promoted in other countries.
Expressing such defaults as %s of ‘System Input Volume’ is no longer recommended by the authors because of the multiple options for SIV (see Figure 3). International experiences since 1999 show there is no perfect solution, but the least problematic ways to express these defaults in Europe are likely to be as follows:
Raw Water
Abstracted
Customer metering errors*
* Customer meter under-registration is significantly higher for
properties supplied through customer storage tanks.
Billed Authorised Consumption
(metered + unmetered)
from Transmission and Distribution system
Potable Water Exported (metered + unmetered)
Potable
Water
Supplied
(excluding
Potable
Water
Exported)
Raw Water
Abstracted
and
Imported
Imported
Raw Water
Raw Water
Abstracted
Apparent
LossesNon-Revenue
Water Water
Losses
Unbilled Authorised Consumption:
Transmission and Distribution
Potable
Water
Produced
and
Imported
From service reservoirs, mains
and service connections up to
point of customer metering
Raw Water
Consumption
Unbilled
Authorised
Consumption:
Treatment
Raw Water
Losses
Potable
Water
Produced
Unauthorised consumption
Real
Losses
Billed
Authorised
Consumption
Exported
Raw Water
Potable
Water
Produced
Potable
Water
Produced
from
Treatment
Works
Potable
Water
Imported
SIV 'A'
SIV 'B'
SIV'E'
SIV 'C'
SIV 'D'
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Unbilled Authorised Consumption: Water Treatment:
o % of metered treatment works potable water output
Unbilled Authorised Consumption: Distribution):
o % of Billed Authorised Metered Consumption (excluding Water Exported)
Apparent Losses:
o % of Billed Authorised Metered Consumption (excluding Water Exported)
o higher default values apply for properties having roof tanks supplied by gravity
In Appendix A, the Authors propose some maximum default values for Europe Water Balance calculations; comments will be invited during the presentation of this paper at the Water Loss 2014 in Vienna. These default values recognise that in some Southern European countries around the Mediterranean (e.g. Cyprus, Malta, Southern Italy, parts of Portugal and Spain), some or most properties have roof tanks supplied by gravity. Low inflow rates to these tanks result in significantly higher customer meter under-registration than in North and Central European properties with direct mains pressure and higher inflow rates.
1.3 Assessing reliability of NRW and Real Losses calculated by Water Balance
It is an inconvenient truth, rarely acknowledged, that all calculations of NRW and Real Losses from Water Balances are ‘best estimates’; even in fully metered systems. Any errors in components of the calculation accumulate in the calculated Real Losses volume.
User-friendly options for calculating confidence limits of NRW and Real Losses volume (and their Performance Indicators) have been available in some water balance software for more than 10 years. This approach also usefully identifies which components of a particular water balance have the greatest influence on the confidence limits of calculated NRW and Real Losses, to prioritise further actions to reduce their uncertainty. An example calculation of confidence limits for a simplified water balance is shown in Table 1.
Table 1: Simplified calculation example of Water Balance Confidence Limits and Priority calculation.
This type of calculation can clearly show that water balances for any European systems with roof tanks supplied by gravity, or with large numbers of unmetered properties (UK), are likely to have wider confidence limits for calculated real losses than direct pressure systems. If Table 1 was a system with roof storage tanks supplied by gravity, and CMI were 10% (not 2%), the Real Losses would be 7.4 Mm3 +/- 22%, much reduced from 11.0 Mm3 +/- 12%, and reduction of CMI would be the second priority.
Accordingly, UK Utilities and Malta WSC use ‘bottom-up’ continuous night flow measurements in district metered areas (adjusted with Night-Day Factors) as an additional method of calculating Real Losses. These can then be compared with results from ‘top-down’ water balance calculations. Some Italian Utilities also use both methods, with confidence limits, for District Metered Areas.
Volume
Mm3 +/-% +/-Mm3
Potable Water Supplied (PWS) 52.0 2.0% 1.0 1
Billed Authorised Consumption (BAC) 40.0 2.0% 0.8 2
Non-Revenue Water (NRW) 12.0 10.9% 1.3
Unbilled Authorised Consumption (UAC) 0.50% of BAC 0.2 20.0% 0.0 4
Customer metering inaccuracies (CMI) 2.00% of BAC 0.8 20.0% 0.2 3
Real Losses 11.0 12.0% 1.3
Subsidiary
calculations
Confidence limitsAnytown
Priority to
reduce CLs
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Some readers may consider that the next few sub-Sections of this paper – relating to water loss expressed as a % of System Input Volume – should be in the ‘Performance Indicators’ Section of the paper. But it is the unanimous view of the authors that the traditional practice of expressing NRW and its components as %s of System Input Volume continues to perpetuate substantial yet avoidable confusion in water loss management, and compromises the efforts of water professionals who prefer to save water rather than to perpetuate misconceptions. The following examples are provided to justify this view.
1.4 Water Loss Volumes as % of System Input Volume – which % did you mean?
When volumes of Non-Revenue Water, Water Losses, Apparent Losses and Real Losses are expressed as %s of System Input Volume (SIV), a single system can produce a wide range of %s, depending on the choice of SIV used as the denominator - especially when there are substantial exports of water - and the NRW or NRW components being used as the numerator. The simple relationship (Aqel, 2013) is:
NRW% based on SIV = NRW% based on Water Supplied x (WS volume/SIV volume)
So if half the volume of potable water entering a system is exported from that system, NRW or Real Losses %s based on SIV will be half of NRW% or Real Losses based on Water Supplied. This makes %s based on SIV useless for performance comparisons between different systems, and for comparisons between sub-systems within a Utility where some sub-systems have exports but other sub-systems do not.
Table 2 shows an example of how calculated % NRW and its components can vary depending upon which System Input Volume and which NRW component(s) ares selected for the calculation. This example is for a supply and distribution system in the Southern part of the EC, which treats a raw water of low quality, and receives imports of treated water from an adjacent system. When a media person or politician asks a general question such as ‘what are your % losses’, 16% 20%, 21%, 26%, 27%, 33%, 35%, 36% or 39% would all be equally valid and truthful responses. A spin doctor’s dream!
Table 2: %s by volume vary with choice of numerator (NRW component) and denominator (SIV).
1.5 Comparisons of European NRW %s –bias against indirect pressure systems
The apparent losses figure of 10% of Water Supplied (excluding exports) in Table 2 represents 14% of billed metered consumption (12.2% of true consumption), and is actually a reasonable performance for a system with low consumption and customer roof tanks supplied by gravity. However, in direct pressure systems in Northern Europe, some countries with rigorous metering standards claim less than 1% customer meter under-registration, and customer meter under-registration of more than 3.0% would be considered high.
Irrespective of which System Input Volume is used as the basis for expressing NRW as a %, the Apparent Losses may be expected (see Appendix A) to be significantly higher for indirect pressure systems with roof tanks around the Mediterranean, than for direct pressure systems in Central and Northern Europe. So all Utility Water Balances should clearly identify if customers’ properties have roof storage tanks supplied by gravity.
NRW UAC Water Loss App. Loss Real Loss
% % % % %
SIV A 39% 7% 33% 13% 20%
SIV B 39% 7% 33% 13% 20%
SIV C 36% 1% 35% 14% 21%
SIV D 27% 1% 26% 10% 16%
SIV E 27% 1% 26% 10% 16%Potable Water Supplied (exc. Water Exported)
A SOUTHERN EUROPEAN COUNTRY
Raw Water Abstracted
Raw Water Abstracted and Imported
Potable Water Produced
Potable Water Produced and Imported
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Failure to identify this fact when making comparisons of NRW or Apparent Losses within EC countries is systematically and significantly biased against systems with roof tanks - almost all of Malta and Cyprus, and parts of Southern Italy, Portugal, Spain..
1.6 Differences in Consumption influence % NRW and % Real Losses, and corrupt the true perception of Real Losses management efficiency
This can be easily demonstrated by adding all the components of consumption in a distribution system (excluding water exported) - billed and unbilled metered and unmetered consumption, and apparent losses – to get the total consumption. The total consumption is then logically expressed in litres/service connection/day, as the service connection is the part of the distribution system through which almost all consumption passes. Annual total consumption for most Utilities in the EC varies from around 300 to 4000 litres/service connection/day, examples are:
300 to 400 l/c/d; rural systems, seasonal holiday resorts
500 to 1500 l/conn/d: Water Utilities with diverse systems, small/medium size cities
1500 to 4000 l/conn/day: large metropolitan European cities
Just as most of total consumption is associated with service connections, component analysis of real losses shows that more than half of distribution system leakage occurs on service connections in most Utilities with more than around 20 connections per km of mains. Real losses for EC Utilities vary from around 50 to 500 litres/service connection/day (the X-axis values in Figure 4).
