CHAPTER 4 ANALYSIS OF DECISION VARIABLES
4.1 THE IWA PERFORMANCE INDICATORS
There are 170 performance indicators in the book “Performance Indicators for Water Supply Services” by Helena Alegre et al., and this text covers many of the indicators that are required to monitor the performance of a Utility and a water distribution network. These indicators are spread across six key areas of the business as shown in Table 4.1.
Table 4.1: The IWA Performance Indicators (Alegre, 2006)
Many of these indicators relate to the Utility as a whole and some of these relate to the performance of the water mains. In addition to this, there are a number of further indicators that can be tracked to provide further information on the distribution system.
Many of these identified indicators are used in the analysis programmes that were discussed in Chapter 2. The complete set of indicators is shown in Appendix B. 22 Indicators have been chosen that are considered to be primary indicators used to inform a mains replacement programme. These are listed in Table 4.2:
IWA Performance Indicator
Abreviated Name
Total Number of Indicators
Water Resource WR 4
Personnel PE 26
Physical Ph 15
Operational Op 44
Quality of Service QS 34
Economic and Financial Fi 47
Totals 170
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Table 4.2: The Primary Performance Indicators for Mains Replacement (Alegre, 2006)
ABBREVIATED
NAME PERFORMANCE INDICATOR DESCRIPTION OF PERFORMANCE INDICATOR
Wr1 Inefficiency of use of Water Resources (%)
Percentage of water that enters the system and is lost by leakage and overflows up to the point of customer metering.
Ph3 Treated Water Storage Capacity (days)
Capacity of transmission and distribution service reservoir per unit volume of system water input.
Op5
Active Leakage Control Repairs (No./100km/year)
Number of leaks detected and repaired due to active leakage control per unit of main length.
Op23
Water Loss per Connection (m³/connection/year)
Total (apparent and real) losses, expressed in terms of annual volume lost per service connection. This indicator is adequate for urban distribution systems.
Op24
Water Losses per Mains Length (m³/connection/year)
Total (apparent and real) losses, expressed in terms of annual volume lost per mains length. This indicator is adequate for bulk supply and low service connection density distibution systems.
Op25 Apparent Losses (%)
Percentage of the water provided to the system (system input volume minus exported water) that corresponds to apparent losses. This indicator is adequate for urban distribution systems.
Op27
Real Losses per Connection (l/connection/day) when system is pressurised)
Real losses, expressed in terms of the average daily volume lost per connection. This indicator is adequate for urban distribution systems.
Op28
Real Losses per Mains Length (l/km/day) when system is pressurised
Real losses, expressed in terms of the average daily volume lost per mains length. This indicator is adequate for bulk supply and low service connection density distribution systems.
Op29 Infrastructure Leakage Index (-)
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.
Op31 Mains Failure (No./100km/year)
Average number if mains failures per 100km of mains and per year.
Op32
Service Connection Failures (No./1000 connections/year)
Average number of service connections failures, expressed per 1000 connections and per year.
Qs10 Pressure of the Supply Adequacy (%)
Percentage of the delivery points (one per service connection) that receive and are likely to receive adequate pressure.
Qs11 Continuity of Supply (%)
Percentage of hours when the (intermittent supply) supply system is pressurised.
Qs14
Interruptions per Connections (No./1000 connections/year)
Average number of interruptions per service connection per year.
Qs18 Quality of Supplied Water (%)
Percentage of the total number of treated water tests performed that comply with the applicable standards or legislation.
Qs21 Physical -Chemical Tests Compliance (%)
Percentage of the total number of physical-chemical tests of treated water performed that comply with the applicable standards or legislation.
Qs28 Pressure Complaints (%)
Percentage of service complaints regarding pressure problems.
Qs30 Water Quality Complaints (%)
Percentage of service complaints regarding water quality problems.
Qs31 Interruption Complaints (%)
Percentage of service complaints regarding interruption problems.
Fi1 Unit Revenue (R/m³) Revenue per cubic meter of authorised consumption.
Fi35 Average Age of Tangible Assets (%)
Percentage of the historical value of tangible assets that corresponds to depreciated historical value of tangible assets.
Fi46 Non-Revenue Water by Volume (%)
Percentage of the system input volume that corresponds to non-revenue water.
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Table 4.3 details another 22 indicators that have not been included in the work of Alegre (2006).
These indicators have been developed by the author and will provide further insight into the performance of the water mains over and above the pipe information that will be stored in the GIS. The indicators highlighted in bold are those deemed to provide direct and useful insight when trying to prioritise mains for investigation / replacement.
Table 4.3: Additional Performance Indicators
In Table 4.4, the 192 indicators have been distilled down into the most useful system indicators, useful DMA indicators and recommended and mandatory indicators for mains replacement.
Table 4.4: Summary of Performance Indicators
ABBREVIATED
NAME PERFORMANCE INDICATOR DESCRIPTION OF PERFORMANACE INDICATOR
AI 1
Reactive Leakage Control Repairs (No./100km/ye ar)
Number of leaks detected and repaire d due to reactive le akage control per unit of main length.
AI 2 Geotechnical Environment Geotechnical Environment / Instability
AI 3 Soil type Soil type
AI 4 Saturated soils Saturated soils
AI 5 Fault lines Fault lines
AI 6 Soil temperature Soil temperature
AI 7 Predominant Failure Mechanism Predominant Pipe Failure Mechanism AI 8 Quality of Installation Quality of Installation by Contractor AI 9 Pressure Fluctuations Dynamic Pressure Fluctuations
AI 10 Residual pipe pressure reserve Difference between pipe class and static pressure
AI 11 Traffic Loading Traffic Loading present over pipe
AI 12 Ille gal Connections Density of Illegal Conne ctions present in area
AI 13 Aggressive Water Aggressive Water Chemical Composition
AI 14 Energy usage Energy usage in pumped system (kw/h)
AI 15 Failure growth rate Failure growth rate pa
AI 16 Pipe Roughness Pipe Roughness coefficient
AI 17 Pipe Criticality Pipe Criticality in ne twork status
AI 18 Flow Delivered Flow Delivered (m3/hr)
AI 19
Critical facilities - Hospitals / industry /
commerce / Schools Critical facilities - Hospitals / industry / commerce / Schools
AI 20 Street Paving Stre et Paving present over pipe
AI 21 Traffic analysis Impact on traffic if main re place d by ope n cut AI 22 Area to be expande d
Area to be expanded and new demand for new connections
PERFORMANCE INDICATOR
ABBRE VIATED
NAME
TOTAL NUMBER
OF INDICATO
RS
NUMBER OF USEFUL SYSTEM INDICATO
RS
NUMBER OF USEFUL
DMA INDICATO
RS
RECOMMENDED INDICATOR INDICATOR FOR
MAINS REPLACEMENT
MANDATORY INDICATOR FOR MAINS REPLACEMENT
Water Resource WR 4 2 1 1 0
Personnel PE 26 20 0 0 0
Physical Ph 15 7 3 1 0
Operational Op 44 32 21 9 3
Quality of Service QS 34 25 23 8 3
Economic and Financial Fi 47 26 3 3 0
Additional Indicators Ai 22 1 22 8 0
Totals 192 113 73 30 6
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