Chapter 5 Infrastructure Leakage Index For Surat City 113

CHAPTER 5

INFRASTRUCTURE LEAKAGE INDEX FOR SURAT CITY

5.1 INTRODUCTION

Water loss from water distribution systems is a major concern to water utilities for several

reasons, including: loss of limited water resources and pumping energy, economic loss, and

increased health risks due to escalating breakage rates and the possibility of intrusion by

contaminants. Water transmission and distribution networks deteriorate naturally with time,

and subsequently lose their initial water tightness. Water is lost mainly due to leakage in

different components of the network: transmission and distribution pipes, service

connections, joints, valves, fire hydrants, storage tanks and reservoirs. In addition, many

networks suffer from what is known as “apparent” (or non-physical) losses, which are caused

primarily by customer meter under-registration, accounting errors, or unauthorized water use.

The amount of water lost can be significant, reaching levels as high as 50% of production for

some utilities. Surprisingly, water loss management is still not widely practiced by utilities in

the world. This could be attributed to the following reasons: absence of regulatory

constraints; lack of concern about water loss due to abundant and cheap water resources;

reserve treatment capacity; and insufficient financial resources to manage leakage and

perform needed repairs. Water utilities around the world are becoming more focused on

adopting a proactive approach to managing water loss.

In this research, the effort is put forward to find out Infrastructure leakage index of Surat city

of India in Gujarat state. The result reflects alarming situation related to water loss and

immediate action is required to control the water leakage. The BENCHLEAK software

developed by South African Water research commission based on International water

association (IWA) methodology was used in the research work for Infrastructure leakage

Index.

5.2 METHODOLOGY FOR INFRASTRUCTURE LEAKAGE INDEX

Following steps were followed for calculation of Infrastructure leakage Index of the Surat

city.

Preparation of simple data form as per IWA water balance performance indicator

Data form sent to the hydraulic engineer at SMC

Chapter 5 Infrastructure Leakage Index For Surat City 114

Collection of data form after 4-5 weeks

Verification of data

Data entered into BENCHLEAK data sheet

Result obtained

The standard IWA water balance was first introduced in the late 1990’s and due to the efforts

of members of various IWA task teams it has gained considerable momentum all over the

world. As a part of the process of undertaking a standard water balance, various performance

indicators have also been produced, the most recent of which is the Infrastructure Leakage

Index or ILI. For research work, following performance indicators were used and data sheet

were prepared. The simple data form includes following detail. The simple data form is

enclosed in appendix IV.

Primary detail

System data

Annual water balance data

Component of authorized consumption

Financial performance indicator

The sample data form was sent to hydraulic engineer by email and purpose for collection of

data was explained to him. Some points were clarified for more accuracy of data. The time

period of one month was given to him for collection of data. After one month data request

from was received back through email. In order to validate the data, the data were thoroughly

checked for any obvious anomalies. The mistakes and incorrect data were identified during

this screening process. Typical errors and mistakes identified included:

Mistakes related to the units of the input data.

Errors in the input data, like % system is pressurized

In case, where dubious data were identified the concerned person from hydraulic department

of SMC was contacted again for verification of the data. At some point discussion was

carried out with hydraulic engineer. The data were then fed into Leakage Benchmarking sheet

of BENCHLEAK Software and Infrastructure Leakage Index was obtained.

The BENCHLEAK Model was used for Infrastructure Leakage Index calculation. It is simply

a spreadsheet (in Microsoft-Excel format) comprising three forms that utilize certain basic

Chapter 5 Infrastructure Leakage Index For Surat City 115

information. This information was obtained from Surat Municipal Corporation by preparing

simple data form. The information received from hydraulic department of Surat Municipal

Corporation is processed in such a way that the leakage can be evaluated and compared with

standard ILI values in a meaningful and realistic manner.

5.3 DETAILS OF BENCHLEAK SOFTWARE

The BENCHLEAK Model was downloaded directly from the WRC web site. It is a relatively

small file at approximately 130K and can be run from anywhere on the user’s PC as long as

the Excel program can be accessed. There is no sophisticated installation shield and it is

simply the case of copying the BENCHLEAK.XLS file into a suitable directory and model

can be used in the same manner as a normal Excel spreadsheet.