Figure 4: How differences in consumption distort perception of Real Losses when %s are used
Figure 4 shows that arbitrary targets (e.g. 10% Real Losses for all systems) are almost meaningless in terms of technical performance comparisons for management of Real Losses (and NRW). The green star is a rural Utility, and the red star a major city, both in the same European country, each with Real Losses of 8.8% of System Input Volume:
The ‘green star’ rural Utility, with 470 litres/service/connection consumption, has had to achieve Real Losses of 49 litres/service connection/day (ILI = 2) to achieve 8.8%
But because the ‘red star’ city has 4200 litres/conn/day consumption, it can have real losses of 426 litres/service connection/day (ILI = 18), or almost 9 times as much leakage as the ‘green star’ city, and still achieve 8.8%!.
0%
10%
20%
30%
40%
50%
60%
70%
0 50 100 150 200 250 300 350 400 450 500
Rea
l lo
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as
% o
f w
ate
r su
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Real losses litres/connection/day
300 lit/conn/d
500 lit/conn/d
700 lit/conn/d
1000 lit/conn/d
1500 lit/conn/d
2000 lit/conn/d
4000 lit/conn/d
Total Consumption
At any fixed Real Losses in l/conn/d, % Real Loss rises as consumption falls (and vice versa)
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From year to year, leakage per connection may rise, stay constant or fall; and total consumption per connection may rise, stay constant or fall. So changes in %s of Real Losses (and % NRW) expressed as a % of SIV are influenced by changes in both leakage and consumption over the same period. The red dashed vertical line in Figure 4 shows that for any particular volume of Real Losses in litres/service connection:
if consumption reduces, Real Losses as a % of Water Supplied increases, giving the impression that Real Losses volume has increased, when in reality it has not changed.
if consumption increases, Real Losses as a % of Water Supplied reduces, giving the the impression that Real Losses has reduced, when in reality it has not changed.
The problem is illustrated in Table 3. Suppose that in a base year, Real Losses are 40 Ml/d (20% of Water Supplied) and the target for Real Losses is calculated as an Economic Leakage Level (ELL) or Sustainable Economic Leakage Level (SELL) as being 32 Ml/d. If this target is expressed as a % (16%) of Water Supplied, and it takes several years to achieve Real Losses of 32 Ml/d, then changes in consumption during these years can significantly influence the perception as to whether the target has been attained, or not.
Table 3: Real Losses targets expressed as %s of a measure of SIV corrupts performance tracking
The various outcomes of incorrect perception are summarised on Table 4.
Table 4: Different outcomes of incorrect perception if Real Loss targets expressed as % of SIV
So continuing widespread use of %s in Europe for tracking changes in NRW and Real Losses is not just a theoretical problem, as the results cannot avoid being compromised by changes in consumption. In recent years, many Utilities throughout Europe have promoted demand management (low flush toilets, taps and shower heads etc) and increased prices of water, and have achieved the desired outcome of reducing consumption substantially. In German utilities with distribution systems already operating at low leakage levels close to the technically achievable minimum, Real Losses expressed as a % have therefore inevitably been increasing as consumption reduces (Tennhardt, 2012; Water Loss Detectives, 2012).
http://www.leakssuite.com/leakage-tracking-percentages/ discusses the two above examples from Germany, and also shows an Australian example of Outcome B in Table 4, where during a 7 year drought a large city reduced both leakage and consumption volumes by around 50%, without any significant change showing in Real Losses as % of System Input Volume. Fortunately the Australian WSAA had accepted IWA recommendations of 1999/2000 and ceased to use or publish %s in National Statistics in 2003. Sadly, the Regulator for that particular Australian State has still not been recognised the fallibility of using %s!
-25% -20% -10% 0% 10% 20%
Water Supplied WS Ml/d 200.0 152.0 160.0 176.0 192.0 208.0 224.0
Total Consumption TC Ml/d 160.0 120 128 144 160 176 192
Real Losses RL Ml/d 40.0 32.0 32.0 32.0 32.0 32.0 32.0 32.0
Real Loss/ Water Supplied % of WS 20.0% 16.0% 21.1% 20.0% 18.2% 16.7% 15.4% 14.3%
% change in consumption during several years
spent in reaching target reduction in Real LossesBase Year
Components
Components of Water
Balance
RL Target
set in
base year
A Consumption reduces by greater % than real losses Real Losses appear to increase
B Consumption reduces by same % as real losses Real Losses seem to be unchanged
C Consumption reduces by smaller % than real losses Real Losses reduction under-estimated
D Consumption remains the same as base year Real Losses slightly under-estimated
E Consumption increases compared to base year Real Losses reduction over-estimated
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In practice, it is preferable that, once Real Losses targets have been calculated in volume per year, they are converted to a ‘per service connection’ or ‘per km of mains’ basis (whichever is most appropriate to a particular country), as that allows for growth in the infrastructure over time, and permits simple tracking of year on year changes in multiple sub-systems, using graphs such as Figure 6 or Figure 7 (in Section 2 of this paper).
There is only perhaps only one situation where Real Losses (or NRW) volume as a % of System Input Volume is a perfect performance indicator. That is for proving that H.L. Mencken’s famous quote, below, is 100% correct
‘For every complex problem, there is a solution that is simple, neat and wrong’ .
2. How Low Could You Go: Technical Minimum Real Losses
2.1 Unavoidable Annual Real Losses (UARL)
In addition to developing a Best Practice Water Balance, the 1st Water Loss Task Force (Lambert et al 1999) was required ‘to review Performance Indicators (PIs) for international comparisons of losses in water supply systems’.
After identifying problems with %s, described in Sections 1.4 to 1.6 of this paper, the Task Force concluded that ‘per service connection’ and ‘per km of mains’ were the best of the traditional performance indicators, as they represented the two parts of the distribution infrastructure where almost all leakage occurred. But neither of these two PIs took account of average pressure, density of connections per km of mains, and average length of service connection between main and customer meter, so they were not suitable for comparisons between systems.
The Task Force therefore developed a performance indicator (Infrastructure Leakage Index ILI) specifically designed for technical comparisons of Real Losses from systems with different key infrastructure and pressure characteristics. The starting point is a formula for technical minimum or ‘Unavoidable Annual Real Losses’ (UARL) based on an auditable component analysis of real losses for well maintained infrastructure in good condition. The Infrastructure Leakage Index (ILI) could then be calculated as the non-dimensional ratio of Current Annual Real Losses/UARL. The ILI could then be used for ‘level playing field’ technical comparisons of real losses management between different systems with different key characteristics.
2.2 Basic Equations for calculating UARL
The UARL formula, based on clearly auditable assumptions, was first published in Lambert et al (1999) as shown in Equation (1) :
UARL (litres/day) = (18 x Lm + 0.8 x Nc + 25 x Lp) x P ………(1)
where Lm = mains length (km), Nc = No of service connections (main to property line)
Lp = total length of service connections (property line to customer meter) in km
P = average operating pressure (metres)
The 1st Performance Indicators Report (2000) preferred to publish the UARL formula in a slightly different format (Equation 2), which assumed that (as in many European countries) the average length of the whole of the service connection, main to meter, is known:
UARL (litres/service conn/day) = (18 x Lm/Nc + 0.7 + 0.025 x Lp) x P ………(2)
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where Lp is the average length of the whole of the service connection (main to customer meter) in metres. The coefficient of 0.8 for Nc in Equation 1 has been reduced to 0.7 in equation (2), assuming approximately 4 metres per service connection, from main to property line. Equations (1) and (2) produce almost identical results for UARL.
Understandably, the existence of two different equations for UARL caused users some confusion, and in the 2nd Edition of the Performance Indicators Report (2007), the UARL formula was changed back to Equation (3), similar to Equation (1) but in which Lp is the average length of the service connection from the property line to the customer meter) in metres (see also Figure 5):
UARL (litres/service conn/day) = (18 x Lm/Nc + 0.8 + 0.025 x Lp) x P ………(3)
Figure 5: Diagram showing Property Line and Lp in UARL Equation (3)
Ns is also sometimes used interchangeably with Nc for number of service connections.
UARL equations (1), (2) and (3) can easily be converted to a wide variety of units (annual, daily, hourly; in m3 or litres; per km mains or per service connection). If UARL in m3/year is required for direct comparisons with CARL in m3/year from a European Water Balance, then equations (1) and (2) can be converted to:
UARL (m3/year) = (6.57 x Lm (km) + 0.292 x Nc + 9.13 x Lp (km)) x P ……..(1a)
UARL (m3/year) = (6.57 x Lm (km) + 0.256 x Nc + 9.13 x Lt (km)) x P ……..(2a)
where Lp in equation 1a is total length (km) of service connections, property line to meter, and Lt in equation 2a is total length (km) of service connections, main to meter
The UARL formula was originally developed for comparing performance of whole Utilities. In 1999, international testing on 27 systems in 18 countries identified only one system (in Netherlands) with an ILI less than 1.0 (0.7), with an average pressure of 35 metres, where almost all leaks appeared to surface, and there was no need for active leakage control.
