Glossary
Home > GlossaryThe majority of this glossary is taken from "Losses from Water Supply Systems: Standard Terminology and Recommended Performance Measures" By Mr A. Lambert, International Water Data Comparisons Ltd, Llandudno, LL30 1SL, UK, and Dr W Hirner, Erlenstegenstrasse 118B, D-90491, Nurnberg, Germany.
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| Term | Definition |
|---|---|
| % of Volume Input | Percentage of system input volume is an appropriate measure to define the financial and ecological views of water losses, as defined in the IWA Manual of Best Practice: Performance Indicators in Water Supply Systems which supports the use of % for the Financial Non-Revenue Water by Volume, and Water Resources Indicators. |
| Apparent Losses | consist of unauthorised consumption (theft or illegal use), and all types of inaccuracies associated with production metering and customer metering. Under-registration of production meters, and over-registration of customer meters, leads to under-estimation of real losses. Over-registration of production meters, and under-registration of customer meters, leads to over-estimation of Real Losses. |
| Authorised Consumption | is the volume of metered and/or unmetered water taken by registered customers, the water supplier and others who are implicitly or explicitly authorised to do so by the water supplier, for domestic, commercial and industrial purposes. It includes water exported. Note that authorised consumption includes items such as fire fighting and training, flushing of mains and sewers, street cleaning, watering of municipal gardens, public fountains, frost protection, building water. These may be billed or unbilled, metered or unmetered according to local practice. |
| CARL | Current Annual Real Losses - total losses from the system as calculated using an IWA water balance. |
| Infrastructure Leakage Index (ILI) | CARL/UARL |
| Non-Revenue Water | is the difference between the System Input Volume and Billed Authorised Consumption. |
| Real Losses | are physical water losses from the pressurised system, up to the point of customer metering. The volume lost through all types of leaks, bursts and overflows depends on frequencies, flow rates, and average durations of individual leaks. |
| System Input Volume | is the volume of water input to a transmission system or a distribution system |
| TIRL | Technical Indicator of Real Losses - this term is no longer used and has been replaced by CARL. |
| Traditional PIs | the simple traditional Technical Performance Indicators for Real Losses which are most widely used in different parts of the world to make comparisons of the Annual Volume of Real Losses are:
|
| Unavoidable Average Real Losses (UARL) | It is recommended that the calculation of the UARL in litres/service connection/day is based on the following form of equation. This recognises separate influences of Real Losses from length of mains (Lm in km), number of service connections (Nc), total length of service connections from the edge of the street to customer meters (Lp in km), and average pressure (P in metres) when the system is pressurised. UARL = (A x Lm/Nc + B + C x Lp/Nc) x P (litres/service connection/day when the system is pressurised) |
| Water Abstracted | is the volume of water obtained for input to raw water mains leading to water treatment plants |
| Water Losses | of a system are calculated as: Water Losses = System Input Volume - Authorised Consumption
Water Losses can be considered as a total volume for the whole system, or for partial systems such as raw water mains, transmission or distribution. In each case the components of the calculation would be adjusted accordingly. Water Losses consist of Real and Apparent losses, and are effectively identical to the previous IWSA definition of Unaccounted-for Water. |
| Water Produced | is the volume of water treated for input to water transmission mains or directly to the distribution system |