The BENCHLEAK Model is colour-coded in such a manner that:

Yellow blocks must be completed by the user

Blue blocks simply provide an example data set;

Green blocks are calculated fields and require no user input.

The user must complete only the yellow blocks which involves the following information:

System name and contact details

System data: length of mains, number of connections, percentage of time system is

pressurised and the average operating pressure of the system;

Period over which the information refers i.e. calendar year, financial year

Details of water input to the system (i.e. water purchased from bulk supplier and

water

Produced from own sources etc);

Details of water supplied to customers including estimates of all unmetered and

unbilled water;

Estimate of Apparent Losses as a percentage of the total losses.

The model contains three parts namely:

The Summary form (1 sheet when printed)

The Detail-1 form (3 sheets when printed)

The Detail-2 form (1 sheet when printed).

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The Summary Sheet

The Summary form simply provides a one-page summary of certain key performance

indicators and requires no input from the user with the exception of the reference number for

the water supply system (optional). It should be noted that most of the cells on the Summary

sheet are protected to prevent the user from over-writing any of the cell formulae. In addition,

all cells are colour coded to indicate which cells require user input (Yellow cells) and which

cells are either examples (blue) or calculated fields (green).

The Detail-1 Sheet

The Detail-1 sheet is the sheet where most of the information required in the model is

supplied by the user or water supplier. Only the yellow cells need to be considered since all

other cells are calculated by the model or are simply examples supplied to help new users to

understand the calculations. The Detail-1 sheet has been split into three sheets for printing

purposes.

The Detail-2 Sheet

Most of the information used in the Detail-2 sheet is taken from the previous sheet and very

little additional information is required. The only information required from the user is the

Target Loss Factor.

DATA PERIOD

The data used for Infrastructure leakage index were collected from time span April 2010 to

March 2011.

5.4 PERFORMANCE INDICATOR USED FOR INFRASTRUCTURE LEAKAGE

INDEX:

The sample calculation of performance indicator used in BENCHLEAK software is shown

below. The detail spreadsheet of BENCHLEAK software is enclosed as Appendix V.

5.4.1 PRIMARY DETAILS:

This detail includes primary information like name, address and contact detail of water

supplier.

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5.4.2 SYSTEM DATA DETAIL:

These details include basic information related to water supply network like length of main,

number of service connection, density of service connection, average operating pressure, %

of time when system is pressurised and population served by supply system. All the data

except % of time when system is pressurised were readily available. % of time when system

is pressurised was calculated on the basis of water supply hours as study area supplies water

intermittently (two-three hrs) daily. Hence, system does not remain under pressure for 24

hours.

Table 5.1 system data for ILI

5.4.2.1 AVERAGE OPERATING PRESSURE

The frequency at which new leaks occur and the rate of flow of leaks are related to operating

pressure. The exact relationship between operating pressure and leakage has not been

established, but simplified assumption adopted that leakage varies linearly with pressure

which yields realistic results. Operating pressure is constrained by local topography and

minimum levels of service and will vary significantly between different water supply

systems. The average operating pressure varies from about 15m to about 45 m of head for the

reference set with an average value of 30 m.

5.4.2.2 PERCENTAGE OF TIME SYSTEM IS PRESSURISED

For continuous water supply the performance indicator percentage of time that system is

pressurised is to be taken 100%. Hence in software sheet value is 1.0. In the research area, the

water supply is for 3 hrs hence PI percentage of time that system is pressurised become15%

which is shown above in system data table 5.1.

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5.4.2.3 DENSITY OF SERVICE CONNECTION

Density of connections (number of connections per km of mains) is an important indicator

and can vary significantly from one system to another. The density of connections can also be

used as a quick check in the verification of data. For example, a low value of 5 connections

per km of mains suggests that on average there is one connection for every 200 m of mains. It

is possible where the supply system consists mainly of large plots and smallholdings. On the

other hand, high density of connections can be expected in some of the large urban centers

due to the existence of high-density low-income areas where erf sizes are relatively small. It

should be noted that care should be taken in cases where the person providing the information

estimates the number of connections as being equal to the number of properties. It is not

always the case that the number of connections is equal to the number of properties, since it is

common practice to have one saddle connection branching to two or more erf connections. It

is also often found that undeveloped properties are often not connected. For comparison

purposes the number of service connections can usually be considered to be equal to the

number of serviced erven.