Since 1999, the UARL formula has proved to be robust in predicting ‘how low could you go’ with Real Losses in best-performing Utilities. Internationally, comparatively few Utilities have been able to achieve Real Losses equal to their predicted UARL (ILI close to 1.0) except in special circumstances (e.g. Netherlands ILI 0.7) which fall outside the original assumptions and the current limits of application of the UARL formula, see Section 2.4.
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2.3 UARL in Litres/connection/day and m3/km mains/day
For systems where customer meters are located at the property line (Lp=0 metres per service connection). , the influence of density of connections and average pressure is shown in Fig. 6 (UARL in litres/conn/day) and Fig. 7 (UARL in m3/km mains/day). Similar graphs can be created for any other value of Lp.
Figures 6 and 7 clearly show that it is not realistic to expect all Utilities to achieve the same technical real losses management performance on a ‘per service connection’ or ‘per km of mains’ basis. Each system has its own specific UARL which, for different combinations of density of connections and pressure, can vary between 92 and 23 litres/connection/day (Figure 6) or between 0.5 and 5.5 m3/km/day (Figure 7). So these performance indicators are not recommended for making technical performance comparisons between systems.
Figure 6: UARL in litres/connection/day, for customer meters at property line
At any specified pressure, UARL in litres/connection/day is more uniform than UARL in m3/km mains/day at connection densities greater than around 40 per km. Conversely, as connection densities fall below around 40 per km, UARL in litres/conn./day starts to increase quite rapidly, while UARL in m3/km/day reduces quite rapidly.
However, losses per connection and losses per km are both excellent PIs for recording and monitoring changes in leakage within any individual system. This is because the key infrastructure parameters that influence UARL are almost fixed for any individual system; the density of connections and meter location (relative to property line) are not likely to vary much even if the system grows in size over a period of years.
In any individual system with a known density of connections and meter location, changes in actual leakage will plot as points on a vertical line drawn through that density of connections on the X-axis (red dashed arrows in Figure 6 and Figure 7). The influence of system pressure on UARL can then be clearly seen, and annual changes in leakage (in litres/connection/day or m3/km mains/day), can easily be tracked.
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Figure 7: UARL in m3/km mains/day, for customer meters at property line
The original IWA Task Force recommendation to use ‘per connection’ if ≥ 20 conns/km, and ‘per km’ if < 20 conns/km, arose because more than half of the UARL occurs on connections when connection density exceeds 20 per km (as seen in Fig 7), and this is a useful Guideline to follow. But as 20 to 40 conns per km is a tricky region, either option is reasonable, so preference should be given to whichever of the two PIs has been used traditionally in any particular country.
However, %s based on any definition of System Input Volume (including Treated Water Supplied) should definitely not be used for tracking progress in NRW or real loss management within individual systems, for reasons explained in Section 1.6, Figure 4 and Tables 3 and 4.
2.4 Range of Application of UARL equation
UARL and ILI were originally developed for application to whole Utilities with mixed pipe materials, using the Background and Bursts Estimates concept for component analysis of real losses, and the FAVAD concept for pressure:leak flow rate relationships. Components for background leakage, reported and unreported leaks and bursts are based on clear and auditable assumptions for frequencies, flow rates and durations of leaks, at 50 metres pressure. These are shown in Table 1 of Lambert (2009).
Lower limits for density of connections, average pressure and system size have always been recommended for application of the UARL formula. Table 5 (from Lambert, 2009) shows changes in these limits between 1999 and 2009 which reflect the increasing international use of ILI and Snapshot ILI (derived from night flows) for small systems and DMAs. The graph referred to in Table 5 is Figure 2 in Lambert (2009), which can be obtained through the weblink
http://173.254.28.127/~leakssui/wp-content/uploads/2012/11/2009_LambertWaterlossCapetown-2009J.pdf
- 12 -
Table 5: Changes in limits of application of UARL formula, 1999 to 2009
Parameter Limits Lambert et al, AQUA
Lambert & McKenzie
Liemberger & McKenzie
Lambert
1999 2001 2005 2009
Density of Connections/km
Minimum 20 20 Removed No lower limit
Maximum 100 Removed No upper limit
Average Pressures (m)
Minimum 20 25 25 See Graph
Maximum See Graph
System Size Minimum Not stated Nc > 5000 Nc > 3000 Nc + 20 x Lm > 3000
Source: Lambert (2009)
Table 6, from the same paper shows the summarised components of the UARL formula at 50 metres pressure, together with the FAVAD N1 exponents which should be used to predict how leak flow rates of UARL components vary with average pressure.
Table 6: Components of Unavoidable Annual Real Losses at 50m pressure
Source: Lambert (2009)
Since 1999, UARL and ILI have been calculated for thousands of systems internationally. At first, most practitioners considered that UARL and an ILI of 1 were simply not achievable, but at least 50 of the best-performing medium and large Utilities internationally are now achieving ILIs close to 1.
Most Utilities in Europe with more than several thousand connections, and average pressures of 35 metres or more, would find it extremely challenging to try to achieve and maintain an ILI close to 1.0. Practical guidance developed in Australia for WSAA (2009) is to check any calculated ILI less than 0.7, and it is remarkable how often this simple quality control quickly identifies one or more of the following data problems:
Systematic and random errors in the Water Balance affect assessed volumes of NRW and Real Losses (see Table 1), and all related performance indicators (not only ILI):
o Bulk metering errors (under-registration of true volume) o Meter Lag errors (bulk and customer meter readings not synchronised) o Billing systems designed for revenue collection, not technical data retrieval o Over-estimates of unmetered consumption o At low leakage, confidence limits for Real Losses are usually at least +/- 10% o Confidence limits widen if there are significant volumes of water exported, or
high estimates of apparent losses (especially with customer storage tanks)
- 13 -
Errors associated with other parameters used to calculate UARL o Number of service connections over-estimated by using number of properties
(higher) as a substitute figure o Average pressure not systematically calculated, and over-estimated o assumptions used in UARL are not all valid for system under consideration
In systems with high burst frequencies, the standard UARL formula can be used for
smaller systems than those in Table 3, as ILIs will be greater than 1.0. However, when the Austrian OVGW adopted the ILI as the decisive PI for Real Losses (OVGW 63, 2009), significant numbers of very small Utilities (most with fewer than 3000 service connections and relatively new infrastructure) began to report ILIs less than 0.7.
A research study (Lambert and Koelbl, 2014) is currently investigating how component analysis, FAVAD and the latest prediction methods for pressure:bursts relationships might be used to predict UARL for small systems (equivalent to District Metered Areas) with good infrastructure. This may result in a further update of Table 4, or possibly a practical prediction method in which corrections are applied to the standard UARL formula depending upon combinations of circumstances in the small systems (notably average pressure, pipe materials and number of service connections).
3. IWA Performance Indicators for NRW and its Components
3.1 Water Loss Task Force & Performance Indicators Report, 1st Ed. (2000)
The 1st Edition of ‘Performance Indicators for Water Supply Systems’ (Alegre et al, 2000), proposed 133 Performance Indicators covering a wide range of Water Utility functions. Table 7 shows the small subset of NRW and Water Loss Performance Indicators, developed by the 1st IWA Water Loss Task Force (Lambert et al, 1999), which were included in the 1st Edition of the PIs Report.
Table 7: Recommended performance Indicators, for different purposes (IWA, 2000)
Indicator PI Group Recommended units Comments
NRW by volume Financial (Fi) Volume of non-revenue water
as % of system input volume
Can be calculated from simple water
balance.
NRW by cost Financial (Fi)
Value of non-revenue water
as % of annual cost of
running system
Allows separate values /m3 for components
of non-revenue water.
Water losses Operational
(Op)
m3/service connection/year Same units as authorised consumption.
Apparent losses Operational
(Op)
m3/service connection/year Same units as authorised consumption.
Real losses Operational
(Op)
litres/service connection/day (1) when system is pressurised
Allows for intermittent supply situations.
Use ‘per km’ if less than 20 connections/km
Infrastructure
Leakage Index ILI
Operational
(Op)
Ratio of real losses to
technical achievable low-level
annual real losses
Technical achievable low-level annual real
losses equal the best estimate of UARL
Includes system-specific allowance for
connection density, customer meter location
on service, and current average pressure.
Inefficiency of use
of water resources
Water
Resources (WR) Real losses as % of system
input volume
Unsuitable for assessing efficiency of
management of distribution systems.
Note: Each indicator was also assigned a Level of Importance (L1 to L3), and a Code (e.g. Op23), but these are not shown in Table 7, as Levels of Importance were removed and some of the Code numbers were changed in the 2nd Edition (Alegre et al, 2007).
