The Zero-Sum Leakage Performance Indicator

Follow this link to Play the %s Game

or this to Play the NRW %s Game

(for PC only not mobile or tablet)

Previous blogs on this website have shown examples of the unintended consequences of using % of System Input Volume (% of SIV) as a performance indicator for setting targets and tracking progress in NRW and leakage reduction, and for comparisons of performance. You can now use the LEAKSSuite ‘Play the Percentages Game’’ quick calculator to show the distorted perception of true achievements that can occur, for any distribution system.

A Zero-Sum Game is an interaction where one party’s gain must equal the other party’s loss. For example, two people play cards for money, player A brings (say) £60 and player B (say) £40, or £100 between them . At the end of the game, if one gains £20, the other must lose £20; the total amount of money is the same (£100) as when they started. The only other option is that nobody gains anything. This is a Win:Lose situation, or Draw:Draw interaction.

To reduce the effect of abstraction on the environment, and the waste of energy used in treating and delivering excess water to customers, modern management of potable water supply seeks to reduce, as far as possible, both consumption and leakage. This is equivalent to a Positive-Sum interaction, or Win-Win situation, where the introduction of combinations of smart technology by a Water Utility – for example, smart metering and advanced pressure management – can reduce both excess consumption and excess leakage volumes.

Unfortunately, % of SIV acts as a Zero-Sum Performance Indicator. The total of Consumption (as % of SIV) and leakage (as % of SIV) must always be 100% of SIV, so if the volumes of both consumption and leakage are actually reduced, it’s impossible for both Consumption (as % of SIV) and Leakage (as % of SIV) to both show reductions at the same time. If consumption increases, leakage management appears to be better than it actually is. If consumption decreases, leakage management appears to be worse than it actually is. The true % changes in leakage volume from year to year, and the resulting perception of achievement or deterioration, become distorted.

You can use the ‘Play the Percentages Game’ to show the distortion of perception that occurs on any distribution system in different situations. The first two examples are for high leakage systems, where a Utility which took action, and reduced leakage, consumption and system input volumes all by around 5%, shows almost no change in leakage as a % SIV. However, a system which took no action, where  leakage, consumption and system input volumes all increased by around 5%, also shows zero change in leakage as a % of SIV!  

Example 1

Game 1








Example 2

Game 2








The 3rd and 4th examples are for systems with low initial values of leakage (ILI around 1.0), which can be around 5% of SIV in a high consumption system. If consumption reduces, leakage as a % of SIV appears to increase, even though leakage volume is unchanged. This is a difficult situation to explain to media and politicians, when the Utility has previously supported use of % of SIV!  Conversely, if consumption increases, leakage as a % of SIV appears to reduce, even though leakage volume is unchanged.

Example 3

Game 3









Example 4

Game 4







No doubt you will find numerous situations of unexpected consequences and distorted perceptions if you use the ‘Play the Percentages Game’

For a more rational approach to setting targets, tracking progress and comparisons of leakage, see ‘Smart Water Loss Performance Indicators for Smart Water Networks. Keynote Speech, IWA Conference ‘Water Ideas 2014: Intelligent Distribution for Efficient and affordable Supplies’. Bologna, Italy, 22-24 October 2014’, available on this website as 2014Q. Global IL’s can be found here, then scroll territories under Global LI’s.

Zero-Sum Leakage PI