5.4.3 OPERATIONAL PERFORMANCE INDICATORS

The apparent losses are simply considered to be a percentage of the total losses. A value to

the order of 20% is normally considered to be appropriate, although it can vary from system

to system. The apparent losses represent a component of the water that escapes the revenue

system and any reduction in apparent losses will result in a greater income to the water

supplier at the effective selling price of the water. In some situations the apparent losses can

be very high and can even exceed the physical losses (or real losses), especially in cases

where levels of payment are low and the payment is based on a flat tariff rather than

measured consumption.

It is evident that expressing real losses per connection shows no definite trends with regard to

grouping, which proves that it is not biased in terms of system size, system input, unit

consumption, etc. As in the case of CARL per connection/day, expressing real losses per

kilometer of mains or per connection per meter of pressure also shows no definite trends or

distribution patterns.

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5.4.3.1 ESTIMATION OF UNAVOIDABLE ANNUAL REAL LOSSES (UARL)

The procedure to estimate the unavoidable annual real losses (UARL) was developed by

Lambert (1999). Basically UARL involves estimating the unavoidable leakage for three

components; namely, mains, connections at street edge and service connections after street

edge. The formula given in BENCHLEAK software was used for calculation of UARL.

The data used were,

Length of mains

Number of service connection

Average operating pressure when system is pressurised

Percentage of time when system is pressurised

Following equations were used for estimation of Annual volume of unavoidable

annual real losses (UARL).

On mains = 18*Lm*P*365*T/108

On Service connection= 0.8*Ns*P*365*T/108

Table 5.2 Unavoidable annual real losses for Surat city

5.4.3.2 ANNUAL WATER BALANCE DATA

The annual water balance was calculated based on system input volume as shown in table

5.3.

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5.4.3.3 SYSTEM INPUT VOLUME

Table 5.3 Volume of water input in the system

The system input comprises the water supplied from the municipal corporation own source as

well as water purchased from other sources. The 2% correction is allowed for the source bulk

meter as well as any input from unmetered sources which would usually be relatively small.

5.4.3.4 COMPONENTS OF AUTHORISED CONSUMPTION:

According to BENCHLEAK software the total authorized consumption is split into several

components including exports, households, non-households, standpipes, firefighting, mains

flushing, building water and the option for adding another two user-defined categories. In

most instances, the categories included are sufficient to allow the supplier to provide a

reasonable breakdown of the water use in the area of supply. Some of the items listed may be

excluded or estimated since they may not be recorded directly. The various headings (billed

metered, billed unmetered etc) are self-explanatory terms.

Table 5.4 Volume of authorised consumption of water

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5.4.3.5 ESTIMATION OF WATER LOSSES:

Table 5.5 Volume of water loss from the system

In BENCHLEAK model basically three elements of water losses are considered. These are

as under.

Total Losses;

Apparent Losses; and

Real Losses.

The total losses are estimated as the difference in the system input and the authorised

consumption.

The apparent losses are generally considered to be losses associated with:

Meter error;

Unauthorised use;

Administration errors.

The BENCHLEAK Model allows the water supplier to provide an estimate of losses

associated with bulk meter error but this does not include the losses associated with the

consumer accounts which are based on the consumer meters. The individual components of

the apparent losses are not listed separately in the model as most of the time this details are

not available with water supplier. Hence, the Apparent Losses are simply considered to be a

percentage of the Total Losses mentioned above. A value to the order of 20% is normally

considered appropriate, although it can vary from system to system. The Apparent Losses

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represent the water that escapes the revenue system and any reduction in Apparent Losses

will result in a greater income to the water supplier at the effective selling price of the water.

As per (R S McKenzie, 2002) In some South African situations the Apparent Losses are very

high and can even exceed the physical losses, especially in cases where levels of payment are

low and the payment is based on a flat tariff rather than measured consumption.