- 14 -
3.2 Performance Indicators Report, 2nd Edition (2006)
Table 8 summarises the NRW and Water Loss Performance Indicators recommended in the 2nd Edition of the PIs Manual, after testing by the IWA Performance Indicators Task Force with 70 volunteer Undertakings in Europe, Asia-Pacific, Africa and South America.
The IWA Water Loss Task Force, which had been assisting several other countries (Australian WSAA, New Zealand NZWWA, North America AWWA) and numerous Utilities to implement the 1st Edition IWA Water Balance and Performance indicators, had no significant input to the 2nd Edition. Consequently some differences of emphasis began to arise as to what were considered to be ‘best practice’ IWA Water Loss Performance Indicators (Liemberger et al, 2007). In North America, Fanner et al (2007) identified that some Water Loss PIs were more suitable for target setting and monitoring of progress within individual Utilities, whilst others were more suitable for comparing technical water loss management performance between Utilities with different key characteristics.
Table 8: Recommended performance Indicators, 2nd
Edition (2006), IWA Performance Indicators Group
Indicator PI Group Recommended units Comments in 2nd Edition
NRW by volume
(%)
Economic and
Financial (Fi46)
Percentage of the system input
volume that corresponds to non-
revenue water
Most popular and easy way to assess
water losses (from an Economic and
Financial viewpoint)
NRW by cost (%) Economic and
Financial (Fi47)
Percentage of the system input
volume that corresponds to NRW
Innovative indicator, but not easy to
assess for sub-systems or DMAs
Water losses Operational
(Op23)
m3/service connection/year Less relevant than specific indicators
for apparent and real losses
Apparent losses Operational
(Op25)
Percentage of ‘Water Supplied’
corresponding to apparent losses.
Adequate for distribution systems.
Changed from m3/conn/yr in 1st Ed.
Apparent losses Operational
(Op26)
Percentage of ‘System Input
Volume’ corresponding to
apparent losses.
Adequate for bulk supply systems.
Changed from m3/conn/yr in 1st Ed.
Real losses Operational
(Op27)
litres/service connection/day
when system is pressurised
A much better operational PI than the
traditional % indicator. Density of
connections is an important factor
affecting leakage volume.
Real losses Operational
(Op28)
litres/km/day when system is
pressurised
Use where density of connections is
very low, and mains length becomes a
dominating explanatory factor.
Infrastructure
Leakage Index ILI
Operational
(Op29)
Ratio between the actual real
losses and an estimate of the
minimum real losses that could be
technically achieved for the
system operating pressure,
average service connection length
and service connection density
Op29 aims to remove other factors not
related to the physical condition of the
network that significantly affect the
leakage volume.
Technical achievable low-level annual
real losses are equal to the best estimate
of so called Unavoidable Average Real
Losses, UARL.
Inefficiency of use
of water resources
(%)
Water
Resources
(WR1)
Percentage of water that enters
the system and is lost by leakage
and overflows up to the point of
customer metering
The environmental indicator of water
losses, but not appropriate to assess
infrastructure condition or economic
water losses; the operational or
economic water losses indicators should
be used for these.
Note: both the 1st
and 2nd
Editions of the PIs Manual clearly stated that %s of System Input Volume should not be used for assessing the efficiency of management of distribution systems, infrastructure condition or real losses. Unfortunately, some users who claim to follow the IWA methodology continue to ignore this important recommendation.
- 15 -
3.3 IWA Performance and Benchmarking Assessment Specialist Group Initiatives
In 2008 a new IWA benchmarking initiative (Cabrera, 2008) split benchmarking into two:
Metric benchmarking: compares PIs of utilities with different characteristics
Process benchmarking: identify and adapt best practices to improve performance
In 2010 the IWA Benchmarking and Performance Assessment Group (Cabrera et al, 2010) implemented an evolution which replaced ‘Metric’ and ‘Process’ Benchmarking with Performance Assessment and Performance Improvement, see Figure 8.
Source, Cabrera et al 2010, with overlay linking to former ‘Metric’ and ‘Process’
Figure 8: The new IWA Benchmarking Framework :
These developments greatly simplified the selection of individual NRW and Water Loss Performance Indicators which are most appropriate for either:
Target setting and monitoring progress in individual systems and sub-systems, or
Technical performance comparisons between systems with/without customer storage tanks, and having different connection densities, meter locations and operating pressures
3.4 Target Setting and Monitoring within Individual Systems and Sub-systems
Table 9 shows Performance Indicators (and variables and context information) which are currently considered by the authors of this paper as being the most appropriate for practical target setting and monitoring of progress in the management of NRW components for individual systems and sub-systems within an individual Utility.
Within each individual system, connection density and customer meter location on the service connection are likely to be reasonably consistent over time. Speed and quality of
METRIC PROCESS
- 16 -
repairs, active leakage control and pressure management are the main short to medium term options used to manage real losses.
Table 9: The Authors’ recommended PIs, variables and context data for target setting and annual progress monitoring in management of NRW components of individual distribution systems
Key points relevant to Table 9 are:
Always use ‘Potable Water Supplied’ as ‘System Input Volume’ for distribution systems, or mixed transmission and distribution systems; any water exported will then have been separately accounted for, and will not compromise the technical PIs for the system under review (see Figures 2 and 3)
Preferred units: in each EC country, familiarity with traditional units (volume per year, per day, per hour; losses per km, per service connection, per billed property) reduces errors and increases acceptability; if there is no traditional measure, ‘per service connection’ would be the usual choice based on ‘density of connections’ guidance
Total Consumption: showing this simplifies direct comparison with Real Losses, and can be used to show if necessary (Fig. 4) that %s distort perceptions of performance
UAC and Apparent Losses as separate %s of Billed Metered Consumption (BMC): a simple practical indicator of effectiveness of customer metering and billing. Expect low %s for direct pressure systems, higher %s where there are customer storage tanks supplied by gravity.
Leak Location + Repair times, for mains and services separately, are key practical indicators; there is no point in finding leaks if they are not fixed quickly and effectively
Low Medium/high
m3/year m3/km/yr m3/conn/yr PWS excludes all Water Exported
Metered BMC m3/year m3/km/yr m3/conn/yr
Unmetered BUC m3/year m3/km/yr m3/conn/yr
m3/year m3/km/yr m3/conn/yr
m3/year m3/km/yr m3/conn/yr
m3/year m3/km/yr m3/conn/yr
m3/year m3/km/yr m3/conn/yr
m3/year m3/km/yr m3/conn/yr
m3/year % of BMC % of BMC
m3/year m3/km/yr m3/conn/yr
m3/year m3/km/yr m3/conn/yr
Use Snapshot ILI for night flows
Mains leaks
Service leaks
No/year
No/year
% subject to ALC interventions
m3/year For ALC Economic Intervention
% subject to pressure management
When system pressurised
Only if intermittent supply
Countries with strong traditional
practice of using per km mains, per
service connection, or per property,
or per day (not per year) should
continue to use that measure, for
familiarity and continuity. Or decide
based on average connection
density for the Utility's systems.
Use of %s is NOT recommended
These measures help to set targets
and interpret performance in the
management of NRW components
% of time system is pressurised % of year
Number per 100 km/yrLeaks on Mains
Average pressure metres
Rate of Rise of Unreported Leakage m3 per year in 1 year
% of total mains lengthActive Pressure Management
% of total mains length in year
UAC + Apparent Losses AL
Total Consumption TC = PWS -RL
Component of Water Balance, and
additional Variables and Context data for
short to medium term real loss
management
Apparent Losses AL
Real Losses RL
Unavoidable Annual Real Losses UARL
Infrastructure Leakage Index = RL/UARL
Billed Authorised
Consumption BAC
Non – Revenue Water NRW
Unbilled Authorised Consumption UAC
Parameter used as PI
Connections/km mains
Potable Water Supplied PWS
Active Leakage Control Interventions
Recommended Water Loss PIs for Target Setting and Monitoring Progress in an Individual Distribution System
Comments
Annual ILI and/or Snapshot ILI
Economic Annual Real Losses EARL
Leaks on Service Connections Number per 1000 conns/yr
Days or Hours
Reported, and unreported leaks
found by ALC. Exclude small leaks
on valves, meters and stop taps.
Location + Repair
time Days
Average time from awareness of
individual leaks to repair/shutoff
Prime
data
units
- 17 -
Frequency of leaks on mains and services: always show these separately (as well as combined, per km, if that is traditional practice) to highlight which part of infrastructure has problems. Separate mains and services figures are needed for predictions of burst reduction from pressure management
Active Leakage Control: ALC installations are only effective if interventions are frequent enough; rate of rise of unreported leakage allows economic frequency of intervention to be quickly assessed, depending on marginal cost of water and intervention cost
Pressure management:: reduction of excess pressures and control over pressure is now recognised as the fundamental foundation of effective real loss management, influencing leak flow rates, leak frequency, rate of rise, asset life etc.
