Key Performance Indicators

ALL Water Loss KPIs have Limitations – understand before you choose!

Traditional measures used to assess and compare Utility technical management performance of water losses from distribution systems often confuse, rather than assist, rational comparisons. Different KPIs calculated for the same Utility frequently produce conflicting impressions of performance.

When, in 1995 to 2000, the 1st IWA Water Loss Task Force reviewed traditional Performance Indicators for losses in water supply systems, they found that the traditional KPIs for NRW and its components (per km mains, per service connection, per property) were not suitable for national or international comparisons, as they each took account of only one of four key system-specific parameters. They also confirmed (1999M) previous conclusions (by DVGW in Germany and OFWAT in the UK) that % of System Input Volume is not fit for purpose as a technical KPI.

Accordingly, the Task Force developed (1999M) the Infrastructure Leakage Index (ILI) for the specific purpose of comparing performance in Real Losses management between Utilities with diverse system characteristics (mains length, number of service connections, meter location, average pressure).

At least 6 different traditional and recent KPIs are currently used in different countries; they each have particular strengths and/or weaknesses making them ‘fit for purpose’ for particular objectives and ‘unfit’ for others. The Table summarizes recommendations of the EU Reference document ‘Good Practices on Leakage Management (2015) which shows that the traditional KPI ‘% of system input volume’ is not in fact fit for purpose for any of these objectives. In fact, in 2014 it was identified as a ‘Zero-Sum’ performance indicator which, if used for setting leakage targets, distorts perceptions of performance and cannot show reductions in NRW, leakage and consumption in the same year.


WLRandA and ILMSS has been active in seeking to promote more rational use of KPIs for NRW and leakage, see published papers, articles and presentations, blogs and free software at KPIs Fit for Purpose:

Since 2013, the LEAKSSuite website promotes, collates and summarises an ever-increasing number of validated ILI data sets for Real Losses from Australia, Europe North America and individual countries, to try to provide the most robust and meaningful international comparisons on technical leakage performance, using the KPI (ILI) specifically designed for that purpose by the IWA Water Loss Task Force in 1999. See Global ILIs.

In 2011, the Apparent Losses team of the Water Loss Specialist Group proposed the use of an Apparent Loss Index ALI (equivalent to the ILI for Real Losses). Whilst the ALI has not been formally adopted by the IWA Water Loss Specialist Group, it uses Apparent Losses calculated as a % of billed metered consumption (excluding Water Exported). In the free CheckCalcs and EurWB&PICalcs software, this concept has also been extended to assessing Unbilled Authorised Consumption and Unauthorised Consumption as a % of billed metered consumption (excluding Water Exported).

Despite considerable efforts, there is as yet no commonly agreed Metric PI for Non-Revenue Water.