The real losses are then calculated directly as the difference between the total losses and the

estimated apparent losses. The real losses represent the physical water lost from the system

and any reduction in Real Losses will result in lower purchases of water by the water

supplier.

5.4.3.6 CURRENT ANNUAL REAL LOSSES PER CONNECTION:

The “Current Annual Real Losses per connection per day helps to remove the influence of the

size of the system, and allows a more direct comparison between different systems and can be

calculated using following formula.

CARL = ARL*106/ (Ns * T/100 * 365)

Table 5.6 Current annual consumption and real losses per connection per day

Different systems operate under different average operating pressures. It is also known that

leakage is influenced directly by pressure and in order to remove this influence the previous

indicators of Real Losses can be divided by the average operating pressure.

5.4.3.7 INFRASTRUCTURE LEAKAGE INDEX

The Infrastructure Leakage Index (ILI) is the most recent and preferred performance indicator

for comparing leakage from one system to another. It is a non-dimensional index representing

the ratio of the current real leakage and the “Unavoidable Annual Real Losses” (UARL). A

high ILI value indicates poor performance with large potential for improvement while a small

ILI value indicates a well-managed system with less scope for improvement.

Chapter 5 Infrastructure Leakage Index For Surat City 123

The detailed Operational Performance Indicators for Real Losses deals with both these

factors. UARL and CARL. The ratio of the Current Annual Real Losses (CARL, calculated

from the standard Water Balance) to the UARL, is the Infrastructure Leakage Index (ILI).

The table 5.7 shows ILI for study area is 85.06. The result reveals the water system falls in D

category (Liemberger, 2005 ) and needs immediate attention to reduce water losses.

Infrastructure Leakage Index ILI = CARL/UARL

Table 5.7 Infrastructure Leakage Index

5.4.3.8 NON-REVENUE WATER AS A PERCENTAGE BY SYSTEM INPUT

VOLUME

The table 5.8 represents that 21.95% of total input volume is non revenue water in study area.

The 21.95% of total input volume is considered high amount and same water can be utilized

to serve more people in the city.

Table 5.8 Non revenue water in context to percentage system input

5.4.4 FINANCIAL PERFORMANCE INDICATORS

Little confidence is attached to the data with regard to non-revenue water and expressed as a

percentage of running cost. As it was evident that water suppliers found it difficult to provide

a reasonably accurate break-up between the components of non-revenue water, which are:

Unbilled authorized Consumption,

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Apparent Losses, and

Real Losses.

It is even more difficult for water suppliers to provide a break-up of the components of the

unbilled authorised portion of non-revenue water.

For financial performance following data were considered as per BENCHLEAK software.

Unit value of real losses

Unit value of apparent losses

Annual cost of running the system

5.4.4.1 LOCAL VALUE OF REAL AND APPARENT LOSSES

“Real Losses” are generally valued in terms of the purchase price of the water by the water

supplier or the cost of producing the water in the case of suppliers who abstract and purify

their own water rather than purchasing from a bulk supplier. The following table shows that

unit value of real losses and apparent losses are 0.45 Rs. and 3.00 Rs. respectively.

Table 5.9 unit value of types of losses

5.4.4.2 ANNUAL COST FOR RUNNING SYSTEM

The following table 5.10 shows that annual running cost is 730500000 Rs./year.

Table 5.10Non-revenue water expressed as percentage of annual running cost

5.4.4.3 NON REVENUE WATER AS A PERCENTAGE BY VALUE OF COST OF

RUNNING SYSTEM

A more meaningful performance indicator for the non-revenue water is to express it as a

percentage of the annual system operating cost. The table 5.11 represents that Rs. 58727000

is lost which is 8.04% of total cost of running system. This money can be saved by

Chapter 5 Infrastructure Leakage Index For Surat City 125

employing sustainable water supply strategies by reducing water losses. Therefore, in the

third phase work is conducted for prediction of pipe leakage / assessment of pipe condition to

prioritize rehabilitation/replacement of pipes of water supply network.

Table 5.11 Non-revenue water as a % of total cost of running system