3.5 Technical Performance Comparisons of NRW Components between Systems with different key characteristics
Table 9 shows Performance Indicators (and variables and context information) which are currently considered by the authors of this paper as being most appropriate for technical performance comparisons of the management of NRW components, between different systems with different key characteristics (comparing apples with pears).
The European Commission’s Water Blueprint (2013), does not advocate a ‘one-size-fits-all’ straitjacket but proposes a tool box that member states can use to improve water management. This leaves each country able to choose its own performance measures for water loss management. Provided that potentially misleading %s of System Input Volume are not used, this approach has the benefit of continuity and familiarity for using m3/km mains per year, litres/connection/day or litres/property/day to set targets and track performance of individual systems in different countries. However, none of these measures are suitable for rational comparisons of technical performance between Utilities.
Superficial comparisons of NRW and Real Losses using %s of System Input Volume
systematically favour large Utilities with high consumption (see Fig 4) and direct pressure, and numerous different % figures can be quoted depending upon which definition of System Input Volume is used (see Figure 3 and Table 2). Also, changes in NRW and Real Losses expressed as %s of SIV only represent true % changes if consumption is constant. However, with increasing unit charges for water and active measures to reduce consumption, European Utilities with low Real Losses have inevitably experienced year-on-year increases in % NRW and Real Losses, as true % reductions in total consumption have been reducing faster that true % reductions in NRW and Real Losses (see Tables 2 and 3). For comparisons of technical management performance of NRW and its components between Utility distribution systems in Europe, the authors make the following recommendations:
No suitable single technical NRW Performance Indicator is yet available, due to significant differences in apparent losses between systems with and without roof tanks
Technical management comparisons should be based on the three principal components of NRW: Unbilled Authorised Consumption, Apparent Losses, Real Losses
Unbilled Authorised Consumption and components of Apparent Losses represent treated water which is used but not paid for, so compare these NRW components directly to the % of distribution system metered consumption which has been used and paid for
- 18 -
o express UAC as % of Billed Metered Authorised Consumption (excluding Water Exported)
o This will normally be less than 2% for direct pressure systems with reliable metering, but more than 5% for systems with roof tanks supplied by gravity (see Appendix B)
Real Losses represent treated water that has been lost from distribution systems by leakage and overflows; the part of this in excess of the Technical Minimum Real Losses (UARL) represents a potentially recoverable water resource
o calculate Unavoidable Annual Real Losses UARL at current average pressure
o express Current Annual Real Losses (CARL) as the ratio CARL/UARL = ILI
o ILI is likely to can range from close to 1.0 for some systems in High Income Countries to as much as 30 for some systems in low income countries
o Use World Bank Institute Banding System to broadly classify ILI performance, and identify appropriate priority actions for individual systems
Use Context Information in Table 9 and Water Balance, together with items below, for further interpretation of relative performance and management opportunities
o Number of billed properties (residential and non-residential) and populaltion
o Infrastructure information:(mains length, number of service connections, average length of service connection, main to meter.
o Average pressure (metres)
4. An updated European set of ILIs
4.1 Previous ILI data for Europe: 1999 to 2005
Of the 27 system that were originally used to test the UARL equation and the ILI concept (Lambert et al 1999), 20 were from European countries (Denmark, England, Finland, France, Germany, Gibraltar, Greece, Iceland, Malta, Netherlands, Northern Ireland, Switzerland, Spain, Sweden and Wales). Many of these were from large cities.
Some ILIs for Utilities in Cyprus and Italy were then added to most of the 1999 ILIs to
produce a 2005 European set of 22 ILIs from 12 European Countries (Figure 9).
The Banding system shown at the right hand side of Figure 9 was introduced by the World Bank Institute into its NRW Training Modules in 2005. It uses a matrix for assessing Real Losses management performance, based on real losses in volume/service connection/day for a range of average operating pressures, and classified into Bands A to D. The targets assume that customer meters are located at the property line boundary, with an average connection density of around 40 per km mains.
Bands A to D in the WBI target matrix were in practice calculated from an equivalent range of ILIs, which can be applied to a wider range of connection densities and customer meter locations. Band limits in terms of ILIs, general descriptions of each Band, and appropriate recommended actions are shown in Tables 10 and 11.
Low and Middle Income (LAMIC) countries receive double the ILI range limits
compared to Higher Income Countries (HIC), based on whether average per capita income is above or below $12k per person per year - see http://www.iwahq.org/contentsuite/upload/iwa/all/2012%20HIC-LIC%20Country%20Listing%281%29.pdf
- 19 -
Figure 9: European data set of 22 ILIs from 12 Countries, 2005
Table 10: WBI General Descriptions of Real Loss Performance Categories (2005)
Table 11: Recommendations for Appropriate Actions for WBI Bands (2005)
. Yes
Identify options for improved maintenance Yes Yes
Yes
Yes Yes
YesDeal with deficiencies in manpower,
training and communications
YesReview burst frequencies
Yes
Yes
Fundamental peer review of all activities
5-year plan to achieve next lowest band
D
Assess Economic Leakage Level
CWBI Recommendations for BANDS A
Yes
Yes
Yes
Investigate speed and quality of repairs
Yes Yes Yes
Yes
Yes
Check economic intervention frequency
Yes
Review asset management policy
Introduce/improve active leakage control Yes Yes
Yes
Yes
B
Yes
Yes
Investigate pressure management options
- 20 -
By 2010, many Utilities internationally had achieved ILIs close to 1.0. In Australia during the multi-year millennium drought so many Utilities achieved ILIs in Band A that it was considered appropriate to split into Bands A1 and A2. The splitting of WBI higher Bands into B1, B2, C1, C2, D1, D2 has also been found to be helpful in a LAMIC country (Malaysia) outside Europe, as it gives incentive for Utilities to celebrate achievements in moving from, say C2 to C1 (which otherwise represents a very long journey, reducing from the top of C (ILI = 8) to the bottom of C (ILI < 4).
Table 11: Sub-Division of World Bank Institute Bands (2010)
4.2 2014 Update of European ILI data set.
Utility performance in NRW and Real Losses management is of course an extremely sensitive issue in most countries, and while some Utilities (often, but not always, those with good performance) accept the challenges of openness, others are willing to participate in comparison exercises using newer improved PIs only if their anonymity can be assured, so that they might identify previously unsuspected strengths or weaknesses in performance which were concealed by the previous use of inappropriate PIs (notably %s!). The authors recognise and understand these concerns.
ILI data from several countries, both European and International, is now published, but
is not yet currently available in one easily accessible location, free of charge to anyone interested. Accordingly, one of the authors has now created an updated set of 71 ILIs from 12 High Income European Countries (Figure 10) and 12 Utilities in 3 Low/Middle Income European Countries (Figure 11), using both attributed and anonymous Utility data. The ILI data for High Income countries has been quality controlled, to a greater or lesser extent, by National organisations or experienced IWA Water Loss Specialist Group experts.
From early April 2014, this ILI data set, together with quality controlled ILI data sets
from other Countries and World regions (Australia (NWC), Balkans, Canada, North America (AWWA) ……) will be freely available for downloading from http://www.leakssuite.com/global-ilis/ .
A brief but only limited review of additional relevant information on Water Balances and performance indicators currently used in the European Countries which provided ILI data is provided in Appendix B. The authors would welcome any feedback on errors or omissions in these reviews, as this is important context information which could also be located, updated and made freely available to European and International leakage
ILI range ILI range
Less than 3 < 1.5 A1
3 to < 4 1.5 to < 2 A2
4 to < 6 2 to < 3 B1
6 to < 8 3 to < 4 B2
8 to < 12 4 to < 6 C1
12 to < 16 6 to < 8 C2
16 to < 24 8 to <12 D1
24 or more 12 or more D2
High
Income
CountriesBAND
General description of Real Loss Management Performance
Categories
(WBI Band limits for ILI for Low and Middle Income Countries are double those for
High Income Countries)
Very inefficient use of resources; leakage reduction programs
imperative and high priority
Further loss reduction may be uneconomic unless there are
shortages; careful analysis needed to identify cost-effective
improvement
Potential for marked improvements; consider pressure
management, better active leakage control practices, and better
network maintenance
Poor leakage record; tolerable only if water is plentiful and cheap;
even then, analyze level and nature of leakage and intensify
leakage reduction efforts
Low and
Middle Income
Countries
- 21 -
specialists through the website. Any further contributions of good quality ILIs and associated information from any European country will of course be welcomed.
Figure 10: ILIs for 71 Water Utilities in 12 European High Income Countries
Austria, Belgium, Croatia, Cyprus, England/Wales, France, Germany, Italy, Malta, Portugal, Spain, Switzerland
Figure 11 shows ILI data for 12 Utilities in 3 European ‘LAMIC’ Countries; the WBI Band limits for ‘LAMIC’ countries are twice the Band Limits for Higher Income Countries.
Figure 11: ILIs for 12 Water Utilities in 3 European Low Income Countries
Bosnia, Bulgaria, Serbia
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
16.0
17.0
18.0
19.0
20.0A
ust
ria
(A
n)
Ge
rma
ny
Lan
d…
Cro
ati
a (A
n)
Be
lgiu
m D
eWg
A
Ge
rma
ny
Lan
d 2
Cro
ati
a (A
n)
Ge
rma
ny
Lan
d 3
Au
stri
a (
An
)
Ge
rma
ny
Lan
d 4
Au
stri
a (
An
)
Eng
/Wal
es
(An
)
Eng
/Wal
es
(An
)
Be
lgiu
m D
eWg_
B
Ita
ly I
REN
A
Be
lgiu
m D
eWg
C
Eng
/Wal
es
(An
)
Eng
/Wal
es
(An
)
Cro
ati
a (A
n)
Eng
/Wal
es
(An
)
Eng
/Wal
es
(An
)
Go
zo (
WSC
)
Be
lgiu
m D
eWg_
D
Fran
ce (A
n)
Fran
ce (A
n)
Eng
/Wal
es
(An
)
Cro
ati
a (A
n)
Ita
ly (
An
)
Eng
/Wal
es
(An
)
Mal
ta (
WS
C)
Ita
ly I
REN
B
Ita
ly I
REN
C
Cro
ati
a (A
n)
Fran
ce (A
n)
Fran
ce (A
n)
Eng
/Wal
es
(An
)
Ita
ly I
REN
D
Ita
ly I
REN
E
Spa
in (
An
)
Ita
ly I
REN
F
Au
stri
a (
An
)
Cyp
rus
(An
)
Ita
ly I
REN
G
Ita
ly I
REN
H
Ita
ly I
REN
I
Ita
ly I
REN
J
Au
stri
a (
An
)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Po
rtu
gal (
An
)
Cyp
rus
(An
)
Ita
ly I
REN
K
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Au
stri
a (
An
)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Ita
ly I
REN
L
Cro
ati
a (A
n)
Au
stri
a (
An
)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Ita
ly I
REN
M
Ita
ly I
REN
N
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Cro
ati
a (A
n)
Infr
astr
uct
ure
Lea
kage
Ind
ex
ILIs for 71 Water Utilities in 12 European High Income Countries , circa 2012 : data set at 28 Feb 2014
WBI Band A
WBI Band B
WBI Band
C
WBI Band
D
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
16.0
17.0
18.0
19.0
20.0
21.0
Bosnia HG(An)
Serbia (An) Bosnia HG(An)
Serbia (An) Serbia (An) Bosnia HG(An)
Serbia (An) Bulgaria (An) Serbia (An) Serbia (An) Bosnia HG Serbia (An)
Infr
ast
ruct
ure
Le
aka
ge
Ind
ex
ILIs for 12 Water Utilities in 3 European Low/Middle Income Countries, circa 2012: Data set as at 28 Feb 2014
WBI Band A1
WBI Band B1
WBI Band
C1
WBI Band
D1 16<ILI <32
WBI Band A2
WBI Band B2
WBI Band
C2
- 22 -
Some quality control has been applied to the LAMIC Water Balances and PI calculations, but it is usually unrealistic to expect a high degree of reliability, without major investments in bulk and customer metering and billing systems.
However, it is recognised that greater consistency of all real losses calculations –
particularly for low leakage systems - could be achieved by the introduction of Europe-wide guidelines relating to maximum default values for some assessed components of Water Balance calculations, with Utilities being required to justify higher values based on Utility-specific data (see Appendix A).
Acknowledgements
The authors wish to thank the many Water Loss Specialist Group members who have contributed to the development and implementation of the IWA Best Practice Performance Indicators; the many Utilities who have contributed ILI data to the European data set; and all those practitioners who seek to continue to improve international understanding and best practice for measurement and management of Non-Revenue Water and its components.
Copyright and free access
The authors of this paper are individually and collectively committed to the free dissemination of information in this paper to anyone who wishes to access it, in accordance with the original aspirations of the IWA Water Loss Task Force. Accordingly copyright will not be assigned to any third party. Copies of this paper may be downloaded from the Leakssuite website http://www.leakssuite.com/outreach/free-papers/ . Please acknowledge the source if you reproduce any part of the paper.
,
References
Lambert A.0, Brown TG, Takizawa M, Weimer D (1999). A review of performance indicators for real losses from water supply systems. J Water SRT – Aqua Vol.48, No.6, pp. 227-237, 1999.
Hirner, W and Lambert, A. (2000) Losses from Water Supply Systems: Standard Terminology and
Recommended Performance Measures. IWA Blue Pages, October 2000 Alegre H, Hirner W, Baptisata J.M., Parena R (2000). Performance Indicators for Water Supply Systems. IWA
Publishing ‘Manuals of Best Practice’ series, ISBN 1 900222 272, July 2000 Alegre H, et al. (2006). Performance Indicators for Water Supply Services, Second Edition. IWA Publishing
‘Manuals of Best Practice’ series, ISBN 1843390515, July 2000 Fanner P.V., et al (2007). Leakage Management Technologies. AWWARF Project Report 2928 Cabrera E Jr, (2008). ‘Benchmarking in the Water Industry: a mature approach. Water 21, August 2008, p. 64 Liemberger et al, (2007). Water Loss Performance Indicators. IWA International Specialised Conference
‘Water Loss 2007’, Bucharest, September 2007. Conference Proceedings (3 vols) ISBN 978-973-7681-24-9; Session B2 of Volume 1
http://173.254.28.127/~leakssui/wp-content/uploads/2012/11/2007_LiembergerBrothers-et-al-IWABucharest-2007T.pdf
Australian Government, National Water Commission: National Performance Report, 2010-11, Urban Water
Utilities. Lambert, A (2009) Ten Years Experience in using the UARL formula to calculate Infrastructure Leakage
Index. IWA Specialist Conference ‘Waterloss 2009’,Cape Town, South Africa, March 2009 http://173.254.28.127/~leakssui/wp-content/uploads/2012/11/2009_LambertWaterlossCapetown-2009J.pdf
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Austrian Association for Gas and Water (2009). Guideline W63 ‘Water losses in water supply systems’ OVGW W63 September 2009
Cabrera et al (2010): Forget ‘metric’ and ‘process’, benchmarking is being reborn: the new IWA benchmarking
framework. IWa Water Utility 21, December 2010., Tennhardt L (2012). Realistic Balance of Water Losses and the Practical Use of Water Loss Indexes. Energie: Wasser-Praxis, 10/2012, pages 34 to 41
Water Loss Detectives, 2012: ‘Operational Efficiencies from permanent leakage monitoring’. Article by F
Tantsky, Albstadtwerke. May 2012 Issue, of magazine published by AQUATIM, Romania ([email protected]).
Aqel S (2013) NRW Comparison equations (Power Point Presentation): personal correpsondence A Water Blueprint for Europe (2013). European Commission, Europa http://ec.europa.eu/environment/water/blueprint/pdf/brochure_en.pdf
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Appendix A:
Default s for Assessed Components of Non-Revenue Water in Water Balance Calculations
When calculating tCurrent Annual Real Losses through a Water Balance, a number of assumptions may be required regarding estimates of unmetered components of NRW. For Unbilled Authorised Consumption, Unauthorised Consumption and Customer Metering Inaccuracies, water utilities may elect to use the default values prescribed below, or determine the actual values for their operations. Should the latter be chosen the water utility would need to be able to satisfy an auditor that the input is not excessive. The defaults presented are currently considered by the authors to represent best practice for European conditions.
Note: default volumes to be calculated as simple % of metered consumption
If a water utility uses values greater than the above defaults, sufficient data should be provided to satisfy an auditor as to the accuracy of the values used. As a minimum, for under-registration of retail meters, the following must be provided:
A profile of the meter fleet, including age and type
The sampling regime used to determine accuracy The water utility should be consistent across reporting years in calculating its Current Annual Real Losses and, where appropriate, have supporting documentation to verify assumptions for the purpose of auditing.
0.5%
0.2%
Residential 2.0% of metered residential consumption
Non-residential 2.0% of metered non-residential consumption
Parameter Suggested Default
Unbilled Unmetered Authorised Consumption of Billed Authorised Metered Consumption
(excluding Water Exported)Unauthorised Consumption
Usually > 5% of metered consumption, influenced
by many factors. Assess on country by country basis.
Customer
Meter
Inaccuracies
Direct pressure
systems
Storage tanks
supplied by gravity
Residential and
Non-Residential
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Appendix B:
Brief Review of use of IWA Water Balance and KPIs in European Countries, as at March 2014
Note: the authors would welcome any feedback on errors or omissions in the following brief reviews.
Austria From 2003 to 2009, the Austrian OVGW used a slightly customised version of the IWA Standard Water Balance, but continued to recommend use of % of System Input volume and m3/km/hour as the preferred performance indicators for NRW and Real Losses. Following several years research into the application of the ILI within Austria, OVGW re-issued their W63 Guideline in 2009 with the addition of ILI as the decisive real losses performance indicator, and also included litres/service connection/day.
In the interests of international consistency, W63 also adopted the WBI Band Limits A to D (for HICs), but with slightly different descriptions for each Class, as shown in the Table below; these can be compared with the WBI category descriptions in Table 11 of the Paper. Because of topography and generally high quality of infrastructure in Austria, pressure management is not as widely practised for management of Real Losses as in other European countries.
ILI Class Evaluation
< 2 A very little till little water losses, further reduction could be counter productive; further analysis before any action should be executed.
2 to 4 B medium water losses, potential for noticeable loss reduction existing, improvement in leakage control and infrastructure management.
4 to 8 C high water losses, volume and reasons for losses have to be analyzed and attempts to reduce the volume of lost water has to be intensified.
>8 D very high water losses, volume and reasons for losses have to be analyzed, distinct leakage control and leakage reduction has to be executed immediately.
Table: Descriptions of Austrian OVGW categories Performance Bands A to D, from OVGW 63 (2009)
Austria has around 5500 Water Utilities, many with fewer than 3000 service connections, which is the 2009 international lower guideline limit for ILI calculations (see Table 5 of paper). During the OVGW trials to evaluate ILI, ILIs less than 1.0 were reported from the smaller systems. Some of these were later identified as having systematic water balance errors (often unmetered public fountains) but it’s clear that ILIs less than 1 are occurring in some small Austrian systems. A current research study (Lambert and Koelbl, 2014), applying component analysis and the latest pressure:bursts prediction methods to check if low ILIs in small systems are consistent with UARL concepts, is now in an advanced stage. This is likely to result in a further update of Table 4.
Austrian OVGW now has a national unpublished data set of more than 100 ILIs. The
data set of 7 Austrian ILIs in Figure 10 of the paper were taken from a study by Koelbl (2007), and appear to roughly represent the range (0.6 to 6) of ILIs in Austrian systems with more than 3000 service connections, although it is expected that many of the smaller Austrian systems will have ILIs close to or somewhat below 1.0. Bosnia and Herzgovina: Water utilities in Bosnia and Herzegovina are still struggling with numerous problems related with political and economic issues. Despite existing problems some Utilities have shown progress, with international recognition of achieved results by Gracanica water utility. A bright point is the activity of the Hydro-Engineering Institute Sarajevo which regularly uses the IWA methodology and PIs in water loss control
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projects. Jurica Kovac has collated ILI data from 4 Utilities as Bosnia’s contribution to the 2014 to the LAMIC European data set. Belgium : most Utilities use the IWA Water Balance and technical measures of the IWA practical approach to NRW management such as sectorisation, active leakage control and pressure management. However, contrary to IWA best practice recommendations, %s by volume are still predominantly used for Real Losses comparisons and target setting.
The Belgian contributions to the ILI data are from De Watergroep, a large Utility serving numerous rural communities in Flanders (2.8 million customers, 1.2 million connections, 31000 km mains length). This is an excellent example of how use of %s by volume can adversely distort the true perception of real losses management performance of Utilities with low consumption. With a high marginal price of water and one of the lowest consumption rates in Europe (300 litres/service connection/day), NRW of 20% actually hides a very creditable average ILI of 1.55, in WBI Band A. ILIs for De Watergroep’s 4 large sub-systems are included in Figure 10. Bulgaria adopted the IWA Water Balance in 2005, but not the IWA performance indicators. However, some Water Companies have started to calculate ILIs using free Water Balance and PI software translated into Bulgarian language (CheckCalcs or EasyCalcs), and are reporting these at Bulgarian Water Association annual National Conferences. Although Bulgarian legislation requires water balances to be carried out, at present system input and output are mostly not being measured, but estimated.
Changes in the political situation lead to changes in Utilities’ management, and systematic implementation of IWA practical know-how is not easy under these circumstances. Probably some years will pass before the Regulator, the Ministry of Regional Development (owner of the water companies), and the water companies begin to move from using more meaningful performance indicators than %s, and improve their efficiency.
However, one active city (Dryanovo) is reporting success in using ILI to monitor improvements in real loss management in small Zones (70 to 200 services, 350 to 1000 service connections) with high burst frequencies. Dr Atanas Paskalev of AQUApartner arranged for an English translation of a paper by Indzhov et al (2013), which showed recently reported Zone ILIs are in the range 2.7 to 33, with weighted system average ILI 13.5; this is Bulgaria’s contribution to the LAMIC data set. Dryanovo is a good example to show that the lower limits of application of ILI need not be applied to systems with poor infrastructure, high burst frequencies, high background leakage, and relatively high ILIs.
Croatia has many relatively small distribution systems dedicated to separate municipalities, with one large Utility (Zagreb). Since 2000, there has been a slow but definitive rise in understanding of water loss importance in the region. In parallel with that, many utilities have accepted the IWA practical approach as beneficial and numerous cases have shown that water loss issues can be tackled successfully with relatively simple and fast implemention programs and strategies based on the IWA practical approach.
A major Conference in 2007 introduced the IWA approach, supported by free IWA Water Balance and PI software in Croatian language. In 2009 the Association of Water Utilities encouraged water utilities to start using the IWA methodology, and from July 2010 Croatia introduced new legislation (planned to be implemented in 2015) which included performance indicators based upon IWA Water Balance and Performance Indicators, and concessions payments for the water extracted by the water utilities, with 4 price categories calculated using a water losses coefficient based on WBI bands and the ILI. However,
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following changes in senior personnel at the Government Agency Croation Waters, a uniform high fixed unit charge has been implemented which should stimulate more leakage control by all Utilities.
The Croatian government plan to unite 150 small and mid-size utilities into 21 large
utilities, starting in 2014. Another interesting development is a dedicated German/Croatian Training and Competence Centre for water utilities established in the town of Karlovac, where pilot courses, including Water Loss topics based on IWA best practice methodology, have been implemented. In 2014 this Training Centre initiative has grown to expand its influence on the whole region. Jurica Kovac has collated ILI data from 23 Utilities as Croatia’s contribution to the 2014 HIC European data set.
Cyprus almost all customers have roof storage tanks on this Mediterranean island. One of the larger Utilities was an early and enthusiastic user of the IWA practical approach, and achieved an ILI below 2.0 by 2007, before a 3-year drought period involving intermittent supply caused substantial increases in bursts and permanent damage to the distribution system in term of increased background leakage. ILIs for two of the three larger Utilities have been contributed anonymously to the international data set.
In February 2014 the Water Development Department of the Ministry of Agriculture, Natural Resources and Environment of the Republic of Cyprus, with the collaboration of the Water Boards, Union of Municipalities and the University of Cyprus, published a “Code of Best Practice for the Management and Operation of Water Distribution Networks” which adopts the IWA WLSG strategies and methodologies.
*Charalambous B.(2011) ‘The effects of Intermittent Supply on Water Distribution Networks’, IWA Efficient 2011 Conference, Dead Sea, Jordan, Proceedings. Free copy: http://173.254.28.127/~leakssui/wp-content/uploads/2012/11/2011_Charalambous-2011J1.pdf
France The AGHTM proposed a standard water balance and performance indicators for France in 1990, and the extent to which the IWA standard Water Balance (2000) has replaced it is not clear to the authors. Use of %s in the form of Rendement (% of system input volume delivered) and Linear Leakage Index LLI (Indice Lineare des Pertes, m3/km mains/day) are the most frequently used PIs for water losses (apparent plus real), but with direct pressure systems apparent losses are normally quite small. LLI values are then usually converted into some kind of descriptive Performance Classification e.g. ‘Worrying/Mediocre.Almost Satisfactory/Satisfactory’ as in the FFNCR Classification of 2003
.
Table: Performance Classification according to FNCCR proposal (2003)
The FNCCR classification uses ILC (Indice Lineare Consumption (m3/km/day) as an additional parameter to represent rural/intermediate/urban systems; other similar French classifications such as Laboratoire GEA use properties/km for this purpose. One of the problems of these types of classification (Fantozzi et al, 2010) is that they produce discontinuities at the Class Boundaries (see Figures below); a small change (up or down) in the X axis parameter (consumption, or properties/km) near the Class Boundary results in a major change in implied performance.
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Class Limit Discontinuities: Examples: FNCCR, Laboratoire Gea (per km, per conn)
Source: Fantozzi, Lambert and Liemberger: Some Examples of European Water Loss Targets, and the Law of Unintended Consequences. IWA Specialised Conference ‘Water Loss 2010’,Sao Paolo, Brazil, June 2010
http://173.254.28.127/~leakssui/wp-content/uploads/2012/11/2010_FantozziLambertLiembergerSanPaolo7AprIWA-2010K.pdf
At least one large French Water Company with international activities has been calculating ILI for several years and using it as one of their key performance indicators, and has provided 4 ILIs for French cities to the European ILI data set for HICs.
Germany The IWA Water Balance and several IWA concepts were adopted in DVGW W392 Guidelines in 2003, but DVGW preferred to continue to use the traditional German performance indicator of specific loss (m3/km/hr) as a performance indicator, whilst continuing to strongly recommend against the use of %s. However, after re-evaluating the advantages of the ILI, the draft 2013 update of W392 now recommends adopting the ILI as the definitive PI for Real Losses, with specific loss as a subsidiary measure, for the 6000 Water Utilities in Germany.
ILI values interpreted visually and very approximately from a graph in Tennhardt (2012) suggests that around 70% of a sample of 35 calculated German ILIs are within Band A, with most being grouped around an ILI of 1.0 +/- 0.5. The remainder are mostly in the range 3.5 to 4.5. Water balance data grouped within 4 of the 16 German Bundesländer (States) has been derived from Consultants reports and assembled by Koelbl and Lambert, and contributed to the 2014 data set on an anonymous basis. The grouped ILIs range from 0.7 to 1.1.
In Italy, the IWA methodology and the ILI are now well known through training courses, workshops and Conferences initiated by Dr Marco Fantozzi, and based mainly at Genova, Ferrara, and Italian Universities; these have taken place on a regular basis since around 2004. A data set of 67 partly validated Italian ILIs in Piedmont, Emilia Romagna and Tuscany, ranging from 1.5 to 16 (median 5.0) were collated by Marco Fantozzi in 2008.
Enia Utility (now part of IREN Utility) is one of a number of Utilities that has been using IWA practical approaches for up to 9 years, and has contributed good quality ILI data from 10 towns (average ILI 2.8) to the 2014 ILI data set; an ILI from 1 anonymous Italian city is also included. The regulator in Emilia Romagna now requires Utilities in that region to calculate ILI, and there is growing interest at National level to consider moving from the traditional %s and losses per km as performance indicators .
References: Calza F and Fantozzi M. Pressure management: the experience of ENIA Reggio Emilia, WATER EFFICIENCY CONFERENCE, Ferrara, Italy May 2010
Calza F and Fantozzi M: Experiences in district metered areas and pressure control in ENIA, IWA WATERLOSSEUROPE CONFERENCE, Ferrara, Italy May 2012
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Malta Water Services Commission adopted the IWA Water balance and began to use the ILI in 2001 as its key performance indicator for Real Losses. In 2007 the Malta Regulator (the Malta Resources Authority) formally recognised the ILI by setting WSC’s performance targets in terms of ILI. Malta has contributed ILIs to all three IWA data sets – 1999, 2005 and 2014 – and the overall ILI for Malta WSC has fallen from 10 in the mid-1990s to 2.0 in 2012 (Galea St John, 2013). Because all properties have customer storage tanks, ILI calculations are based on night flows using ‘Snapshot’ ILI. The WSC has contributed 2 ILIs to the 2014 data set, for the islands of Malta and Gozo.
Galea St John, S (2013). Awareness of Leakage & NRW in Malta. Global Leakage Summit, 12th
/13th
March 2013, London,
Portugal The single ILI for Portugal in the European data set was a late entry, and a more informative overview of progress in implementing the IWA Best Practice approach will be provided in an update in later in 2014. Most systems operate with direct pressure, Porto is one of a limited number of Portuguese Utilities where customers have roof storage tanks.
Serbia Progress in the introduction and implementation of the IWA Practical Approach is occurring mainly through inter-municipal cooperation developed and supported by the German development agency GIZ (previously GTZ). A 2010/2011 implementation project provided rising awareness of the IWA approach, and free Water balance and PI software was provided in Serbian language. Activities included promotional presentations, workshops, water network audits, training of employees from utilities, on-field education, webinars and visits to good example case studies (even between different countries). Altogether 8 utilities were directly involved with participating personnel from another 20 utilities, with an IWA water loss expert as main consultant and trainer.
IPM is a new association of professionals from the Serbian water sector in Serbia, formed to help Water Utilities’ future cooperation, to promote efforts and achievements with increase public awareness, and to seek political support and financial assistance from different donation programs and associations. Associated initiatives include the Water Loss Working Group of the Water Operators' Partnerships for South East Europe (WOP-SEE), and publications promoting IWA methodology and translations of Water 21 articles.
Jurica Kovac has collated ILI data from 7 Utilities as Serbia’s contribution to the 2014 LAMIC European data set.
Spain There are around 2800 Water Utilities in Spain, and many municipalities operate their own systems. Most of the properties receive direct pressure from the mains, but in some areas of the East coast of Spain there are cities where the properties have roof tanks. The benefits of pressure management are well known in technical forums, and all large cities have pressure management schemes, some with over 100 pressure managed zones. Economic benefits including some reductions in burst frequencies are being obtained, but there is little published data and reports. The Spanish Water Supply Association publishes a book of water supply statistics, with figures of average NRW%, so this remains the most commonly used performance indicator. Other figures, performance indicators and practices are generally published or delivered. Some Companies calculate an ILI but do not publish it, and one of these Companies has provided an anonymous ILI for the European data set.
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Switzerland The single ILI for Switzerland in the European data set was a late entry, and a more informative overview of progress in implementing the IWA Best Practice approach will be provided in an update in later in 2014. The Swiss guideline SVGW W4 “Water distribution”, published in 2013, consists of 5 parts (Part 1: General, Part 2: Planning and Design, Part 3: Construction and Control, Part 4: Operation and Maintenance, Part 5: a collection of loose sheets of examples from practice, check lists etc.). Water Losses are addressed in Part 4. Prior to 2013, calculation and assessment of water losses were not described in any other guideline. In the SVGW W4 guideline it is recommended to use the IWA Water Balance. For performance indicators, the guideline follows the DVGW W 392 (2003) guideline approach with a classification of qVR (m³/km/h) for rural, urban und large urban networks, with class limits based on system input rate. However, the Guideline does not describe details of water balance and performance indicator calculations. Some utilities have started calculating the ILI for the purpose of international comparisons, but the use of percentages and qVR is still widespread.
United Kingdom There are only around 25 Water Utilities in the UK, half of which are very large organisations. Leakage calculation based on Water Balances, Night Flows and associated data for England and Wales are independently audited. Until 2009/10, three separate figures for leakage in each Company were published annually by OFWAT, the Economic Regulator, each in 3 sets of units: Ml/day, litres per property per day and m3/km of mains per day.:
Distribution losses, up to the property line
Total supply pipe losses, on privately owned pipes after the property line
Total leakage, the sum of Distribution Losses and Total Supply Pipe Losses
OFWAT clearly stated in 1996 that leakage as a % of Water into Supply can be misleading, as a reduction of volume into supply, following successful water efficiency measures by a Utility’s customers, would make its leakage performance appear to worsen.
In 1996, OFWAT began to set England/Wales Companies targets for Total Leakage, based on calculations of economic intervention policies for active leakage control and Economic Leakage Levels (ELL) carried out by the companies. These were broadly achieved by 2000. However, it is now recognised that the ELL calculations did not take enough account of the several influences of pressure management (which is widely practised in the UK). Prediction methods for the Sustainable ELL (SELL) now being used by the Companies include allowances for costs of social disruption and cost of carbon, but there are concerns that pressure management benefits and meter location issues influencing supply pipe leakage are still not receiving sufficient weight in most SELL calculations.
OFWAT ceased to publish detailed water balance and associated data in 2010, and introduced a risk-based approach to regulations. As part of this new way of regulation they introduced a number of key indicators which includes Leakage. From 2011-12, the only Company leakage figure published on the OFWAT Website is ‘Total Leakage’ in Ml/d, usually derived from both ‘top-down’ water balance and ‘bottom-up’ night flows. In the absence of other traditional UK leakage performance indicators previously published by OFWAT (litres/property/day, m3/km mains/day), the media fill the gap by publishing their own diverse interpretations of the Ml/d figures, which tends to confuse public perceptions of leakage management performance.’
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The Environment Agency also collects leakage data and requires the companies to develop Water Resource Management Plans, which contain details of current leakage and leakage targets within the context of the supply demand balance.
Leakage targets in Scotland are agreed between Scottish Water and WICS (the Water Industry Commission for Scotland). Water Resource Management Plans are also published in Northern Ireland and Scotland.
Since 2003 a number of UK Water Suppliers (including Northern Ireland and Scotland) contribute leakage performance data to a Water UK Leakage Network group, but this unaudited data is not published or available to researchers or the media. All members of the Leakage Network can now calculate their ILIs using free software provided by WLSG members, and nine members have contributed ILIs to the European data set on an anonymous basis.